{"id":15944,"date":"2026-08-25T10:51:16","date_gmt":"2026-08-25T02:51:16","guid":{"rendered":"https:\/\/www.drillpipes.com\/%d9%85%d8%a7-%d9%87%d9%88-a-%d8%b3%d8%a7%d9%82-%d8%a7%d9%84%d8%ad%d9%81%d8%b1\/"},"modified":"2026-09-18T16:17:10","modified_gmt":"2026-09-18T08:17:10","slug":"%d9%85%d8%a7-%d9%87%d9%88-a-%d8%b3%d8%a7%d9%82-%d8%a7%d9%84%d8%ad%d9%81%d8%b1","status":"publish","type":"post","link":"https:\/\/www.drillpipes.com\/ar\/%d9%85%d8%a7-%d9%87%d9%88-a-%d8%b3%d8%a7%d9%82-%d8%a7%d9%84%d8%ad%d9%81%d8%b1\/","title":{"rendered":"\u0645\u0627 \u0647\u0648 a \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">\u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 connects the \u0627\u0644\u062d\u0641\u0631 rig at the surface to the \u0645\u062b\u0642\u0627\u0628 \u0627\u0644\u062d\u0641\u0631 at the bottom of the \u0627\u0644\u0628\u0626\u0631. It is not a \u0645\u0641\u0631\u062f \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628, but a complete assembly made from connected sections of \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 and the heavier, more specialized tools installed near the bit.<\/p>\n\n<p class=\"has-primary-color has-text-color has-link-color wp-elements-1 wp-block-paragraph\">During \u0627\u0644\u062d\u0641\u0631, the <a href=\"__PROTECTED_0__\">\u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631<\/a> turns or guides the bit, carries \u0627\u0644\u062d\u0641\u0631 fluid down to the bottom of the hole, and allows the rig to lower or retrieve downhole tools. <a href=\"__PROTECTED_1__\">\u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631<\/a> makes up most of its length, while heavy-\u0627\u0644\u0648\u0632\u0646 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631, \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s, stabilizers, subs, directional tools, and the \u0645\u062b\u0642\u0627\u0628 \u0627\u0644\u062d\u0641\u0631 form the lower working section.<\/p>\n\n<p class=\"wp-block-paragraph\">The exact structure is dIFferent for every \u0627\u0644\u062d\u0641\u0631 program. A simple vertical \u0627\u0644\u0628\u0626\u0631 may use a relatively basic assembly, while a deep directional or horizontal \u0627\u0644\u0628\u0626\u0631 may require a mud motor, measurement tools, rotary steering equipment, jars, and several types of transition components.<\/p>\n\n<figure class=\"wp-block-image size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"1672\" height=\"941\" src=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-running-into-well.jpg\" alt=\"\" class=\"wp-image-14602\" style=\"aspect-ratio:1.7768616335995877;width:867px;height:auto\" srcset=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-running-into-well.jpg 1672w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-running-into-well-300x169.jpg 300w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-running-into-well-768x432.jpg 768w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-running-into-well-1024x576.jpg 1024w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-running-into-well-1536x864.jpg 1536w\" sizes=\"auto, (max-width: 1672px) 100vw, 1672px\" \/><\/figure>\n\n<h2 class=\"wp-block-heading\">\u0645\u0627 \u0647\u0648 a \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 in Rotary \u0627\u0644\u062d\u0641\u0631?<\/h2>\n\n<p class=\"wp-block-paragraph\">A \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 is the assembled column of \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 and downhole tools \u0645\u0633\u062a\u0639\u0645\u0644 to \u0627\u0644\u062d\u0641\u0631 a \u0627\u0644\u0628\u0626\u0631. It creates a continuous mechanical and hydraulic \u0627\u0644\u0648\u0635\u0644\u0629 \u0628\u064a\u0646 the surface \u0627\u0644\u062d\u0641\u0631 equipment and the bit.<\/p>\n\n<p class=\"wp-block-paragraph\">The upper part normally consists \u0627\u0644\u0631\u0626\u064a\u0633\u064aly of \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631. The lower, mechanically stIFfer part is called the bottom-hole assembly, or BHA. Depending on the \u0627\u0644\u062d\u0641\u0631 program, the BHA may contain \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s, stabilizers, heavy-\u0627\u0644\u0648\u0632\u0646 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631, jars, crossovers, a mud motor, MWD\/LWD tools, a rotary steerable system, and the bit.<\/p>\n\n<p class=\"wp-block-paragraph\">The top drive supplies rotation and supports the suspended string, but it re\u0627\u0644\u0631\u0626\u064a\u0633\u064as surface equipment. In a conventional rotary-table system, the kelly transfers rotation from the rotary table. A kelly may appear in broader descriptions of the \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631, but it should not be conf\u0645\u0633\u062a\u0639\u0645\u0644 with the downhole tubular and BHA components evaluated during \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 design.<\/p>\n\n<p class=\"wp-block-paragraph\">This boundary matters when engineers calculate tensile load, torsional capacity, hydraulic pressure loss, \u0627\u0644\u062a\u0639\u0628 exposure, or inspection requirements. These calculations must follow the actual load path from the uppermost tubular \u0627\u0644\u0648\u0635\u0644\u0629 to the bit.<\/p>\n\n<h2 class=\"wp-block-heading\">\u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 Components<\/h2>\n\n<p class=\"wp-block-paragraph\">\u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 components can be divided into three fuNCtional zones:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>The \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 section that provides most of the string length<\/li>\n\n\n\n<li>The transition section that manages the change in \u0627\u0644\u0648\u0632\u0646 and stIFfness<\/li>\n\n\n\n<li>The BHA that applies \u0627\u0644\u0648\u0632\u0646, controls the bit, and carries downhole tools<\/li>\n<\/ul>\n\n<figure class=\"wp-block-image size-large is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/complete-drill-string-components-diagram-1024x576.jpg\" alt=\"\" class=\"wp-image-14595\" style=\"width:862px;height:auto\" srcset=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/complete-drill-string-components-diagram-1024x576.jpg 1024w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/complete-drill-string-components-diagram-300x169.jpg 300w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/complete-drill-string-components-diagram.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Component<\/th><th>Typical position<\/th><th>Primary fuNCtion<\/th><th>\u0627\u0644\u0631\u0626\u064a\u0633\u064a para\u0645\u062a\u0631s to verIFy<\/th><\/tr><\/thead><tbody><tr><td><a href=\"https:\/\/www.octalpipe.com\/drill-pipes\/drill-pipe.html\"><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-secondary-color\">Drill pipe<\/mark><\/a><\/td><td>Upper and middle string<\/td><td>Carries tensile load, transmits \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646, and circulates \u0627\u0644\u062d\u0641\u0631 fluid<\/td><td>OD, \u0633\u0645\u0627\u0643\u0629 \u0627\u0644\u062c\u062f\u0627\u0631, \u0627\u0644\u062f\u0631\u062c\u0629, upset, length, tool-joint OD\/ID, and \u0627\u0644\u0648\u0635\u0644\u0629<\/td><\/tr><tr><td>\u0627\u0644\u0648\u0635\u0644\u0629s<\/td><td>Welded to both ends of each \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 joint<\/td><td>Connect individual joints and transfer \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 and axial load<\/td><td>\u0627\u0644\u062e\u064a\u0637 form, shoulder condition, OD, ID, and make-up \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646<\/td><\/tr><tr><td>Heavy-\u0627\u0644\u0648\u0632\u0646 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631<\/td><td>\u0628\u064a\u0646 regular \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 and the lower BHA, or within the BHA<\/td><td>Reduces the stIFfness transition and adds coNCentrated \u0627\u0644\u0648\u0632\u0646<\/td><td>Body wall, center upset, \u0627\u0644\u062a\u0622\u0643\u0644 pads, \u0627\u0644\u0648\u0635\u0644\u0629, and \u0627\u0644\u062a\u0639\u0628 condition<\/td><\/tr><tr><td>\u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s<\/td><td>Lower BHA<\/td><td>Supply \u0627\u0644\u0648\u0632\u0646 on bit and iNCrease stIFfness<\/td><td>OD, ID, length, \u0627\u0644\u0645\u0627\u062f\u0629, \u0627\u0644\u0648\u0635\u0644\u0629, and bending stIFfness<\/td><\/tr><tr><td>Stabilizers<\/td><td>\u0627\u062e\u062a\u064a\u0627\u0631ed positions in the BHA<\/td><td>Centralize the BHA and influeNCe directional behavior<\/td><td>Blade OD, undergauge, placement, and contact area<\/td><\/tr><tr><td>Crossover subs<\/td><td>\u0628\u064a\u0646 components with dIFferent \u0627\u0644\u0648\u0635\u0644\u0629s<\/td><td>Adapt dIFferent \u0627\u0644\u0648\u0635\u0644\u0629 sizes or \u0627\u0644\u062e\u064a\u0637 forms<\/td><td>\u0627\u0644\u062f\u0628\u0648\u0633\/\u0627\u0644\u0635\u0646\u062f\u0648\u0642 combination, shoulder, bore, and tensile capacity<\/td><\/tr><tr><td>\u0627\u0644\u062d\u0641\u0631 jars<\/td><td>Normally within or above the BHA<\/td><td>Deliver an iMPact load to help release a stuck string<\/td><td>Firing load, stroke, tensile rating, and placement<\/td><\/tr><tr><td>Mud motor<\/td><td>Near the bit<\/td><td>Converts hydraulic energy into downhole rotation<\/td><td>Flow range, pressure drop, \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646, speed, bend setting, and temperature rating<\/td><\/tr><tr><td>MWD\/LWD tools<\/td><td>Within the BHA<\/td><td>Measure trajectory, \u0627\u0644\u062d\u0641\u0631 conditions, and formation properties<\/td><td>OD, flow range, pressure rating, temperature rating, and telemetry system<\/td><\/tr><tr><td>Float valve or float sub<\/td><td>Commonly in the lower string<\/td><td>Restricts reverse flow through the \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631<\/td><td>Flow area, pressure rating, and valve configuration<\/td><\/tr><tr><td>\u0645\u062b\u0642\u0627\u0628 \u0627\u0644\u062d\u0641\u0631<\/td><td>Bottom of the string<\/td><td>Cuts or fractures the formation<\/td><td>Dia\u0645\u062a\u0631, cutter structure, nozzle area, WOB, \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646, and speed limits<\/td><\/tr><\/tbody><\/table><\/figure>\n\n<p class=\"wp-block-paragraph\">The BHA does not follow one universal parts list. Its lower section may iNClude the bit, bit sub, mud motor, stabilizers, \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s, heavy-\u0627\u0644\u0648\u0632\u0646 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631, jars, and crossovers. Directional and measurement equipment may also be installed.<\/p>\n\n<h3 class=\"wp-block-heading\">\u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631<\/h3>\n\n<p class=\"wp-block-paragraph\">\u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 usually occupies most of the measured length of a conventional \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631. Finished \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 consists of a <a href=\"__PROTECTED_0__\"><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-secondary-color\">\u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 body<\/mark><\/a><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-secondary-color\"> <\/mark>with weld-on \u0627\u0644\u0648\u0635\u0644\u0629s. Its priNCipal structural features iNClude:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>A seamless steel \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 body<\/li>\n\n\n\n<li>Internally upset, externally upset, or internally and externally upset ends<\/li>\n\n\n\n<li>\u0627\u0644\u062f\u0628\u0648\u0633 and \u0627\u0644\u0635\u0646\u062f\u0648\u0642 \u0627\u0644\u0648\u0635\u0644\u0629s<\/li>\n\n\n\n<li>Rotary-shouldered \u0627\u0644\u062e\u064a\u0637ed \u0627\u0644\u0648\u0635\u0644\u0629s<\/li>\n\n\n\n<li>Friction-welded tool-joint-to-\u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 transitions<\/li>\n\n\n\n<li>Optional internal coating and external hardbanding<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/www.octalsteel.com\/resources\/drill-pipe-specification\/\"><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-secondary-color\">API Spec 5DP<\/mark><\/a> establishes technical requirements for steel drill pipe, including dimensions, grades, mechanical properties, weld areas, inspection, marking, and traceability.<\/p>\n\n<p class=\"wp-block-paragraph\">Common API \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 \u0627\u0644\u0642\u0637\u0631 \u0627\u0644\u062e\u0627\u0631\u062c\u064as extend from 2 3\/8 to 6 5\/8 \u0628\u0648\u0635\u0629es. Range 2 joints are normally 27\u201330 ft long, while Range 3 joints are 38\u201345 ft long. The purchase specIFication should identIFy the required range because joint length affects rig handling, transportation, the number of \u0627\u0644\u0648\u0635\u0644\u0629s, and the total assembled string configuration. The supplier should confirm the finished length, iNCluding \u0627\u0644\u0648\u0635\u0644\u0629s, rather than stating only an approximate \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body length.<\/p>\n\n<h3 class=\"wp-block-heading\">Heavy-\u0627\u0644\u0648\u0632\u0646 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631<\/h3>\n\n<p class=\"wp-block-paragraph\">Heavy-\u0627\u0644\u0648\u0632\u0646 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631, commonly abbreviated as HWDP, creates a more gradual stIFfness transition \u0628\u064a\u0646 regular \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 and the much stIFfer \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s. It normally uses a thick-walled tube with enlarged \u0627\u0644\u0648\u0635\u0644\u0629s and a center upset.<\/p>\n\n<p class=\"wp-block-paragraph\">HWDP may be installed directly above the \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s or positioned higher in a directional string. Its size and quantity should follow the approved BHA and \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 design because the required \u0627\u0644\u0648\u0632\u0646, stIFfness transition, and \u0627\u0644\u062a\u0639\u0628 exposure vary with the \u0627\u0644\u0628\u0626\u0631 profile. Purchasing HWDP only by nominal OD can result in an iNCoMPatible \u0627\u0644\u0648\u0635\u0644\u0629, insufficient unit \u0627\u0644\u0648\u0632\u0646, or an unsuitable transition \u0628\u064a\u0646 regular \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 and \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s.<\/p>\n\n<p class=\"wp-block-paragraph\">API Spec 7-1 covers standard HWDP dimensions and manufacturing requirements. Standard API HWDP is commonly supplied at a nominal length of approximately 31 ft, subject to the applicable toleraNCe. The purchase specIFication should also identIFy the body configuration, tool-joint OD and ID, center-upset dimensions, \u0627\u0644\u0648\u0635\u0644\u0629 type, hardbanding, and whether spiral \u0627\u0644\u062a\u0622\u0643\u0644 pads are required.<\/p>\n\n<h3 class=\"wp-block-heading\">\u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s<\/h3>\n\n<p class=\"has-primary-color has-text-color has-link-color wp-elements-2 wp-block-paragraph\"><a href=\"https:\/\/www.drillpipes.com\/ar\/%d8%af%d8%b1%d9%8a%d9%84-%d9%83%d9%88%d9%84%d8%b1\/\">Drill collars<\/a> concentrate mass near the bit and increase BHA stiffness. Conventional steel drill collars are commonly machined from solid alloy-steel bars to produce a thick wall and relatively small internal bore.<\/p>\n\n<p class=\"wp-block-paragraph\">Their \u0627\u0644\u0648\u0632\u0646 supplies part of the force available for \u0627\u0644\u0648\u0632\u0646 on bit. In a vertical \u0627\u0644\u0628\u0626\u0631, engineers normally seek to keep the regular \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 above the BHA in tension while placing the required compression in the lower, stIFfer assembly.<\/p>\n\n<p class=\"wp-block-paragraph\">Nonmagnetic \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s are \u0645\u0633\u062a\u0639\u0645\u0644 around directional survey instruments because ordinary alloy steel can interfere with magnetic measurements. A \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631 purchase specIFication should state the OD, ID, finished length, \u0627\u0644\u0645\u0627\u062f\u0629 type, \u0627\u0644\u0648\u0635\u0644\u0629, spiral or slick configuration, and required fishing clearaNCe. Nominal OD alone is not sufficient to confirm coMPatibility with the bit, stabilizers, directional tools, or the re\u0627\u0644\u0631\u0626\u064a\u0633\u064aing BHA components.<\/p>\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1672\" height=\"941\" src=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-hwdp-and-drill-collar-comparison.jpg\" alt=\"\" class=\"wp-image-14603\" srcset=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-hwdp-and-drill-collar-comparison.jpg 1672w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-hwdp-and-drill-collar-comparison-300x169.jpg 300w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-hwdp-and-drill-collar-comparison-768x432.jpg 768w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-hwdp-and-drill-collar-comparison-1024x576.jpg 1024w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-hwdp-and-drill-collar-comparison-1536x864.jpg 1536w\" sizes=\"auto, (max-width: 1672px) 100vw, 1672px\" \/><\/figure>\n\n<h3 class=\"wp-block-heading\">Stabilizers and Downhole Tools<\/h3>\n\n<p class=\"wp-block-paragraph\">Stabilizers centralize the lower assembly and help control the behavior of the BHA. Directional \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631s may also iNClude mud motors, MWD\/LWD tools, or rotary steerable systems near the bit. The \u0627\u0644\u0627\u062e\u062a\u064a\u0627\u0631 of these components depends on the planned \u0627\u0644\u0628\u0626\u0631 trajectory and measurement requirements, while their dimensions, \u0627\u0644\u0648\u0635\u0644\u0629s, flow ranges, and operating limits must re\u0627\u0644\u0631\u0626\u064a\u0633\u064a coMPatible with the rest of the BHA.<\/p>\n\n<h2 class=\"wp-block-heading\">FuNCtion of \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631<\/h2>\n\n<p class=\"wp-block-paragraph\">\u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 performs five connected mechanical and hydraulic fuNCtions during \u0627\u0644\u062d\u0641\u0631. It does more than rotate the bit: it supports the \u0627\u0644\u0648\u0632\u0646 of the downhole assembly, transfers surface movement to the bottom of the \u0627\u0644\u0628\u0626\u0631, carries \u0627\u0644\u062d\u0641\u0631 fluid, and helps keep the bit operating in the required direction.<\/p>\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/five-functions-of-drill-string-diagram-1-1024x576.jpg\" alt=\"\" class=\"wp-image-14599\" srcset=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/five-functions-of-drill-string-diagram-1-1024x576.jpg 1024w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/five-functions-of-drill-string-diagram-1-300x169.jpg 300w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/five-functions-of-drill-string-diagram-1.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n<p class=\"wp-block-paragraph\">The five \u0627\u0644\u0631\u0626\u064a\u0633\u064a fuNCtions are:<\/p>\n\n<h3 class=\"wp-block-heading\">1.Transmitting Rotary \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646<\/h3>\n\n<p class=\"wp-block-paragraph\">The top drive or rotary table applies \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 at the surface. That \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 passes through every \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 body, friction weld, \u0627\u0644\u0648\u0635\u0644\u0629, sub, and BHA component before reaching the bit.<\/p>\n\n<p class=\"wp-block-paragraph\">In motor \u0627\u0644\u062d\u0641\u0631, \u0627\u0644\u062d\u0641\u0631 fluid powers a downhole motor. The surface string may rotate continuously, rotate intermittently, or re\u0627\u0644\u0631\u0626\u064a\u0633\u064a stationary while the motor turns the bit. The load case therefore changes with the \u0627\u0644\u062d\u0641\u0631 mode.<\/p>\n\n<p class=\"wp-block-paragraph\">\u0627\u0644\u0648\u0635\u0644\u0629 capacity may control the usable \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 before the nominal \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 body reaches its torsional yield limit. \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 OD, nominal \u0627\u0644\u0648\u0632\u0646, and \u062f\u0631\u062c\u0629 \u0627\u0644\u0641\u0648\u0644\u0627\u0630 are therefore not sufficient to determine the \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 capacity of a \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 joint.<\/p>\n\n<p class=\"wp-block-paragraph\">Published data for several proprietary \u0627\u0644\u0648\u0635\u0644\u0629 configurations on 5 in \u00d7 19.50 lb\/ft S135 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 show how widely the result can vary:<\/p>\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u0627\u0644\u0645\u0642\u0627\u0631\u0646\u0629 item<\/th><th>Published configuration range<\/th><\/tr><\/thead><tbody><tr><td>\u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 OD<\/td><td>5.000 in<\/td><\/tr><tr><td>Nominal \u0627\u0644\u0648\u0632\u0646<\/td><td>19.50 lb\/ft<\/td><\/tr><tr><td>\u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 \u0627\u0644\u062f\u0631\u062c\u0629<\/td><td>S135<\/td><\/tr><tr><td>Tool-joint OD<\/td><td>6.250\u20136.625 in<\/td><\/tr><tr><td>Tool-joint ID<\/td><td>3.500\u20133.750 in<\/td><\/tr><tr><td>Maximum make-up \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646<\/td><td>38,200\u201349,800 ft-lb<\/td><\/tr><tr><td>\u0627\u0644\u0641\u0631\u0642 \u0628\u064a\u0646 lowest and highest published values<\/td><td>11,600 ft-lb<\/td><\/tr><tr><td>INCrease from lowest to highest value<\/td><td>Approximately 30%<\/td><\/tr><\/tbody><\/table><\/figure>\n\n<p class=\"wp-block-paragraph\">The \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 size, nominal \u0627\u0644\u0648\u0632\u0646, and \u062f\u0631\u062c\u0629 \u0627\u0644\u0641\u0648\u0644\u0627\u0630 re\u0627\u0644\u0631\u0626\u064a\u0633\u064a the same throughout this \u0627\u0644\u0645\u0642\u0627\u0631\u0646\u0629, but the published maximum make-up \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 varies by 11,600 ft-lb. The \u0627\u0644\u0641\u0631\u0642 results from the combined effect of \u0627\u0644\u0648\u0635\u0644\u0629 design, \u0627\u0644\u062e\u064a\u0637 and shoulder geometry, tool-joint OD and ID, and \u0627\u0644\u0645\u0627\u062f\u0629 capacity. It should not be attributed to one dimensional change alone.<\/p>\n\n<p class=\"wp-block-paragraph\">These figures are \u0627\u0644\u0645\u0642\u0627\u0631\u0646\u0629 data from dIFferent proprietary \u0627\u0644\u0648\u0635\u0644\u0629 configurations. They do not represent a universal API value, an Octal \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631s standard supply specIFication, or the allowable operating \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 for every 5 in \u00d7 19.50 lb\/ft S135 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631.<\/p>\n\n<p class=\"wp-block-paragraph\">For procurement, the purchase specIFication should identIFy the exact \u0627\u0644\u0648\u0635\u0644\u0629, tool-joint OD, tool-joint ID, \u0627\u0644\u0645\u0627\u062f\u0629 strength, and required dimensional condition. The supplier should provide the recommended make-up \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 and corresponding torsional rating for the actual supplied configuration.<\/p>\n\n<p class=\"wp-block-paragraph\">Make-up \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646, allowable operating \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646, and torsional yield describe dIFferent limits. They should be listed separately in the technical documentation and should not be treated as interchangeable values.<\/p>\n\n<h3 class=\"wp-block-heading\">2.Carrying Axial Load<\/h3>\n\n<p class=\"wp-block-paragraph\">The upper \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 normally carries the highest tensile load because it supports the buoyed \u0627\u0644\u0648\u0632\u0646 of all components below it. Dynamic loads, drag, acceleration, and planned overpull iNCrease this load.<\/p>\n\n<p class=\"wp-block-paragraph\">In a vertical \u0627\u0644\u0628\u0626\u0631, the load generally iNCreases toward the surface. In a deviated or horizontal \u0627\u0644\u0628\u0626\u0631, contact friction redistributes axial force. Sections of \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 may enter compression even though the surface hook load re\u0627\u0644\u0631\u0626\u064a\u0633\u064as positive.<\/p>\n\n<p class=\"wp-block-paragraph\">The required tensile capacity should be established by the \u0627\u0644\u062d\u0641\u0631 contractor or project engineering team using the planned trajectory, fluid density, tubular dimensions, expected drag, dynamic load, and required overpull. The supplier should provide verIFied \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body and \u0627\u0644\u0648\u0635\u0644\u0629 ratings for the actual purchased configuration. Catalog values based only on nominal air \u0627\u0644\u0648\u0632\u0646 should not be treated as the allowable hook-load limit for a high-angle or horizontal \u0627\u0644\u0628\u0626\u0631.<\/p>\n\n<h3 class=\"wp-block-heading\">3.Applying \u0627\u0644\u0648\u0632\u0646 on Bit<\/h3>\n\n<p class=\"wp-block-paragraph\">\u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s and \u0627\u062e\u062a\u064a\u0627\u0631ed sections of HWDP provide the \u0627\u0644\u0648\u0632\u0646 available near the bit. Only part of this available buoyed \u0627\u0644\u0648\u0632\u0646 should be transferred as WOB. The re\u0627\u0644\u0631\u0626\u064a\u0633\u064aing margin helps keep the neutral point within a sufficiently stIFf part of the lower assembly.<\/p>\n\n<p class=\"wp-block-paragraph\">Required WOB depends on bit design, hole size, formation strength, rotary speed, hydraulic cleaning, and vibration response. Excessive WOB can cause bit damage, stick-slip, lateral vibration, buckling, or unstable tool-face control rather than producing a higher penetration rate.<\/p>\n\n<h3 class=\"wp-block-heading\">4.Circulating \u0627\u0644\u062d\u0641\u0631 Fluid<\/h3>\n\n<p class=\"wp-block-paragraph\">\u0627\u0644\u062d\u0641\u0631 fluid flows down the internal bore of the \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631, passes through downhole tools and bit nozzles, and returns to the surface through the annulus.<\/p>\n\n<p class=\"wp-block-paragraph\">The circulation system:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>Cools and cleans the bit<\/li>\n\n\n\n<li>Carries cuttings away from the bottom<\/li>\n\n\n\n<li>Transports cuttings to the surface<\/li>\n\n\n\n<li>Powers mud motors and hydraulic tools<\/li>\n\n\n\n<li>Supports mud-pulse telemetry<\/li>\n\n\n\n<li>Contributes to \u0627\u0644\u0628\u0626\u0631-pressure control<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">Hydraulic calculations must use the smallest effective flow area in the assembled string. A tool-joint bore, float valve, motor power section, measurement tool, or bit nozzle may create more restriction than the \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 body.<\/p>\n\n<p class=\"wp-block-paragraph\">INCreasing \u0627\u0644\u0648\u0635\u0644\u0629 ID can reduce internal pressure loss, but removing metal from the \u0627\u0644\u0648\u0635\u0644\u0629 may reduce torsional capacity. \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 design therefore involves a measurable hydraulics-\u0636\u062f-strength trade-off.<\/p>\n\n<h3 class=\"wp-block-heading\">5.Controlling the \u0627\u0644\u0628\u0626\u0631 Path<\/h3>\n\n<p class=\"wp-block-paragraph\">The \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 also behaves as a long, flexible structural system. BHA stIFfness, stabilizer spacing, WOB, rotary speed, hole curvature, and wall contact affect iNClination, azimuth, vibration, and tool-face response.<\/p>\n\n<p class=\"wp-block-paragraph\">When \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 rotates through a dogleg, each revolution produces a bending-stress cycle. \u0627\u0644\u062a\u0639\u0628 damage can accumulate even when the maximum stress re\u0627\u0644\u0631\u0626\u064a\u0633\u064as below the \u0627\u0644\u0645\u0627\u062f\u0629\u2019s \u0645\u0642\u0627\u0648\u0645\u0629 \u0627\u0644\u062e\u0636\u0648\u0639. Slip marks, \u0627\u0644\u062a\u0622\u0643\u0644 pits, friction-weld transitions, \u0627\u0644\u062e\u064a\u0637 roots, and other stress coNCentrators can shorten \u0627\u0644\u062a\u0639\u0628 lIFe.<\/p>\n\n<h2 class=\"wp-block-heading\">\u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 \u0645\u0642\u0627\u0628\u0644 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631<\/h2>\n\n<p class=\"wp-block-paragraph\">The \u0627\u0644\u0641\u0631\u0642 \u0628\u064a\u0646 \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 \u0645\u0642\u0627\u0628\u0644 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 coNCerns the scope of the equipment being described.<\/p>\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"562\" src=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-vs-drill-pipe-comparison-1024x562.jpg\" alt=\"\" class=\"wp-image-14600\" srcset=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-vs-drill-pipe-comparison-1024x562.jpg 1024w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-vs-drill-pipe-comparison-300x165.jpg 300w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-vs-drill-pipe-comparison.jpg 1692w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u0627\u0644\u0645\u0642\u0627\u0631\u0646\u0629<\/th><th>\u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631<\/th><th>\u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631<\/th><\/tr><\/thead><tbody><tr><td>Meaning<\/td><td>Complete assembled system extending to the \u0645\u062b\u0642\u0627\u0628 \u0627\u0644\u062d\u0641\u0631<\/td><td>Individual tubular product \u0645\u0633\u062a\u0639\u0645\u0644 within the string<\/td><\/tr><tr><td>Contents<\/td><td>\u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631, transition components, BHA tools, subs, and bit<\/td><td>\u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 body, upsets, friction welds, and \u0627\u0644\u062f\u0628\u0648\u0633\/\u0627\u0644\u0635\u0646\u062f\u0648\u0642 \u0627\u0644\u0648\u0635\u0644\u0629s<\/td><\/tr><tr><td>\u0627\u0644\u0631\u0626\u064a\u0633\u064a role<\/td><td>Performs the complete mechanical and hydraulic \u0627\u0644\u062d\u0641\u0631 operation<\/td><td>Provides length, \u0645\u0642\u0627\u0648\u0645\u0629 \u0627\u0644\u0634\u062f, \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 transmission, and a fluid passage<\/td><\/tr><tr><td>Configuration<\/td><td>Changes with the hole section and \u0627\u0644\u062d\u0641\u0631 objective<\/td><td>\u0627\u062e\u062a\u064a\u0627\u0631ed by OD, nominal \u0627\u0644\u0648\u0632\u0646, \u0627\u0644\u062f\u0631\u062c\u0629, \u0627\u0644\u0648\u0635\u0644\u0629, length, and condition<\/td><\/tr><tr><td>\u0627\u0644\u0631\u0626\u064a\u0633\u064a product standard<\/td><td>Depends on the individual components<\/td><td>API Spec 5DP for finished steel \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631<\/td><\/tr><tr><td>\u0645\u0633\u062a\u0639\u0645\u0644-equipment inspection<\/td><td>Component-specIFic inspection program<\/td><td>API RP 7G-2 or an approved equivalent program<\/td><\/tr><\/tbody><\/table><\/figure>\n\n<p class=\"wp-block-paragraph\">One 30 ft joint of \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 is not a \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631. Conversely, calling the complete downhole assembly \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 excludes the BHA, \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s, directional tools, subs, and bit.<\/p>\n\n<p class=\"wp-block-paragraph\">A deep \u0627\u0644\u0628\u0626\u0631 may contain hundreds of \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 joints, but those joints operate as one \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 only after they are connected to the required transition components and BHA.<\/p>\n\n<h2 class=\"wp-block-heading\">Typical API \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 \u0627\u0644\u062f\u0631\u062c\u0629s<\/h2>\n\n<p class=\"wp-block-paragraph\">API \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 \u0627\u0644\u062f\u0631\u062c\u0629 designations reflect the specIFied \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body strength range. They do not define the capacity of the complete \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631.<\/p>\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>API \u0627\u0644\u062f\u0631\u062c\u0629<\/th><th>\u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body yield-strength range<\/th><th>Minimum \u0645\u0642\u0627\u0648\u0645\u0629 \u0627\u0644\u0634\u062f<\/th><\/tr><\/thead><tbody><tr><td><a href=\"https:\/\/www.octalsteel.com\/product\/e75-drill-pipe\/\"><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-secondary-color\">E75<\/mark><\/a><\/td><td>75\u2013105 ksi \/ 517\u2013724 MPa<\/td><td>100 ksi \/ 689 MPa<\/td><\/tr><tr><td><a href=\"https:\/\/www.octalsteel.com\/product\/x95-drill-pipe\/\"><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-secondary-color\">X95<\/mark><\/a><\/td><td>95\u2013125 ksi \/ 655\u2013862 MPa<\/td><td>105 ksi \/ 724 MPa<\/td><\/tr><tr><td>G105<\/td><td>105\u2013135 ksi \/ 724\u2013931 MPa<\/td><td>115 ksi \/ 793 MPa<\/td><\/tr><tr><td>S135<\/td><td>135\u2013165 ksi \/ 931\u20131,138 MPa<\/td><td>145 ksi \/ 1,000 MPa<\/td><\/tr><\/tbody><\/table><\/figure>\n\n<p class=\"wp-block-paragraph\">Higher \u0645\u0642\u0627\u0648\u0645\u0629 \u0627\u0644\u062e\u0636\u0648\u0639 iNCreases the nominal \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body load capacity, but it does not compensate for:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>An undersized or worn \u0627\u0644\u0648\u0635\u0644\u0629<\/li>\n\n\n\n<li>INCorrect make-up \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646<\/li>\n\n\n\n<li>A damaged shoulder or \u0627\u0644\u062e\u064a\u0637 root<\/li>\n\n\n\n<li>\u0627\u0644\u062a\u0639\u0628 cracks in the slip or weld area<\/li>\n\n\n\n<li>Excessive dogleg severity<\/li>\n\n\n\n<li>An unsuitable stIFfness transition<\/li>\n\n\n\n<li>\u0627\u0644\u062a\u0622\u0643\u0644 or internal erosion<\/li>\n\n\n\n<li>Combined tension and torsion<\/li>\n<\/ul>\n\n<h3 class=\"wp-block-heading\">\u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-Body Tensile Calculation Example<\/h3>\n\n<p class=\"wp-block-paragraph\">Consider nominal 5 in \u00d7 19.50 lb\/ft S135 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 with a 0.362 in \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body wall:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>\u0627\u0644\u0642\u0637\u0631 \u0627\u0644\u062e\u0627\u0631\u062c\u064a: 5.000 in<\/li>\n\n\n\n<li>Nominal \u0633\u0645\u0627\u0643\u0629 \u0627\u0644\u062c\u062f\u0627\u0631: 0.362 in<\/li>\n\n\n\n<li>Calculated \u0627\u0644\u0642\u0637\u0631 \u0627\u0644\u062f\u0627\u062e\u0644\u064a: 4.276 in<\/li>\n\n\n\n<li>Nominal metal area: approximately 5.28 in\u00b2<\/li>\n\n\n\n<li>Minimum S135 \u0645\u0642\u0627\u0648\u0645\u0629 \u0627\u0644\u062e\u0636\u0648\u0639: 135,000 psi<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">The nominal \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body tensile load at minimum yield is:<\/p>\n\n<p class=\"wp-block-paragraph\"><strong>5.28 in\u00b2 \u00d7 135,000 psi \u2248 713,000 lbf<\/strong><\/p>\n\n<p class=\"wp-block-paragraph\">This equals approximately <strong>3,170 kN<\/strong>.<\/p>\n\n<p class=\"wp-block-paragraph\">The result is a theoretical \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body yield load based on nominal geometry. It is not an allowable hook load and should not be \u0645\u0633\u062a\u0639\u0645\u0644 directly as a safe working limit.<\/p>\n\n<p class=\"wp-block-paragraph\">An operating limit must account for actual re\u0627\u0644\u0631\u0626\u064a\u0633\u064aing \u0633\u0645\u0627\u0643\u0629 \u0627\u0644\u062c\u062f\u0627\u0631, dimensional toleraNCe, \u0627\u0644\u0648\u0635\u0644\u0629 capacity, \u0627\u0644\u062a\u0622\u0643\u0644 classIFication, combined \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 and tension, dogleg bending, dynamic load, overpull, \u0627\u0644\u062a\u0639\u0628 history, \u0627\u0644\u062a\u0622\u0643\u0644, and the operator\u2019s design factor.<\/p>\n\n<h2 class=\"wp-block-heading\">How \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 Capacity Is Evaluated<\/h2>\n\n<p class=\"wp-block-paragraph\">\u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 capacity cannot be represented by one \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body strength value. It is governed by the lowest applicable limit among the \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 body, upset, friction weld, \u0627\u0644\u0648\u0635\u0644\u0629, \u0627\u0644\u062e\u064a\u0637ed \u0627\u0644\u0648\u0635\u0644\u0629, crossover subs, and other load-carrying BHA components. The controlling location may also change \u0628\u064a\u0646 \u0627\u0644\u062d\u0641\u0631, rotating, trip\u0627\u0644\u062f\u0628\u0648\u0633g, and overpull operations.<\/p>\n\n<p class=\"wp-block-paragraph\">Evaluation begins with the actual dimensions and condition of every critical component. \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 OD, re\u0627\u0644\u0631\u0626\u064a\u0633\u064aing \u0633\u0645\u0627\u0643\u0629 \u0627\u0644\u062c\u062f\u0627\u0631, \u062f\u0631\u062c\u0629 \u0627\u0644\u0641\u0648\u0644\u0627\u0630, tool-joint OD and ID, \u0627\u0644\u0648\u0635\u0644\u0629 type, weld condition, and \u0645\u0633\u062a\u0639\u0645\u0644-\u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 classIFication all affect the available capacity. The applied loads must then iNClude buoyed string \u0627\u0644\u0648\u0632\u0646, drag, rotary \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646, internal pressure, bending through doglegs, compression, dynamic loading, and the required overpull.<\/p>\n\n<p class=\"wp-block-paragraph\">Published tensile or torsional yield values describe individual components under defined conditions; they are not automatically allowable operating limits for the complete \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631. The supplier should provide configuration-specIFic dimensions, \u0627\u0644\u0645\u0627\u062f\u0629 properties, \u0627\u0644\u0648\u0635\u0644\u0629 ratings, and inspection records. The project engineering team must then apply the planned \u0627\u0644\u0628\u0626\u0631 profile, combined-load analysis, and required design factors to establish acceptable operating limits.<\/p>\n\n<h3 class=\"wp-block-heading\">Tension and Overpull<\/h3>\n\n<p class=\"wp-block-paragraph\">The tensile-load calculation begins with the \u0627\u0644\u0648\u0632\u0646 suspended below each point in the \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631. Because the tubulars are partly supported by the \u0627\u0644\u062d\u0641\u0631 fluid, their buoyed \u0627\u0644\u0648\u0632\u0646 rather than their full air \u0627\u0644\u0648\u0632\u0646 is \u0645\u0633\u062a\u0639\u0645\u0644 for the initial static-load estimate. Expected drag, dynamic loading, pressure effects, and the required overpull margin are then added.<\/p>\n\n<p class=\"wp-block-paragraph\">For a steel \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 surrounded by \u0627\u0644\u062d\u0641\u0631 fluid of unIForm density, a simplIFied buoyaNCy factor can be estimated as:<\/p>\n\n<p class=\"wp-block-paragraph\"><strong>Buoyancy factor = 1 \u2212 mud density \u00f7 65.5<\/strong><\/p>\n\n<p class=\"wp-block-paragraph\">For example, 10.0 ppg \u0627\u0644\u062d\u0641\u0631 fluid gives a buoyaNCy factor of approximately 0.847. A string weighing 300,000 lbf in air would therefore have an estimated buoyed \u0627\u0644\u0648\u0632\u0646 of:<\/p>\n\n<p class=\"wp-block-paragraph\"><strong>300,000 \u00d7 0.847 \u2248 254,100 lbf<\/strong><\/p>\n\n<p class=\"wp-block-paragraph\">This value represents only the simplIFied static suspended \u0627\u0644\u0648\u0632\u0646. IF the predicted upward drag is 40,000 lbf, the estimated hook load while pulling becomes approximately:<\/p>\n\n<p class=\"wp-block-paragraph\"><strong>254,100 + 40,000 = 294,100 lbf<\/strong><\/p>\n\n<p class=\"wp-block-paragraph\">The allowable load must then be established from the lowest effective tensile capacity in the string. Using the earlier 5 in \u00d7 19.50 lb\/ft S135 example, the nominal \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body tensile load at minimum yield is approximately 713,000 lbf. IF the project applies an illustrative tensile design factor of 1.30, the preliminary \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body allowable load would be:<\/p>\n\n<p class=\"wp-block-paragraph\"><strong>713,000 \u00f7 1.30 \u2248 548,000 lbf<\/strong><\/p>\n\n<p class=\"wp-block-paragraph\">The corresponding preliminary margin of overpull would be:<\/p>\n\n<p class=\"wp-block-paragraph\"><strong>548,000 \u2212 294,100 \u2248 253,900 lbf<\/strong><\/p>\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Calculation item<\/th><th>Illustrative value<\/th><\/tr><\/thead><tbody><tr><td>\u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 air \u0627\u0644\u0648\u0632\u0646<\/td><td>300,000 lbf<\/td><\/tr><tr><td>Mud density<\/td><td>10.0 ppg<\/td><\/tr><tr><td>BuoyaNCy factor<\/td><td>0.847<\/td><\/tr><tr><td>Estimated buoyed \u0627\u0644\u0648\u0632\u0646<\/td><td>254,100 lbf<\/td><\/tr><tr><td>Predicted upward drag<\/td><td>40,000 lbf<\/td><\/tr><tr><td>Estimated pulling hook load<\/td><td>294,100 lbf<\/td><\/tr><tr><td>Nominal \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body yield load<\/td><td>713,000 lbf<\/td><\/tr><tr><td>Illustrative tensile design factor<\/td><td>1.30<\/td><\/tr><tr><td>Preliminary allowable load<\/td><td>548,000 lbf<\/td><\/tr><tr><td>Preliminary overpull margin<\/td><td>253,900 lbf<\/td><\/tr><\/tbody><\/table><\/figure>\n\n<p class=\"wp-block-paragraph\">This example is not a universal operating limit. The 1.30 design factor is an illustrative project assumption rather than a fixed API requirement. Final overpull must be checked against the actual re\u0627\u0644\u0631\u0626\u064a\u0633\u064aing \u0633\u0645\u0627\u0643\u0629 \u0627\u0644\u062c\u062f\u0627\u0631, tool-joint and \u0627\u0644\u0648\u0635\u0644\u0629 capacity, friction weld, crossovers, jars, combined \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646, cyclic bending, dynamic loading, and the operator\u2019s approved design criteria.<\/p>\n\n<h3 class=\"wp-block-heading\">Combined Tension and \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646<\/h3>\n\n<p class=\"wp-block-paragraph\">Tension and \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 act simultaneously during many \u0627\u0644\u062d\u0641\u0631 operations. \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 carrying substantial axial tension cannot be assumed to retain its full independent torsional capacity.<\/p>\n\n<p class=\"wp-block-paragraph\">Supplier load tables should not be interpreted as allowing 100% of the published tensile rating and 100% of the published torsional rating at the same time. The project engineering team should verIFy the combined-load envelope for the planned \u0627\u0644\u0628\u0626\u0631, while the supplier should provide the \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body and \u0627\u0644\u0648\u0635\u0644\u0629 data required for that evaluation.<\/p>\n\n<h3 class=\"wp-block-heading\">Compression and Buckling<\/h3>\n\n<p class=\"wp-block-paragraph\">Compression does not develop unIFormly throughout the \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631. In a conventional vertical \u0627\u0644\u0628\u0626\u0631, the lower \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s carry compression as \u0627\u0644\u0648\u0632\u0646 is applied to the bit, while the regular \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 above them is normally kept in tension. The point at which the effective axial force changes from tension to compression is commonly called the neutral point, and it should normally re\u0627\u0644\u0631\u0626\u064a\u0633\u064a within the \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s or another sufficiently stIFf part of the lower BHA.<\/p>\n\n<p class=\"wp-block-paragraph\">In directional and horizontal \u0627\u0644\u0628\u0626\u0631s, compression can extend farther up the string. The compressed section may iNClude the \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s, heavy-\u0627\u0644\u0648\u0632\u0646 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631, and lower joints of regular \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631. This commonly occurs while applying \u0627\u0644\u0648\u0632\u0646 on bit, sliding with a mud motor, running into the hole, or pushing the string through an interval with high wall-contact friction. The surface hook load can re\u0627\u0644\u0631\u0626\u064a\u0633\u064a positive while part of the lower \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 is already in compression.<\/p>\n\n<p class=\"wp-block-paragraph\">Regular \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 does not need to reach its \u0627\u0644\u0645\u0627\u062f\u0629 compressive-yield load before it becomes unstable. A long tubular constrained inside a larger \u0627\u0644\u0628\u0626\u0631 can first develop sinusoidal buckling, in which it follows a wave-shaped path along the low side of the hole. With further compression, it may progress to helical buckling and wrap around the inside of the \u0627\u0644\u0628\u0626\u0631. Helical buckling produces greater wall-contact force and can sharply iNCrease \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646, drag, \u0627\u0644\u062a\u0622\u0643\u0644, bending stress, and \u0627\u0644\u062a\u0639\u0628. It can also reduce the amount of surface-applied force that reaches the bit.<\/p>\n\n<p class=\"wp-block-paragraph\">The compression that can be carried before buckling depends on:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>\u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 OD, ID, \u0633\u0645\u0627\u0643\u0629 \u0627\u0644\u062c\u062f\u0627\u0631, and bending stIFfness<\/li>\n\n\n\n<li>Tool-joint dimensions and spacing<\/li>\n\n\n\n<li>Buoyed \u0627\u0644\u0648\u0632\u0646 per unit length<\/li>\n\n\n\n<li>\u0627\u0644\u0628\u0626\u0631 iNClination and local curvature<\/li>\n\n\n\n<li>ClearaNCe \u0628\u064a\u0646 the tubular and \u0627\u0644\u0628\u0626\u0631<\/li>\n\n\n\n<li>Friction \u0628\u064a\u0646 the string and \u0627\u0644\u0628\u0626\u0631<\/li>\n\n\n\n<li>Applied \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 and internal pressure<\/li>\n\n\n\n<li>Whether the string is rotating, sliding, or being tripped<\/li>\n\n\n\n<li>Existing \u0627\u0644\u062a\u0622\u0643\u0644, bending, and \u0627\u0644\u062a\u0639\u0628 condition<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">For a straight, highly iNClined \u0627\u0644\u0628\u0626\u0631, a simplIFied estimate of the sinusoidal buckling load can be expressed as:<\/p>\n\n<p class=\"wp-block-paragraph\"><strong>F\u209b \u2248 2\u221a(EIw sin \u03b8 \u00f7 r)<\/strong><\/p>\n\n<p class=\"wp-block-paragraph\">Where:<\/p>\n\n<ul class=\"wp-block-list\">\n<li><strong>F\u209b<\/strong> = estimated sinusoidal buckling load<\/li>\n\n\n\n<li><strong>E<\/strong> = Young\u2019s modulus of the tubular material<\/li>\n\n\n\n<li><strong>I<\/strong> = pipe-body moment of inertia<\/li>\n\n\n\n<li><strong>w<\/strong> = buoyed unit weight<\/li>\n\n\n\n<li><strong>\u03b8<\/strong> = well inclination<\/li>\n\n\n\n<li><strong>r<\/strong> = radial clearance between the pipe body and wellbore<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">Consider 5 in \u00d7 19.50 lb\/ft S135 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 in a horizontal 8.50 in \u0627\u0644\u0628\u0626\u0631 under the following simplIFied conditions:<\/p>\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Calculation input<\/th><th>Illustrative value<\/th><\/tr><\/thead><tbody><tr><td>\u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 OD<\/td><td>5.000 in<\/td><\/tr><tr><td>Nominal \u0633\u0645\u0627\u0643\u0629 \u0627\u0644\u062c\u062f\u0627\u0631<\/td><td>0.362 in<\/td><\/tr><tr><td>Calculated \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 ID<\/td><td>4.276 in<\/td><\/tr><tr><td>\u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body moment of inertia<\/td><td>Approximately 14.27 in\u2074<\/td><\/tr><tr><td>Young\u2019s modulus<\/td><td>30 \u00d7 10\u2076 psi<\/td><\/tr><tr><td>Mud density<\/td><td>10.0 ppg<\/td><\/tr><tr><td>Estimated buoyaNCy factor<\/td><td>0.847<\/td><\/tr><tr><td>Estimated buoyed unit \u0627\u0644\u0648\u0632\u0646<\/td><td>16.52 lb\/ft<\/td><\/tr><tr><td>\u0627\u0644\u0628\u0626\u0631 dia\u0645\u062a\u0631<\/td><td>8.500 in<\/td><\/tr><tr><td>\u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body radial clearaNCe<\/td><td>1.750 in<\/td><\/tr><tr><td>\u0627\u0644\u0628\u0626\u0631 iNClination<\/td><td>90\u00b0<\/td><\/tr><\/tbody><\/table><\/figure>\n\n<p class=\"wp-block-paragraph\">Under these simplIFied assumptions, the calculated onset of sinusoidal buckling is approximately:<\/p>\n\n<p class=\"wp-block-paragraph\"><strong>F\u209b \u2248 36,700 lbf<\/strong>, or about <strong>36.7 klbf<\/strong><\/p>\n\n<p class=\"wp-block-paragraph\">The nominal \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body load at minimum yield for the same 5 in \u00d7 19.50 lb\/ft S135 \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 is approximately 713,000 lbf. The large \u0627\u0644\u0641\u0631\u0642 \u0628\u064a\u0646 36,700 lbf and 713,000 lbf shows why \u0627\u0644\u0645\u0627\u062f\u0629 \u0645\u0642\u0627\u0648\u0645\u0629 \u0627\u0644\u062e\u0636\u0648\u0639 does not establish the acceptable compression limit. In this example, geometric instability can begin at only about 5% of the nominal \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body yield load.<\/p>\n\n<p class=\"wp-block-paragraph\">The 36.7 klbf result is not a universal allowable compression value. It is an illustrative sinusoidal-buckling estimate for the stated \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 size, hole dia\u0645\u062a\u0631, iNClination, mud density, and simplIFied straight-hole condition. Actual critical loads change when \u0627\u0644\u0648\u0635\u0644\u0629s, \u0627\u0644\u0648\u0635\u0644\u0629 spacing, \u0627\u0644\u0628\u0626\u0631 curvature, \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646, friction, varying fluid density, and post-buckling behavior are iNCluded.<\/p>\n\n<p class=\"wp-block-paragraph\">IF the \u0627\u0644\u062d\u0641\u0631 program does not permit regular \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 to buckle, the predicted compressive force should re\u0627\u0644\u0631\u0626\u064a\u0633\u064a below the approved sinusoidal-buckling limit with the required engineering margin. Some extended-reach \u0627\u0644\u062d\u0641\u0631 programs may permit controlled sinusoidal buckling when \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646-and-drag modelling and field experieNCe show that force transfer and \u0627\u0644\u062a\u0639\u0628 re\u0627\u0644\u0631\u0626\u064a\u0633\u064a manageable. Helical buckling requires more restrictive evaluation because it produces much higher contact force and a greater risk of lock-up, \u0627\u0644\u062a\u0622\u0643\u0644, and \u0627\u0644\u062a\u0639\u0628 damage.<\/p>\n\n<p class=\"wp-block-paragraph\">The useful check is therefore not whether the \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 is below its compressive \u0645\u0642\u0627\u0648\u0645\u0629 \u0627\u0644\u062e\u0636\u0648\u0639. Engineers should coMPare the predicted compressive-force profile at each measured depth with the calculated sinusoidal and helical buckling limits for that location. This identIFies whether compression re\u0627\u0644\u0631\u0626\u064a\u0633\u064as within the stIFf \u062f\u0631\u064a\u0644 \u0643\u0648\u0644\u0631s and HWDP or has extended into the more flexible regular \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631.<\/p>\n\n<h3 class=\"wp-block-heading\">\u0627\u0644\u062a\u0639\u0628<\/h3>\n\n<p class=\"wp-block-paragraph\">\u0627\u0644\u062a\u0639\u0628 evaluation must consider more than \u062f\u0631\u062c\u0629 \u0627\u0644\u0641\u0648\u0644\u0627\u0630. Relevant factors iNClude:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>Dogleg severity<\/li>\n\n\n\n<li>Number of rotations through the curved interval<\/li>\n\n\n\n<li>Local axial tension<\/li>\n\n\n\n<li>\u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 OD and \u0633\u0645\u0627\u0643\u0629 \u0627\u0644\u062c\u062f\u0627\u0631<\/li>\n\n\n\n<li>Tool-joint and \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628 stIFfness<\/li>\n\n\n\n<li>\u0627\u0644\u062a\u0622\u0643\u0644 pits or mechanical damage<\/li>\n\n\n\n<li>Previous service history<\/li>\n\n\n\n<li>Inspection sensitivity and reject criteria<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">S135 provides higher minimum \u0645\u0642\u0627\u0648\u0645\u0629 \u0627\u0644\u062e\u0636\u0648\u0639 than G105, but higher \u0627\u0644\u062f\u0631\u062c\u0629 alone does not guarantee longer \u0627\u0644\u062a\u0639\u0628 lIFe. For critical service, procurement records should identIFy the manufacturing batch, inspection status, previous service class where applicable, and any available operating history. \u0627\u0644\u062f\u0631\u062c\u0629 markings alone cannot establish the re\u0627\u0644\u0631\u0626\u064a\u0633\u064aing \u0627\u0644\u062a\u0639\u0628 condition of \u0645\u0633\u062a\u0639\u0645\u0644 \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631.<\/p>\n\n<div data-wp-interactive=\"core\/file\" class=\"wp-block-file\"><object data-wp-bind--hidden=\"!state.hasPdfPreview\" hidden class=\"wp-block-file__embed\" data=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-load-capacity-calculation-reference-3.pdf\" type=\"application\/pdf\" style=\"width:100%;height:600px\" aria-label=\"\u062a\u0636\u0645\u064a\u0646 drill-string-load-capacity-calculation-reference.\"><\/object><a id=\"wp-block-file--media-c99c60b8-58e1-4c15-8c14-20747d442be7\" href=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-load-capacity-calculation-reference-3.pdf\">\u0627\u0644\u062d\u0641\u0631-string-load-capacity-calculation-refereNCe<\/a><a href=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-string-load-capacity-calculation-reference-3.pdf\" class=\"wp-block-file__button wp-element-button\" download=\"\" aria-describedby=\"wp-block-file--media-c99c60b8-58e1-4c15-8c14-20747d442be7\">Download<\/a><\/div>\n\n<h2 class=\"wp-block-heading\">Inspection and AcceptaNCe<\/h2>\n\n<p class=\"wp-block-paragraph\">\u062c\u062f\u064a\u062f \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 should be verIFied against the applicable edition of API Spec 5DP and the approved purchase specIFication. Manufacturing records should identIFy the \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body heat, \u0627\u0644\u062f\u0631\u062c\u0629, dimensions, tool-joint \u0627\u0644\u0645\u0627\u062f\u0629, weld lot, mechanical-test results, NDT status, \u0627\u0644\u0648\u0635\u0644\u0629, and traceable marking.<\/p>\n\n<figure class=\"wp-block-image size-large is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"576\" src=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-inspection-and-wall-thickness-measurement-1024x576.jpg\" alt=\"\" class=\"wp-image-14604\" style=\"width:832px;height:auto\" srcset=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-inspection-and-wall-thickness-measurement-1024x576.jpg 1024w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-inspection-and-wall-thickness-measurement-300x169.jpg 300w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-inspection-and-wall-thickness-measurement.jpg 1672w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n<p class=\"wp-block-paragraph\">\u0645\u0633\u062a\u0639\u0645\u0644 \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 elements are inspected and classIFied under API RP 7G-2 or an operator-approved equivalent. The inspection program should establish the required inspection level, inspection methods, personnel qualIFication, equipment calibration, evaluation criteria, and marking procedure.<\/p>\n\n<p class=\"wp-block-paragraph\">A practical \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 inspection program may iNClude:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>Full-length visual inspection<\/li>\n\n\n\n<li>\u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body OD and wall-thickness measurement<\/li>\n\n\n\n<li>Electromagnetic inspection<\/li>\n\n\n\n<li>Ultrasonic wall-thickness verIFication<\/li>\n\n\n\n<li>Wet fluorescent magnetic-particle inspection of critical end areas<\/li>\n\n\n\n<li>\u0627\u0644\u062e\u064a\u0637 and shoulder inspection<\/li>\n\n\n\n<li>Tool-joint OD and ID measurement<\/li>\n\n\n\n<li>Straightness inspection<\/li>\n\n\n\n<li>Friction-weld inspection<\/li>\n\n\n\n<li>Hardbanding-condition assessment<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">\u0645\u062a\u0645\u064a\u0632-class \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 is commonly classIFied with at least 80% of nominal body wall re\u0627\u0644\u0631\u0626\u064a\u0633\u064aing. For a nominal wall of 0.362 in:<\/p>\n\n<p class=\"wp-block-paragraph\"><strong>0.362 \u00d7 0.80 = 0.290 in<\/strong>, or approximately <strong>7.36 mm<\/strong>.<\/p>\n\n<p class=\"wp-block-paragraph\">This classIFication threshold does not automatically approve the joint for a particular \u0627\u0644\u0628\u0626\u0631. A critical, high-load, corrosive, or high-\u0627\u0644\u062a\u0639\u0628 \u0627\u0644\u062a\u0637\u0628\u064a\u0642 may require a greater re\u0627\u0644\u0631\u0626\u064a\u0633\u064aing wall, additional inspection methods, or more restrictive retirement criteria.<\/p>\n\n<p class=\"wp-block-paragraph\">A joint can retain more than 80% of its nominal wall and still be rejected because of a crack, damaged \u0627\u0644\u062e\u064a\u0637, washed-out shoulder, excessive tool-joint \u0627\u0644\u062a\u0622\u0643\u0644, slip-area damage, or an unacceptable friction-weld indication.<\/p>\n\n<div data-wp-interactive=\"core\/file\" class=\"wp-block-file\"><object data-wp-bind--hidden=\"!state.hasPdfPreview\" hidden class=\"wp-block-file__embed\" data=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-inspection-and-acceptance-reference.pdf\" type=\"application\/pdf\" style=\"width:100%;height:600px\" aria-label=\"\u062a\u0636\u0645\u064a\u0646 drill-pipe-inspection-and-acceptance-reference.\"><\/object><a id=\"wp-block-file--media-65317bd5-698c-47da-ae06-62a194644760\" href=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-inspection-and-acceptance-reference.pdf\">\u0627\u0644\u062d\u0641\u0631-\u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-inspection-and-acceptaNCe-refereNCe<\/a><a href=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/08\/drill-pipe-inspection-and-acceptance-reference.pdf\" class=\"wp-block-file__button wp-element-button\" download=\"\" aria-describedby=\"wp-block-file--media-65317bd5-698c-47da-ae06-62a194644760\">Download<\/a><\/div>\n\n<h2 class=\"wp-block-heading\">Common \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 \u0627\u0644\u0627\u062e\u062a\u064a\u0627\u0631 Errors<\/h2>\n\n<p class=\"wp-block-paragraph\">Several recurring errors reduce \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 \u0627\u0644\u0645\u0648\u062b\u0648\u0642\u064a\u0629:<\/p>\n\n<ul class=\"wp-block-list\">\n<li>\u0627\u062e\u062a\u064a\u0627\u0631ing S135 solely because it has the highest conventional API \u0627\u0644\u062f\u0631\u062c\u0629<\/li>\n\n\n\n<li>CoMParing \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628-body tensile capacity without checking the \u0627\u0644\u0648\u0635\u0644\u0629<\/li>\n\n\n\n<li>Treating maximum make-up \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646 as allowable \u0627\u0644\u062d\u0641\u0631 \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646<\/li>\n\n\n\n<li>Using nominal \u0633\u0645\u0627\u0643\u0629 \u0627\u0644\u062c\u062f\u0627\u0631 for worn \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 calculations<\/li>\n\n\n\n<li>Ignoring the smallest bore through the BHA<\/li>\n\n\n\n<li>Placing an abrupt stIFfness transition in a severe dogleg<\/li>\n\n\n\n<li>Assuming \u0645\u062a\u0645\u064a\u0632 Class means suitable for every \u0627\u0644\u0628\u0626\u0631<\/li>\n\n\n\n<li>Reusing the same BHA configuration for dIFferent hole sections<\/li>\n\n\n\n<li>Ignoring accumulated rotating hours through high-curvature intervals<\/li>\n\n\n\n<li>Evaluating tension, \u0639\u0632\u0645 \u0627\u0644\u062f\u0648\u0631\u0627\u0646, bending, and pressure as unrelated loads<\/li>\n<\/ul>\n\n<p class=\"wp-block-paragraph\">The correct \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 is the assembly that provides adequate mechanical, hydraulic, and \u0627\u0644\u062a\u0639\u0628 margin for the planned \u0627\u0644\u0628\u0626\u0631. Simply choosing the heaviest \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628, highest \u0627\u0644\u062f\u0631\u062c\u0629, or largest \u0627\u0644\u0648\u0635\u0644\u0629 does not establish a balaNCed design.<\/p>\n\n<div class=\"wp-block-buttons is-content-justification-center is-layout-flex wp-container-core-buttons-is-layout-d61d70aa wp-block-buttons-is-layout-flex\">\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link wp-element-button\" href=\"https:\/\/www.drillpipes.com\/ar\/%d8%a7%d8%aa%d8%b5%d9%84-%d8%a8%d9%86%d8%a7\/\">Free Quotation<\/a><\/div>\n<\/div>\n\n<h2 class=\"wp-block-heading\">FAQ<\/h2>\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Q: What is a drill string in oil and gas drilling?<\/strong><\/summary>\n<p class=\"wp-block-paragraph\"><strong>A:<\/strong> Drill string refers to the complete assembled column connecting the surface drilling equipment to the drill bit. It normally contains drill pipe, transition components such as heavy-weight drill pipe, and a project-specific bottom-hole assembly.<\/p>\n<\/details>\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Q: Is drill pipe the same as a drill string?<\/strong><\/summary>\n<p class=\"wp-block-paragraph\"><strong>A:<\/strong> No. Drill pipe is one tubular component and normally forms most of the string\u2019s length. The drill string includes drill pipe together with the BHA, drill collars, subs, directional tools, and drill bit.<\/p>\n<\/details>\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Q: What is the main function of drill string equipment?<\/strong><\/summary>\n<p class=\"wp-block-paragraph\"><strong>A:<\/strong> The function of drill string equipment is to rotate or guide the bit, carry drilling fluid, apply controlled weight on bit, support downhole tools, and allow the complete assembly to be lowered into or retrieved from the well.<\/p>\n<\/details>\n\n<details class=\"wp-block-details is-layout-flow wp-block-details-is-layout-flow\"><summary><strong>Q: What determines the safe capacity of a drill string?<\/strong><\/summary>\n<p class=\"wp-block-paragraph\"><strong>A:<\/strong> Safe capacity is determined by the lowest applicable limit among the pipe body, tool joints, connections, weld areas, subs, and BHA tools. Actual dimensions, wear, tension, torque, pressure, bending, buckling, fatigue, and the required design factor must all be considered.<\/p>\n<\/details>\n\n<figure class=\"wp-block-image size-large is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"410\" src=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/05\/OCTAL-Certifications-1024x410.png\" alt=\"\" class=\"wp-image-12635\" style=\"width:1191px;height:auto\" srcset=\"https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/05\/OCTAL-Certifications-1024x410.png 1024w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/05\/OCTAL-Certifications-300x120.png 300w, https:\/\/www.drillpipes.com\/wp-content\/uploads\/2026\/05\/OCTAL-Certifications-2000x800.png 2000w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>\u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 connects the \u0627\u0644\u062d\u0641\u0631 rig at the surface to the \u0645\u062b\u0642\u0627\u0628 \u0627\u0644\u062d\u0641\u0631 at the bottom of the \u0627\u0644\u0628\u0626\u0631. It is not a \u0645\u0641\u0631\u062f \u0627\u0644\u0623\u0646\u0627\u0628\u064a\u0628, but a complete assembly made from connected sections of \u0623\u0646\u0628\u0648\u0628 \u0627\u0644\u062d\u0641\u0631 and the heavier, more specialized tools installed near the bit. During \u0627\u0644\u062d\u0641\u0631, the \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 turns or guides the &hellip; <\/p>\n<p class=\"link-more\"><a href=\"https:\/\/www.drillpipes.com\/ar\/%d9%85%d8%a7-%d9%87%d9%88-a-%d8%b3%d8%a7%d9%82-%d8%a7%d9%84%d8%ad%d9%81%d8%b1\/\" class=\"more-link\">Read more<span class=\"screen-reader-text\"> &#8220;\u0645\u0627 \u0647\u0648 a \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631&#8221;<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":15945,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_eb_attr":"","footnotes":""},"categories":[105],"tags":[],"class_list":["post-15944","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-105"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.1.1 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>\u0645\u0627 \u0647\u0648 a \u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 - Octal Drill Pipe<\/title>\n<meta name=\"description\" content=\"\u0633\u0627\u0642 \u0627\u0644\u062d\u0641\u0631 connects surface equipment to the \u0645\u062b\u0642\u0627\u0628 \u0627\u0644\u062d\u0641\u0631. 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