G105 tubería de perforación and S135 tubería de perforación are high-strength API 5DP tubería de perforación grados used in rotaria perforación sartas to carry axial load, transmit par, circulate fluido de perforación and connect the equipo de perforación to the bottom-pozo assembly. Both are normally manufactured from heat-treated seamless alloy steel tubería bodies with upset ends, then fricción-welded to alloy steel unións with rotaria shouldered unións. G105 has a 105 ksi minimum límite elástico, while S135 has a 135 ksi minimum límite elástico.
The difference between G105 and S135 is not only a strength number. S135 provides higher tensile and par margin, but the final selection should also consider pozo depth, gancho load, dogleg severity, fatiga exposure, unión capacity, sour-service risk, unión condition and inspection documents. For controlled medium-to-pozo profundos, G105 may be enough; for deeper, longer or higher-par perforación sections, S135 may be required.
Quick Answer: When to Choose G105 or S135 Drill Pipe
| Selection Question | G105 Drill Pipe | S135 Drill Pipe |
| Strength level | 105 ksi minimum límite elástico | 135 ksi minimum límite elástico |
| Best fit | Medium-to-pozo profundos, directional pozos, controlled high-load sections | pozo profundos, high-par perforación, extended-reach and complex pozo profiles |
| Main advantage | Balanced strength, availability and cost control | Higher tensile capacity and stronger load margin |
| Main caution | Still needs fatiga and unión review | Higher strength does not remove fatiga, H₂S or unión risk |
| Typical review point | Whether X95 is not enough but S135 is not necessary | Whether G105 leaves insufficient load or par margin |
| Inspection focus | MTC, dimensional report, NDT, rosca gauge record, unión check | MTC, iMPact/hardness review, NDT, rosca inspection, weld-zone and unión control |
If the pozo has moderate depth, controlled dogleg severity and no extreme par demand, G105 may be enough. If the pozo has high suspended sarta peso, high overpull risk, long horizontal displacement or severe rotaria par, S135 should be reviewed.
API 5DP Strength Difference Between G105 and S135
In API 5DP tubería de perforación grados, the number in G105 and S135 refers to the specified minimum límite elástico in thousands of psi. G105 means a 105 ksi minimum límite elástico grado, while S135 means a 135 ksi minimum límite elástico grado.
| Grade | Minimum Yield Strength | Maximum Yield Strength | Minimum Tensile Strength | Practical Meaning |
| G105 | 105,000 psi / 724 MPa | 135,000 psi / 931 MPa | 115,000 psi / 793 MPa | Higher-load perforación where X95 may not provide enough margin |
| S135 | 135,000 psi / 931 MPa | 165,000 psi / 1138 MPa | 145,000 psi / 1000 MPa | Deep, high-tension, high-par and extended-reach perforación |
This strength gap is important, but it is only the first layer of selection. A tubería de perforación sarta is not loaded by static tension alone. During perforación, the tubería body works under combined tension, par, internal pressure, bending stress, vibration, contact desgaste and repeated make-up / break-out cycles.
That is why a stronger grado cannot be treated as a universal upgrado. If the unión is mismatched, the unión shoulder is worn, the hardbanding is damaged, or the tubería de perforación lacks traceable inspection records, higher límite elástico will not solve the field acceptance problem.
G105 and S135 tubería de perforación Selection by Strength and Service Demand
G105 and S135 tubería de perforación are both high-strength API 5DP grados, but they are usually selected for different perforación demands. G105 is often used when the perforación program needs higher strength than X95, while S135 is selected when deeper pozos, longer horizontal sections or higher par demand require a stronger tubería body. The selection should not be based on grado name alone. pozo depth, tensile load, par, fatiga exposure, unión type, unión dimensions and inspection records should be reviewed together.
G105 tubería de perforación for Controlled High-Load perforación
G105 drill pipe is commonly selected when the drilling string needs more strength than X95, but the full drilling program does not require S135. It is suitable for medium-to-deep wells, directional sections, build-and-hold intervals and controlled high-load drilling conditions where tensile load, torque and bending fatigue are higher than conventional service.
The main value of G105 is balance. It provides a useful strength increase while keeping the specification close to common API tubería de perforación supply ranges. For many perforación programs, this avoids unnecessary grado escalation when the pozo profile is demanding but still controlled.
G105 drill pipe is often reviewed for:
- deeper vertical pozos where X95 leaves limited tensile margin;
- directional pozos with combined axial load and bending fatiga;
- build sections where par and arrastre increase;
- perforación sartas that need higher load capacity without moving directly to S135;
- replacement or mixed-sarta orders where unión coMPatibility is a major control point.
The key risk for G105 is not only whether the tubería body meets the grado requirement. fatiga may start at slip marks, corrosión pits, hardbanding defects, rosca shoulder damage or the upset transition area. A G105 order should therefore be checked by OD, nominal peso, espesor de pared, range, upset type, unión, unión OD/ID, drift diametro, hardbanding condition and inspection class.
S135 tubería de perforación for Deep and High-par pozos
S135 drill pipe is the higher-strength option in this comparison. It is normally selected when the drilling program needs more tensile capacity, more torque reserve or a higher safety margin under complex well conditions. Compared with G105, S135 provides a stronger pipe body, but it also requires closer control of toughness, hardness, connection condition and traceability documents.
S135 tubería de perforación is often reviewed for:
- deep and ultra-pozo profundos with high suspended sarta peso;
- long horizontal sections and extended-reach perforación;
- high-par rotaria perforación and reaming operations;
- high overpull risk during tripping or stuck-tubería recovery;
- complex directional pozos with severe dogleg or long build sections;
- perforación programs where G105 does not provide enough load margin.
S135 can improve the strength margin of the sarta de perforación, but it should not be treated as an automatic upgrado. Higher-strength tubería de perforación still needs careful review of fatiga exposure, sour-service risk, fricción weld quality, rosca condition, unión performance and make-up par control.
For S135 tubería de perforación, the full specification should include tubería size, nominal peso, espesor de pared, range, upset type, unión, unión OD/ID, drift requirement, internal coating, hardbanding, make-up par, inspection tramoard and document package. The grado name is only one part of the technical description. Field acceptance depends on whether the complete tubería de perforación junta matches the perforación program and the required inspection records.
Load, Torque and Fatigue Factors in G105 and S135 Drill Pipe Selection
G105 and S135 tubería de perforación should be coMPared under real perforación loads, not only by límite elástico. In the equipo de perforación, the tubería body and unión may work under axial tension, rotaria par, internal pressure, bending, vibration, contact desgaste and repeated make-up / break-out cycles. These loads often act together in directional, horizontal and extended-reach pozos.
| perforación Condition | Main Load Concern | G105 Review Point | S135 Review Point |
|---|---|---|---|
| Deeper vertical pozos | Suspended sarta peso and overpull margin | Suitable when the load is higher than X95 can comfortably handle but still controlled | Reviewed when sarta peso, overpull risk or safety margin requires a stronger tubería body |
| Directional and horizontal pozos | par, arrastre and bending fatiga | Check dogleg severity, unión capacity, unión condition and fatiga-sensitive areas | Consider when par, arrastre and repeated bending exceed the comfortable margin of G105 |
| Extended-reach perforación | High par and long lateral displacement | May be limited when horizontal displacement and par increase | Often reviewed for higher tensile and par reserve, but still depends on unión and unión control |
| Replacement or mixed-sarta orders | CoMPatibility with the existing sarta | Must match OD, peso, range, unión, unión OD/ID and drift | Must also match make-up par, shoulder condition, hardbanding and inspection class |
fatiga-sensitive areas should be reviewed carefully. Slip marks, hardbanding edges, corrosión pits, upset transitions, fricción weld zones and rosca shoulders can become initiation points under repeated bending or vibration.
A pozo-specified G105 sarta may perform better than a poorly matched S135 sarta if the unión, inspection class and fatiga exposure are properly controlled. A tubería that is correct by grado but wrong by unión or unión dimension may still fail field matching.
Sour Service and H₂S Risk in G105 and S135 Drill Pipe
H₂S exposure changes the selection logic. In sour or H₂S-containing perforación conditions, higher-strength steels can become more sensitive to sulfide stress cracking and hydrogen embrittlement. This does not mean G105 or S135 can never be used in such environments. It means the grado cannot be selected by strength alone.
For G105 and S135 tubería de perforación, sour-service review should consider:
- H₂S partial pressure and exposure condition;
- CO₂, chloride, temperature and fluido de perforación chemistry;
- hardness control of tubería body, unión and weld zone;
- surface condition, corrosión pits and mechanical damage;
- NACE / ISO sour-service requirement, when applicable;
- PMI, MTC, hardness records and third-party inspection;
- whether a sour-service or special material tubería de perforación route is required.
S135 has higher strength than G105, but in H₂S conditions that higher strength can also require stricter crack-resistance review. For this reason, S135 should not be treated as an automatic solution for sour pozos. If the project specification includes H₂S, CO₂, chloride or high temperature, the material route, hardness limit, inspection class and document package should be confirmed before order release.
Connection and Tool Joint Control
G105 and S135 tubería de perforación are not only tubería bodies. A complete tubería de perforación junta includes the seamless tubería body, upset transition, fricción weld zone, unión, pin / box rosca, shoulder, drift path and sometimes internal coating or hardbanding.
unión control is often where field problems appear.
Common unión-related checks include:
| Check Item | Why It Matters |
| unión type | NC, IF, FH, REG or premium unión must match the existing sarta |
| unión OD | Affects desgaste, handling and coMPatibility with sarta de perforación design |
| unión ID | Controls hydraulic clearance and drift path |
| Make-up par | Must match unión design and equipo de perforación practice |
| rosca gauge record | Confirms rosca form, shoulder condition and unión acceptance |
| Shoulder condition | Controls par transfer and sealing contact |
| Hardbanding | Affects unión desgaste and revestimiento-friendly performance |
| rosca protector | Prevents handling damage before field use |
A common market example is 5″ tubería de perforación with NC50 unión. But “5″ G105 NC50” or “5″ S135 NC50” is still not a complete order description. unión OD, unión ID, upset type, range, drift diametro, hardbanding and inspection documents must also be confirmed.
When unión geometry, shoulder contact or make-up par becomes the controlling factor, special roscaed tubería de perforación can be reviewed to match the existing sarta de perforación and equipo de perforación-side unión requirements.
If the unión is not suitable, the tubería may meet API 5DP mechanical requirements but still fail during equipo de perforación-site matching or make-up par control. grado strength cannot compensate for wrong unión geometry.
Inspection and Document Review for G105 and S135 tubería de perforación
Inspection is the step that turns a grado name into verifiable tubería de perforación. For G105 and S135, the review should cover the tubería body, upset area, fricción weld zone, unión, rosca unión, drift path, marking and final document package. The purpose is not only to prove the límite elástico, but also to show that each junta can be matched, made up, inspected and traced before shipment release.
Main Inspection Items Before Shipment
| Inspection Item | How It Is Usually Performed | What It Verifies |
|---|---|---|
| Visual and marking inspection | Each junta is checked for tubería number, size, grado, range, unión, heat number, stencil marking, color band and rosca protector condition. | Confirms that the physical tubería matches the order, MTC and packing list. |
| Dimensional inspection | OD, espesor de pared, length, straightness, upset dimensions, unión OD/ID and shoulder dimensions are measured with calibrated tools. | Confirms fit-up, sarta coMPatibility, drift clearance and compliance with the ordered specification. |
| Pipe body NDT | Ultrasonic testing, electromagnetic inspection or other project-specified NDT methods are applied to detect internal or surface defects. | Screens the tubería body for cracks, laminations, wall-loss areas or unacceptable discontinuities. |
| Friction weld zone inspection | The weld area between tubería body and unión is visually checked and normally reviewed by NDT according to the ITP. | Controls one of the most critical transition areas under par, bending and tensile load. |
| Tool joint inspection | unión OD, ID, shoulder face, hardbanding area and pin / box condition are checked before release. | Ensures par transfer, desgaste resistance, unión matching and handling reliability. |
| Thread gauge inspection | Pin and box roscas are checked by proper rosca gauges. Shoulder condition, rosca form, machueloer and visible damage are reviewed. | Confirms that the unión can be made up correctly at the equipo de perforación site. |
| Drift test | A specified drift mandrel is passed through the tubería bore and unión ID. | Verifies internal clearance for fluido de perforación flow and downpozo tool passage. |
| Hardness test | Hardness readings are taken on the tubería body, unión or weld zone when required by grado, sour-service review or project ITP. | Helps control high-strength material condition and cracking sensitivity, especially for S135 or sour-service programs. |
| Impact test | Charpy V-notch specimens are machined from the required material location, cooled to the specified temperature and broken by pendulum iMPact testing. | Measures absorbed energy and supports toughness review for low-temperature, offshore or project-specified service. |
| Hydrostatic or pressure-related test | When specified by the order or ITP, pressure testing is performed under controlled pressure and holding time. | Verifies pressure integrity, sealing performance and absence of leakage under the required test condition. |
| Document review | MTC, heat records, test reports, NDT records, dimensional reports, rosca gauge records and packing list are coMPared against tubería marking. | Confirms traceability from material heat to final shipped junta. |
How the Key Tests Are Reviewed
Mechanical test review
Mechanical testing verifies whether the pipe body meets the required API 5DP grade. The report should show actual yield strength, tensile strength and elongation values, with heat number and specimen reference, not only a general “passed” result.
Impact test review
Impact testing is required when toughness or low-temperature performance needs verification. Charpy V-notch specimens are tested at the specified temperature, and the absorbed energy value is recorded to assess resistance to brittle fracture under dynamic loading.
Hardness review
Hardness testing helps control cracking sensitivity in high-strength drill pipe, especially around the tool joint, friction weld zone and sour-service exposure. Results may be recorded by HB, HRC or HV method according to the project requirement.
NDT review
NDT is used to detect defects that visual inspection cannot confirm. The pipe body, upset area, weld zone, tool joint or thread area may be checked by ultrasonic, electromagnetic, magnetic particle or other project-specified methods according to the ITP.
Thread and connection review
Thread gauge inspection confirms the pin / box connection, shoulder condition and make-up compatibility. Even when the pipe body meets G105 or S135 strength requirements, incorrect thread geometry or shoulder damage can still cause rig-site matching problems.
For S135, hardness and weld-zone control deserve closer attention because the grado is higher strength. For G105, fatiga, unión coMPatibility and mixed-sarta traceability are often the practical control points.
Selection Risks When CoMParing G105 and S135 tubería de perforación
Strength grado Is Only One Part of the Selection
S135 provides higher límite elástico than G105, but higher strength does not automatically make the sarta de perforación safer. fatiga exposure, unión damage, rosca shoulder desgaste, weld-zone quality and H₂S sensitivity may still become the controlling service risks.
G105 Is Still a High-Strength API 5DP grado
G105 should not be treated as a low-grado option. It is a high-strength API 5DP tubería de perforación grado that can be suitable for medium-to-pozo profundos, perforación direccional and controlled high-load sections when par, arrastre and fatiga exposure remain within the accepted range.
unión and unión Details Control Field Matching
A tubería de perforación specification should not stop at grado and OD. unión type, unión OD/ID, shoulder condition, make-up par and rosca gauge records directly affect equipo de perforación-site matching, par transfer and unión acceptance.
Sour-Service Conditions Need Separate Review
H₂S exposure requires material, hardness and environmental review. A higher-strength tubería body does not automatically improve sour-service performance, especially when sulfide stress cracking or hydrogen embrittlement risk is part of the project specification.
Document Traceability Supports Final Acceptance
The MTC, heat number, inspection report and packing list should match the tubería marking. When the document chain is incomplete, receiving inspection becomes difficult and field acceptance risk increases.
Conclusion
G105 and S135 tubería de perforación are both high-strength API 5DP grados, but they are not selected by strength number alone. G105 is often the balanced choice for medium-to-pozo profundos and controlled perforación direccional where X95 is not enough but S135 may be unnecessary. S135 is selected when deeper, longer, higher-par or more complex perforación profiles require a stronger tubería body and higher load margin.
FAQ
Is S135 drill pipe always better than G105?
No. S135 has higher límite elástico, but it is not automatically better for every pozo. G105 may be suitable when load, par, dogleg severity and fatiga exposure remain within a controlled range
What is the main difference between G105 and S135 drill pipe?
The main difference is strength level. G105 has 105 ksi minimum límite elástico, while S135 has 135 ksi minimum límite elástico. Final selection should also include unión, unión, fatiga, sour-service condition and inspection documents.
Can G105 drill pipe be used in directional wells?
Yes, G105 is commonly reviewed for directional pozos where higher load margin than X95 is required. Dogleg severity, par, arrastre, fatiga exposure and unión capacity should be checked before selection.
S135 drill pipe be used in sour service??
S135 should not be selected for sour service by grado name alone. H₂S exposure requires review of material condition, hardness, environment, NACE / ISO requirement, inspection scope and project-specific approval.
What documents should be supplied with G105 or S135 drill pipe?
Common documents include MTC, heat number record, mechanical test record, hardness record, dimensional report, NDT report, rosca gauge record, drift test record and packing list.
