The Influence of Titanium Properties on the Design and Application of Downhole Oil & Gas Equipment. Mitchell Dziekonski Titanium Engineers, Inc.

Transcription

1 The Influence of Titanium Properties on the Design and Application of Downhole Oil & Gas Equipment Mitchell Dziekonski Titanium Engineers, Inc. Joel Ogburn Titanium Engineers, Inc. Titanium alloys have successfully been used in the oil industry for a variety of applications. Some of the applications are both offshore and downhole and consist of titanium stress joints, riser systems, drill pipe, logging and drilling tools, safety valves, packers, and tubing hangers. Titanium was chosen for its corrosion resistance, strength, and low density for the aforementioned systems. As the search for oil and gas encounters significant aggressive downhole environments, a new category of hydro carbon reserves are being identified as high pressure, high temperature (HPHT). These environments can exceed 30,000 PSI and temperatures of 450 F with an excessive amount of H 2 S sour gas, CO 2 and chloride levels. One must carefully review titanium s unique physical and mechanical property characteristics for the evaluation and design of HPHT components. Historically, many oilfield components are substituted with titanium using prints based on nickel, stainless or steel alloys systems. Titanium s characteristics require design engineers to consider things such as mechanical property degradation at high temperatures, low thermal expansion, and its unique stress-strain curve compared to other alloys. Tensile residual stresses generated by a variety of manufacturing methods can have a major impact on the performance of a downhole titanium component. Finite Element Analysis (FEA) is highly recommended as a design method in order to incorporate titanium s unique property characteristics.

2 The Influence of Titanium Properties on the Design and Application of Downhole Oil & Gas Equipment Mitchell Dziekonski Joel Ogburn Stafford, Texas USA TITANIUM 2008 Las Vegas, Nevada

3 Titanium s Unique Characteristics High Strength th Superior Corrosion Resistance Low Density Low Modulus Low Thermal Expansion Non-Magnetic Low Wear Resistance

4 Stress-Strain Strain Curves Y.S. x T.S. x 30 ksi Y.S. x T.S. x 10 ksi Stre ess (σ) Stre ess (σ) Fe Ti Strain (Є) Strain (Є)

5 Titanium vs. Steel Spring

6 Titanium 6AL-4V Heat Treat Options Ref.: Titanium-A Technical Guide, ASM International

7 Tensile Strength vs. Temperature Ref.: Titanium-A Technical Guide, ASM International

8 Titanium Crevice Corrosion Aerated NaCL Brines C Maximum ph at Alloy which attack occurred Ti 6-4 (least resistant) >9 Grades 1, 2, 3, 9 >8 Ti-550, Ti , Ti Grade Ti , Ti Grades 28 and 29, Ti Beta- C/Pd, Beta-21S, Ti-15-5 All Ti-Pd and Ti-Ru alloys (most resistant) <0.7 ASM Handbook Corrosion: Materials Vol 13B, 2005

9 Titanium Alloys in Sour Environments Maximum Limits Temperature ASTM Grade Product Forms (condition) (a) NaCl, wt% H 2 S, MPa CO 2, MPa Elemental S, g/l Minimum ph C F Grade 2(b) All (MA) >25(c) NL NL NL Grade 12(b) All (MA) >25(c) NE NL NL Grade 9 All (MA) >25(c) NL NL NL Grade 28(b) All (MA or TB) >25(c) NL (6.89)(d) NL (3.45)(d) NL (1)(d) (d) 625(d) Grade5 All (MA) >25(c) NL NL NL Grade 23 All (MA or TB) >25(c) NL NL NL Grade 29(b) All (MA or TB) >25(c) NL (6.89)(d) NL (3.45)(d) NL (1)(d) (d) 625(d) Ti6246(b) All (duplex or triplex annealed) >25(c) NL (1.03)(d) NL (1.03)(d) NL Grade 19 (Ti ) Tubulars (cold-pilgered +STA) >25(c) NL (6.89)(d) NL (3.45)(d) NL (1)(d) Grade 19 (Ti ) Tubulars (extruded + STA) >25(c) NL (6.89)(d) NL (3.45)(d) NL (1)(d) Grade 19 (Ti ) Forgings (STA) >25(c) NL (6.89)(d) NL (3.45)(d) NL (1)(d) Grade 20 (Ti /Pd) Tubulars (cold-pilgered + STA) >25(c) NL (6.89)(d) NL (3.45)(d) NL (20) (d) Grade 20 (Ti /Pd) Tubulars (extruded + STA) >25(c) NL (6.89)(d) NL (3.45)(d) NL (1)(d) Grade 20 (Ti /Pd) Forgings (STA) >25(c) NL (6.89)(d) NL (3.45)(d) NL (1)(d) NI., no limit indicaled or known. (a) MA, mill annealed; T, transformed beta (acicular alpha); 5TA. anlution treated and aged. (b) Approved under NACE MR0I-75 standard feraauraervice. (C) Up to the chloride saturation limit. (d) Documented test level but with no limit revealed in test. ASM Handbook Corrosion: Materials Vol 13B, 2005

10 Corrosion Induced Cracking Environments Methanol Acidizing Fluids Corrosive Completion (Packer) Fluids Hydrogen Embrittlement likely resulting from corrosion attack, galvanic reaction or effects from cathodic protection system in offshore applications.

11 Properties of Common Oilfield Ti Alloys

12 Titanium Oilfield Design Metallurgy Design-FEA Manufacturing

13 Titanium Oil Tool Design FEA Design Review Effects of YS/TS Ratio Modulus of Elasticity it Surface Stresses (Residual / Applied) Localized Plasticity (Yielding) Do not allow Titanium substitution until reviewed

14 Inner Mandrel Packer

15 5 Drillpipe Make-Break Test

16 5 Titanium Drill Pipe Fatigue Test 1,000,000 Cycles No Failure 47 o per 100 ft

17 Thank you. For Additional Information Contact: P.O. Box 1527 Stafford, Texas USA Phone: Fax: