New Technologies for BOP Shearing

Transcription

1 New Technologies for BOP Shearing 09 October 2013 Covey Hall Global Manager for Consulting Services Lloyd s Register Energy Drilling

2 Agenda Motivation for the study GTC Shear Study Ongoing project Future project phases Acknowledgements References

3 History 2003 and 2004 Shear Studies Performed by WEST Engineering for the MMS

4 Understanding the Shear Function Last resort is to shear pipe and secure the well with the sealing shear ram. Failure to shear could result in a major safety and/or environmental event. Improved strength, larger and heavier drill pipe adversely affects the ability to successfully shear and seal.

5 Actual Shearing or Breaking Action Upper and Lower Shear Blades crushing the drill pipe and beginning the shearing (or breaking) operation. Upper Shear Blade Tension Drill Pipe being collapsed during the shearing process Shear Blade Rake Angles that apply tension to the pipe during the separation process Tension Lower Shear Blade

6 Observations as a Third Party Verifier There is a small but significant percentage of shear tests where the actual test exceeds the OEM calculation method. Degree of deviation between actual shear pressure tests and theoretical calculations varies between OEMs Data input requirements vary between OEMs Some use nominal yield, some use measured stress from tensile test

7 Observations (cont d) Metallurgical advances in drill pipe S-135 grades are now produced with improved ductility Z-140 and V-150 grades Higher strength, lower ductility, brittle fracture More common in deepwater Will ductility improve as it did with S-135? Material Test Reports What material tests produce the most accurate shear predictions? Tensile? Charpy?

8 Shear Examples Low & High Ductility Low ductility or brittle pipe (left) and high ductility pipe (right). The high ductility pipe required almost 2,000 psi (over 300K lb) more to shear than the low ductility pipe even though the grades were the same, S-135. The brittle pipe had cracking on the sides and did not collapse as much as the ductile pipe.

9 Since the 2004 study Larger OD pipes, thicker walls Pipe Geometry Longer internal upsets and tool joints Increase in verifications for concentric tubulars, completion strings, wirelines, etc. Maximum fold-over limit in some model BOP models

10 Observations (cont d) Shear test repeatability What does the distribution look like? What are the important variables? Same grade & dimension, different vendor - may produce different test results Same pipe heat variations in measured yield strength, UTS, and percent elongation Same pipe variations in properties along the length of a single joint New vs. used (premium) pipe Testing Protocol Shear AND Seal Successful pressure tests LP and HP Normal shop tests don t replicate pipe stress conditions down hole.

11 Observations (cont d) Attention to unusual loading conditions Side load Bending load Drill string in tension, compression, or torsion Evolution of ram geometry Replaceable blade components Low force geometries Pipe Centering

12 Shear Study Being Conducted by Lloyd s Energy Group Technology Centre (GTC) Singapore

13 Project Goals Scientific: Understand shearing, verify theoretical modeling with new fracture and plasticity theory. Practical: Explore variation of shear force within one pipe, within one heat batch, within a pipe grade. Long term: develop theoretical prediction tool based on standard material testing.

14 Target Outcome(s)/Benefits Develop or refine shear ram calculations and modelling techniques based on empirical evidence, using appropriate statistical methods, and determine appropriate factors of safety. Develop more accurate mathematic models for predicting shear capability, and statistical reliability

15 Shear Ram Reliability Study Phase 1 Objectives 1. Develop FEA modeling method using fracture theory and determine what material tests are required to obtain accurate results vs. actual shear tests of same pipe. 2. Evaluate the relationship between material properties and forces applied during BOP shearing scenarios. 3. Evaluate the relationship between thin-wall and thick walled tubulars. 4. Collect and analyze joint industry shearing data for all grades of tubulars, BOP models, and shearing ram configurations. 5. Repeatability/variance of shear pressures for a given set of drill pipe.

16 Fracture Theory and FEA Modeling Application of a different fracture theory in Engineering Mechanics Literature (Mohr- Coulomb Criterion) crack initiation as an extension of plasticity theory. FEA Modeling element removal when fracture criterion is met simulated crack initiation and propagation. Critical is the determination of plasticity and fracture coefficients from material testing.

17 Plasticity Theory The distortion energy theory says that failure occurs due to distortion of a part, not due to volumetric changes in the part (distortion causes yielding, but volumetric changes due not). Distortion Energy Theory is less conservative than Maximum Shear Strength Theory (Tresca Criterion), but more conservative than the Maximum Normal Stress Theory (von Mises Yield Criterion) Assumes compressive and tensile yield criteria are equal F = x S Y x A Where: F = Force, lbs S Y = material tensile yield strength, psi converts tensile yield to shear A = cross-sectional area of drill pipe, in 2

18 Mohr Coulomb Yield (failure) Criterion (aka Coulomb Criterion) Similar to Maximum Shear Strength Theory (Tresca Criterion), but take also applies to materials for which the compressive strength far exceeds the tensile strength Mostly used geotechnical and structural engineering to determine shear strength and fracture angle. Has been applied to modeling steel in ship hulls in recent years. Source: MIT Paper

19 Coulomb Criterion Applied to Finite Element Modeling (FEA)Phase 1 Methodology Create advanced material test coupons from pipe Preferably on fish that have already been tested Data analysis to get material coefficients from material tests. Plug those material coefficients in FEA modeling of BOP/Pipe shearing Compare those FEA results against actual shear test results and calculations using existing Distortion Energy Theory techniques

20 Material Testing to support the MCC

21 Material Testing results are then mapped and a 3-D best fit is determined This determines the yield surface as predicted by the Coulomb Criterion Source: MIT Paper

22 Project Procedure Material data (From LR/vendor) σ e First stage Second stage Mathematical analysis (IHPC) Calibrate model parameters C i Load condition Shear ram FE model Shear force & stress profile Benchmark failure criterion ε f ε e

23 FEA Model That material property data is then applied to every element in the FEA model, and the simulation is then run.

24 Very preliminary FEA analysis.

25 Very preliminary FEA analysis.

26 Variability Correlate FEA results against current theoretical calculation methods and actual shear test results Repeatability/variance of shear pressures for a given set of drill pipe. Variations in shearing force: 1) Variations in yield, ultimate strength, elongation, ductile/brittle fracture, etc Within one pipe 2) Among pipes from the same heat/metallurgical batch identical MTR row 3) Among various heats on the Same Purchase order 4) Within a pipe grade (S-135, Z-140, V-150)

27 Current Project Status FEA Model in Development Establishing JIP Obtaining shear test data Corresponding material test data

28 Coulomb Criterion Applied to Finite Element Modeling (FEA) Future Phases of Research Practical Applications

29 Future Proposed Extension of the Study Practical Applications 1. Shear Prediction tool possible with existing MTR data, pipe & ram geometry. 2. Shear prediction tool possible if additional test(s) added to MTR standard (compressive, torsion, charpy, etc.) Provide recommendations for modifications to standard industry shear testing and material testing protocols, if warranted. 3. Investigate the effects of loading on the drill string and how that affects force required to shear Tension, compression, bending, torsion, Side Load

30 Future Proposed Extension of the Study Practical Applications (cont d) 4. Evaluate the effectiveness of existing shear designs relative to of complex tubular geometries, such as VIT, concentric tubulars, wirelines, etc. 5. Have a theoretical method for looking at new materials 6. Have a theoretical method for looking at alternate rams ram geometries. 7. Ability to affect multiple shears prior to changing out ram blocks and rubber goods. 8. Ability to shear tool joints using casing shear rams or modified blind shear rams.

31 Acknowledgements Ted Cole Andy Frankland Manfred Lin Greg Childs Jeff Sattler A*Star Micron Optics Students, Faculty and Staff at MIT

32 References International Journal of Fracture, Application of extended Mohr- Coulomb criterion to ductile failure, Yuanli Bai, Thomasz Wierzbicki, May 2009 International Journal of Plasticity, A new model of metal plasticity and fracture with pressure and Lode dependence, Yuanli Bai, Thomasz Wierzbicki, 2007 MIT Thesis Paper, Numerical Analysis of a Shear Ram and Experimental Determination of Fracture Parameters Evangelos Koutsolelos, 2012 Mini Shear Study West Engineering Services, 2002 Shear Ram Capabilities Study for the US Minerals Management Service, Rev 1 WEST Engineering Services, November 2004

33 For more information, please contact: Covey Hall Global Manager for Consulting Services Lloyd s Register Energy Drilling Lloyds Register Drilling Integrity Services, Inc Enclave Parkway, Suite 200 Houston, TX T E covie.hall@lr.org W Integrating ModuSpec and WEST Engineering Services to advance excellence in drilling safety, integrity and performance