36 th Gas-Lift Workshop. Reverse Flow Check Valve Reliability and Performance Testing of Gas Lift Barrier Check Valves

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1 36 th Gas-Lift Workshop Stavanger, Norway February 4 8, 2013 Reverse Flow Check Valve Reliability and Performance Testing of Gas Lift Barrier Check Valves Jason Kamphaus, Senior Project Manager Schlumberger Gas Lift Engineering (EMS) Thomas White, Global Business Manager Schlumberger Gas Lift Systems Dzung Le, Reliability Metier Manager Schlumberger Gas Lift Engineering (EMS) Jacob Hahn, Mechanical Engineer Schlumberger Gas Lift Engineering (EMS) Shao Chong Oh, Design for Manufacturability Engineer Schlumberger Gas Lift Engineering (EMS) 2013 Gas-Lift Workshop 1

2 Agenda Current Gas Lift barrier check valve validation testing Industry standards Common check valve failures Forensic analysis Simulations and check valve dynamic testing Use of Design of Experiments (DOE) Check valve actuation and sealing reliability Conclusions 2013 Gas-Lift Workshop 2

3 Barrier Qualified Gas Lift Check Valves The Barrier Qualified Reverse Flow Check Valve The primary and most critical component in the barrier qualified Gas Lift valve is presently tested to the latest industry acceptance standards: API 19G2 and TR2385 design performance, validation and qualification testing Reliability Testing and Design Validation Issue A check valve can successfully pass the currently prescribed laboratory and flow loop qualification and validation tests however the industry has learned that additional and more robust tests are required for in-line check valve systems to ensure better long term reliability in the real world of in situ Gas Lift operations Fluctuating well conditions flow rates, pressure differentials and gas injection volumes Mechanical Oscillation and Vibration Solids formation (scale) and debris Industry Issue? Significant claims of Gas Lift product superiority and reliability are made based on one s ability to successfully pass the currently prescribed Lab and Flow Loop performance tests, but is this enough? 2013 Gas-Lift Workshop 3

4 Industry Prescribed GL Check Valve Performance and Qualification Testing Problem: Current performance testing does not adequately address the long term reliability of in-line reverse flow check valves with respect to actual dynamic down hole operating conditions Clean/steady-state controlled test environments versus multi-phase flow in less than clean/steady-state conditions found in typical in Gas Lifted wells Assumption: All GLV check valves are fully open during all flow periods, injection rates and differential pressures (liquid and gas flow) how is this validated? Reality: Spring assisted reverse flow check valves are impacted by differential pressure, flow rate fluctuations and solids and may not always be in the full open position. All gas lift valve suppliers providing valves in the barrier qualified market place, as articulated by user/operators, have seen the real world results of this phenomenon. Currently prescribed performance /validation testing does not address this. Going beyond currently accepted design and validation testing is required 2013 Gas-Lift Workshop 4

5 Industry Standard Gas Lift Qualification Tests Industry standard and operator specific test procedures ANSI/API Specification 19G2 Statoil TR2385 Industry standard tests address the common performance requirements across valve types, but do not address design specific requirements for long term check valve (Barrier) reliability Each valve design has failure modes and operational parameters that require design specific testing beyond the current standard qualification tests 2013 Gas-Lift Workshop 5

6 Gas Lift Check Valve Failures Common Check Valve Failures Damaged check spring Damaged check valve trim Fails in the open position Scale and Solids build-up Damage from erosion Failure of body pieces during run/pull operations Shear/burst mechanism fails to operate as needed 2013 Gas-Lift Workshop 6

7 Forensic Analysis of Failures Failure modes are often best identified through the use of material forensic analysis Sealing failure modes include Galling Scratches/poor surface finish Damage from debris Forensic analysis can also be used to compare successes to failures for insight into failure mechanisms Experimental Valve Sealing Surface 2013 Gas-Lift Workshop 7

8 Role of Simulations Computational Fluid Dynamics (CFD) Set baseline for flow performance of check system Aid in diagnosing failures relating to flow Finite Element Analysis (FEA) Determine any structural problems during design Explore possible stress states due to geometric perturbations 2013 Gas-Lift Workshop 8

9 Understanding Check Valve Dynamics Pressure Dart Position Understanding the valve dynamics is critical to understanding long term reliability of check system As dp or flow rate increases, the check system will open according to its own dynamic properties Necessary to understand the sensitivity of the check system mechanics to injection pressure Important that check system is robust for various flow conditions encountered downhole dp crit Differential Pressure Dart Position Time 2013 Gas-Lift Workshop 9

10 Use of DOE to Explore Several Design and Operational Factors Half factorial Taguchi L8 Inputs: Port type, Port size, Nose design, Spring design 2 levels each 8 runs Objective: achieve full travel of the dart Results coincide with prior CFD work 2013 Gas-Lift Workshop 10

11 Use of DOE to Explore Several Design and Operational Factors Robust Design Engineering (Taguchi Method) Taguchi technique is a well proven reliability technique in the aerospace, automotive, and electronic industries for producing reliable and robust products. Noise factor (upstream pressure) was injected into the test. Noise deviates valve functionality from its ideal performance. Five design parameters (factors) were tested against Noise. S/N ratio is used to measure robustness. The higher the better. Robustness achieved with optimal levels of particular design factors which are insensitive to the noise condition Design Parameters Noise Port Type Port Size Spring Design Dart Design Nose Design Upstream Pressure 1 Upstream Pressure 2 A A A A A Data Data A A A B B Data Data A B B A A Data Data A B B B B Data Data B A B A B Data Data B A B B A Data Data B B A A B Data Data B B A B A Data Data 2013 Gas-Lift Workshop 11

12 Taguchi Analysis Results 2013 Gas-Lift Workshop 12

13 Check System Actuation Reliability Current barrier qualification standard testing actuates the check valve system a maximum of 100 cycles using gas flow on a single sample at a single flow rate Small fluctuations in injection pressure/flow rate can cause cycling of the check system and mechanical cycling of spring was shown to reveal potential failure modes and the ultimate effects of design improvements Multiple check valve assembly samples cycled 500,000 times each Design improvements resulted in more than doubling of MTTF 2013 Gas-Lift Workshop 13

14 Sealing System Reliability Test to success (Bogey test) Much improvement on large sample size to demonstrate high system reliability and confidence level. 18 samples to demonstrate 90% Reliability at 85% CL Pressure cycles at max temp and pressure All samples must continue to meet current barrier standard s leak rate criteria 2013 Gas-Lift Workshop 14

15 Conclusions Each check valve design has failure modes and operational parameters that require design specific testing beyond the current standard qualification tests Understanding the dynamics of down hole fluid flow and pressure variability and lesson learned on how those impact check valve operation has lead to better design functionality and predicted run life improvement (MTTF) 2013 Gas-Lift Workshop 15

16 Thank You - Questions? Schlumberger Artificial Lift High Performance Gas Lift Systems 2013 Gas-Lift Workshop 16

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