Evaluating the Benefit of Continuous Foam Injection. Mauricio Farinas Production Technologist Shell Global Solutions Upstream

Transcription

1 Evaluating the Benefit of Continuous Foam Injection Mauricio Farinas Production Technologist Shell Global Solutions Upstream

2 Agenda Abstract Methodology - Well modelling: Inflow Performance Relationship (IPR) history matching - Reservoir model - Well modelling with foam - Forecasting with Foam Conclusions Acknowledgements

3 Abstract Gas Well Deliquification (GWD) has grown in importance in recent years because liquid loading has been observed in an increasing number of mature depleting gas reservoirs. This study outlines the methodology used to quantify the impact of continuous foam injection on well capacity and ultimate reserves for ten candidate wells in Southern North Sea and presents the results for one example case

4 Methodology 1) Match the inflow and outflow performance in PROSPER against historic well surveillance data 2) Simulate the well performance with foam in PROSPER Set the water-to-gas ratio (WGR) to zero. The well model will then revert to condensate loading which happens at a gas rate that is down to 50% of the gas rate at which water loading occurs, Modified Gray is used The condensate-gas ratio (CGR) must be non-zero. 3) Couple the foam PROSPER well model (WGR=0) with the MBAL reservoir model via GAP and determine the new abandonment pressure and the associated ultimate recovery with foam injection.

5 Well modeling: IPR History Matching The well IPR and VLP are matched against relevant well test data The VLP is modelled using the Modified Gray flow correlation The IPR model should be matched against flow data that are yet unaffected by liquid loading Once the IPR is set, the curve should be validated over time by comparing the accuracy of the PROSPER model in predicting production well tests performed after this event

6 Well modeling: Inflow Performance Relationship (IPR) History Matching (Example) Well A: IPR matched against a multi-rate test data done in May 2000

7 Well modeling: Inflow Performance Relationship (IPR) Validation (Example) PLT Nov 2007 Well A: IPR validation against a Production Logging Test done in November 2007

8 Reservoir Model (Example) Material balance technique was used for the purpose of this study A tank model based on historic pressure/depth (P/z) data plotted against the cumulative gas production was used. Latest reservoir pressure obtained by the material balance or CITHP Well A: Material Balance model using MBAL.

9 Well Modeling: Current Conditions (Example) VLP and IPR no longer cross Liquid loading conditions in place Well A: November 2008, 14 barg

10 Well Modeling: Foam Injection (Example) Foaming reduces the critical velocity for lifting water Presence of foam is simulated by setting the water-gas ratio (WGR) to zero while maintaining a non-zero condensate-gas ratio (CGR) This reduces the minimum stable rate by up to 50% This also reduces the hydrostatic head reduced which could be optimistic in high WGR wells Foam lift Application No foam

11 Forecasting with Foam (Example) Well model coupled with reservoir model via GAP Continuous production assumed through time Provides abandonment reservoir pressure and ultimate reserves with foam Reservoir Pressure Gas Rate Well A: abandonment reservoir pressure and gas rate plotted versus time

12 Forecasting with Foam (Example) Ultimate Reserves Gas Rate Well A: cumulative gas production and gas rate plotted versus time

13 Foam Injection: Evaluation (Example) Scenario Qg Minimum (e3sm3/d) Pres Abandonment (bara) Gp Ultimate (Msm3) FTHP = 13.3 barg (No Foam) FTHP = 14 barg (Foam) Incremental Reserves: 214 Msm3

14 Conclusions A method is presented for evaluating the benefit of continuous foam injection for deliquification of gas wells The method makes use of IPM software and approximates the impact of foam by switching off water The well IPR is a critical factor for evaluating any lifting method for a well, hence emphasis must be given on its evaluation The results can be used to justify application of continuous foam injection in the field

15 Acknowledgements The presenter would like to thank the ONEGas team for their help during the execution of this study and for their permission to publish this paper, special thanks to Kees Veeken, Subject Matter Expert on GWD for giving this opportunity to Shell Global Solutions to execute this work.

16 Questions? Q & A