Reservoir Simulation for Unconventional Reservoirs - Advances and Future Challenges

Development of unconventional resources is accelerating, and the technology for the recovery of unconventional gas and oil is rapidly advancing, being in part responsible for continuing low price of the hydrocarbon-based energy. The term “unconventional” can include a variety of resources, such as coalbed methane gas, tight and shale gas, CO2 injection based enhanced recovery, thermal recovery (Cyclic steam stimulation (CSS) and Steam/Solvent Gravity Assisted Drainage (SAGD)), gas from hydrates, in-situ coal gasification, etc. Of these, the main commercial impact for oil production comes from the CSS and SAGD operation, and for gas (and condensate) production from tight, and recently shale, plays. Since shale gas reserves are geographically more pervasive compared to heavy oil and bitumen deposits, this presentation will deal primarily with the unconventional gas resources and the methods for their simulation analysis and recovery optimization. While commercial applications of tight gas date back to 1970’s, continued improvements in exploration/imaging tools, horizontal drilling, and advances in reservoir engineering interpretation techniques in the following decades have made tight gas a significant part of the current North American gas production. Kuuskraa (2006) estimated that in 1994, unconventional gas (including tight gas, CBM and shale gas) already accounted for 40% of US natural gas production. Recently the multi-stage fracturing technology for horizontal wells spurred unprecedented increase of production from shale gas and oil deposits in North America and today the trend is expanding worldwide.