Design and Evaluation of Hydraulic Fracture Stimulation of Gas and Coalbed MethaneReservoirs Under Complex Geology and Stress Conditions

摘要

As exploitation of unconventional resources such as coalbedrnmethane (CBM) reservoirs becomes increasingly essential,rnthere is a growing need to develop hydraulic fracture treatmentrndesign for these reservoirs with complex geology and stressrnconditions. Conventional methodologies have failed to addressrnthe difficulties involved in the design and execution of fracturerntreatments in these complex conditions. These includernunrestricted height growth breaking through the roof and floorrnof the coal seam, massive fluid loss as a consequence of thernhigh leak-off formation and poroelastic effects. This paperrnpresents an integrated approach to optimise hydraulic fracturerntreatments and addresses the associated problems encounteredrnduring the hydraulic fracturing process.rnA 3D poroelastic, finite element based numerical designrntool has been developed to describe the fracture geometry forrngiven reservoir and operating conditions. This is coupled withrna production model appropriately quantifying the post-fracrnproductivity of a CBM reservoir. Finally, cost analysisrncarried out to optimise design parameters against differentrnproduction scenarios using a hybrid genetic-evolutionaryrnoptimisation tool.rnOur study has shown a significant improvementrnunderstanding the fracture containment mechanisms andrnimpact of poroelastic effects in stimulating CBM reservoirs.rnFurthermore, results of this study demonstrate that use of anrnintegrated approach in the design of hydraulic fracturerntreatments results in a higher yield and cost-effectivernexploitation of CBM prospects.