Reservoir Engineering Aspects of Horizontal Wellsin Stochastic Naturally Fractured Gas Reservoirs

摘要

This work presents the application of a newly developed gasrnreservoir numerical model for simulating gas flow in naturallyrnfractured reservoirs capable of handling stochastically generatedrnnatural fracture network systems. The motivation for this study isrnbased on the inability of traditional dual-porosity reservoir modelsrnto represent effectively fracture networks, in the form of eitherrnclusters of intersecting fractures or fracture discontinuums. Thernsimulator assumes single-phase, dry-gas flow in a bounded,rnnaturally fractured gas reservoir. The model decouples fluid flowrnin fracture and matrix domains, thus solving a one-dimensionalrnmatrix flow problem to compute the volumetric flow rates fromrnmatrix into fractures and/or wellbore(s). Subsequently, the modelrnuses the recharge fluid rates entering the fractures at the middlernpoint of each fracture segment to compute the pressure and flowrnrate distributions at each node of the system by solving a twodimensionalrnfluid flow problem in the fracture domain. The systemrnof natural fractures is produced using a stochastic fracture-porosityrnmodel which generates fracture network realizations and providesrndata regarding the natural fractures (location, apertures, density,rnclustering, etc.). The gas reservoir simulator is validated, forrnsimplified reservoir problems, against a commercially availablernthree-dimensional, three-phase, black-oil simulator and used tornconduct a preliminary study of the pressure behavior and recoveryrnof natural gas from a tight gas formation in Paludal Sands of thernRulison Field, Piceance Creek Basin in Colorado. Simulationrnresults of a horizontal well in this naturally fractured gas reservoirrnindicate that well location within the flow region, degree of clustering,rnfracture density, fracture aperture distribution, and degree ofrnfracture interconnectedness are very significant factors influencingrngas production rates, gas recovery and reservoir drainage effectiveness.