The Effect of Reservoir Fluid Pressure on Steam Flooding of Heavy Oil Reservoirs

摘要

Steam flooding is a successful technology to developrncertain heavy oil reservoirs. It can also be used in somernconventional oil reservoirs that have been water floodedrnto improve the oil recovery factor. In the operation ofrnsteam flooding, one of the important factors that affect itsrneconomic benefit is the reservoir fluid pressure. Basedrnon the numerical simulation of steam flooding processrnand geomechanical analysis, this paper discusses that itrnis vital to obtain an initially low reservoir fluid pressurernby primary recovery or cyclic steam stimulation and tornmaintain a relatively lower reservoir fluid pressurernduring steam flooding process.rnThree reasons exist. Firstly, it is much easier tornobtain a high steam quality in the bottom injector andrnmake full use of heat (latent) energy in the reservoir.rnSecondly, if the reservoir fluid pressure Is low, therneffective stress in the reservoir becomes higher.rnTherefore, the reservoir rock is more stable, and failurerndoes not occur for certain effective stress range. Thisrnimproves the sweep efficiency of steam flooding andrnserious steam channeling is greatly reduced.rnThirdly, in a sand body with a normal distribution ofrnsand grain sizes, the permeability could go down withrnincreasing deformation. However, if the effective stressrnin the reservoir is maintained at a relatively high value,rndeformation of reservoir rock will be very small becausernof the limited grain dilation. Thus, the variation ofrnpermeability, porosity, and compressibility is not a majorrnconcern. Steam flooding performance can also bernpredicted more accurately.rnSome critical measures must be taken in order tornreach the expected results. Meanwhile, certain field casernhistories can prove this conclusion.