Study On Reasonable Injection-Production Technology Policy In Low Permeability Reservoir

The start-up pressure gradient and stress sensitivity generally exist in low permeability reservoirs. The characteristics may cause the problem that it’s so hard for water injection and oil production. In order to improve the effect of loe permeability reservoir water drive development, this paper try to adjust the well spacing and technology policy to enhance oil recovery. So, this thesis chose layer K1g22of Ya er xia cretaceous low permeability reservoir as the research object, then carried out reasonable injection-production technology policy research in low permeability reservoirs by using the method of core mercury injection experiment, reservoir engineering and numerical simulation. The research results can provide reference for the development of low permeability reservoir.Firstly, based on the research of low permeability reservoir non-darcy seepage and stress sensitivity, the well production equation concerned start-up pressure gradient and stress sensitivity was deduced, determined the reservoir stress sensitivity coefficient, and analysed the influence of stress sensitivity coefficient for oil productivity. Combining with core mercury injection experiment data, the reservoir start-up pressure gradient was determined with the mercury injection method. At the same time, this paper expounded low permeability fracture reservoir permeability imbibition experiment law, to guide cyclic water flooding development.Then, in view of the low permeability reservoir is very difficult to establish an effective displacement system, carry out the study of interwell pressure distribution. The displacement pressure gradient is biggest. Near by the injection well and production well, and the displacement pressure gradient between wells is diminishing. The injection energy consumed mainly near by the well. Class Ⅰ reservoir fracturing has little effect on pressure distribution, and class Ⅱ reservoir fracturing has more effect on pressure distribution. Used reservoir engineering method to determine that reasonable well spacing density was27～22wells per square kilometer, and the corresponding well spacing was190～211mters.Next, based on the low permeability reservoir production equation which considered start-up pressure gradient and stress sensitivity factors, then drawn the relationship curve of productivity index and producing pressure drop, and the bottom inflow performance curve respectively. So determined that the reasonable producing pressure drop was5～10MPa, the reasonable well bottom flowing pressure was14-20.6MPa. In view of the well pattern was not perfect, so it’s necessary to improve the well pattern in order to keep formation pressure. For low permeability fracture reservoirs, in order to prevent injection water breakthrough along the fissures, moderate water injection should be adopted. So used the material balance method and determined that the reasonable injection-production ratio was1-1.2.Finally, this paper has carried out the study of reasonable technology policy with numerical simulation software Eclipse, which based on fine geologic modeling after improved well pattern. Mainly included injection-production ratio,oil production rate, and injection time, and cyclic waterflooding reasonable conversion time and reasonable working system. Research shows that it is reasonable to maintain the present formation pressure, injection-production ratio1.0, oil recovery rate2%and single well water injection35m3/d. In order to improve water drive recovery, when the conventional composite water cut of conventional waterflooding reservoir is40%, then turn to cyclic waterflooding and use the short injection working system.