Research On Variation Mechanism Of Reservoir Parameter Under The Condition Of Layered Water Injection And Dynamic Allocation Method Of Injection Allocation Parameters

During the process of reservoir water flooding development, because of the input well was continuously flooded and flushed, the physical property parameters of reservoir in different development phase have significant change. Interlayer interference would be happened in which layers interact longitudinal during layered water injection, obviously in mid-low permeability layers, and this problem could affect the design of development program and the project of injection allocation in late stage of water flooding development. In the past, the variation model of reservoir parameter was not considered the concept of time, so the variation law of reservoir parameter during a period of time could not be predicted and also could not be considered interlayer interference which caused by parameter variation meanwhile interlayer inference was increased and injection flow rate changed by this variation, so the designed layered water injection rate could not be satisfied actual requirement of water injection development, rational layered injection rate also could not be predicted precisely, development effect of injection well and oil recovery factor were affectedIn this paper, considering the cubic strain caused by deformation of rock skeleton as the couple parameter characterizing time variable to be called in as the pattern variation, the model of reservoir physical property parameters which considered variation of time and space was established. According to this model, variation law of porosity and permeability could be predicted and interlayer interference law of layered water injection was analyzed, the rate of layered injection allocation was calculated and time of injection allocation was predicted and program of layered water injection allocation was optimized by utilizing the method of BP neural network, The main research and achievements in this paper were finished as follows:(1) The affects of injected water on reservoir physical parameters were analyzed:The affect of injected water on reservoir porosity could be reflected in mechanical transportation and vergent action of clay mineral and other articles which could increase radius of pore throat, flowability and reservoir porosity also increased in development of water injection; To mid-high permeability layer, the affect of injected water could made reservoir permeability decreased at first stage and subsequently increased; After water injection, affected by injecting water, the contradiction of fluid properties between interlayer or in layer was prominent, which made distribution of fluid properties in space were inhomogeneous and viscosity was increased in water flood development.(2) Considered affect of rock deformation on variation of reservoir porosity with water injection reservoir. The dynamic model of reservoir physical parameters including porosity and permeability which considered rock volume strain as variable was established. With rock volume strain as coupling variable, solid deformation mathematical model and reservoir fluid-solid coupling permeability model were established; Through the finite difference method and finite element method, the reservoir fluid-solid coupling permeability model was solved, and reservoir pore pressure distribution and saturation distribution under different time and different space was got, and the corresponding rock volume strain value was also got. So physical parameters value caused by volume strain under different time through the reservoir physical property parameter dynamic model could be got..(3) Analyzed affects of individual water injection rate with BP neural network method in layered water injection, a new individual water injection rate calculation method was established. And the mutual affect among reservoir permeability coefficient, transformation analysis, effective thickness, oil saturation and porosity, and other important factors were analyzed with the new method. So variation law of layered water injection allocation parameters which considered changing parameters was got.(4) A new optimization allocation program of layered water injection rate was established. Using this new program, optimized the layered injection rate, predicted injection adjusted time. Layered water injection parameters optimization allocation software was work out. According to the proposed water injection allocation optimization program, water injection rate was optimized. Using this software in a particular injection, the calculated result compared with actual injection was accurately. Also water injection allocation program could be optimized and corresponding water injection allocation program could be worked out using with this software.Finally through the study of this thesis, the variation mechanism of reservoir parameters after water injection could be identified, and the dynamic model of reservoir physical parameters was established, dynamic allocation method of layered injection was proposed which have theoretical significance for delicate layered injection allocation to realize the integration of design, regulation and tracking.