Study Of Percolation Theory And Its Application Under Complicated Condition

Fluid mechanics in porous medium is a basic subject of oil development. In the process of oil development , due to different oil developing methods, flow of formation fluid becomes very complex for low-permeability oilfield . For example, the shape of pressure drop funnel becomes anomalous under intermittent pre-production, and the inner boundary condition under various parameter perforation type shows diversity and uncertainty, and so on. Solution of percolation equation also becomes more difficult when boundary geometry or initial pressure distribution of formation is complex enough. In view of the new problems in well test and pre-production, this thesis focuses on the fluid mechanics of intermittent pre-production (pressure distribution of formation is complex) and casing perforation (boundary condition is complex) at complex flow by integrating theory derivation with test data verification. Main study content and achievement of the thesis is as follows:1. The filtration theory of intermittent production well testingThe filtration theory of complex flow was studied under the condition of intermittent production well testing. The physical model was developed according to the actual producing condition; and the percolation equation solutions were studied systematically and resolved respectively for multiple well types and anisotropic layers. The semi-numerical and semi-analytical expression was obtained, by which, we can deal with very complex mathematics problems due to the initial condition nonlinearity and multi-pulse filtration flow (including the resolution methods, the grid division and numerical methods etc.), providing the theory basis for well testing analysis, design and productivity evaluation of intermittent producing wells. It is the first time that the method and idea ofδfunction was presented to figure out the flow equation and analyze the down-hole pressure. Compared with the field data, it is demonstrated that the method ofδfunction is feasible and effective to resolve the percolation mechanics equation under the condition of intermittent production test.2. Fluid flow mechanics of complex inner boundary condition of perforationThe factors that affect perforation efficiency at steady and transient flow condition are intensively studied, and a series of study methods for fluid percolation theory under complicated perforation is established. It is operated in Shuguang macro computer for 3D pressure distribution, downhole pressure curve, sandface flowrate curve and radial flow initial area, etc under unsteady flow perforation. We first obtain radial flow initial radius by transient flow equation, and analyze downhole pressure of constant flow rate and slug flow production. Therefore, the optimized perforation plan is closer to actual production behavior. Parallel algorithm is first applied in downhole pressure simulation of various perforation types. It is showed by the analysis and comparison with the computational solutions that the ultimate prospective rate of production is achieved in the optimized perforation plan..