Research From Low Permeability Reservoir Seepage Mechanism And Reasonable Well Digital Core Technology

With small pore throat, complex pore structure, large flltrational resistance, low permeability reservoir has slower velocity of flow and faster decline of production. The pressure gradient and the flow speed presents non-linear relation when the fluid flow through low permeability porous medium because of the existence of threshold pressure gradient. It is necessary to take the threshold pressure gradient into account when optimize the well spacing and well pattern. Based on the existing research achievements, which is related to the flowing mechanism and the well-spacing optimization of low-permeability reservoir, the micro-characteristics of pore structure, the oil-water flowing performance, the nonlinear flow-phenomenon, the threshold pressure gradient and the reservoir flowing boundary in low permeability reservoir is researched through the core-flooding experiments, digital core methodology, reservoir numerical simulation in this dissertation. It is significant to understand the microscopic flowing mechanism to the low-permeability reservoir, determining the reasonable pressure drawdown of the injection and production as well as well spacing and maximum the recoverable reserves.The following research work is conducted in this thesis:1) Special flowing phenomena and mechanism in the low-permeability reservoir is study based on the core flooding experimental data2) Mechanism of the micro-nonlinear flowing and the start-up pressure gradient is analysis and the scope of application of Darcy-law is discussed3) Digital-core methodology is applied to study the characteristics of the non-linear flowing in low-permeability porous media and mobility expression of start-up pressure gradient are obtained by numerical regression4) Flowing-boundary models of the natural producer and the stimulation producer are derived from the equivalent seepage resistance theory. Take a low-permeability reservoir as an example, the optimized well spacing with maximum controlled reserves and the reasonable pressure drawdown from the economical limitation well-spacing is calculated5) Post-process is programmed to the ECLIPSE simulator based on the flowing boundary theory. The influencing factors of the flowing boundary are quantitatively analysis. Well spacing strategies to maximum reserves control is compared to the low-permeability reservoir.The study shows that,with small pore throat.micro-deformation can reduce the amount of effective flow channel and presents a notable permeability sensitivity in low permeability reservoir. With different fluid and driving pressure, the number and position of participated flow channel are different.So are the tested permeabilities. That’s the main factor that caused non-linear seepage flow phenomenon of low permeability. When optimizing the well spacing and well pattern, it is important to calculate threshold pressure gradient and well flow boundary reasonably.