Unstable non-Newtonian two-phase fluid displacement simulation method based on pore network model

Abstract

The invention relates to the technical field of oil and gas field development, in particular to an unstable non-Newtonian two-phase fluid displacement simulation method based on a pore network model, which comprises the following steps: 1) acquiring radius distribution of a conical pore throat through a nuclear magnetic resonance experiment and a constant-speed mercury injection experiment; 2) obtaining the length and coordination number of a conical pore throat; 3) establishing a pore network model; and 4) introducing an unsteady-state seepage theory into the pore network model, and meanwhile, researching water-displacing-oil two-phase unsteady-state seepage in the pore type medium according to the process of fluid flow in pores, interface movement and pore pressure diffusion to form a non-Newtonian two-phase fluid displacement simulation method. A dynamic network simulation algorithm and an unsteady-state seepage theory are combined to simulate a non-Newtonian two-phase fluid displacement process. The method can accurately reflect the unstable seepage characteristics of the fluid and pore throat compression coefficient, fluid viscosity and the like which change along with pressure propagation in the process that the non-Newtonian two-phase fluid flows in the porous medium pore throat.

Description

technical field [0001] The invention relates to the technical field of oil and gas field development, in particular to an unsteady non-Newtonian two-phase fluid displacement simulation method based on a pore network model. Background technique [0002] Underground crude oil has large reserves and wide uses. It is the "blood" of modern industry and an indispensable strategic resource for the country's survival and development. How to maximize the underground energy and transform it into the driving force for economic development is particularly important. Fundamentally, it is how to enhance oil recovery. After years of research, the development methods of conventional oil reservoirs have become mature. Most researchers use pore network models that conform to the microstructure characteristics of reservoir rocks for reservoir numerical simulation research, and this type of technology has become increasingly mature, but in In the pore network model, there are relatively few st...

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Problems solved by technology

Compared with Newtonian fluids, non-Newtonian fluids are mostly composed of polymer substances, and polymer substances tend to form various coiled network or chain structures under the action of molecular forces, causing viscosity changes during the flow process. Therefore, The obvious macroscopic difference between Newtonian fluid and non-Newtonian fluid is that the viscosity is different under different shearing effects, so the rheological characteristics of Newtonian fluid and non-Newtonian fluid (the property of fluid flow and deformation when subjected to external force is called rheology) There is a big difference, and the seepage properties shown by the flow inside the porous medium are also very different, and it is difficult to study

[0004] At present, there are many studies on non-Newtonian fluid flow based on lattice Boltzmann method at home and abroad, but there are still few studies on immiscible displacement simulation of two-phase non-Newtonian fluid based on pore network model, and most of them cannot accurately reflect the flow of two-phase fluid in porous media pore throats. In the internal flow process, it is impossible to describe the unsteady seepage characteristics of the fluid and pore throat compressibility coefficients that change with the pressure propagation. The results of this type of numerical simulation are often not very reliable and cannot provide scientific guidance for on-site production

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