System for determining critical pressure gradient of foams generated at permeability mutation site

Abstract

The invention belongs to the field of air driving exploitation of reservoirs and particularly relates to a system for determining a critical pressure gradient of foams generated at a permeability mutation site. The system comprises a sand filling pipe, a liquid supplying device, an air supplying device, a data collection device and an observation device, wherein the data collection device is connected with the sand filling pipe; the sand filling pipe is provided with an injection end and a flow-out end, two sections of filling mediums with different grain diameters are arranged in the sand filling pipe, the filling mediums with relatively small grain diameters are used for filling close to the injection end to form a front sand filling section, the filling mediums with relatively large grain diameters are used for filling close to the flow-out end to form a rear sand filling section, the sand filling pipe is a transparent tempered glass pipe, and the filling mediums are black glass beads; and the observation device comprises a microscope and a computer, the microscope is arranged opposite to the outer circumferential surface of the sand filling pipe, the computer is connected withthe microscope, and a camera is arranged on the microscope. According to the system, the critical pressure gradient of the foams at the permeability mutation site can be determined, and the foams arearranged in a porous medium environment to be researched, so that the influences caused by the mutation of the permeability in a heterogeneous reservoir to the generation of the foams are truly reflected.

Description

technical field [0001] The invention belongs to the field of oil reservoir air flooding, and in particular relates to a system for measuring the critical pressure gradient of foam formation at a sudden change in permeability. Background technique [0002] Foam fluid has high apparent viscosity and good plugging performance. It can not only be used as plugging agent to increase swept volume and water injection profile, but also can be used as oil displacement agent to improve the oil displacement efficiency of heterogeneous oil layers. In actual mines, the gas and foaming agent system are generally injected into the formation at the same time, and the two are mixed in the formation to form foam and then play a role. There is a minimum pressure gradient in the foam in the porous medium, that is, the critical pressure gradient. When the formation pressure gradient is less than the critical pressure gradient, a weak foam with large bubble size, looseness and high gas velocity i...

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Problems solved by technology

[0004] Aiming at the problem that the existing laboratory foam flooding experiments do not consider the impact of sudden changes in permeability on foam generation, the purpose of the present invention is to provide a system for measuring the critical pressure gradient of foam generation at sudden changes in permeability, considering the impact of sudden changes in permeability on foam generation. The effect of foam formation can measure the critical pressure gradient of foam formation at the sudden change of permeability, and the foam is placed in a porous medium environment to study the real reflection of the impact of sudden change of permeability on foam formation in heterogeneous reservoirs

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