True triaxial sand fracturing test machine and its test method

Abstract

The invention relates to a true triaxial sand fracturing testing machine, which comprises a confining pressure system and an injecting system, wherein the injecting system comprises a first fracturing fluid container, a second fracturing fluid container and a piston container; two piston sheet baffle plates are arranged in the piston container. A true triaxial sand fracturing testing method comprises the following steps that stirring is performed in the second fracturing fluid container to form sand-carrying fracturing fluid; prepositive fracturing fluid is injected into the first fracturing fluid container; the prepositive fracturing fluid and the sand-carrying fracturing fluid are respectively injected into a middle cavity and an upper cavity of the piston container by pressure; through a first constant-pressure constant-speed plunger pump and / or a second constant-pressure constant-speed plunger pump, water is discharged into a lower cavity of the piston container; the prepositive fracturing fluid, the sand-carrying fracturing fluid and displacement fracturing fluid sequentially enter a downhole core for fracturing; after the fracturing is finished, the downhole core is taken out; the crack expanding condition is observed. The technical scheme is simple and is easy to understand; the operation is convenient and fast; the unified control on the confining pressure system and the injecting system can be realized; the fracturing fluid replacement is convenient.

Description

technical field [0001] The invention belongs to the technical field of oil and gas reservoir development, and in particular relates to a true triaxial sanding fracturing test machine and a test method thereof. Background technique [0002] During the development of oil and gas reservoirs, due to the low-permeability geological characteristics of the reservoirs, the migration of oil and gas is hindered. At this time, sand fracturing has become an important means for the efficient development of such reservoirs. Sand fracturing can form a complex large-scale fracture network with high conductivity, thereby increasing the drainage area of ​​oil and gas and reducing the flow resistance of oil and gas in the reservoir. Therefore, indoor physical simulation experiments are carried out to study the initiation and expansion of fractures. Behavior is very important. The fracturing site often adopts sand fracturing method, calculates the volume of fracturing fluid required according ...

AI Technical Summary

Problems solved by technology

The existing technology of indoor test true triaxial experimental device is mainly composed of true triaxial experimental frame, triaxial hydraulic pressure stabilizer, oil-water separator, MTS booster and controller, data acquisition and processing system, etc. Only single-acting fracturing fluid can be injected into the rock, which cannot truly simulate the on-site fracturing process, and there are deficiencies in pressurization stability, experimental efficiency, operability, safety and maintenance, etc.

On the one hand, the triaxial confining pressure device for simulating the stress state of the formation rock and the injection device for simulating the fracturing process are controlled by two independent systems, which cannot be coordinated and controlled on the same platform. , the lack of unified monitoring measures, which not only increases the operating procedures, affects the efficiency of the experiment, but also brings certain safety hazards; on the other hand, the hydraulic pressure source with triaxial confining pressure is pressurized in the form of a plunger pump During the operation, the pressurization rate cannot be effectively controlled, resulting in excessive triaxial pressure difference of the rock mass, causing crushing and deformation, and affecting the experimental results; in addition, the disassembly and assembly of the oil-water separator is not easy to operate, and there are certain difficulties in replacing the fracturing fluid

[0003] With the continuous deepening of the scope of oil and gas reservoir research, the existing equipment can no longer meet the requirements of the experiment, and the role of fracturing fluid is single, which does not match the real process on site

There are many control lines and high-pressure pipelines connected between fracturing equipment, which bring certain safety hazards and are not easy to maintain

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