Visual simulation shale micro-crack plugging capacity test system and method

Abstract

The invention relates to a visual simulation shale micro-crack plugging capacity test system and a visual simulation shale micro-crack plugging capacity test method. Displacement evaluation experiment is performed on a single or combined micro-crack rock sample by a solution or a drilling fluid which contains the plugging agents with different concentrations and different types at different experiment conditions, such as pressure differences and times, indexes, such as the invasion depth, are compared, the formation conditions of inner mud cakes in drilling are directly described, and microscopic observation and analysis are performed on percolation substances invade into the micro-cracks by utilizing amplification imaging instruments, such as a high-definition microscope, so that the plugging mechanisms and the effects of various drilling fluid plugging agents and drilling fluids are analyzed and researched intuitively and microscopically, a proper drilling fluid plugging agent is selected preferably, a drilling fluid system formula is optimized, the problem about the experimental conditions that the visual simulation evaluation cannot be performed on shale micro-crack plugging in the past is solved, and a new evaluation experimental research means is provided for related research and production in the technical field of fractured shale strata borehole wall stability in petroleum engineering.

Description

technical field [0001] The present invention relates to the field of petroleum exploration and development experimental equipment, more specifically, relates to a visual simulation evaluation device and usage method of shale micro-fracture plugging ability, which can be used in the research of well wall stability technology in petroleum engineering, and can be visualized and simulated to evaluate downhole Plugging ability of drilling fluid plugging agent to shale micro-fractures under static conditions. Background technique [0002] The problem of wellbore stability is a worldwide problem in the process of oil drilling, which seriously affects normal operations and causes a large amount of economic losses every year. Statistics show that more than 90% of wellbore instability problems occur in shale formations, of which Hard and brittle shale formations with micro-fractures account for about two-thirds, and wellbore instability in this formation is a common and difficult prob...

AI Technical Summary

Problems solved by technology

[0005] The 42-type or 71 high-temperature and high-pressure filter loss tester is a high-temperature and high-pressure sand bed water loss tester after filling sand. It uses a certain number and quality of sand instead of filter paper, and evaluates the plugging effect by measuring the filter loss. To a certain extent It can reflect the plugging effect of drilling fluid plugging agent and drilling fluid system formula on sandstone pores, but the simulation of micro-fractures in hard and brittle shale is indirect, and the width of fractures cannot be determined, and human factors are greatly affected, and the repeatability is poor. The evaluation method of measuring the size of filtration loss as a measure is indirect and non-visual and intuitive

[0006] The artificial crack simulation method of splitting rock samples is to use the Brazilian splitting method to make cracks in the formation rocks, and then fix them together with tape and other materials to form artificial rock samples containing cracks; Slits of different sizes are cut to simulate rock cracks, and artificial crack rock samples or simulated crack steel blocks are put into the leak plugging tester for plugging effect evaluation experiments; split rock samples combined with steel block sleeve methods are cylindrical The formation rock sample is split into two pieces, and put into a steel casing larger than its diameter at the same time. There is a crack between the two pieces, and the plugging effect evaluation experiment is directly carried out; the crack width simulated by these three simulation methods is generally more than 100 microns. However, the micro-cracks of hard and brittle shale are less than tens of microns, and the artificial crack simulation method of splitting rock samples cannot determine the crack width. Although the crack simulation method of splitting steel blocks can accurately know the crack width, the crack surface of the steel plate is smooth. It is impossible to simulate the roughness of the real rock fracture surface. The split rock sample combined with the steel block sleeve method can simulate the crack width by subtracting the rock sample diameter from the inner diameter of the steel sleeve. Due to the influence of the regularity of the rock sample, there are errors in the crack width and it is difficult to make The outer wall of the rock sample combined with the inner wall of the steel sleeve, without the protection of the rubber sleeve with confining pressure, the experimental liquid will flow between the inner wall of the steel sleeve and the outer wall of the rock sample during the evaluation test, resulting in errors in the results; the steel sheet is superimposed on the core The simulation method is based on the fact that the fluid flow between fractures can be equivalent to the fluid flow between parallel plates, and the fracture simulation is performed directly by stacking steel sheets or filling sheets. For example, Wang Jianhua et al. ("Petroleum Drilling and Production Technology" 2006.02) introduced three methods of superimposing steel sheets into cores to simulate 1-50μm micro-cracks: No. 1 core is made of steel columns cut into 6 pieces and superimposed to simulate 30-50μm micro-cracks; Core No. 3 is made of 6 steel sheets superimposed and sealed with glue A and B to simulate 10-20μm micro-cracks; Made of 20 layers of paper, simulating 1-10μm micro-cracks

This method can simulate fractures at the micron level, which is closer to the actual shale micro-fractures, but the fracture width is only in a range, which is not conducive to the research of plugging mechanism, the development of plugging agents and the optimization of drilling fluid formulations. Surface roughness, and water absorption changes during the No. 3 core paper clamping experiment

[0007] Although the above methods are all simulations of formation rock fractures, which have a certain guiding effect on improving the plugging capabilities of plugging agents and drilling fluids, the measurement of fluid loss, pressure bearing size or fluid loss rate is used as the plugging effect evaluation index. It is also indirect and non-visual and intuitive, and the repeatability is relatively poor. It is impossible to analyze and study the plugging mechanism of the plugging agent from an intuitive and microscopic point of view, evaluate and optimize the suitable plugging agent and drilling fluid system formula, etc.

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