Method and device for making physical fault model and empirically evaluating sealing performance

A method for making a physical fault model and empirically evaluating its sealing performance, comprising the following steps:

• S1 preparing a fault filling zone model using a sample-making mold, comprising the following steps:
• S1.1 collecting a fault zone filler from a fault zone at a site and determining its main physical parameters in a laboratory, comprising moisture content, composition, grain gradation, compactness and density;
• S1.2 taking an appropriate amount of the fault zone filler, measuring its initial mass m0, adding an appropriate amount of water to achieve a plastic state and measuring a mass m1 of the fault zone filler after the addition of water;
• S1.3 recording a mass m2 of the sample-making mold, filling the fault zone filler into the sample-making mold to prepare a fault filling zone model, calculating a corresponding sample volume under a condition that the compactness remains unchanged, based on the compactness and moisture content of the fault zone filler determined in the S1.1 so as to determine a compaction depth h, and recording a total mass m3 of the fault zone filler and the sample-making mold once the compaction depth h is reached;
• and
• S1.4 drying a sample at a low temperature, continuously monitoring the mass of the sample during a drying process, and when the mass drops from m3 to m0±m2, stopping the drying process to complete the fault filling zone model;
• wherein the sample-making mold consists of a sleeve, a bottom cover and a squeeze rod;
• the sleeve is designed to hold the fault zone fillers and comprises two detachably connected sleeve columns;
• the bottom cover is detachably connected to a base of the sleeve;
• the squeeze rod comprises a rod body and a squeeze disc attached to one end of the rod body, with the squeeze disc designed to fit an inner diameter of the sleeve;
• S2 using a permeability test device to test an initial permeability K1 of the fault filling zone model prior to sealing it with a nano-microsphere infused slurry, comprising the following steps:
• S2.1 installing permeability test caps at both the upper and lower ends of the fault filling zone model;
• S2.2 connecting the fault filling zone model with permeability test caps installed to the permeability test device;
• and
• S2.3 maintaining a constant water flow rate during test, recording data once the flow and pressure data at the upper and lower ends of the fault filling zone model are stabilized, and calculating an initial permeability K1 of the fault filling zone model prior to sealing it with a nano-microsphere infused slurry;
• wherein the permeability test device comprises permeability test caps;
• each of the permeability test caps is detachably connected to an upper and lower ends of the sleeve;
• one side of the permeability test cap is provided with a plurality of communicating grooves, with each groove containing a series of water leakage through-holes at intervals;
• wherein both ends of the sleeve, which is filled with the fault filling zone model, are connected to the permeability test caps to form a testing unit;
• one end of the testing unit is connected to a high-pressure constant-speed pump and a water tank through pipelines, while the other end of the testing unit is connected to a liquid collection container through additional pipelines;
• a flow sensor and a pressure sensor are installed on a water inlet pipeline and a water outlet pipeline at the upper and lower ends of the testing unit, respectively, and the flow sensor and the pressure sensor are connected to a screen display device through transmission lines;
• S3 placing the fault filling zone model into reservoir rocks, drilling slurry injection wellbores in the reservoir rocks on both sides of the fault filling zone model, creating a perforation section near a bottom of the slurry injection wellbores directed towards the fault filling zone model, and injecting the nano-microsphere infused slurry into the slurry injection wellbores to perform a sealing experiment utilizing a nano-microsphere slurrying experimental system;
• wherein the nano-microsphere slurrying experimental system comprises a rock bracket, wherein the reservoir rocks are installed in the rock bracket, and water leakage holes are located at four corners and a center of the rock bracket;
• perforations are created at the center of the reservoir rocks for filling the fault filling zone model to simulate a fault core;
• a first monitoring well, with a shallow buried depth, is drilled into the fault core near an edge of the reservoir rocks, and a second monitoring well, also with a shallow buried depth, is drilled within the reservoir rocks;
• the slurry injection wellbores are drilled into the reservoir rocks on both sides of the fault core, and the perforation section is created towards the fault core located near the bottom of the slurry injection wellbores;
• and
• wherein the slurry injection wellbores are connected to a high-pressure constant-speed pump and a nano-microsphere slurry tank via pipelines;
• furthermore, the first monitoring well, the second monitoring well, the water leakage holes at the four corners of the rock bracket, and the water leakage hole at the center of the rock bracket are respectively connected to independent liquid collectors via pipelines;
• S4 extracting the fault filling zone model after a slurrying process in the S3, and repeating S2 comprising S2.1 to S2.3 to measure the permeability K2 of the model after sealing;
• and
• S5 calculating the sealing performance index η of the fault filling zone model using the following equation:
• η
• =
• K
• 1
• -
• K
• 2
• K
• 1
• ×
• 100
• ⁢
• %
• .