CN111691871A - Crack propagation monitoring method for hydrofracturing ore rock pretreatment test - Google Patents

Abstract

The invention relates to a method for monitoring crack propagation in a water fracturing ore-rock pretreatment test, comprising the following steps: 1. using a geological drilling rig to drill fracturing holes and 6 to 8 observation holes; 2. in each observation hole Install signal exciter, water level monitor and microseismic detector in sequence from bottom to top in the hole; 3. Carry out the test and data acquisition; 4. Compare the longitudinal wave velocity of the rock mass in the test area before and after fracturing to evaluate the fracturing effect. The microseismic signal data in the geophone is inverted to locate the source to determine the extension position of the hydraulic fracture. The advantages of the invention are: 1) intuitively and effectively determine the expansion range of the fracture; 2) avoid the interference of the underground production on the monitoring system; 3) lay the foundation for the expansion and application of the hydraulic fracturing technology to the mining industry.

Description

A fracture propagation monitoring method for hydraulic fracturing ore-rock pretreatment test

technical field

The invention belongs to the technical field of hydraulic fracturing, and in particular relates to a crack propagation monitoring method suitable for a hydraulic fracturing ore-rock pretreatment test for metal mine mining.

Background technique

Hydraulic fracturing technology is a reservoir stimulation technology widely used in the field of oil and gas development, and has been popularized and applied in the fields of coal mine pressure relief and permeability enhancement, deep in-situ stress measurement and other fields. Every other section is used as a fracturing section, and by injecting high-pressure fluid into the fracturing section, the rock on the pore wall is broken and the cracks expand outward to form a fracture network. For mines mined by natural caving method, hydraulic fracturing technology as a ore pretreatment technology is of great significance to improve ore rock cavability and reduce the bulk rate.

The expansion range of hydraulic fractures in the process of hydraulic fracturing determines the layout and spacing of drilling engineering for hydraulic fracturing ore-rock pretreatment, and the layout and spacing of drilling engineering are directly related to the distribution of mined ore bulk and mining costs. . Before the engineering application of hydraulic fracturing ore and rock pretreatment, it is of great significance to carry out corresponding industrial test research and obtain the fracture expansion range under different fracturing conditions, which is of great significance for guiding the selection of engineering application equipment and engineering layout. The existing hydraulic fracture propagation monitoring methods are mainly based on microseismic monitoring, and a single method brings uncertainty in the assessment of the hydraulic fracture propagation range. The monitoring of hydraulic fracture propagation and the evaluation of fracturing effect are carried out jointly by two or more means, which lays a solid foundation for the effectiveness of hydraulic fracturing ore-rock pretreatment tests.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a crack propagation monitoring method for hydraulic fracturing ore rock test, lay a foundation for the expansion and application of hydraulic fracturing technology to the mining industry, and provide reference for mining technicians to carry out similar research.

The purpose of this invention is to realize through following technical scheme:

A method for monitoring crack propagation in a hydraulic fracturing ore-rock pretreatment test of the present invention is characterized in that the method specifically includes the following steps:

Step 1. Drilling the fracturing borehole and the observation borehole

Use a geological drilling rig to drill a fracturing hole in the roadway with a depth of 100 m-200 m. Arrange and drill several observation holes around the fracturing hole. The depth of the observation hole is 1.2% of the depth of the fracturing hole. ~1.5 times;

Step 2. Arrange a packer group consisting of an upper packer and a lower packer, a sealing water injection pipeline and a fracturing water injection pipeline in the fracturing borehole;

Step 3. Install monitoring equipment

First, install the signal exciter at a distance of 2 m-4m from the bottom of the hole in the observation hole, then lower the water level monitor to 2 m-4m above the signal exciter, and then inject water into the observation hole to make the liquid level higher than the water level monitor Then install the microseismic detector at a distance of 10m-20m from the orifice of the observation borehole, and finally lead the data transmission cables of the signal exciter, water level monitor and microseismic detector out of the observation borehole and connect to the data of the monitoring station collection and processing system;

Step 4. Hydraulic fracturing rock pretreatment test and data acquisition and processing

First, water is injected into the packer group through the sealing water injection pipeline, and the pressure fluid is injected into the packer group through the water injection pipeline joint and the control connection device, so that the upper and lower packers are inflated and abutted on the inner wall of the fracturing hole at the same time. The upper and lower isolation sections form a closed fracturing test section between the upper and lower isolation sections; then water is injected into the fracturing test section through the fracturing water injection pipeline, and the fracturing test section side wall of the fracturing hole is exposed to high pressure water. Under the action of the fracturing test section, cracks are gradually generated, and the cracks gradually expand to form cracks and gradually expand to the periphery of the fracturing test section. the digital signal;

Step 5. Determine the test result, which is performed synchronously with step 4.

Step 5.1. Evaluate the effect of hydraulic fracturing

The hydraulic fracturing effect is evaluated by comparing the longitudinal wave velocity of the rock mass in the test area before and after fracturing. When the integrity index is between 1 and 0.90, the fracturing effect is extremely poor, and when it is between 0.89 and 0.70, the fracturing effect is poor. When it is between 0.69 and 0.50, the fracturing effect is average, when it is between 0.49 and 0.30, the fracturing effect is better, and when it is between 0.29 and 0.01, the fracturing effect is good;

Step 5.2. Determine the expansion range of hydraulic fractures

By preprocessing the microseismic data obtained by the microseismic geophones in several observation boreholes, such as screening and time-of-arrival calibration, the nonlinear equation of seismic wave travel time is linearized by the linearized seismic positioning method, and the magnitude of the microseismic event is obtained. According to the source parameters, microseismic location is carried out, and the expansion range of hydraulic fractures at different times is obtained.

Several observation drilling holes described in step 1 are 6-8 observation drilling holes;

The specific steps in the step 4 are as follows:

Step 4.1. When cracks are formed and expanded, microseismic signals are generated by the fractures inside the ore rock, and the microseismic geophones identify and collect the microseismic signals transmitted to the microseismic geophones through the rock mass;

Step 4.2. When the crack spreads to or penetrates the observation hole, the high pressure water enters the observation hole, and the water level monitor sends a signal; at the same time, the signal generated by the signal exciter is also picked up by the microseismic detector;

In step 4.3, the digital signals of the water level monitor and the microseismic detector are input into the data acquisition and processing system through the data transmission cable for further processing.

Compared with the prior art, the advantages of the present invention are:

(1) Visually and effectively determine the expansion range of fractures during the hydraulic fracturing rock test;

(2) Effectively avoid the interference of the underground production operation of the mine to the monitoring system;

(3) Conduct an overall assessment of the effect of hydraulic fracturing of ore and rocks, lay a foundation for the expansion and application of hydraulic fracturing technology to the mining industry, and provide a reference for mining technicians to carry out similar research.

Description of drawings

FIG. 1 is a schematic diagram of the plane layout of the fracturing borehole and the observation borehole of the present invention.

FIG. 2 is a schematic diagram of the installation arrangement and connection of the monitoring equipment of the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

Figure 1 shows a schematic diagram of the plane layout of the fracturing hole 1 and the observation hole 2, and Figure 2 shows a schematic diagram of the installation and connection of the monitoring equipment.

As shown in Figures 1 and 2, a hydraulic fracturing ore-rock pretreatment test study was carried out in an open-pit converted underground iron mine in Anshan. During the test, the fracture propagation monitoring method of the present invention was used to monitor the fracture propagation.

A method for monitoring crack propagation in a hydraulic fracturing ore-rock pretreatment test of the present invention is characterized in that the method specifically includes the following steps:

Step 1. Drill Frac Hole 1 and Observation Hole 2

The fracturing hole 1 was drilled in the roadway with a geological drilling rig, and six observation holes 2 were drilled around the fracturing hole 1. The depth of the fracturing hole 1 was 100 m, and the depth of the observation hole 2 was 120 m. m, the horizontal distances between fracturing borehole 1 and observation borehole 2 are 15 m and 30 m, respectively;

Step 2, arranging a packer group consisting of an upper packer 8 and a lower packer 9, a sealing water injection pipeline and a fracturing water injection pipeline in the fracturing borehole;

Step 3. Install monitoring equipment

First, install the signal exciter 3 at a distance of 2 m from the bottom of the hole in the observation hole, and tightly couple the signal exciter 3 with the wall of the observation hole 2 through cement; then lower the water level monitor 4 to the top of the signal exciter 3 At m, inject water into the observation hole 2 to make the liquid level higher than the water level monitor 4, and then install the microseismic detector 5 at a distance of 20 m from the orifice of the observation hole 2. The hole wall of hole 2 is tightly coupled; finally, the data transmission cable 7 of the signal exciter 3, the water level monitor 4 and the microseismic detector 5 is led out of the observation hole 2 and connected to the data acquisition and processing system 6 of the monitoring station.

Step 4. Hydraulic fracturing rock pretreatment test and data acquisition and processing

Firstly, water is injected into the packer group through the sealing water injection pipeline, so that the upper packer 9 and the lower packer 9 are inflated and abutted on the inner wall of the fracturing borehole 1 at the same time to form the upper and lower sealing sections. A closed fracturing test section is formed between the compartments; then water is injected into the fracturing test section through the fracturing water injection pipeline, and the fracturing test section side wall of fracturing hole 1 is gradually cracked under the action of high-pressure water, and the cracks gradually expand. Form cracks and gradually expand to the distance around the fracturing test section side wall; at the same time, the data acquisition and processing system 6 displays and records the digital signal of the water level monitor 4 and the digital signal of the microseismic detector 5 in the observation hole 2 in real time;

Step 5. Determine the test result, which is performed synchronously with step 4.

Step 5.1. Evaluate the effect of hydraulic fracturing

The signal is generated by the signal exciter 3 at the bottom of the observation hole 2, and the rock mass around the observation hole 2 propagates to the orifice and is received by the microseismic detector 5. From this, the wave velocity of the longitudinal wave propagation of the rock mass is calculated. After fracturing The ratio of the longitudinal wave velocity of the rock mass to the test area before fracturing is used as the rock mass integrity index to evaluate the effect of hydraulic fracturing. The fracturing effect is poor, when it is between 0.69 and 0.50, the fracturing effect is average, when it is between 0.49 and 0.30, the fracturing effect is good, and when it is between 0.29 and 0.01, the fracturing effect is good;

Step 5.2. Determine the expansion range of hydraulic fractures

By preprocessing the microseismic data obtained by the microseismic detector 5 in the six observation boreholes 2, and preprocessing the arrival time calibration, the nonlinear equation of the seismic wave travel time is linearized by the linearized seismic positioning method, and the microseismic wave is obtained. According to the source parameters of the event, the microseismic location was performed to obtain the expansion range of hydraulic fractures at different times; after the microseismic location analysis at the later stage of the test, it was determined that the final expansion radius of the fracture was about 25 m. At the same time, by observing the data of the water level monitor 4, it can be determined whether the hydraulic fracture reaches or penetrates the position where the observation borehole 2 is located.

The specific steps that the data acquisition and processing system displays and records in real time in the step 4 are as follows:

Step 4.1. When the cracks form and expand, the fractures inside the ore rock generate microseismic signals, and the microseismic detector 5 identifies and collects the microseismic signals transmitted through the rock mass;

Step 4.2. When the crack spreads to or penetrates the observation hole 2, which is 15 m away from the fracturing hole 1, high-pressure water enters the observation hole 2, the water level rises, and the water pressure value increases, and the water level monitor 4 sends a signal. It can be judged that the hydraulic fractures generated in the hydraulic fracturing ore-rock test have expanded over 15 m, and the signals generated by the signal exciter 3 are also picked up by the microseismic detector 5;

Step 4.3: The digital signals of the water level monitor 4 and the microseismic detector 5 are input to the data acquisition and processing system 6 through the data transmission cable 7 for further processing.

Based on the hydraulic fracture propagation monitoring method in the pretreatment process of hydraulic fracturing ore rock proposed by the present invention, intuitive and effective monitoring of ore rock fractures caused by hydraulic fracturing can be realized.

Claims (3)

1. a crack propagation monitoring method of hydraulic fracturing ore-rock pretreatment test, is characterized in that, this method specifically comprises the following steps: Step 1. Drilling the fracturing borehole and the observation borehole Use a geological drilling rig to drill a fracturing hole in the roadway with a depth of 100m-200m. Arrange and drill several observation holes around the fracturing hole. The depth of the observation hole is 1.2 to 1.5 of the depth of the fracturing hole. times; Step 2. Arrange a packer group consisting of an upper packer and a lower packer, a sealing water injection pipeline and a fracturing water injection pipeline in the fracturing borehole; Step 3. Install monitoring equipment First, install the signal exciter at a distance of 2 m-4m from the bottom of the hole in the observation hole, then lower the water level monitor to 2 m-4m above the signal exciter, and then inject water into the observation hole to make the liquid level higher than the water level monitor Then install the microseismic detector at a distance of 10-20 m from the orifice of the observation borehole, and finally lead the data transmission cable of the signal exciter, water level monitor and microseismic detector out of the observation borehole, and access the data of the monitoring station collection and processing system; Step 4. Hydraulic fracturing rock pretreatment test and data acquisition and processing First, water is injected into the packer group through the sealing water injection pipeline, and the pressure fluid is injected into the packer group through the water injection pipeline joint and the control connection device, so that the upper and lower packers are inflated and abutted on the inner wall of the fracturing hole at the same time. The upper and lower isolation sections form a closed fracturing test section between the upper and lower isolation sections; then water is injected into the fracturing test section through the fracturing water injection pipeline, and the fracturing test section side wall of the fracturing hole is exposed to high pressure water. Under the action of the fracturing test section, cracks are gradually generated, and the cracks gradually expand to form cracks and gradually expand to the periphery of the fracturing test section. the digital signal; Step 5. Determine the test result, which is performed synchronously with step 4. Step 5.1. Evaluate the effect of hydraulic fracturing The hydraulic fracturing effect is evaluated by comparing the longitudinal wave velocity of the rock mass in the test area before and after fracturing. When the integrity index is between 1 and 0.90, the fracturing effect is extremely poor, and when it is between 0.89 and 0.70, the fracturing effect is poor. When it is between 0.69 and 0.50, the fracturing effect is average, when it is between 0.49 and 0.30, the fracturing effect is better, and when it is between 0.29 and 0.01, the fracturing effect is good; Step 5.2. Determine the expansion range of hydraulic fractures By preprocessing the microseismic data obtained by the microseismic geophones in several observation boreholes, such as screening and time-of-arrival calibration, the nonlinear equation of seismic wave travel time is linearized by the linearized seismic positioning method, and the magnitude of the microseismic event is obtained. According to the source parameters, microseismic location is carried out, and the expansion range of hydraulic fractures at different times is obtained. 2 . The method for monitoring crack propagation of a hydraulic fracturing ore-rock pretreatment test according to claim 1 , wherein the several observation drilling holes described in step 1 are 6-8 observation drilling holes. 3 . . 3. the method for monitoring crack propagation of a kind of hydraulic fracturing ore rock pretreatment test according to claim 1, is characterized in that, in described step 4, the concrete steps that data acquisition and processing system displays and records in real time are as follows: Step 4.1. When cracks are formed and expanded, microseismic signals are generated by the fractures inside the ore rock, and the microseismic geophones identify and collect the microseismic signals transmitted to the microseismic geophones through the rock mass; Step 4.2. When the crack spreads to or penetrates the observation hole, the high pressure water enters the observation hole, and the water level monitor sends a signal; at the same time, the signal generated by the signal exciter is also picked up by the microseismic detector; In step 4.3, the digital signals of the water level monitor and the microseismic detector are input into the data acquisition and processing system through the data transmission cable for further processing.

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