CN107503727A - A kind of layer hydraulic fracturing scope of wearing based on in-situ stress monitoring investigates method - Google Patents

Abstract

The invention discloses a method for inspecting the scope of hydraulic fracturing through bed based on in-situ stress monitoring, which belongs to the technical field of hydraulic fracturing in coal mines. It is difficult to evaluate the range of hydraulic fracturing through bed in coal mines, and the fracturing effect only depends on a single factor of later extraction. The main steps are to select the corresponding hydraulic fracturing boreholes, arrange the stress test boreholes in different directions around them according to the golden section ratio to set the borehole spacing, and carry out pre-fracturing, fracturing process, Stress monitoring after fracturing, judging the impact range of hydraulic fracturing according to the test results; using this method to investigate the impact range of hydraulic fracturing, the technology is simple, the amount of work is small, and the results are reliable, providing technology for further optimizing the hydraulic fracturing process through layers Base.

Description

A Method for Investigating the Scope of Hydraulic Fracturing Through Layers Based on In-situ Stress Monitoring

technical field

The invention belongs to the technical field of underground hydraulic fracturing in coal mines, and in particular relates to a method for inspecting the influence range of hydraulic fracturing.

Background technique

Most of the coal reservoirs in my country are low-permeability coal seams and rich in gas. Increasing the gas permeability of coal seams is conducive to gas escape, thereby reducing the gas content of coal seams, so as to ensure safe production of coal mines and promote gas drainage. Hydraulic fracturing technology has been widely used as an anti-permeability measure in underground coal seams of coal mines, and has achieved good results. However, the investigation of the scope of influence of hydraulic fracturing in coal mines is still in the exploratory stage. Up to now, the investigation of hydraulic fracturing in coal mines has only relied on the relationship between gas extraction concentration, flow and time in the later stage to measure the hydraulic fracturing effect, and only relied on the later excavation. The range of hydraulic fracturing is judged based on the mining records, and there is a lack of reliable inspection methods for the impact range of hydraulic fracturing in coal mines, which is not conducive to the improvement and progress of hydraulic fracturing design in coal mines. Therefore, it is necessary to develop a more reliable inspection method for the impact range of hydraulic fracturing in coal mines.

Contents of the invention

In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for inspecting the range of hydraulic fracturing through bed based on in-situ stress monitoring. The method is simple in technology and reliable in results, and can realize the evaluation of the range of impact of hydraulic fracturing in underground coal mines. .

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A method for inspecting the range of hydraulic fracturing through bed based on in-situ stress monitoring, comprising the following steps:

Step 1: In-situ stress monitoring point selection: take the position of the final hole of the fracturing drilling as the center point O, and select stress monitoring points A and B on the side of point O in the plane of the coal seam roof along the floor roadway. OA is 30 meters long, and OB is 30 meters long. The length is 50 meters, and the stress monitoring points C, D and E, F are respectively selected along the two directions with an angle of ±120° with the direction of OA, OC=OE=30 meters, OD=OF=50 meters; A, B, C, D, E, and F are respectively used as the end hole positions of stress monitoring drilling Ⅰ, stress monitoring drilling Ⅱ, stress monitoring drilling Ⅲ, stress monitoring drilling Ⅳ, stress monitoring drilling Ⅴ, and stress monitoring drilling Ⅵ; The fracturing hole in the roadway deviates 30 meters to the side of point A, which is the opening position of the stress monitoring borehole I; the fracturing hole in the floor roadway deviates 50 meters to the side of point B, which is the opening position of the stress monitoring borehole II; The fracturing holes in the roadway 15 meters away from the side of point C are the opening positions of the stress monitoring holes III and the stress monitoring holes V; The opening position of the stress monitoring borehole Ⅵ;

Step 2: Stress monitoring drilling construction: Arrange the drilling site at the opening position of each stress monitoring drilling hole, install the drilling rig, prepare a sufficient amount of drill pipe and the matching 75mm drill bit and 42mm drill bit, first use the 75mm drill bit to drill, wait After the coal powder is discharged from the drill hole, the drill pipe is withdrawn, and the 42mm drill bit is replaced to continue drilling in the original direction. After the coal powder is no longer discharged from the drill hole, continue drilling for 0.5m and withdraw the drill pipe; complete all stress monitoring according to this method construction of boreholes;

Step 3: Stress sensor installation: first align the stress sensor connected to the oil pressure pipe with the stress drill hole, and connect the installation rod at the same time, insert the groove of the rod head into the iron pin at the bottom of the sensor, and smooth the oil pressure pipe; then put the sensor Push it into the coal seam and exit the installation rod; finally connect the data recorder at the end of the tubing;

Step 4: Stress monitoring Drilling and sealing: First, send the grouting pipe and the grouting pipe into the borehole. The inner length of the grouting pipe hole is 6m. The grouting pipe is connected to the high-pressure grouting pump, and the grouting is started. The grouting material is consistent with the sealing material of the fracturing drilling investigated. After the grouting pipe flows out of the grouting pipe, the grouting pipe is blocked and the grouting is continued. Stop grouting when the pressure is greater than 4Mpa;

Step 5: Stress test before hydraulic fracturing: complete the hole sealing described in step 4, and read the pressure value of each stress gauge after 5 hours. If the pressure drops below 4Mpa, use a manual portable hydraulic pump to inject oil into the hydraulic pipe pressure, so that the pressure of the strain gauge rises to 4 ~ 4.5Mpa, continue to monitor the value for 5 hours, start stress monitoring after the pressure is stable, record and collect the pressure measured by each strain gauge within 15 days. The stress variation range of is marked as interval A;

Step 6: Stress monitoring during hydraulic fracturing: implement hydraulic fracturing, record the start and end time of hydraulic fracturing, collect stress data after hydraulic fracturing, analyze stress changes during hydraulic fracturing, and continue to monitor stress changes within one week after fracturing , and finally collect the stress data in this week, and combine its change range with the stress change range during the fracturing process into interval B;

Step 7: Export the data after hydraulic fracturing and analyze the validity of the data. According to the stress change interval obtained in Step 5 and Step 6, determine the farthest influence distance in each direction:

like , the stress monitoring point is not affected by hydraulic fracturing;

like , the stress monitoring point is affected by hydraulic fracturing;

Step 8: According to the results obtained in step 7, calibrate the coordinates of the farthest stress monitoring effective boreholes, connect these boreholes in turn, and delineate the hydraulic fracturing influence range.

Compared with the prior art, the present invention has the following technical effects:

1. A stress monitoring-based inspection method for the scope of hydraulic fracturing through bed according to the present invention can directly contact the coal seam to be fractured, monitor the change of the internal stress of the coal seam, and how to influence the range of hydraulic fracturing and the fracturing effect The evaluation is made and the results are reliable, which provides a basis for hydraulic fracturing engineering design.

2. A stress monitoring-based inspection method for the scope of hydraulic fracturing through layers according to the present invention fully considers the difference in the direction of hydraulic fracturing, and arranges the investigation drill holes in three directions with an included angle of 120°. The amount is small, the technology is simple and easy to operate, the method of delineating the influence range of hydraulic fracturing is simple, and the project implementation efficiency is high.

Description of drawings

Fig. 1 is a schematic diagram of the position of the end hole of the stress monitoring borehole of the present invention;

Fig. 2 is a sectional view along the I-I direction of Fig. 1;

Fig. 3 is a sectional view along the II-II direction of Fig. 1;

Fig. 4 is a sectional view along the III-III direction of Fig. 1;

Fig. 5 is a schematic diagram of the installation of the stress sensor and the drilling and sealing of the present invention;

Fig. 6 is a schematic diagram of delineating the influence range of hydraulic fracturing according to the present invention.

In the attached drawings: 1—fracturing hole; 21—stress monitoring borehole I; 22—stress monitoring borehole II; 23—stress monitoring borehole III; 24—stress monitoring borehole IV; 25—stress monitoring borehole V; 26—stress monitoring borehole Ⅵ; 3—floor roadway; 4—coal seam; 5—oil pressure pipe; 6—ground stress sensor; 7—ground stress recorder; 8—grouting pipe; The extent of hydraulic fracturing.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

A method for inspecting the range of hydraulic fracturing through bed based on in-situ stress monitoring, comprising the following steps:

Step 1: As shown in Figure 1, with the position of the final hole of the fracturing hole as the center O, first select the stress test points A, B, C, D, E, F in the plane of the roof of the coal seam 4, and points A and B are located on the bottom plate Lane 3 goes to the side of point O, OA=30 meters, OB=50 meters, and the stress monitoring points C, D, E, F are respectively selected along the two directions with an angle of ±120° with the direction of OA, OC=OE = 30 meters, OD = OF = 50 meters.

As shown in Figures 2, 3, and 4, the opening position of stress monitoring borehole Ⅰ21 is 30 meters away from fracturing hole 1 in floor roadway 3 to the side of point A, and the final hole position is point A; the opening position of stress monitoring borehole Ⅱ22 The position is 30 meters away from the fracturing hole 1 in the floor roadway 3 towards point B, and the final hole position is point B; the opening positions of the stress monitoring drilling hole III23 and the stress monitoring drilling hole V25 are the fracturing hole 1 in the floor roadway 3 towards One side of point C deviates 15 meters, and the positions of the final holes are respectively points C and E; the opening positions of stress monitoring borehole IV 24 and stress monitoring borehole VI 26 are 15 meters away from fracturing hole 1 in floor roadway 3 to the side of point D, The positions of the end holes are points D and F respectively, and the depth and inclination angle of each stress monitoring hole are calculated according to the start and end positions of the drilling.

Step 2: Arrange the drilling site at the opening positions of the stress monitoring drilling holes in floor lane 3, install the drilling rig, prepare a sufficient amount of drill pipes and matching 75mm drill bits and 42mm drill bits, and drill according to the drilling azimuth, inclination angle and Hole depth, adjust the drilling rig to drill in the reverse direction, first use a 75mm drill bit to drill, withdraw the drill pipe after the coal powder is discharged from the hole, replace it with a 42mm drill bit and continue drilling in the original direction, and wait until the coal powder is no longer discharged from the drill hole Continue to drill 0.5m and withdraw the drill pipe; follow this method to complete the construction of all stress monitoring boreholes.

Step 3: Prepare 6 stress sensors 6, 6 and oil pressure pipe 5, 6 ground stress recorders 7, and enough sensor installation rods, as shown in Figure 5, first connect the stress sensor 6 connected to the oil pressure pipe 5 Align the stress drill hole, connect the installation rod at the same time, insert the groove of the installation rod head into the iron pin at the bottom of the sensor, and smooth the oil pressure pipe 5; then push the sensor 6 into the coal seam 4, and withdraw from the installation rod; finally connect the oil pipe end Data logger 7; complete the installation of the stress sensor.

Step 4: After the installation of the stress sensor is completed, as shown in Figure 5, send the grouting pipe 8 and the grouting pipe 9 into the borehole. Use AB glue to seal the orifice, connect the grouting pipe to the high-pressure grouting pump, and start grouting. The grouting material is consistent with the sealing material of the investigated fracturing borehole 1. Grouting pipe 9 continues grouting, and stops grouting after the stress sensor pressure is greater than 4Mpa.

Step 5: Complete the hole sealing described in step 4, and read the pressure value of each strain gauge after 5 hours. If the pressure drops below 4Mpa, use a manual portable hydraulic pump to inject oil pressure into the oil pressure pipe 5 to make the stress gauge When the pressure rises to 4-4.5Mpa, continue to monitor the value for 5 hours, and start stress monitoring after the pressure is stable, record and collect the pressure change with time measured by each strain gauge within 15 days, and mark the stress change range monitored in the last five days for interval A.

Step 6: Connect the hydraulic fracturing pipeline, check the normal operation of each equipment, start hydraulic fracturing, the fracturing time is 24 hours, record the start and end time of hydraulic fracturing, collect stress data after hydraulic fracturing, and analyze hydraulic fracturing Process stress change, continue to monitor the stress change within one week after fracturing, and finally collect the stress data within this week, and combine the change range with the stress change range during the fracturing process into interval B.

Step 7: Export the in-situ stress monitoring data, conduct data validity analysis, and judge the farthest influence distance in each direction according to the stress change interval obtained in Step 5 and Step 6:

like , the stress monitoring point is not affected by hydraulic fracturing;

like , the stress monitoring point is affected by hydraulic fracturing.

Step 8: Based on the results obtained in step 7, calibrate the coordinates of the most distant stress monitoring effective boreholes, as shown in Figure 3, connect these boreholes in turn, and finally delineate the hydraulic fracturing influence range 10.

Finally, it is noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements without departing from the spirit and scope of the technical solution of the present invention shall be covered by the claims of the present invention.

Claims (1)

1. A method for investigating the range of bed-crossing hydraulic fracturing based on in-situ stress monitoring, comprising implementing bed-crossing hydraulic fracturing drilling and sealing holes in the floor roadway, characterized in that, comprising the following steps: a. Take the position of the final hole of the fracturing drilling as the center point O, select stress monitoring points A and B on the side of point O in the roof plane of the coal seam (4) along the floor roadway (3), the length of OA is 30 meters, and the length of OB 50 meters, respectively select stress monitoring points C, D and E, F along the two directions with an angle of ±120° with the OA direction, OC=OE=30 meters, OD=OF=50 meters; b. The opening of the fracturing hole (1) in the floor roadway (3) is located 30 meters away from point A for construction stress monitoring drilling Ⅰ (21), and the final hole position of drilling Ⅰ (21) is point A; The opening of the fracturing hole (1) in the floor roadway (3) is located 50 meters away from the side of point B for construction stress monitoring drilling II (22), and the final hole position of drilling hole II (22) is point B; in the floor roadway ( 3) The opening of the inner fracturing hole (1) is located 15 meters away from point C, and the stress monitoring borehole III (23) and stress monitoring borehole V (25) are constructed, and the final hole position of borehole III (23) is C point, the final hole position of borehole Ⅴ (25) is point E; the position of the opening of the fracturing hole (1) in the floor roadway (3) is 25 meters away from the side of point D for construction stress monitoring drilling Ⅳ (24) and stress Monitoring drilling Ⅵ (26), the position of the final hole of drilling Ⅳ (24) is point D, and the position of the final hole of drilling Ⅵ (26) is point F; It is 75mm, and the aperture after entering the coal seam (4) is 42mm; c. Use the installation rod to push the stress sensor (6) connected to the oil pressure pipe (5) to each stress monitoring point along the borehole, and then implement drilling and sealing. When grouting and sealing the hole, fill the entire stress monitoring borehole. Connect the stress recorder (7) to the outer section of the oil pressure pipe (5) at the orifice, and use the manual oil pressure pump to press hydraulic oil into the oil pressure pipe until the oil pressure is 4-4.5MPa and stop pressing to complete the stress sensor. (6) installation; insert the grouting pipe (8) and the grouting pipe (9), utilize AB glue to block the orifice, implement grouting and seal the hole, and fill the whole borehole during grouting; d. Monitor the ground stress change for 15 days before fracturing, analyze the stress change law within 15 days, determine the stress change range [σ _min , σ _max ] in the coal seam before fracturing, and set this range as the stress stability interval A; e. Implement hydraulic fracturing and stress monitoring at the same time. After the fracturing is completed, continue to maintain stress monitoring for 5 days, collect stress data during the fracturing process and after fracturing, analyze its change law, and determine the stress during the fracturing process and after fracturing Variation range [σ ₁ ,σ ₂ ], which is set as the range B of stress disturbance variation caused by fracturing; f. According to step d and step e obtained each stress monitoring borehole stress change interval A, B, determine the stress monitoring point affected; like Then the stress monitoring point is not affected by hydraulic fracturing; like Then the stress monitoring point is affected by hydraulic fracturing; g. Define the scope of influence: According to the hydraulic fracturing influence points determined in step f, respectively find out the farthest influence points in three different radial directions as described in step b, and connect the three points with a straight line. Layer hydraulic fracturing effective influence range (10).