A two-stage active fracturing grouting method

Abstract

The application discloses a double-period active fracturing grouting method, and belongs to the technical field of shaft gushing water plugging. Firstly, a plurality of fracturing boreholes are vertically and equidistantly constructed along the shaft side of a working face, cross-hole detection is performed by using a focusing electric method to determine that an existing fracture is located between two fracturing boreholes, then a first period of fracturing is performed by using cement-silicate double-liquid slurry based on one of the fracturing boreholes, and near 90-degree rotation of the near-field main stress direction of the existing fracture is realized; after the slurry solidifies, the borehole is swept, and a second period of fracturing is performed by using ordinary cement slurry, when the fracturing cracks are connected with the existing fracture, the cement slurry fills the crack network formed by the fracturing cracks and the existing fracture, so that targeted grouting plugging is completed. The application is suitable for targeted grouting plugging of the existing structural fracture in the working condition that the structural fracture and the fracturing borehole are separated.

Description

TECHNICAL FIELD

[0001] The application relates to a two-stage active fracturing grouting method, and belongs to the technical field of shaft inrush water plugging. BACKGROUND

[0002] High-angle (close to 90º) cross-shaft structure cracks are the main channels of water inrush at the working face of a deep shaft, and targeted grouting plugging thereof can eradicate the risk of water inrush at the working face of the shaft and maximally reduce water inrush at the working face, which is of great significance to the safe and efficient construction of a deep shaft.

[0003] Existing technologies are mostly aimed at coal measures (sedimentary rocks) with soft surrounding rocks and loose pores, while magmatic rocks commonly seen in metal mines belong to hard rocks with low porosity. The applicability of high-energy gas fracturing technology mainly characterized by pulse load needs to be verified, and an active fracturing grouting method with slow pressure increase, long duration and quantitatively controllable effect is urgently needed to solve the problem of grouting plugging of high-angle cracks in the shaft side of a magmatic rock during shaft construction.

[0004] The existing technology with the publication number CN114482913A discloses a method for determining the plugging length of a fractured water-bearing oil well horizontal well and a plugging method. The method comprises the following steps: 1) determining the main water outlet section of the oil well horizontal well; 2) predicting the comprehensive water cut and water drive volume wave coefficient of the oil reservoir injection-production well group under different plugging schemes; the various plugging schemes are centered on the main water outlet section, and the plugging length proportions of the well sections are different; the plugging sections of each plugging scheme include the main water outlet section; 3) weighting and averaging the comprehensive water cut and water drive volume wave coefficient of each plugging scheme to obtain an evaluation index parameter, and then determining the plugging length of the fractured oil reservoir oil well horizontal well. It can only be used for the plugging of small-diameter oil wells and cannot well direct the pretreatment of cracks existing in large-diameter shafts.

[0005] Existing fracturing technologies are mostly aimed at fracturing of large-volume strata, and the expansion distance of fracturing cracks during fracturing is much larger than the expansion distance of active fracturing cracks in the local range before connecting the existing cracks. However, due to the interference of stratum heterogeneity, the ground stress distribution around the existing cracks is uneven, so the local active stress direction reconstruction effect is uncertain. Moreover, existing fracturing technologies mostly use water with different viscosities, and the main purpose is to open up the oil and gas outflow channels in the strata or to inject water for mining. However, the slurry is injected from the outflow into the surrounding rock cracks during fracturing and grouting. The principles of the physical interaction of the fluid viscosity and the fluid-rough crack wall surface involved in the two processes are different. Therefore, the existing fracturing technology cannot be simply applied to the fracturing and grouting of deep well surrounding rocks. SUMMARY

[0006] Technical problems: In view of the above problems, considering that the filling and extension process of the fracturing cracks has a regulating effect on the direction of the principal stress of the existing cracks, and according to the idea of first regulating the direction of the principal stress and then connecting the main cracks, a two-stage active fracturing grouting method is provided, which provides an innovative idea for effectively preventing and controlling the water inrush disaster of the deep well working surface and reducing the water gushing of the working surface.

[0007] Technical content: In order to achieve the above technical purpose, a two-stage active fracturing grouting method is disclosed, and the steps are as follows:

[0008] S1, a plurality of cracking drill holes are constructed along the vertical well working surface well side ring vertically downward at equal intervals, two cracking drill holes are selected in the plurality of cracking drill holes in turn to implement cross-hole focusing electric method detection, and it is judged that the existing cracks are located between the two cracking drill holes;

[0009] S2, the first stage of slurry pressure cracking is implemented in any one of the two cracking drill holes containing the existing cracks, the direction of the principal stress in the near field of the existing cracks is controlled, the cracking cracks will extend along the direction parallel to the existing cracks, and the double effects of the grouting pressure and the shear stress caused by the slurry flow to the crack wall during the crack extension process increase, the small principal stress of the region surrounded between the cracking drill hole and the existing crack gradually rotates to the direction parallel to the existing cracks;

[0010] S3, after the first stage of slurry pressure cracking, the slurry fills the first stage of fracturing cracks and solidifies, the principal stress adjustment of the local area is completed, then a drill bit with a diameter smaller than that of the cracking drill hole is used to scan the cracking drill hole of the first stage of slurry pressure cracking, and the second stage of slurry pressure fracturing is implemented, because the direction of the small principal stress after the first stage of slurry pressure cracking has changed to the direction parallel to the existing cracks, therefore the second stage of slurry pressure cracking cracks will extend perpendicular to the direction of the existing cracks, until the existing cracks are connected;

[0011] S4, the pressure grouting operation is implemented through the second stage of slurry pressure cracking cracks to the existing cracks, and the slurry fills the existing cracks and the second stage of cracking cracks.

[0012] Further, the cracking drill holes vertically downward along the well side ring of the vertical well working surface are 3-n, n=1.5*well circumference.

[0013] Further, the slurry used for the first stage of slurry pressure cracking is cement-silicate double liquid slurry, the water-cement ratio of cement is 0.6:1-1:1, and the volume ratio of cement to water glass is 1:1, so as to realize the rapid solidification and good interface bonding performance of the slurry, and the slurry used for the second stage of slurry pressure cracking and the pressure grouting operation is ordinary cement slurry, the water-cement ratio is 0.6:1-1:1, so as to realize the filling of the existing cracks.

[0014] Further, the process of determining which two fracture drilling holes the existing crack is located between by using cross-hole focusing electrical method is: setting the transmitting electrode and the loop electrode at the same height in the two fracture drilling holes to obtain the opposite resistivity, setting the transmitting electrode and the loop electrode at different heights in one fracture drilling hole to obtain the adjacent resistivity, and determining which two fracture drilling holes the existing crack is located between based on the principle that the opposite resistivity and the adjacent resistivity are not equal, wherein the transmitting and receiving electrodes in the opposite measurement are located at the same height in the two fracture drilling holes, and the transmitting and receiving electrodes in the adjacent measurement are located at different heights in the same fracture drilling hole.

[0015] Further, the first-stage fracturing crack length and the second-stage fracturing crack length are both controlled to be not more than the interval between adjacent two fracture drilling holes, and the second-stage fracturing crack length is approximately equal to the vertical distance between the fracture drilling hole and the existing crack.

[0016] Further, the principal stress rotation angle of the small principal stress in the region surrounded by the first-stage slurry pressure fracturing and the existing crack gradually rotates towards the direction parallel to the existing crack. is expressed as follows:

[0017] ;

[0018] wherein represents the shear stress on the plane composed of the vertical and hoop directions, respectively represent the vertical and hoop stresses.

[0019] Further, considering the local extension characteristics of the crack on the shaft working face, the pressure grouting equipment is used as the active fracturing equipment to realize the integration of the fracturing and grouting system.

[0020] Further, in the second-stage slurry pressure fracturing process, the communication time of the fracturing crack and the existing crack is determined through the pressure drop and flow instantaneous increase phenomena monitored in real time.

[0021] Further, in the pressure grouting operation to the existing crack, the grouting pressure is observed through the orifice pressure gauge, and when the grouting pressure suddenly increases, it is determined that the slurry fills the existing crack and the second-stage fracturing crack.

[0022] Beneficial effects: After the fracturing drilling hole construction, the method determines which two fracture drilling holes the existing crack is located between based on the cross-hole detection results, then selects one fracture drilling hole to implement two-stage fracturing operation, and efficiently completes the communication with the existing crack. Since the shaft size is smaller than the oil and gas formation fracturing size, the influence of the heterogeneity of the stressed formation on the crack extension is effectively reduced, and the communication path is the shortest. Due to the influence of the high water pressure of the formation, the surrounding rock rupture strength is comparable to its tensile strength, and high pressure conditions required for maintaining large-scale crack extension are not required, so only one set of grouting equipment needs to be arranged on the ground during the fracturing and grouting operation to meet the requirements of fracturing and grouting plugging. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Figure 1 is a schematic diagram of spatial relationship of existing cracks, fracturing boreholes and shaft space in an embodiment of the present application.

[0024] Figure 2 Figure 2 is a schematic diagram of process of the two-stage active fracturing grouting method of the present application. DETAILED DESCRIPTION

[0025] Embodiments of the present application will be further described below with reference to the accompanying drawings.

[0026] As shown in Figure 1, the present application discloses a two-stage active fracturing grouting method, the vertical shaft working surface well ring circumferential downward fracturing boreholes are 3-n, n=well circumference / 1.5, and the existing cracks are structure cracks (main control cracks) penetrating the well, which intersect the well once, as shown in Figure 2. Figure 2 Figure 1

[0027] The specific steps of the method are as follows:

[0028] S1, two fracturing boreholes are selected in the vertical shaft working surface well ring circumferential fracturing boreholes to implement cross-hole focused electric method detection, and the existing cracks are determined to be located between the two fracturing boreholes, Figure 2 the small principal stress trajectory is indicated by a dashed line;

[0029] The process of determining the existing cracks to be located between the two fracturing boreholes by using the cross-hole focused electric method is as follows: the transmitting electrode and the loop electrode are arranged at the same height in the two fracturing boreholes to obtain the opposite resistivity, the transmitting electrode and the loop electrode are arranged at different heights in one fracturing borehole to obtain the adjacent resistivity, and the existing cracks are determined to be located between the two fracturing boreholes based on the principle that the opposite resistivity and the adjacent resistivity are not equal, wherein the transmitting and receiving electrodes are located at the same height in the two fracturing boreholes in the opposite measurement, and the transmitting and receiving electrodes are located at different heights in the same fracturing borehole in the adjacent measurement.

[0030] S2, the first-stage slurry pressure fracturing is implemented in any one of the two fracturing boreholes containing the existing cracks, the slurry used in the first-stage slurry pressure fracturing is a cement-silicate double-liquid slurry, the water-cement ratio of the cement is 0.6:1-1:1, and the cement-silicate volume ratio is 1:1, so as to realize the rapid solidification and good interface bonding performance of the slurry; the fracturing crack expands along the direction parallel to the existing crack under the control of the near-field principal stress direction of the existing crack, the shearing stress on the crack wall caused by the slurry pressure and the slurry flow increases in the crack expansion process, the small principal stress in the region surrounded between the fracturing borehole and the existing crack gradually rotates toward the direction parallel to the existing crack, and the near-field principal stress direction of the existing crack is rotated by nearly 90°;

[0031] ​​The small principal stress in the region is gradually rotated to be parallel to the direction of the existing crack by the first slurry pressure fracturing is expressed as follows:

[0032] ,

[0033] In the formula represents the shear stress on the plane composed of the vertical and hoop directions, respectively represent the vertical and hoop stresses.

[0034] S3, after the first slurry pressure fracturing, the slurry fills the first fracturing crack and solidifies, the principal stress adjustment of the local region is completed, then a drill bit with a diameter smaller than that of the fracturing drill hole is used to scan the fracturing drill hole of the first slurry pressure fracturing, and the second slurry pressure fracturing is carried out. Since the small principal stress direction has been changed to be parallel to the direction of the existing crack after the first slurry pressure fracturing, the second slurry pressure fracturing crack will expand perpendicular to the direction of the existing crack until it connects the existing crack. The length of the first fracturing crack and the length of the second fracturing crack are both controlled to be not more than the interval between two adjacent fracturing drill holes. Considering the local expansion characteristics of the shaft working surface crack, the pressure grouting equipment is used as the active fracturing equipment to realize the integration of the fracturing and grouting system. The connection time of the fracturing crack and the existing crack is determined by the real-time monitoring of the pressure drop and the instantaneous increase of the flow, and the length of the second fracturing crack is approximately equal to the interval between the fracturing drill hole and the existing crack. The slurry used in the second slurry pressure fracturing and the pressure grouting operation is ordinary cement slurry, and the water-cement ratio is 0.6:1~1:1, so as to realize the filling of the existing crack. In the pressure grouting operation towards the existing crack, the grouting pressure is observed through the orifice pressure gauge. When the grouting pressure suddenly increases, it is determined that the slurry fills the existing crack and the second fracturing crack.

[0035] S4, the pressure grouting operation towards the existing crack through the second slurry pressure fracturing crack is carried out, so that the slurry fills the existing crack and the second fracturing crack.

[0036] There are many specific implementation ways of the present application, and the above description is only the preferred embodiment of the present application. It should be pointed out that for ordinary skilled persons in the technical field, some improvements can be made without departing from the principle of the present application, and these improvements should also be regarded as the protection scope of the present application.

Claims

1. A dual-stage active fracturing grouting method, characterized in that... The steps are as follows: S1. Construct multiple fracturing boreholes at equal intervals along the circumferential direction of the shaft working face. Select two fracturing boreholes in sequence to perform cross-hole focusing electrical resistivity tomography to determine which two fracturing boreholes the existing fracture is located between. S2. The first stage of grouting fracturing is carried out in either of the two fracturing boreholes containing the existing crack. Under the control of the near-field principal stress direction of the existing crack, the fracturing crack will extend in the direction parallel to the existing crack. During the crack extension process, the small principal stress direction in the area surrounded by the fracturing borehole and the existing crack gradually rotates towards the direction parallel to the existing crack. S3. After the first stage of grouting fracturing, the grout immediately fills the first stage fracturing crack and solidifies, completing the adjustment of the principal stress in the local area. Then, a drill bit with a diameter smaller than the diameter of the fracturing borehole is used to clean the fracturing borehole of the first stage of grouting fracturing, and the second stage of grouting fracturing is implemented. Since the direction of the minor principal stress has become parallel to the direction of the existing crack after the first stage of grouting fracturing, the second stage of grouting fracturing crack will extend perpendicular to the direction of the existing crack until it connects with the existing crack. S4. Pressure grouting is carried out on the existing cracks through the second-stage grouting-induced cracks, so that the grout fills the existing cracks and the second-stage induced cracks. The process of determining which two fracturing boreholes an existing fracture is located between using cross-hole focusing electrical resistivity is as follows: A transmitting electrode and a loop electrode are set at the same height in two fracturing boreholes to obtain the resolvability at the apex. A transmitting electrode and a loop electrode are set at different heights in a single fracturing borehole to obtain the resolvability at the adjacent position. Based on the principle that the resolvability at the apex and the resolvability at the adjacent position are not equal, the process determines which two fracturing boreholes the existing fracture is located between. Specifically, in the apex measurement, the transmitting and receiving electrodes are located at the same height in two fracturing boreholes, while in the adjacent measurement, the transmitting and receiving electrodes are located at different heights in the same fracturing borehole. During the first phase of grouting fracturing, the small principal stress in the region enclosed by the fracturing hole and the existing fracture gradually rotates towards a direction parallel to the existing fracture. It is expressed as follows: , In the formula This represents the shear stress in the plane formed by the vertical and circumferential directions. These represent vertical and circumferential stresses, respectively.

2. The dual-stage active fracturing grouting method according to claim 1, characterized in that, The number of vertically downward fracturing boreholes in the circumferential direction of the shaft working face is 3 to n, where n = shaft circumference / 1.

5.

3. The dual-stage active fracturing grouting method according to claim 1, characterized in that, The first stage of grouting for crack initiation uses a cement-water glass two-component grout with a cement-cement ratio of 0.6:1 to 1:1 and a cement-water glass volume ratio of 1:1 to achieve rapid curing and good interfacial bonding performance. The second stage of grouting for crack initiation and pressure grouting uses ordinary cement grout with a water-cement ratio of 0.6:1 to 1:1 to fill existing cracks.

4. The dual-stage active fracturing grouting method according to claim 1, characterized in that, The lengths of the first-stage and second-stage fracturing fractures are both controlled to not exceed the distance between two adjacent fracturing boreholes, and the length of the second-stage fracturing fracture is approximately equal to the vertical distance between the fracturing borehole and the existing fracture.

5. The dual-stage active fracturing grouting method according to claim 1, characterized in that, Considering the local propagation characteristics of fractures at the shaft working face, the pressure grouting equipment also serves as an active fracturing equipment, realizing the integration of fracturing and grouting systems.

6. The dual-stage active fracturing grouting method according to claim 1, characterized in that, During the second phase of grout-induced fracturing, the connection time between the fracturing crack and the existing crack was determined by real-time monitoring of sudden pressure drops and instantaneous flow increases.

7. The dual-stage active fracturing grouting method according to claim 1, characterized in that, During pressure grouting of existing cracks, the grouting pressure is observed through the pressure gauge at the orifice. When the grouting pressure suddenly increases, it is determined that the grout has filled the existing cracks and the second-stage cracking cracks.

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