CN109827694B - Ground stress measurement method for presetting artificial cracks under ultra-deep buried condition - Google Patents
Ground stress measurement method for presetting artificial cracks under ultra-deep buried condition Download PDFInfo
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- CN109827694B CN109827694B CN201910221850.7A CN201910221850A CN109827694B CN 109827694 B CN109827694 B CN 109827694B CN 201910221850 A CN201910221850 A CN 201910221850A CN 109827694 B CN109827694 B CN 109827694B
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Abstract
The invention provides a ground stress measuring method for presetting artificial cracks under an ultra-deep buried condition, which greatly reduces the requirement of ground stress measurement on a pressurizing system. The method comprises the following steps: drilling a caving observation hole, placing the caving observation drill hole until continuous caving phenomenon appears on the hole wall of the caving observation hole, and obtaining the average caving direction of the caving; drilling a hydraulic fracturing test hole, and cutting a plurality of pairs of preset cracks along the position of a vertical line of an average caving position measured by a caving observation hole before each test section is tested; performing water injection pressurization on the test section to perform a hydraulic fracturing test, and obtaining the re-tensioning pressure of the preset crack of the test section, wherein the re-tensioning pressure is used as the magnitude of the horizontal minimum main stress of the test section; and positioning the expanded cracks, taking the average value direction of the expanded cracks of the test section as the horizontal maximum main stress direction, wherein the horizontal minimum main stress direction is vertical to the horizontal maximum main stress direction.
Description
Technical Field
The invention relates to an earth stress measuring method, in particular to an earth stress measuring method under an ultra-deep buried condition, which is particularly suitable for an engineering area with the level of the earth stress and the main stress of more than 60MPa and even up to 100 MPa.
Background
The foundation of the challenges of measuring the ground stress under the condition of ultra-deep burial is that the two existing ground stress test methods have adaptability problems and cannot work normally under the condition that the ground stress exceeds 60 MPa. Because the traditional hydrofracturing ground stress measurement method is used, under the high confining pressure condition of more than 60MPa, the pressurizing equipment can expand the hole wall to crack until the pressure reaches 120MPa, the whole test process needs to last for 60-90 minutes, the requirement on the pressurizing equipment is high, and no powerful complete equipment is arranged in the field of hydrofracturing in China. Another common ground stress testing method is a stress relief method, but under the condition of extremely high ground stress, the phenomenon of core caking is easy to occur in the drilling process, so that the test fails.
Disclosure of Invention
The invention aims to overcome the defect that the existing crustal stress detection method is difficult to detect the crustal stress of a high confining pressure region exceeding 60MPa under the condition of ultra-deep burial, and provides the crustal stress measurement method which greatly reduces the requirement of crustal stress measurement on a pressurizing system and ensures that the conventional equipment can also be suitable for the presetting artificial cracks under the condition of the ultra-deep burial of an engineering region exceeding 60 MPa.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention discloses a ground stress measuring method for presetting artificial cracks under an ultra-deep buried condition, which comprises the following steps:
step 1, vertically and downwardly drilling a caving observation hole in an area to be measured with an earth stress, placing the caving observation drill hole until continuous caving phenomena occur on the hole wall of the caving observation hole, measuring the caving position of the caving, and obtaining the average caving direction of the caving;
step 2, vertically downwards drilling a hydrofracturing test hole in a to-be-measured ground stress area, arranging a plurality of test sections in the hydrofracturing test hole for hydrofracturing test, and cutting a plurality of pairs of preset cracks along the vertical line position of the average caving direction measured by a caving observation hole before each test section is tested;
step 3, injecting water and pressurizing to the test section to perform a hydraulic fracturing test, and acquiring the re-tensioning pressure of the preset cracks of the test section, wherein the re-tensioning pressure is used as the magnitude of the horizontal minimum main stress of the test section;
step 4, taking the average value of the horizontal minimum principal stress of each test section as the minimum horizontal principal stress measurement value of the depth of the region to be tested; and positioning the expanded cracks, taking the average value direction of the expanded cracks of the test section as the horizontal maximum main stress direction, wherein the horizontal minimum main stress direction is vertical to the horizontal maximum main stress direction.
Preferably, the depth of the collapse observation hole in the step 1 is greater than or equal to 20m, and the diameter is 50 mm-76 mm; the measured caving position is a caving position of 12-18 m in the caving observation hole.
Preferably, the step 1 specifically comprises the following steps:
step 1a, vertically and downwards drilling a breakout observation hole in a to-be-measured ground stress area, wherein the depth of the breakout observation hole is more than or equal to 20m, and the diameter of the breakout observation hole is 50-76 mm;
step 1b, placing the caving observation hole, and monitoring the caving situation of the rib of the caving observation hole with the thickness of 10-20 m at the same time until the continuous rib caving phenomenon occurs on the hole wall of the caving observation hole, wherein the placing time is 1-3 weeks;
and step 1c, measuring the orientations of the connecting lines of the caving walls which appear in pairs after penetrating through the circle center of the caving observation hole, and calculating the average orientation of the connecting lines of the caving walls in the depth section of 12-18 m of the caving observation hole as the average caving orientation of the caving walls.
Preferably, the number of the preset cracks in the step 2 is set to 3 pairs, each pair of the preset cracks is symmetrically arranged relative to the average ledge collapse direction, the direction of the first preset crack in the middle pair is perpendicular to the average ledge collapse direction, and the included angles between the other two pairs of the second preset cracks and the third preset cracks and the first preset cracks are 10-15 degrees.
Preferably, the depth of the preset crack is 3cm, and the thickness of the preset crack is less than or equal to 3 mm.
Preferably, the number of the test segments in the step 2 is at least 10, the interval between adjacent test segments is greater than or equal to 3m, and the length of a single test segment is 1.2-1.5 m; packers are arranged at two ends of the test section, the part of the test section between the packers is a water pressurizing section, and the length of the water pressurizing section is 50-80 cm.
Preferably, the step 3 further comprises the following steps:
step 3a, injecting water into a water pressing section of the testing section for pressurization, pressurizing in 3-6 stages within 30 minutes until a preset crack is expanded, and maintaining the pressure for not less than 2 minutes to fully expand the crack;
and 3b, injecting water again to the water pressing section of the testing section for pressurization, pressurizing for 4-5 levels within 20 minutes until the expanded crack is opened again, and measuring the re-tensioning pressure which is used as the magnitude of the horizontal minimum main stress of the testing section.
The crustal stress measuring method is improved in the existing hydraulic fracturing test method, and the wall of the test section of the hydraulic fracturing test hole is cut with the preset cracks before the hydraulic fracturing test is carried out, so that the performance requirement on pressurizing equipment can be effectively reduced. The position of the preset crack is determined based on the caving condition of the caving observation hole. The average ledge caving orientation is the average direction of the connecting line of the ledges passing through the circle centers of the holes, which is measured to appear in pairs in the caving observation holes. The rib caving is formed on the hole wall of the caving observation hole under the extrusion action of the ground stress, and the rib caving usually appears in pairs through the center of the hole. The average caving direction can be regarded as the minimum ground stress direction of the region, and the propagation direction of the cracks in the hydraulic fracturing test method is along the maximum ground stress direction, so that the preset cracks are arranged in the direction vertical to the average caving direction and are provided with 3 pairs, and the preset cracks can destroy the strength of the hole wall of the hydraulic fracturing test hole in advance, so that the performance requirement on the pressurizing equipment is effectively reduced, and the conventional equipment can be also suitable for ground stress measurement of engineering regions exceeding 60MPa under ultra-deep buried conditions.
Drawings
FIG. 1 is an illustration of the caving condition of the caving observation hole in the invention.
FIG. 2 is a cross-sectional view of a hydraulic fracturing test hole according to an embodiment of the present invention.
Fig. 3 is a diagram showing a structure example of a test section of a hydraulic fracturing test hole in the invention.
FIG. 4 is a pressure-time curve during the fracturing period of the present invention.
FIG. 5 is an exemplary diagram of the crack propagation in the present invention.
In the figure: the method comprises the steps of 1 caving observation hole, 101 caving, 102 average caving direction, 201 packer, 202 water pressing section, 3 hydraulic fracturing test hole, 301 first preset crack, 302 second preset crack and 303 third preset crack.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
The invention discloses a ground stress measuring method for presetting artificial cracks under an ultra-deep buried condition.
Step 1, vertically and downwardly drilling a caving observation hole 1 in an area to be measured with ground stress, placing the caving observation drill hole until continuous caving phenomena of the wall of the caving observation hole occur, measuring the caving position of the caving, and obtaining an average caving direction 102 of the caving.
The step 1 specifically includes the following three steps in the specific implementation process:
step 1a, vertically and downwards drilling a breakout observation hole in an earth stress area to be measured, wherein the depth of the breakout observation hole is more than or equal to 20m, and the diameter of the breakout observation hole is 50-76 mm.
And step 1b, placing the caving observation hole, and monitoring the caving situation of the rib of the caving observation hole with the thickness of 10-20 m at the same time until the continuous rib caving phenomenon appears on the hole wall of the caving observation hole, wherein the placing time is 1-3 weeks.
And step 1c, measuring the orientations of the connecting lines of the caving walls which appear in pairs after penetrating through the circle center of the caving observation hole, and calculating the average orientation of the connecting lines of the caving walls in the depth section of 12-18 m of the caving observation hole as the average caving orientation of the caving walls.
FIG. 1 is an illustration of the caving condition of the caving observation hole in the invention. The average ledge caving orientation is the average direction of the connecting line of the ledges passing through the circle centers of the holes, which is measured to appear in pairs in the caving observation holes.
And 2, vertically downwards drilling a hydraulic fracturing test hole 3 in the crustal stress area to be measured, arranging a plurality of test sections in the hydraulic fracturing test hole for hydraulic fracturing test, and cutting a plurality of pairs of preset cracks along the vertical line position of the average caving direction of the caving edge measured by the caving observation hole before each test section is tested.
In this embodiment, as shown in fig. 2, the number of the preset cracks in step 2 is set to 3 pairs, wherein each pair of the preset cracks is symmetrically arranged with respect to the average spalling direction, the direction of the first preset crack 301 in the middle pair is perpendicular to the average spalling direction, and the included angles between the other two pairs of the second preset cracks 302 and the third preset cracks 303 and the first preset crack are 10 to 15 °. The depth of the preset crack is 3cm, and the thickness of the preset crack is less than or equal to 3 mm.
As shown in fig. 3, the number of the test segments is at least 10, the interval between adjacent test segments is greater than or equal to 3m, and the length of a single test segment is 1.2-1.5 m; the testing section is characterized in that packers 201 are arranged at two ends of the testing section, a water pressurizing section 202 is arranged between the packers of the testing section, and the length of the water pressurizing section is 50-80 cm.
And 3, injecting water and pressurizing to the test section to perform a hydraulic fracturing test, and obtaining the re-tensioning pressure of the preset cracks of the test section, wherein the re-tensioning pressure is used as the magnitude of the horizontal minimum main stress of the test section.
The step 3 specifically includes the following two steps in the specific implementation process:
and 3a, injecting water into a water pressing section of the testing section for pressurization, pressurizing in 3-6 stages within 30 minutes until the crack is preset to expand, and maintaining the pressure for not less than 2 minutes to fully expand the crack.
And 3b, injecting water again to the water pressing section of the testing section for pressurization, pressurizing for 4-5 levels within 20 minutes until the expanded crack is opened again, and measuring the re-tensioning pressure which is used as the magnitude of the horizontal minimum main stress of the testing section.
FIG. 4 is a graph of pressure versus time in the press section in step 3a and step 3 b. And the re-opening pressure is the pressure value at the turning point of the pressure curve in the pressurized-water section caused by the re-opening of the crack in the step 3 b.
Step 4, taking the average value of the horizontal minimum principal stress of each test section as the minimum horizontal principal stress measurement value of the depth of the region to be tested; and positioning the expanded cracks, taking the average value direction of the expanded cracks of the test section as the horizontal maximum main stress direction, wherein the horizontal minimum main stress direction is vertical to the horizontal maximum main stress direction.
FIG. 5 is a diagram showing an example of the crack propagation in the present invention, in which a third pre-set crack 303 is expanded, and the average of the orientations of the propagated cracks in the respective test sections is measured as the horizontal maximum principal stress orientation. The horizontal minimum principal stress orientation is perpendicular to the horizontal maximum principal stress orientation.
The crustal stress measuring method is improved in the existing hydraulic fracturing test method, and the wall of the test section of the hydraulic fracturing test hole is cut with the preset cracks before the hydraulic fracturing test is carried out, so that the performance requirement on pressurizing equipment can be effectively reduced. The position of the preset crack is determined based on the caving condition of the caving observation hole. The average ledge caving orientation is the average direction of the connecting line of the ledges passing through the circle centers of the holes, which is measured to appear in pairs in the caving observation holes. The rib caving is formed on the hole wall of the caving observation hole under the extrusion action of the ground stress, and the rib caving usually appears in pairs through the center of the hole. The average caving direction can be regarded as the minimum ground stress direction of the region, and the propagation direction of the cracks in the hydraulic fracturing test method is along the maximum ground stress direction, so that the preset cracks are arranged in the direction vertical to the average caving direction and are provided with 3 pairs, and the preset cracks can destroy the strength of the hole wall of the hydraulic fracturing test hole in advance, so that the performance requirement on the pressurizing equipment is effectively reduced, and the conventional equipment can be also suitable for ground stress measurement of engineering regions exceeding 60MPa under ultra-deep buried conditions.
Claims (7)
1. A ground stress measurement method for presetting artificial cracks under an ultra-deep buried condition is characterized by comprising the following steps:
step 1, vertically and downwardly drilling a caving observation hole in an area to be measured with an earth stress, placing the caving observation drill hole until continuous caving phenomena occur on the hole wall of the caving observation hole, measuring the caving position of the caving, and obtaining the average caving direction of the caving;
step 2, vertically downwards drilling a hydrofracturing test hole in a to-be-measured ground stress area, arranging a plurality of test sections in the hydrofracturing test hole for hydrofracturing test, and cutting a plurality of pairs of preset cracks along the vertical line position of the average caving direction measured by a caving observation hole before each test section is tested;
step 3, injecting water and pressurizing to the test section to perform a hydraulic fracturing test, and acquiring the re-tensioning pressure of the preset cracks of the test section, wherein the re-tensioning pressure is used as the magnitude of the horizontal minimum main stress of the test section;
step 4, taking the average value of the horizontal minimum principal stress of each test section as the minimum horizontal principal stress measurement value of the depth of the region to be tested; and positioning the expanded cracks, taking the average value direction of the expanded cracks of the test section as the horizontal maximum main stress direction, wherein the horizontal minimum main stress direction is vertical to the horizontal maximum main stress direction.
2. The method according to claim 1, wherein the depth of the breakout observation hole in the step 1 is 20m or more and the diameter thereof is 50mm to 76 mm; the measured caving position is a caving position of 12-18 m in the caving observation hole.
3. The method as claimed in claim 1, wherein the step 1 comprises the steps of:
step 1a, vertically and downwards drilling a breakout observation hole in a to-be-measured ground stress area, wherein the depth of the breakout observation hole is more than or equal to 20m, and the diameter of the breakout observation hole is 50-76 mm;
step 1b, placing the caving observation hole, and monitoring the caving situation of the rib of the caving observation hole with the thickness of 10-20 m at the same time until the continuous rib caving phenomenon occurs on the hole wall of the caving observation hole, wherein the placing time is 1-3 weeks;
and step 1c, measuring the orientations of the connecting lines of the caving walls which appear in pairs after penetrating through the circle center of the caving observation hole, and calculating the average orientation of the connecting lines of the caving walls in the depth section of 12-18 m of the caving observation hole as the average caving orientation of the caving walls.
4. The method according to claim 1, wherein the number of the predetermined cracks in the step 2 is set to 3 pairs, each pair of the predetermined cracks is symmetrically arranged relative to the average spalling direction, the first predetermined crack in the middle pair is perpendicular to the average spalling direction, and the second and third predetermined cracks in the other two pairs respectively form an angle of 10-15 ° with the first predetermined crack.
5. The method of claim 4, wherein the predetermined crack has a depth of 3cm and a predetermined crack thickness of 3mm or less.
6. The method as claimed in claim 1, wherein the number of the test segments in the step 2 is at least 10, the interval between the adjacent test segments is greater than or equal to 3m, and the length of the single test segment is 1.2-1.5 m; packers are arranged at two ends of the test section, the part of the test section between the packers is a water pressurizing section, and the length of the water pressurizing section is 50-80 cm.
7. The method of claim 1, wherein said step 3 further comprises the steps of:
step 3a, injecting water into a water pressing section of the testing section for pressurization, pressurizing in 3-6 stages within 30 minutes until a preset crack is expanded, and maintaining the pressure for not less than 2 minutes to fully expand the crack;
and 3b, injecting water again to the water pressing section of the testing section for pressurization, pressurizing for 4-5 levels within 20 minutes until the expanded crack is opened again, and measuring the re-tensioning pressure which is used as the magnitude of the horizontal minimum main stress of the testing section.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102829899A (en) * | 2012-08-22 | 2012-12-19 | 武汉大学 | Quick surrounding rock stress measuring method applicable to buried circular tunnels |
| CN105716747A (en) * | 2016-02-18 | 2016-06-29 | 中国矿业大学 | Crustal stress rapid measuring device and method of rock stratum under coal mine |
| CN105716780A (en) * | 2015-12-30 | 2016-06-29 | 中国地震局地壳应力研究所 | Corrective natural fracture hydraulic fracturing in-situ stress measurement method |
| CN109339776A (en) * | 2018-10-30 | 2019-02-15 | 中国石油大学(北京) | A method for measuring in-situ stress in anisotropic formations |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US5353637A (en) * | 1992-06-09 | 1994-10-11 | Plumb Richard A | Methods and apparatus for borehole measurement of formation stress |
| US5492175A (en) * | 1995-01-09 | 1996-02-20 | Mobil Oil Corporation | Method for determining closure of a hydraulically induced in-situ fracture |
| AUPP209498A0 (en) * | 1998-03-02 | 1998-03-26 | Commonwealth Scientific And Industrial Research Organisation | Hydraulic fracturing of ore bodies |
| US9260921B2 (en) * | 2008-05-20 | 2016-02-16 | Halliburton Energy Services, Inc. | System and methods for constructing and fracture stimulating multiple ultra-short radius laterals from a parent well |
| CN107542468A (en) * | 2017-08-17 | 2018-01-05 | 东北大学 | A kind of natural caving method |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102829899A (en) * | 2012-08-22 | 2012-12-19 | 武汉大学 | Quick surrounding rock stress measuring method applicable to buried circular tunnels |
| CN105716780A (en) * | 2015-12-30 | 2016-06-29 | 中国地震局地壳应力研究所 | Corrective natural fracture hydraulic fracturing in-situ stress measurement method |
| CN105716747A (en) * | 2016-02-18 | 2016-06-29 | 中国矿业大学 | Crustal stress rapid measuring device and method of rock stratum under coal mine |
| CN109339776A (en) * | 2018-10-30 | 2019-02-15 | 中国石油大学(北京) | A method for measuring in-situ stress in anisotropic formations |
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