A method and apparatus for conducting a drill-in water injection test in a dry hole

Abstract

The application relates to the technical field of survey and detection, and particularly discloses a method and device for conducting a drilling water injection test in a dry hole. The method comprises the following steps: a test hole is formed on a film tube, the film tube is placed in a drilling hole so that the test hole is aligned with a formation to be tested, water is injected into the tube so that the film tube adheres to the hole wall to block a fissure water leakage passage, the water in the tube only enters the target formation from the test hole, and the water injection is continuously conducted until the water injection is stable, and then the permeability coefficient is calculated. The specific site test device adopts an orifice chuck, a joint, a test section film tube, a water plugging ball valve and a conical water leakage funnel, the test section is only bored, and the un-bored section adheres to the wall to form an equivalent plug; the full section test device adopts an orifice chuck, a joint, a full section bored film tube, a plastic gasket and a heavy hammer. The application realizes water storage by plugging fissures on the hole wall through the film tube, so that the water injection test in a serious water leakage formation can be conducted, the permeability coefficient of a specific formation position can be accurately measured, and a permeability coefficient correction formula and a judgment method for the maximum free outflow are provided.

Description

Technical Field

[0001] This invention relates to the field of exploration and testing technology, and in particular to a method and apparatus for conducting borehole water injection tests in dry boreholes. Background Technology

[0002] Borehole water injection testing is a common method for determining the permeability of soil and rock formations in the field. Its principle is similar to pumping testing, but instead of pumping, water is injected into the borehole to create a stable water level and a constant injection volume. The permeability coefficient (k) and unit water absorption (ω) of the soil and rock formation are calculated based on the injection data during the stable period. Borehole water injection testing is typically applicable to the following conditions: firstly, when the groundwater level is deep and pumping testing is inconvenient; secondly, in dry, permeable soil and rock formations, water injection testing is often used to obtain the formation's permeability parameters. The stabilization time varies depending on the purpose and requirements, generally lasting 2 to 8 hours.

[0003] However, in actual engineering projects, severe formation leakage is frequently encountered, causing the water in the borehole to drain quickly and making it difficult to establish a stable water level. In such cases, pumping and pressure tests are not feasible, and the formation permeability coefficient is difficult to determine. To address this problem, existing technologies mainly employ the following solutions: Firstly, segmented drilling and segmented testing. This method divides the long borehole section into several short segments, drilling and testing each segment sequentially to reduce leakage and establish a stable water level within each segment. However, this method still measures the overall permeability coefficient of each stratum, making it impossible to conduct precise permeability tests at specific stratum locations. Furthermore, segmented drilling and testing significantly increase the number of construction procedures, extend the construction period, and increase economic costs.

[0004] Secondly, a borehole plug is used to separate most of the borehole section from the test section. This method seals the non-test section by installing a plug inside the borehole, reducing the length of the leaking section and allowing a stable water level to be formed in the test section. However, the length of the plugged section is still relatively large, and the measured value is still the overall permeability coefficient of the formation in the longer borehole section, which cannot accurately reflect the permeability characteristics of a specific formation location; moreover, the installation and removal of the plug is relatively cumbersome, with high time and economic costs.

[0005] Third, a perforated pipe is placed at a specific stratum, while a waterproof sleeve is installed at other locations. This method attempts to conduct permeability tests only on the stratum corresponding to the perforated pipe through the combination of the perforated pipe and the waterproof sleeve. However, the perforated pipe and the sleeve are often difficult to fit tightly against the borehole wall, and there is an annular gap between them. The injected water flows into other strata along the gap between the borehole wall and the sleeve, causing the test results to be affected by leakage water from non-target strata. It is impossible to guarantee that the permeability test is conducted only on the specific stratum location. At the same time, the installation of the perforated pipe and the waterproof sleeve is relatively cumbersome and has low construction efficiency.

[0006] Chinese patent CN205636708U discloses a borehole water injection test device for measuring the permeability of soil and rock. This device primarily uses a filter installed in the test section to conduct water injection testing. The filter's function is to block sediment particles from entering the borehole, preventing them from clogging the test section and affecting water injection and testing. While this solution considers the impact of sediment in the borehole on the water injection test, the filter's function is limited to intercepting sediment particles and does not address the core issue of the difficulty in maintaining a stable water level in the borehole when there is severe formation leakage. In formations with severe leakage, even if the filter effectively blocks sediment, the injected water will still rapidly leak out through cracks in the borehole wall, making it impossible to maintain a stable water level and conduct the water injection test. Therefore, this solution fails to solve the problem of difficulty in measuring formation permeability under conditions of severe leakage.

[0007] Therefore, how to conduct precise water injection tests at specific formation locations in boreholes with severe water leakage, so as to form a stable water level in the borehole to determine the permeability coefficient of the target formation, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the technical problem solved by this invention is to provide a method and apparatus for conducting borehole water injection tests in dry boreholes, thereby solving the problem of difficulty in measuring formation permeability under conditions of severe water leakage.

[0009] To solve the above problems, the technical solution adopted by the present invention is as follows: A method for conducting borehole water injection tests in dry boreholes, comprising the following steps: Step 1: Opening test holes on a test membrane tube, wherein the test holes are opened at positions on the test membrane tube corresponding to the formation to be tested, and the size and number of test holes are such that the equivalent permeability coefficient of the formation corresponding to the maximum free outflow is greater than the actual permeability coefficient of the formation to be tested; Step 2: Placing the test membrane tube with the test holes into the borehole, aligning the test holes of the membrane tube with the formation to be tested; Step 3: Injecting water into the test membrane tube, the water pressure causing the test membrane tube to adhere to the borehole wall, and sealing the water leakage channels in the borehole wall fissures at the un-holeed parts of the test membrane tube, with water entering the formation to be tested only from the test holes; Step 4: Continuously injecting water until a stable water level and constant injection volume are formed in the borehole, recording the injection volume, water head height, and time data during the stable period, and calculating the formation permeability coefficient.

[0010] Furthermore, in step 1, before the formal water injection test, the maximum flow rate during free outflow from the membrane tube is measured. During the formal test, the actual stable water injection volume will be measured. Q and Comparison: If Q Approaching or equal to This indicates that the formation permeability is extremely high, and the borehole is actually in a free outflow state. Therefore, the calculated permeability coefficient at this point is only considered as the lower limit of the formation permeability coefficient. If...Q Exceed This indicates that there is a leak at the bottom of the membrane tube.

[0011] Furthermore, in step 1, the flow rate of the test membrane tube is calculated according to the following formula; when the test hole is a single circular hole, the maximum flow rate of a single hole is: ;in The flow coefficient is determined by actual measurement. Single-hole area, The water head height at the center of the orifice, Acceleration due to gravity; when n identical circular holes are opened at the same depth, the maximum water flow rate is: When n identical circular holes are opened at intervals from top to bottom, the maximum water flow rate is the sum of the flow rates of each hole: ;in Let be the vertical distance from the center of the i-th orifice to the water surface. When the test orifice is a long rectangular orifice, the maximum outflow rate of n long rectangular orifices is: ; in, h 1 represents the vertical distance from the top edge of the uppermost hole to the water surface; i This is the i-th hole from top to bottom; a The vertical height of a single elongated rectangular hole; b The width of a single long rectangular hole; d This is the vertical distance between the top edges of adjacent holes.

[0012] Furthermore, in step 4, when the entire membrane tube is perforated and the water injection head height is... h Not greater than the length of the test section When, permeability coefficient Calculated according to the modified formula; ;in, Q Indicates a stable water injection volume; h The water head height caused by water injection Indicates the length of the test section. This represents the area of ​​all test wells below the water level; and satisfies 50 < h / r' <200; among which .

[0013] Furthermore, in step 4, for testing specific locations, when the water injection head h is greater than the test section length l, the permeability coefficient k is calculated according to the following correction formula; ;in, Q Indicates a stable water injection volume; h The water head height caused by water injection Indicates the length of the test section. This represents the area of ​​all test wells below the water level.

[0014] An apparatus for conducting borehole water injection tests in dry holes, employing the test method described in any one of claims 1-5, comprises, from top to bottom, a limiting head, a connector, a test diaphragm tube, a water-blocking ball valve, and a drain funnel. The test section of the test diaphragm tube has a test hole. The lower end of the water-blocking ball valve is detachably fixed to the lower end of the drain funnel via an elastic rope. The other end of the water-blocking ball valve is fixed with a pull rope, one end of which extends upward beyond the limiting head. The limiting head includes a circular disc with a diameter larger than the diameter of the borehole to be tested. The circular disc is detachably connected to the connector. Both ends of the test diaphragm tube are detachably connected to the connector and the drain funnel, respectively.

[0015] Furthermore, the connector includes an upper connector, a small-diameter membrane tube, and a reducing connector arranged sequentially from top to bottom. The reducing connector has different diameters at both ends and multiple connecting grooves on its sidewall. The small-diameter membrane tube is tied to the connecting groove at the small-diameter end of the reducing connector, and the test membrane tube is tied to the connecting groove at the large-diameter end of the reducing connector.

[0016] Furthermore, the circular disk includes two arc-shaped disks, one end of which is hinged and the other end is connected by bolts; and the inner wall of the arc-shaped disk is provided with a protrusion that mates with the groove.

[0017] Furthermore, the upper and lower ends of the drain funnel are provided with funnel grooves for binding and fixing with the test membrane tube.

[0018] An apparatus for conducting borehole water injection tests in dry holes, employing the test method described in any one of claims 1-5, comprises, from top to bottom, a limiting head, a connector, a test membrane tube, an isolation pad, and a gravity component. The limiting head is annular and detachably connected to the connector. The connector has a limiting ring groove. The upper end of the test membrane tube is tied to the limiting ring groove of the connector, and the lower end of the test membrane is tied to the isolation pad and the gravity component respectively. Multiple test holes are arranged at intervals along the vertical direction along the entire length of the test membrane tube.

[0019] The technical principle of this solution is: A test membrane tube is placed as a water-proof lining in a borehole with severe leakage. The test membrane tube is elastic and thin-walled, with test holes drilled at the specific stratum where the permeability coefficient is to be tested, and no holes drilled at other locations. When water is injected into the test membrane tube, the water pressure causes the test membrane tube to fit tightly against the borehole wall. The un-drilled sections of the membrane tube block the leakage channels in the borehole wall fissures, preventing water from leaking out from non-target locations; the water inside the tube can only enter the specific stratum to be tested through the test holes. Since the total area of ​​the test holes is much smaller than the original leakage area of ​​the borehole wall, the equivalent leakage area of ​​the borehole wall is greatly reduced. Even in strata with severe leakage, the water injection volume can be maintained within the range that the water supply capacity of the exploration site can bear, and a stable water level can be formed in the borehole, thus ensuring the normal conduct of the water injection test.

[0020] For formations with severe leakage throughout the entire borehole, test holes are opened along the entire length of the test membrane tube to artificially reduce the effective leakage area of ​​the borehole wall, so that the on-site water supply capacity can meet the requirements for maintaining a stable water level, thereby enabling the determination of the comprehensive permeability coefficient of the entire formation.

[0021] Because the introduction of the membrane tube changes the boundary conditions of the original borehole water injection test, the seepage area of ​​the cylindrical surface represented by the borehole radius r in the original formula is no longer applicable. It needs to be replaced by the total area A of the test hole. The permeability coefficient of the formation to be tested is calculated by the modified permeability coefficient calculation formula.

[0022] The beneficial effects of this plan are: This invention solves the problem of water injection testing being impossible in formations with severe leakage by sealing water leakage channels through membrane tubes that plug cracks in the borehole wall. It allows for the maintenance of a stable water level within the tubes. The test can be completed without a large external water supply, making it particularly suitable for situations where water supply is difficult at exploration sites. By opening a test hole only at the location of the formation to be tested, the membrane tubes above and below the test hole adhere to the borehole wall under water pressure, forming an equivalent plug. Water enters the target formation only through the test hole, avoiding the problem in existing technologies where the overall permeability coefficient is measured over a longer borehole section, thus achieving precise determination of permeability at a specific formation location.

[0023] Under water pressure, the membrane tube fits tightly against the borehole wall. Compared to existing perforated pipe with a water-proof casing scheme, which suffers from an annular gap between the casing and the borehole wall, allowing injected water to flow into non-target formations, this invention fundamentally eliminates flow along the wall, resulting in more reliable test results. Compared to existing plugging and perforated pipe with a water-proof casing schemes, this invention only requires inserting the membrane tube into the borehole, injecting water, testing, draining water, and removing it. The operation process is simple, efficient, and cost-effective in both time and money. After draining water, the membrane tube detaches from the borehole wall and can be removed from the borehole for reuse.

[0024] This invention addresses the changes in boundary conditions after the introduction of the membrane tube by deriving a correction formula for the permeability coefficient. The borehole radius in the original formula is replaced with an equivalent radius, ensuring the accuracy of the calculation results. Simultaneously, a method for calculating the maximum free outflow rate is provided, offering a means to verify the validity of the test results. By combining two test modes, it can adapt to different working conditions ranging from localized leakage to full-hole leakage: the specific location test mode is suitable for situations where only a few formations have severe permeability; the full-section test mode is suitable for situations where the entire borehole is in the same formation and leakage is severe, or where only the overall permeability coefficient needs to be measured. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the square hole in the device of Example 1; Figure 2 This is a schematic diagram of the circular hole in the device of Example 1; Figure 3 This is a schematic diagram of the device in Example 2.

[0026] The reference numerals in the accompanying drawings of the instruction manual include: limit head 1, arc-shaped disc 11, connector 2, small diameter membrane tube 3, reducing connector 4, test membrane tube 5, test hole 51, water-blocking ball valve 6, elastic rope 61, pull rope 62, conical drain funnel 7, upper groove 71, lower groove 72, isolation gasket 8, and counterweight 9. Detailed Implementation

[0027] The following detailed description illustrates the specific implementation method: Example 1 is a test for a specific geological formation. The basic apparatus is shown in the attached figure. Figure 1-2 As shown: As attached Figure 1 and Figure 2 As shown, this embodiment is applicable to situations where only a few formations in a formation have severe permeability and their permeability coefficients need to be measured. The device, from top to bottom, includes a limiting head 1, a connector 2, a small-diameter membrane tube 3, a reducing connector 42, a test section membrane tube, a water-blocking ball valve 6, and a conical drain funnel 7. The circular disk includes two arc-shaped disks 11, one end of which is hinged and the other end is connected by bolts; and the inner wall of the arc-shaped disks 11 is provided with convex strips that cooperate with the grooves.

[0028] The conical drain funnel 7 is used for bottom drainage after the test. Its size is selected according to the orifice diameter and is smaller than the orifice diameter to ensure that the device can be smoothly placed into the orifice. The conical drain funnel 7 can be made of metal, such as stainless steel or aluminum alloy, so that it has a certain weight so that the entire device can be smoothly lowered into the orifice to the predetermined depth by its own weight. The conical drain funnel 7 has two grooves, including a lower groove 72 at the bottom and an upper groove 71 at the top. The upper groove 71 is used to bind and connect with the test section membrane tube, and the lower groove 72 is used to bind the elastic rope 61.

[0029] The water-blocking ball valve 6 is used to seal the conical drain funnel 7 during the water injection test to prevent water leakage from the bottom during the test. The lower pull ring of the water-blocking ball valve 6 is connected to an elastic rope 61, which is made of elastic rubber band. The rubber band passes through the lower hole of the conical drain funnel 7 and is fixed by binding, so that the water-blocking ball valve 6 remains closed under the tension of the rubber band. The upper pull ring of the water-blocking ball valve 6 is connected to a pull rope 62. After the test, the water-blocking ball valve 6 is lifted by pulling the pull rope 62, so that water can be discharged from the bottom.

[0030] A test hole 51 is opened in the middle of the test section membrane tube. The test hole 51 can be a rectangular hole or a circular hole. The size and position of the hole are determined and recorded according to the actual needs of the stratum to be tested. The opening of the test hole 51 must meet two requirements: first, ensure that the test section membrane tube has sufficient strength to avoid breakage when the device is lowered or raised; second, the total area of ​​the test hole 51 must be large enough so that the upper limit of the stratum permeability coefficient corresponding to the maximum free outflow is more than 3 times the actual permeability coefficient of the stratum being tested. The test section membrane tube above and below the test hole 51 must leave a length of not less than 1.5m so that the membrane tube can stick tightly to the hole wall under water pressure, forming a sealing effect equivalent to plugging. The test membrane tube 5 can be selected from agricultural irrigation water hoses or fire hoses of appropriate specifications according to the hole diameter, and its length is adjusted according to the length of the section to be tested.

[0031] The test membrane tube 5 is made of elastic PVC or rubber hose, which can elastically deform and conform to the irregular hole wall under a water pressure of 0.1 to 0.3 MPa. When there is obvious collapse or enlargement of the hole wall, the collapsed section should be backfilled or a variable diameter membrane tube should be used before lowering the device to ensure that the test membrane tube 5 can conform to the hole wall.

[0032] The lower end of the water-blocking ball valve 6 is detachably fixed to the lower end of the drain funnel via an elastic rope 61. The reducing connector 42 has unequal diameters at both ends and multiple connecting grooves on its side wall. The lower part of the reducing connector 42 is connected to the test section membrane tube and the upper part is connected to the small-diameter membrane tube 3 by binding. The diameter of the small-diameter membrane tube 3 is 0.7-0.8 times the diameter of the test membrane tube 5 to facilitate the removal of the entire device from the hole. Its length is adjusted according to the depth to be tested. The upper connector 2 has grooves on its side wall. The lower part of the upper connector 2 is connected to the small-diameter membrane tube 3 by binding, and the upper part of the upper connector 2 is snapped into the limiting head 1. The convex ring inside the arc block corresponds to the groove of the connector 2. After the two arc blocks are closed, the diameter is much larger than the orifice, so that the entire device will not fall off.

[0033] During testing, the device is first installed and placed into the borehole, with test hole 51 aligned with the formation to be tested. Then, water is injected into the membrane tube, and the water pressure causes the membrane tube to adhere to the borehole wall. The unperforated sections of the membrane tube above and below test hole 51 form a plug seal, and water enters the target formation only through test hole 51. Water is continuously injected until a stable water level and constant injection volume are formed in the borehole. Using equipment such as a steel ruler water level gauge and flow meter, data such as injection volume and time are recorded according to the requirements of conventional borehole water injection tests. After the test is completed, the pull rope 62 is pulled to raise the water-blocking ball valve 6, and water is discharged from the bottom. After the membrane tube separates from the borehole wall, the device is removed.

[0034] A method for conducting borehole water injection tests in dry boreholes includes the following steps: Step 1: Opening test holes on a test membrane tube at positions corresponding to the formation to be tested. The size and number of test holes ensure that the equivalent permeability coefficient of the formation corresponding to the maximum free outflow is greater than the actual permeability coefficient of the formation being tested. Step 2: Inserting the test membrane tube with the test holes into the borehole, aligning the test holes with the formation to be tested. Step 3: Injecting water into the test membrane tube. The water pressure causes the test membrane tube to adhere to the borehole wall, sealing the water leakage channels in the borehole wall fissures at the un-holeed portions of the test membrane tube. Water enters the formation to be tested only through the test holes. Step 4: Continuously injecting water until a stable water level and constant injection volume are formed in the borehole. Recording the injection volume, water head height, and time data during the stable period, and calculating the formation permeability coefficient.

[0035] In step 1, before the formal water injection test, the maximum flow rate during free outflow from the membrane tube is measured. During the formal test, the actual stable water injection volume will be measured. Q and Comparison: If Q Approaching or equal to This indicates that the formation permeability is extremely high, and the borehole is actually in a free outflow state. Therefore, the calculated permeability coefficient at this point is only considered as the lower limit of the formation permeability coefficient. If... Q Exceed This indicates that there is a leak at the bottom of the membrane tube.

[0036] The flow rate of the test membrane tube is calculated using the following formula; when the test hole is a single circular hole, the maximum flow rate of a single hole is: ;in The flow coefficient is determined by actual measurement. Single-hole area, The water head height at the center of the orifice, Acceleration due to gravity; when n identical circular holes are opened at the same depth, the maximum water flow rate is: When n identical circular holes are opened at intervals from top to bottom, the maximum water flow rate is the sum of the flow rates of each hole: ;in Let be the vertical distance from the center of the i-th orifice to the water surface. When the test orifice is a long rectangular orifice, the maximum outflow rate of n long rectangular orifices is: ; in, h 1 represents the vertical distance from the top edge of the uppermost hole to the water surface; i This is the i-th hole from top to bottom; a The vertical height of a single elongated rectangular hole; b The width of a single long rectangular hole; dThis is the vertical distance between the top edges of adjacent holes.

[0037] C d Through actual measurement, it was determined that before the formal test, the membrane tube was vertically fixed at the orifice, water was injected into the tube to maintain a known water head height h, and the actual outflow rate Qactual was measured. The actual outflow rate Qactual was then compared with the theoretical value Qtheoretical. The ratio is determined as Cd = Qactual / Qtheoretical, and this measured Cd value is used for subsequent calculations of maximum flow rate and permeability coefficient.

[0038] For testing specific locations, when the water injection head... h Greater than the test segment length When the permeability coefficient k is calculated, the following correction formula is used; ;in, Q Indicates a stable water injection volume; h The water head height caused by water injection Indicates the length of the test section. This represents the area of ​​all test wells below the water level.

[0039] Example 2 is a full-section test, and the basic apparatus is as shown in the attached figure. Figure 3 As shown.

[0040] This embodiment is applicable to situations where the entire borehole is in the same formation and leakage is severe, or where only the comprehensive permeability coefficient needs to be measured but the borehole leakage is severe. The device includes, from top to bottom, a limiting head 1, a connector 2, a test membrane tube 5, an isolation gasket 8, and a gravity component. The limiting head 1 is annular and detachably connected to the connector 2. The connector 2 is provided with a limiting ring groove. The upper end of the test membrane tube 5 is tied to the limiting ring groove of the connector 2, and the lower end of the test membrane tube 5 is tied to the isolation gasket 8 and the gravity component respectively. Multiple test holes 51 are arranged at intervals along the vertical direction along the entire length of the test membrane tube 5.

[0041] The gravity component uses a weight 9, which has a groove for binding with the test membrane tube 5. The weight 9 is a solid metal structure, and its weight is used to place the entire device into the hole. Its size is selected according to the hole diameter and is smaller than the hole diameter. Plastic gaskets are used to enhance the bottom water-proof effect. Drainage holes are opened at intervals along the vertical direction along the entire length of the membrane tube. The size and spacing of the drainage holes are adjusted according to the leakage situation of the borehole. Long strip drainage holes can also be made. The position, spacing, shape and area of ​​the drainage holes need to be recorded. After the test, the static... After a period of time, the water poured into the hole can flow out through the drain hole. A drain hole is provided near the bottom for easy removal of the device after draining. The test membrane tube 5 should not be too thin, with a thickness of 0.2-0.5mm. If it is inserted into the hole to a greater depth, it may break due to its own weight. Use an agricultural irrigation hose or fire hose of appropriate specification according to the hole diameter. The upper end of the test membrane tube 5 is tied to the connector 2, and the lower end is tied to the plastic gasket and the counterweight 9. The limiting head 1 is a circular disc and is snapped or threaded to the connector 2. At least one drain hole must be opened at the bottom of the test membrane tube 5, no more than 20cm away from the counterweight 9, to ensure that residual water at the bottom can drain out.

[0042] During testing, the device is first fabricated and tied up, then placed into the hole at the appropriate depth and securely fixed at the hole opening. Water is then poured into the membrane tube, and the water injection volume is adjusted to maintain a stable water level in the hole. In conjunction with equipment such as a steel ruler water level gauge and flow meter, data such as water injection volume and time are recorded according to the requirements of conventional borehole water injection tests.

[0043] The permeability coefficient is calculated using the following corrected formula: ;in, Q Indicates a stable water injection volume; h The water head height caused by water injection Indicates the length of the test section. This represents the area of ​​all test wells below the water level; and satisfies 50 < h / r' <200; among which .

[0044] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics in the solutions is not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for conducting a borehole water injection test in a dry borehole, characterized in that: Includes the following steps: Step 1: Open test holes on the test membrane tube. The test holes are opened at the positions on the test membrane tube corresponding to the formation to be tested. The size and number of test holes are such that the equivalent permeability coefficient of the formation corresponding to the maximum free outflow is greater than the actual permeability coefficient of the formation being tested. Step 2: Insert the test film tube with the test hole into the borehole, aligning the test hole of the film tube with the formation to be tested. Step 3: Inject water into the test membrane tube. The water pressure causes the test membrane tube to adhere to the borehole wall. The unopened part of the test membrane tube seals the water leakage channel in the borehole wall crack. Water in the tube only enters the formation to be tested from the test hole. Step 4: Continuously inject water into the borehole until a stable water level and constant injection volume are formed. Record the injection volume, water head height, and time data during the stable period, and calculate the formation permeability coefficient.

2. The method for conducting a borehole water injection test in a dry borehole according to claim 1, characterized in that: In step 1, before the formal water injection test, the maximum flow rate during free outflow from the membrane tube is measured. During the formal test, the actual stable water injection volume will be measured. Q and Comparison: If Q Approaching or equal to This indicates that the formation permeability is extremely high, and the borehole is actually in a free outflow state. Therefore, the calculated permeability coefficient at this point is only considered as the lower limit of the formation permeability coefficient. If... Q Exceed This indicates that there is a leak at the bottom of the membrane tube.

3. The method for conducting a borehole water injection test in a dry borehole according to claim 2, characterized in that: In step 1, the flow rate of the test membrane tube is calculated according to the following formula; when the test hole is a single circular hole, the maximum flow rate of a single hole is: ;in The flow coefficient is determined by actual measurement. Single-hole area, The water head height at the center of the orifice, Gravitational acceleration; When n identical circular holes are opened at the same depth, the maximum outflow rate is: ; When n identical circular holes are opened at intervals from top to bottom, the maximum water flow rate is the sum of the flow rates of each hole: ;in is the vertical distance from the center of the i-th orifice to the water surface. When the test holes are elongated rectangular holes, the maximum outflow rate of n elongated rectangular holes is: ; in, h 1 represents the vertical distance from the top edge of the uppermost hole to the water surface; i This is the i-th hole from top to bottom; a The vertical height of a single elongated rectangular hole; b The width of a single long rectangular hole; d This is the vertical distance between the top edges of adjacent holes.

4. The method for conducting a borehole water injection test in a dry borehole according to claim 2, characterized in that: In step 4, when the entire membrane tube is perforated and the water injection head height is... h Not greater than the length of the test section When, permeability coefficient Calculated according to the modified formula; ;in, Q Indicates a stable water injection volume; h The water head height caused by water injection Indicates the length of the test section. This represents the area of ​​all test wells below the water level; and satisfies 50 < h / r' <200; among which .

5. A method for conducting a borehole water injection test in a dry borehole according to claim 2, characterized in that: In step 4, for testing specific locations, when the water injection head h is greater than the test section length l, the permeability coefficient k is calculated according to the following correction formula; ;in, Q Indicates a stable water injection volume; h The water head height caused by water injection Indicates the length of the test section. This represents the area of ​​all test wells below the water level.

6. An apparatus for conducting borehole water injection tests in dry holes, employing the test method described in any one of claims 1-5, characterized in that: The device includes, from top to bottom, a limiting head, a connector, a test diaphragm tube, a water-blocking ball valve, and a drain funnel. The test section of the test diaphragm tube has a test hole. The lower end of the water-blocking ball valve is detachably fixed to the lower end of the drain funnel via an elastic rope. The other end of the water-blocking ball valve is fixed with a pull rope, one end of which extends upward beyond the limiting head. The limiting head includes a circular disc with a diameter larger than the diameter of the hole to be tested. The circular disc is detachably connected to the connector. Both ends of the test diaphragm tube are detachably connected to the connector and the drain funnel, respectively.

7. The apparatus for conducting borehole water injection tests in dry holes according to claim 4, characterized in that: The connector includes an upper connector, a small-diameter membrane tube, and a reducing connector arranged sequentially from top to bottom. The reducing connector has different diameters at both ends and multiple connecting grooves on its sidewall. The small-diameter membrane tube is tied to the connecting groove at the small-diameter end of the reducing connector, and the test membrane tube is tied to the connecting groove at the large-diameter end of the reducing connector.

8. The apparatus for conducting borehole water injection tests in dry holes according to claim 5, characterized in that: The circular disk includes two arc-shaped disks, one end of which is hinged and the other end is connected by bolts; and the inner wall of the arc-shaped disks is provided with convex strips that cooperate with the groove.

9. The apparatus for conducting borehole water injection tests in dry holes according to claim 4, characterized in that: The upper and lower ends of the drain funnel are provided with funnel grooves for binding and fixing with the test membrane tube.

10. An apparatus for conducting borehole water injection tests in dry holes, employing the test method described in any one of claims 1-5, characterized in that: The device includes, from top to bottom, a limiting head, a connector, a test membrane tube, an isolation pad, and a gravity component. The limiting head is circular and detachably connected to the connector. The connector has a limiting ring groove. The upper end of the test membrane tube is tied to the limiting ring groove of the connector, and the lower end of the test membrane is tied to the isolation pad and the gravity component respectively. Multiple test holes are arranged at intervals along the vertical direction along the entire length of the test membrane tube.

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