Drilling method for geological drilling under carbonate rock stratum

Abstract

The invention discloses a drilling method for geological drilling under a carbonate rock stratum. The technical problems that an existing drilling method is large in drilling difficulty and high in construction cost under a carbonate rock stratum, the stratum environment is damaged, and the accuracy of geological exploration data is low are mainly solved. According to the method, when carbonate rock stratum drilling is carried out, circulating liquid is switched into clean water, so that the clean water in a well body can take away rock debris generated by drilling and can also take away heat generated by drilling of a drill bit, and the operation that in-well slurry needs to be circulated to a slurry pool in existing slurry circulation is avoided; and meanwhile, the original geological environment of the stratum can be prevented from being damaged by slurry permeating into the stratum. Clear water is used for replacing slurry or chemical materials for drilling carbonate rock strata, so that the clear water can carry rock debris to directly diffuse into surrounding strata, and the rock debris has the same geological composition as the surrounding strata and contains underground water, so that the rock debris does not cause adverse effects on the surrounding strata environment; and compared with slurry, the construction cost can be greatly saved.

Description

Technical Field

[0001] The present invention relates to the field of mineral exploration technology, and in particular to a drilling method for geological drilling under carbonate rock formations. Background Art

[0002] Carbonate rock is an important type of sedimentary rock, mainly including limestone, dolomite, dolomitic limestone, etc. Its composition is composed of carbonate minerals (calcite, dolomite) such as calcium carbonate and magnesium carbonate. Carbonate rock has the characteristics of developing karst. This rock layer is the aquifer of groundwater in bedrock areas, and also the storage layer of resources such as oil and natural gas. Therefore, carbonate rock formations are geological objects that need to be faced in the implementation of projects such as mineral resource exploration, hydrogeological exploration, geothermal resource exploration and development and utilization.

[0003] In the process of geological drilling, mud is an indispensable circulating fluid, which is used to maintain the stability of the hole wall, cool the drill bit, carry rock cuttings and suspended rock powder, etc. However, carbonate rock is hard in texture. Due to the geological structure and the cracks, caves and karst crevices developed by the composition characteristics, the carbonate rock strata have good water conductivity and large local underground space. The existence of cracks, karst crevices and caves in carbonate strata leads to the frequent leakage of circulating mud during geological drilling construction in such strata, and the leakage speed is fast and the permeability is large, resulting in a large amount of mud as a circulating fluid lost during rotary drilling, which cannot return to the borehole orifice and cannot flow back to the mud pool on the ground, and cannot form a complete circulation system. Furthermore, when the mud cannot complete the circulation, the slag produced by drilling cannot be carried out of the borehole with the mud, which is easy to cause accidents such as buried drill and stuck drill. Moreover, since the mud cannot take away the heat through circulation, the heat generated by grinding the rock in the drill bit accumulates, which will cause the problem of burning drill at the bottom of the hole.

[0004] In order to solve the problem of mud leakage, the commonly used treatment method in the field is to inject thick mud or chemical materials to plug the leakage, or to lower casing to plug the cave; however, in the process of realizing the technical solution in the embodiment of the present application, the inventors of the present application found that the above-mentioned technology has at least the following technical problems: due to the large underground space and many uncertain factors, it is very difficult to implement plugging in carbonate rock formations with developed cavities such as cracks, caves, and karst crevices, and the construction cost is high and the implementation period is long; in addition, due to the large water channels in carbonate rock formations, the wide distribution and good water conductivity, the penetration distance of chemical materials or thick mud used for plugging is very long, and they are eventually retained in the rock gaps, blocking the water channels and changing the original natural state of the formation; as a result, after the drilling is completed, the hydrogeological parameters obtained through the drilling pumping test and the water injection test are quite different from the actual situation of the original formation, and the accuracy deviation of the geological exploration data is relatively large.

[0005] The information disclosed in this background technology section is only used to deepen the understanding of the background technology of the present disclosure, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art known to those skilled in the art. Summary of the invention

[0006] In view of at least one of the above technical problems, the present disclosure provides a drilling method for geological drilling in carbonate rock formations; it mainly solves the technical problems that the existing drilling methods are difficult to drill in carbonate rock formations, have high construction costs, damage the formation environment, and result in low accuracy of geological exploration data.

[0007] According to one aspect of the present disclosure, a drilling method for geological drilling in carbonate formations is provided, which comprises the following steps: (1) Use mud wall positive circulation rotary drilling to drill into the loose overburden to the carbonate rock formation, conduct pumping test and recharge test, and obtain hydrogeological parameter information of the loose overburden; (2) switching the drilling circulating fluid into clean water, and continuing to drill downward into the carbonate rock layer borehole coaxial with the loose overburden borehole; (3) inserting a groundwater level observation meter into the carbonate rock formation borehole, and adjusting the supply speed of the clean water according to the measurement information of the groundwater level observation meter to ensure that the water level in the carbonate rock formation borehole is at least 2m higher than the groundwater level; (4) Real-time monitoring of the clean water flow rate. When the clean water flow rate is greater than 50m 3 / h, the drilling speed of the carbonate rock formation is correspondingly increased; when the clean water flow rate is less than 40 m 3 / h, stop drilling the carbonate rock formation borehole and increase the supply of clean water; (5) When drilling into a fractured zone in a carbonate rock formation, a wall protection flower pipe having an array of through holes is lowered into the carbonate rock formation borehole; (6) After the carbonate rock formation is drilled to the designed depth, the supply of clean water is stopped after the drill is started for at least 3 m.

[0008] In some embodiments of the present disclosure, in the step (1), the drilling of the loose covering layer borehole is stopped after leakage occurs, and a cementing casing having a diameter matching the diameter of the loose covering layer borehole is lowered into the loose covering layer borehole.

[0009] In some embodiments of the present disclosure, in the step (2), the diameter of the carbonate rock layer drilled is smaller than the diameter of the loose overburden layer drilled.

[0010] In some embodiments of the present disclosure, in step (2), the water supply capacity of the clean water source is not less than 60m 3 / h; when drilling the carbonate rock formation hole normally, the water supply speed is controlled to be 40 to 50 m 3 / h.

[0011] In some embodiments of the present disclosure, in the step (2), before drilling the carbonate rock formation, a filter and a water pressure monitor are correspondingly arranged at the connection between the drill bit and the drill rod; the filter includes a backwash module.

[0012] In some embodiments of the present disclosure, in the step (4), when the water pressure monitor detects that the pressure is greater than 0.25 MPa, the drilling of the carbonate rock formation is stopped and the supply of clean water is increased.

[0013] In some embodiments of the present disclosure, in the step (4), after the drilling of the carbonate rock formation borehole is stopped and the clean water supply is increased and the water supply flow cannot be restored, the drilling tool including the drill bit and the drill rod is correspondingly intermittently raised or lowered.

[0014] In some embodiments of the present disclosure, in the step (5), a plurality of water-permeable holes with a hole diameter of 8 to 12 mm are evenly arranged in an array on the wall of the wall-protecting flower tube, and the spacing between the water-permeable holes is 280 to 320 mm.

[0015] One or more technical solutions provided in the embodiments of the present application have at least any of the following technical effects or advantages: 1. When drilling in carbonate formations, the circulating fluid is switched to clean water. The clean water in the wellbore can not only take away the cuttings generated by drilling, but also take away the heat generated by the drill bit, thus avoiding the need to circulate the mud in the well to the mud pool in the existing mud circulation, and at the same time preventing the mud slurry from seeping into the formation and destroying the original geological environment of the formation.

[0016] 2. Use clean water instead of mud or chemical materials to drill carbonate rock formations, so that clean water can carry rock cuttings and spread directly into the surrounding strata. Since the rock cuttings have the same geological composition as the surrounding strata and the underground itself contains groundwater, it will not have an adverse effect on the surrounding strata environment, and compared with mud, it can greatly save construction costs.

[0017] 3. By monitoring and adjusting the clean water supply flow, the different structures of carbonate formations can be adapted to the drilling response during the drilling process. There is no need to inject additional chemical materials. Only by adjusting the clean water flow and the drilling rig working parameters, drilling problems such as large formation space and blocked diffusion channels can be easily dealt with.

[0018] 4. On the one hand, the wall protection flower pipe can support the well wall in the fracture zone of carbonate rock formation. On the other hand, it can ensure good water permeability through the water permeable holes on the pipe wall to avoid affecting the cuttings and drill bit heat generated during the drilling process. At the same time, the diameter of the water permeable holes set according to the geological characteristics can also prevent large pieces of gravel from falling into the borehole wall and causing accidents such as drill sticking. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the working of a mud wall positive circulation rotary drilling operation in one embodiment of the present application.

[0020] Figure 2 This is a schematic diagram of a drilling operation using clean water as the circulating fluid in an embodiment of the present application.

[0021] In the above figures, 1 is a drilling rig, 2 is a mud pool, 3 is a mud pump, 4 is a drill pipe, 5 is a drill bit, 6 is a clean water pool, and 7 is a filter. DETAILED DESCRIPTION

[0022] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "top", "bottom", "inside", "outside", "vertical", "horizontal", "clockwise", "counterclockwise", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0023] In order to better understand the technical solution of the present application, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0024] In order to solve the problems of large mud leakage, high construction cost, drill sticking and drill burning in existing geological drilling methods when facing carbonate rock formations, and affecting the original natural state of the formation, resulting in deviations in geological exploration results, this example discloses a drilling method for geological drilling under carbonate rock formations. Taking a geothermal resource feasibility survey project in Henan Province as an example, the designed hole depth of the geothermal exploration borehole is 2150m, the thickness of the upper covering layer is 1085m, and the lower bedrock formation is Ordovician limestone with developed fissures and karst. Specifically, this drilling method includes the following steps: (1) Use mud wall positive circulation rotary drilling to drill into the loose overburden to the carbonate rock formation, conduct pumping tests and reinjection tests, and obtain hydrogeological parameter information of the loose overburden.

[0025] The upper part of the carbonate rock formation is covered with a loose overburden. In this embodiment, a borehole in the loose overburden is drilled in the loose overburden based on a mud wall positive circulation rotary drilling. Figure 1 After the pile point is staked out and positioned, the pile driver 1 is moved to the side of the pile point, the pile driver drill rod 4 is aligned with the staked pile point, and vertical drilling is performed. During the drilling process, the mud pump 3 continuously extracts mud from the mud pool 2 and transports it to the drill rod. By injecting mud into the borehole, a mud wall is formed to protect the stability of the borehole wall; at the same time, the mud is returned from the borehole to the mud pool, thereby taking out the slag and rock cuttings in the borehole through the mud, avoiding problems such as drill sticking.

[0026] When the mud leaks obviously, that is, the amount of mud returned to the mud pool is significantly less than the amount pumped by the mud pump, it means that the drilling rig has drilled into carbonate rock formations with developed fissures and karst. At this time, the drilling rig should be stopped to avoid the loss of mud and the spread of leaked mud underground to affect the original geological environment. At the same time, the pumping test and recharge test are carried out through the drilled loose cover holes to obtain the relevant hydrogeological parameters of the loose cover.

[0027] Among them, in this embodiment, in order to ensure the structural stability of the loose covering layer borehole, a cementing wall protection casing is lowered into the loose covering layer borehole. The diameter of the cementing wall protection casing matches the diameter of the loose covering layer borehole. The cementing wall protection casing is used to stabilize the hole wall of the loose covering layer borehole to avoid collapse and other problems in the subsequent drilling process.

[0028] (2) Switch the drilling circulating fluid to clean water and continue drilling downward into the carbonate rock borehole coaxial with the loose overburden borehole.

[0029] After the loose cover borehole is drilled, the drilling operation of the carbonate rock layer under the carbonate rock formation is carried out. Considering the development of fractures and karst in the carbonate rock formation, in order to avoid the loss of a large amount of mud slurry, which increases the drilling cost and affects the original formation environment, see Figure 2 In this embodiment, the drilling circulating fluid is switched to clean water. Specifically, a clean water tank 6 is dug on the ground in advance, and the clean water tank is connected to a water source and a certain amount of clean water is stored in advance to ensure that the water supply capacity of the clean water tank is not less than 60m 3 / h, the clean water is pumped into the drill pipe 4 through the mud pump 3 and sprayed out from the drill bit 5. In addition, the mud pump is adjusted so that the water supply speed of the drill tool during the drilling of the carbonate formation is 40-50 m 3 / h range, in this case, the corresponding control water supply speed is 45m 3 / h, and the drilling rig drill bit adopts a three-cone drill bit for top water rotary drilling. As a result, the core of the borehole is ground into powdered rock cuttings by the drill bit, and then carried out of the borehole by the flowing clean water flow, and diffused to the water conduction channel of the surrounding formations by utilizing the good water conductivity of the carbonate rock formation. Since clean water is used as the conveying medium in this process, the adverse effects of the existing use of mud or chemical materials on the surrounding formation environment are avoided.

[0030] Among them, in this embodiment, the diameter of the carbonate rock layer drill hole is smaller than the diameter of the loose covering layer drill hole, and the two are coaxially arranged, thereby forming a shoulder at the intersection of the two hole bodies, and then the shoulder is used to support the cementing casing at the loose covering layer drill hole, and at the same time helps to fix the cement filled outside the casing to prevent leakage.

[0031] (3) A groundwater level observation meter is inserted into a borehole in the carbonate rock layer, and the supply rate of clean water is adjusted accordingly based on the measurement information of the groundwater level observation meter.

[0032] Considering that groundwater has a certain pressure, in order to ensure that the water in the borehole can effectively carry the rock cuttings and spread smoothly to the surrounding strata, in this embodiment, during the drilling of the carbonate rock formation, a groundwater level observation meter is lowered into the carbonate rock formation borehole to obtain groundwater level information. At the same time, the mud pump is controlled in real time according to the water level information output by the groundwater level observation meter to ensure that the water level in the carbonate rock formation borehole is at least 2m higher than the groundwater level, that is, the clean water circulating fluid in the carbonate rock formation borehole maintains a head height of at least 2m, so that the clean water returned from the drill bit can diffuse into the surrounding strata under the pressure of the head height, thereby smoothly carrying and transporting the rock cuttings in the carbonate rock formation borehole to the cavities, cracks and other places in the strata around the well body through a stable water flow. At the same time, the flowing water can also exchange heat with the drill bit, take away the heat generated during the drilling process of the drill bit, and avoid the occurrence of problems such as burning the drill. As the carbonate rock formation is continuously drilled, the rock cuttings generated by the drilling operation at the corresponding depth will flow with the water flow to the underground cavity of the corresponding layer, avoiding blockage of the drilling well while not affecting the normal water conduction of the formation.

[0033] In order to prevent the rock debris generated during the drilling process of the carbonate rock formation from clogging the water path at the drill bit, in this embodiment, before drilling the carbonate rock formation, see Figure 2A filter 7 and a water pressure monitor are provided at the connection portion between the drill bit 5 and the drill rod 4. In this example, the filter screen diameter of the filter is 1.0-1.5 mm. The filter is used to filter out debris in the water body, and the water pressure monitor is used to detect the water pressure on both sides of the filter and the change of the water pressure at the bottom of the well, and judge whether the filter has a blockage problem according to the pressure difference. In this example, the filter includes a backwashing module. When the filter is judged to be blocked according to the pressure value output by the water pressure monitor, the backwashing module is started to backwash the filter screen of the filter, thereby restoring the filtering capacity of the filter screen.

[0034] (4) Real-time monitoring of the clean water flow rate. When the clean water flow rate is greater than 50m 3 / h, the drilling speed is increased accordingly; when the clean water flow rate is less than 40 m 3 / h, stop drilling and increase the supply of clean water; during the drilling process of carbonate rock formation drilling, the clean water supply is monitored in real time. In this example, the clean water supply is controlled at 45m / h by adjusting the mud pump. 3 / h. Since the stratum is heterogeneous, the clean water supply will be at 45m 3 / h, when the water flow rate is greater than 50m 3 / h, it means that the current drilling space is large. At this time, adjust the drilling rig, increase the drilling rig rotation rate, increase the drilling speed of the drilling rig, and drain and drain water stably. 3 / h or when the water pressure monitor detects that the filter pressure is greater than 0.25MPa, it means that the diffusion channel of the bottom formation of the borehole is blocked by rock debris, and the drainage channel is blocked by rock debris. At this time, stop drilling and increase the supply of clean water, thereby increasing the water head height in the hole, accelerating the water flow rate, and thus improving the ability of the water flow to carry rock debris, and transporting the rock debris to a farther underground cavity. In some other embodiments, while increasing the supply of clean water, the drill bit and drill rod are intermittently raised or lowered, and the sediment in the drill tool is dumped out through the movement of the drill tool and the clean water delivery pressure. In addition, in some other embodiments, after stopping drilling and increasing the clean water flow, the normal water supply flow cannot be restored and the mud pump pressure increases, the backwash module of the filter is started to backwash the filter screen of the filter to eliminate the problem of the filter blocking the waterway.

[0035] (5) When drilling into a fractured zone in a carbonate rock formation, a wall protection flower pipe with an array of through holes is lowered into the borehole in the carbonate rock formation.

[0036] With the drilling of the carbonate layer well body, when the hole collapse phenomenon occurs during the drilling process, such as the drilling footage increase speed slows down or the drill cannot be drilled to the original drilling depth after the drill is pulled out, it means that the drilling encounters a broken zone in the carbonate formation. In order to solve the hole collapse problem caused by the broken zone, in this embodiment, a wall protection flower pipe is placed in the corresponding depth formation, and the wall protection flower pipe is used to support the borehole wall. Among them, a number of water-permeable holes with a diameter in the range of 8 to 12 mm and a hole spacing of 280 to 320 mm are uniformly arrayed on the wall of the wall protection flower pipe. In this example, the diameter of the water-permeable hole is 10 mm and the hole spacing is 300 mm. Therefore, under the premise that the wall protection flower pipe can effectively support the borehole wall, the water-permeable hole can ensure the good water permeability of the wall protection flower pipe, and can also prevent large pieces of gravel from falling into the borehole wall to cause a stuck drill accident.

[0037] (6) After the carbonate rock formation is drilled to the designed depth, the supply of clean water shall be stopped after the drill is pulled at least 3 m.

[0038] In this embodiment, after the carbonate rock formation is drilled to the designed depth, in order to avoid the residual rock cuttings in the hole settling at the bottom of the hole and causing the drill to be buried and stuck, the drilling rig is first lifted and the drill rod is drilled at least 3m. During the lifting of the drill rod, the supply of clean water is guaranteed. After the drill rod is lifted into place, the supply of clean water is stopped and normal drilling is started, thereby completing the drilling.

[0039] In this case, the drilling method of the present invention was used to implement drilling construction in carbonate rock formations. It took 17 days to drill the 1085m covering soil layer above the carbonate rock formation. When drilling the lower Ordovician limestone, it took 41 days to drill to a depth of 2151.5m, with an average daily footage of 26.0m. The daily work efficiency was increased by more than 80% compared with the ordinary drilling method, and a large amount of construction costs could be saved. In this case, the geothermal well after drilling was subjected to three depth-reducing pressure-bearing complete well stable flow pumping tests, with a maximum pumping flow of 182.04m 3 / h, water temperature 64℃, unit water inflow 15.3 m 3 / h, the single well water output and unit water output are more than 50% higher than the drilling method constructed by the existing method, and the permeability coefficient of the formation can be accurately obtained.

[0040] Although some preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0041] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the inventive concept. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A drilling method for geological drilling in carbonate rock formations, characterized in that: The steps include: (1) Use mud wall positive circulation rotary drilling to drill into the loose overburden to the carbonate rock formation, conduct pumping test and recharge test, and obtain hydrogeological parameter information of the loose overburden; (2) switching the drilling circulating fluid into clean water, and continuing to drill downward into the carbonate rock layer borehole coaxial with the loose overburden borehole; (3) inserting a groundwater level observation meter into the carbonate rock formation borehole, and adjusting the supply speed of the clean water according to the measurement information of the groundwater level observation meter to ensure that the water level in the carbonate rock formation borehole is at least 2m higher than the groundwater level; (4) Real-time monitoring of the clean water flow rate. When the clean water flow rate is greater than 50m 3 / h, the drilling speed of the carbonate rock formation is correspondingly increased; when the clean water flow rate is less than 40 m 3 / h, stop drilling the carbonate rock formation borehole and increase the supply of clean water; (5) When drilling into a fractured zone in a carbonate rock formation, a wall protection flower pipe having an array of through holes is lowered into the carbonate rock formation borehole; (6) After the carbonate rock formation is drilled to the designed depth, the supply of clean water is stopped after the drill is started for at least 3 m.

2. The drilling method according to claim 1, characterized in that: In the step (1), the drilling of the loose covering layer borehole is stopped after the slurry leakage occurs, and a cementing casing with a diameter matching the diameter of the loose covering layer borehole is lowered into the loose covering layer borehole.

3. The drilling method according to claim 1, characterized in that: In the step (2), the diameter of the carbonate rock layer drilled is smaller than the diameter of the loose covering layer drilled.

4. The drilling method according to claim 1, characterized in that: In step (2), the water supply capacity of the clean water source is not less than 60m 3 / h; the water supply speed of the clean water is controlled to be 40-50m during normal drilling of the carbonate rock formation. 3 / h.

5. The drilling method according to claim 1, characterized in that: In the step (2), before drilling the carbonate rock formation, a filter and a water pressure monitor are correspondingly arranged at the connection between the drill bit and the drill rod; the filter includes a backwash module.

6. The drilling method according to claim 5, characterized in that: In the step (4), when the water pressure monitor detects that the pressure is greater than 0.25 MPa, the drilling of the carbonate rock layer is stopped and the supply of clean water is increased.

7. The drilling method according to claim 1, characterized in that: In the step (4), after the drilling of the carbonate rock formation is stopped and the clean water supply is increased and the water supply flow cannot be restored, the drilling tool including the drill bit and the drill rod is correspondingly intermittently raised or lowered.

8. The drilling method according to claim 1, characterized in that: In the step (5), a plurality of water-permeable holes with a diameter of 8 to 12 mm are evenly arranged in an array on the wall of the wall-protecting flower tube, and the spacing between the water-permeable holes is 280 to 320 mm.

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