JP2005127131A - Method for examining bore-hole collective, apparatus to inject water into such bore-hole collective and blocking of cracks - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method to test a collective body of bore holes, an apparatus for injecting water into such a bore hole collective and blocking of the cracks. <P>SOLUTION: In a group of the bore holes drilled in a rock M which cracks F pierce through and extend across, a main bore hole (1) which is a water injecting bore hole for water to be injected into and interconnects the cracks and a surrounding bore hole (2) which is at least one surrounding bore hole for collecting water connected to the main bore hole via at least one crack F so as to take in the water injected into the main bore hole and reached the surrounding bore hole through the crack F are included. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an assembly of boreholes or a group of boreholes drilled in a rock through which a crack extends. The present invention also relates to a device for injecting or injecting water into such an assembly of boreholes (hereinafter also referred to as borehole groups). In addition, the present invention also provides a method for testing clogging of rock cracks provided with a borehole group associated with a water injector for injecting water into such a borehole group. Related.

  The technical field of the present invention is that of excavation storage cavities for containing liquid and / or gaseous fluids. Such storage cavities are used in particular for storing liquid or gaseous hydrocarbons. In the context of the present invention, such cavities are in particular unlined drilling cavities that keep the fluid stored in the cavity based on hydrodynamic confinement principles. Therefore, since the cavity excavated in the rock is located in the groundwater, the water above the cavity applies pressure according to its height, so that the fluid can be kept in the state stored in the cavity.

  Such drilling cavities with hydrodynamic confinement effects are often associated with devices that make it possible to ensure that the fluid is stored in the cavity. Such a device can be referred to as a “water curtain”. FIG. 1 is a vertical cross-sectional view of a conventional storage location with a drilling cavity C and a water curtain. The water curtain is generally constituted by a main tunnel G excavated vertically above the excavation cavity C and below the groundwater. As can be seen from FIG. 1, the mine shaft G is also provided with an array of bore holes B extending from the mine shaft G substantially perpendicular to both the cavity and the shaft. Furthermore, the well P connects the tunnel G to the ground surface S. It can be seen that the cavity C is located deep below the upper surface N of the groundwater. A water layer, that is, a water curtain, can be formed on the cavity C by injecting water through the well P into the tunnel G and its bore hole B. The water thus injected flows through the natural crack in the rock from the water curtain and reaches the cavity C. The water stream E is necessarily directed in the direction of the cavity. This is because the pressure spreading inside the cavity is lower than the pressure of groundwater in the rock. Therefore, the water injected through the water curtain reaches the wall of the cavity C and flows down to the bottom of the cavity C. The amount of water in the cavity is indicated by O. When the gas stored in the cavity is a gas, the pressure governing the inside of the cavity needs to be a pressure sufficient for the gas to harmonize with the liquid phase L. Above this liquid phase, the gas is the vapor phase V.

  Thus, the water curtain can ensure that the fluid stored in the cavity is reliably stored so that the fluid stored in the cavity does not leak from cracks in the rock.

  However, experience has shown that cracks in rocks tend to become clogged or clogged after water has been injected through the water curtain for an extended period of time. As a result, in the long term, the flow rate of water from the water curtain to the cavity decreases. Thus, the sealing of the cavities, ie more precisely the hydrodynamic confinement effect, is not assured any more or is not completely guaranteed. Therefore, the fluid stored inside the cavity can leak out. In order to reduce the tendency of the cracks to plug or plug, the characteristics of the water injected by the water curtain can be changed. Such blockage of the cracks can be known by measuring the pressure and flow rate of water injected by the water curtain. It should be noted here that if the cavity is filled with the fluid to be stored, it is impossible to work directly on the cavity or water curtain. Therefore, as a real problem, natural cracks in rocks tend to block water by passing water through these cracks from the water curtain into the cavity for a long period of time.

  The object of the present invention is to identify the above-mentioned problems associated with the plugging of the natural crack connecting the water curtain to the drilling cavity and to repair the natural crack. Since it is already impossible to act on the cavity or water curtain, the present invention consists in testing in-situ the tendency of natural cracks occurring in the rock from which the storage cavity is excavated.

To this end, the present invention provides a collection of boreholes or a group of boreholes drilled in a rock through which a crack extends. This group of boreholes is a group of boreholes.
A main borehole for water injection serving to contain injected water, said main borehole interconnecting cracks;
-At least one peripheral borehole for recovering water connected to said main borehole through at least one crack, injected into said main borehole and reaching the peripheral borehole through the crack And a surrounding borehole for collecting water.

  Preferably, the borehole group includes a plurality of peripheral boreholes that are perforated around the main borehole to collect water. This borehole group provides samples of the environment for testing the tendency of cracks to occur naturally in rocks.

The present invention provides a water injector for injecting water into the group of boreholes described above.
-The water injector is connected to the inlet of the main borehole and has a pressurized water injection line provided with an injection pump;
-At least one water recovery line connected to the inlet of at least one surrounding borehole.

  Preferably, a pressure gauge for measuring the injection and recovery pressure is provided in the injection and recovery line.

  Further, it is preferable to provide a flow meter for measuring the flow rate of the recovered water in the above-described at least one recovery line.

  It is also preferable to provide a pressurized water acquisition device in the injection and recovery line.

  Preferably, a stop valve is provided in at least one recovery line described above.

  In another aspect of the water injector, the pump in the injection line removes or collects water coming from the recovery line so that the water circulates in the closed circuit.

  Circulating water through the closed circuit promotes crack closure. Therefore, the test time can be shortened. Since water is not supplied from the outside or removed to the outside, the circulating water is highly filled and increasingly filled.

  According to another advantageous feature of the invention, the water injector comprises a setting tank that serves to contain water from the recovery line.

  Preferably, the water injector includes an aeration tank to which water coming from the precipitation tank is supplied.

  Preferably, the infusion pump takes water out of the aeration tank.

  Preferably, a means for enriching the oxygen content of the water is provided in the aeration tank.

  Furthermore, the water injector may include a booster line for supplying water to the aeration tank.

  The precipitation tank makes it possible to collect deposits and particles of any size that accumulate at the bottom of the precipitation tank. Therefore, the type of collected sediment and particles can be analyzed. The aeration tank is preferably fed from the precipitation tank over the weir. Therefore, the water overflowing into the aeration tank is substantially free of precipitates and particles. By concentrating the oxygen in the water present in the aeration tank, it becomes possible to refill the water pumped out by the pump of the injection line. Thus, the oxygen injected into the main injection hole flows through natural cracks and oxidizes certain elements present in the rock. Such oxidation is thought to affect crack closure. With this water injection machine, it is possible to test a sample in an environment where the tendency of crack closure to be obtained in a relatively short time and relatively easily. Furthermore, the means required for the water injector is a conventional means that is simple and relatively inexpensive. Thus, the tendency of the natural cracks present in the excavated rock to be excavated or to be excavated can be evaluated in a relatively short time.

  In a preferred practical embodiment, the water injector includes a plurality of recovery lines connected to each of a plurality of surrounding boreholes for recovering water. The preferred arrangement of the borehole group is to drill a central main borehole and provide a peripheral borehole around the main borehole to collect water so that as much water as possible is injected through the main borehole. It is the structure which collects.

  The present invention also provides a method for testing the closure of cracks F in the rock M provided with a group of boreholes associated with a water injector, the method comprising: Determining the characteristics of each of the rock, the injected water, and the water naturally present in the rock during the first stage before injecting water into the main borehole, and second, after the water injection stage, Re-determining each characteristic.

Additionally or alternatively, the present invention is a method for testing the closure of a crack F in a rock M provided with a group of boreholes associated with a water injector, with the following parameters:
-Water injection pressure into the main borehole;
-The flow rate of water collected in the surrounding borehole;
-The pressure in the recovery line;
-Monitoring at least one change in the physicochemical and biological properties of the water circulating in the system (water, dissolved gas, bacterial content) during or after the long-term water injection phase .

  It is preferred that the two test methods be combined to ensure that the crack closure tendency is as complete as possible. It should be noted that according to the invention it is possible to test the crack closing tendency in situ, ie directly in the rock in which the excavation cavity has been excavated or excavated. This is not a theoretical test in the laboratory.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 2 shows a non-limiting example configuration for explaining one embodiment of the present invention, in which a group of boreholes drilled in a rock through which a natural crack extends. It is a figure which shows roughly the water injection machine connected to the borehole group.

  In order to test in situ the cracking tendency of rocks in which excavated storage cavities have been excavated, a group of boreholes consisting of a plurality of boreholes, ie borehole aggregates, are first drilled in the rock in the excavated cavity. The boreholes are drilled before starting to use the cavity, ie before filling with a liquid or gaseous fluid.

  For example, a group of boreholes can be drilled at a height level position in a water curtain tunnel. The borehole group may be drilled at a height level position of the excavation cavity. The borehole group is drilled from the height of the wall of the mine or cavity that allows it to be accessed into the mine or cavity, or to the height of the wall, otherwise to the height of the access mine. The borehole group includes a main borehole 1 for water injection and at least one surrounding borehole 2 for collecting water. Preferably, in practice, a plurality of peripheral boreholes 2 are drilled around the main borehole 1. As shown in FIG. 2, the rock M has an overall arrangement of crossing cracks F that connect the main borehole 1 to the surrounding borehole 2. Thus, for each sample in-situ and for environmental testing, it replicates the same conditions that extend between the water curtain and the drilling cavity, albeit on a relatively small scale. The main borehole 1 can have a diameter from X to Y for a length from Z to W. The bore hole is preferably linear in terms of ease of drilling. The peripheral borehole 2 is preferably straight and has a diameter from x to y for a length from z to w. The surrounding borehole is separated from the main borehole by Rcm to Sm. The main borehole and the surrounding borehole can extend in parallel. But this is not essential. Since the boreholes are drilled from the walls of the tunnels or cavities, each borehole has an inlet, ie the inlet 11 of the main borehole 1 and the inlet 21 of the surrounding borehole 2. In this example, only one main borehole is provided, but in some cases, a plurality of main boreholes may be provided.

  Since the arrangement of the cracks F passes through the rock M, the main borehole and the surrounding borehole intersect with the cracks. Therefore, the bore holes are connected to each other through the crack F.

  In the present invention, the borehole groups that constitute the environmental test samples are provided in association with the water injector. This water injector can be installed in a mine shaft with a borehole group in the wall. The water injector mainly comprises a water injection line 12 connected to the inlet 11 of the main borehole 1 and a water recovery line 22 connected to the inlet 21 of the surrounding borehole. Actually, since there are a plurality of surrounding boreholes, the corresponding plurality of water recovery lines 22 are connected to the respective inlets 21 of the plurality of surrounding boreholes 2. Infusion line 12 is connected upstream of infusion pump 15 to produce a pressurized supply. Thus, pressurized water is injected through the injection line 12 into the main borehole 1 and from there through the crack F to the surrounding borehole 2 from which water can be recovered via the recovery line 22. Thus, a water flow circuit is formed that passes through some of the natural cracks F, and the tendency of these cracks to block or plug during extended water injection periods can be tested. The occlusion tendency or the occlusion itself can be detected by variations in the water injection parameters, i.e., the pressure or flow rate of water flowing through the borehole group and the water injector, or physicochemical and biological properties. For example, the reference parameters and characteristics can be read before starting the water injection and monitored during or after the water injection phase. Variation (decrease) in injection pressure in the main borehole is a characteristic of cracks that tend to plug. The fluctuation (decrease) in the flow rate collected in the surrounding borehole is also a characteristic of blockage tendency. A fluctuation (decrease) in the pressure of the recovery line is also a characteristic of the blockage. In addition, variations in the physicochemical and biological properties of the water flowing through the system (water, gas dissolved in water, bacterial content) are also indications of cracks that have a tendency to plug.

The occlusion phenomenon is specified as follows.
-In case of blockage of geochemical origin (origin) ・ In the liquid phase (water and dissolved gas), the results of the obtained samples are analyzed,
• For the rock itself, over-coring the center of the injection and recovery boreholes, over-coring, studying the flakes under a microscope, and identifying the relevant mineral species by X-ray diffraction.
-In the case of a biological source blockage, samples of cracks located around the injection and recovery boreholes are taken and analyzed for deposits or sediments, and the cylindrical specimen is over-extracted.

  The characteristic elements or parameters that make it possible to reveal and identify the occlusion tendency or the occlusion itself are diverse and diverse. Analysis and determination methods other than those described herein can be used to realize and identify occlusions without departing from the scope of the present invention. In other words, any test technique can be used to evaluate the blockage tendency of the borehole groups and associated water injectors of the present invention without departing from the scope of the present invention. The various testing tasks aimed at determining some property or parameter are not critical to the present invention. Rather, the present invention provides a sample of the environment to which test procedures can be applied that allow the drilling storage cavity to be drilled or to identify or identify the cracking propensity or blockage itself in the rock being drilled. It aims to reproduce each.

  In order to facilitate the acquisition of a sample to perform a test or to evaluate the results of an analysis, a water injector provides multiple means that can be performed simultaneously or alternately. In particular, the injection line 12 and the recovery line 22 can be provided with pressure gauges 13 and 23 for measuring the respective injection and recovery pressures. The recovery line 22 can be provided with a flow meter 26 for measuring the flow rate of the recovered water. The injection line 12 and the recovery line 22 may be provided with means 14, 24 for acquiring a sample of pressurized water, ie a pressurized water acquisition device. A stop valve 25 can be provided in the recovery line 22.

  The present invention provides a water injector that can circulate water through a closed circuit to facilitate the process of crack closure. That is, the water recovered by the recovery line 22 is injected again into the injection line 12.

  In a preferred embodiment, closed-circuit water circulation is achieved by means of a precipitation tank 4 and an aeration tank 5. The water recovered by the recovery line 22 is collected in the precipitation tank 4 where deposits and particles of any size can be deposited at the bottom of the precipitation tank. As can also be seen from FIG. 2, the bottom of the sedimentation tank 4 is covered with a layer of sediment 41. This deposit can be collected and analyzed. Therefore, information regarding the type of rock and its blockage tendency can be acquired. The sedimentation tank 4 is equipped with a weir 42 that allows water from the sedimentation tank 4 to overflow into the adjacent aeration tank 5. Therefore, water from the precipitation tank 4 is injected into the aeration tank 5. This water is substantially free of sediment. The aeration tank 5 is provided with means for injecting oxygen into water to concentrate the oxygen content of the water, for example, an aeration system 51. Therefore, the oxygen content of the water in the aeration tank 5 can be concentrated. Aeration systems also exist in water curtain equipment to remove traces of hydrocarbons in the recovered water. In order to close the circuit, the inlet 17 of the injection line 12 is connected to a pump 15 immersed in the aeration tank 5. Advantageously, the water booster line 32 is connected to the aeration tank 5 and serves the function of allowing first supply to the closed circuit and priming, and then maintaining the system at a constant volume. The water booster line 32 can also be provided with a device 34 for taking pressurized water, a stop valve 35 and a flow meter 36.

  Therefore, the water taken into the aeration tank 5 by the pump 15 comes from the precipitation tank 4, and the precipitation tank 4 itself is supplied with water through the outlet of the recovery line 22. The water taken in by the pump 15 is substantially free of deposits and enriched with oxygen, so that water containing a high oxygen content is injected into the crack F. Oxygen oxidizes certain constituent elements of the rock in the crack. This oxidation can cause crack closure.

Such a water injector for injection in connection with the borehole group of the present invention allows water to flow effectively through the cracks F in the rock M. Prior to the start of the water injection phase, certain reference characteristics must be obtained or determined and then monitored during the water injection stage to detect variations in these reference characteristics. Therefore, it is possible to establish a baseline or initial budget at various levels. For example, it is possible to consider:
− Geochemistry. This budget is established by creating flakes for analysis by X-ray diffraction diagrams of samples obtained from cracks in rocks under a polarizing microscope based on the core sample.
− Hydrogeology. A zero budget is established by testing the permeability of the borehole (Horner-type injection-relaxation type test in the injection borehole, and testing the effect between the injection and recovery boreholes). These tests make it possible to accurately determine the properties of the surrounding rock layer that are in direct contact with the injection borehole.
-Physical chemistry. Analyze injected water (booster line), and water naturally present in rocks, to detect initial ions (anions and cations containing certain rare earth elements), physical (pH, redox potential, etc.), and Provide biological (bacterial identification in sterile culture) status.

  Of course, other areas can be considered to determine the reference characteristics. After the initial phase is complete, a water injection phase can be started in which water is injected into the rock. Therefore, after injecting water into the injection main borehole, it is recovered through the surrounding borehole for recovering water. Accordingly, the water is precipitated in the precipitation tank 4, oxidized in the aeration tank 5, and then injected again into the main borehole. This closed circuit circulation can last from weeks to months to account for detectable variations in the predetermined characteristics.

  Periodically, the injection or recovery flow rate and the injection or recovery pressure can be measured. It is also possible to obtain samples with the devices 14, 24 and 34. It is also possible to measure physicochemical or biological parameters.

  Variations in these measurements can account for occlusion or at least an occlusion tendency as described above.

  The occlusion phenomenon is identified by investigating the presence of water and rock surrounding the crack as described above and examining the bacteria present around the injection and recovery boreholes.

  When the blockage tendency becomes clear, for example, the characteristics of the injected water can be changed and corrected. One element in the water may increase and / or another element may decrease. Additives can be added to the injected water.

  With the assembly of boreholes and corresponding water injectors, it is possible to carry out various types of blockage test procedures directly on the rock where the excavation storage cavity is installed.

1 is a vertical cross-sectional view of a conventional storage location including a drilling cavity and a water curtain. 1 is a schematic view of a water injector connected to a collection of boreholes drilled in a rock through which natural cracks extend.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main bore hole 2 Surrounding bore hole 4 Settling tank 5 Aeration tank 11 Inlet 12 Water injection line 13 Pressure gauge 14 Pressurized water acquisition device 15 Injection pump 17 Inlet 21 Inlet 22 Water recovery line 23 Pressure gauge 24 Pressurized water acquisition device 25 Stop valve 26 Flow meter 32 Water booster line 34 Pressurized water acquisition device 35 Stop valve 36 Flow meter 41 Sediment 42 Weir 51 Aeration system B Borehole C Drilling cavity E Water flow F Crack G Tunnel L Liquid phase M Rock N Top surface O Amount of water in the cavity P Well S Ground surface V Vapor phase

Claims (16)

In the assembly of boreholes drilled in the rock through which the crack F extends,
-A main borehole for water injection which functions to contain the injected water, said main borehole interconnecting the cracks;
-At least one peripheral borehole for recovering water connected to the main borehole through at least one crack, injected into the main borehole and through the crack into the peripheral borehole; An assembly of boreholes, including the surrounding boreholes for recovering the reaching water.   The assembly of boreholes according to claim 1, comprising a plurality of peripheral boreholes for recovering water drilled around the main borehole. A water injector for injecting water into the borehole of the borehole assembly according to claim 1 or 2,
-A pressurized water injection line connected to the inlet of the main borehole, the water injection line provided with an injection pump;
A water injector comprising at least one water recovery line connected to an inlet of the at least one peripheral borehole.   The water injector according to claim 3, wherein a pressure gauge for measuring an injection pressure and a recovery pressure is provided in the injection line and the recovery line.   The water injector according to claim 3 or 4, wherein the at least one recovery line is provided with a flow meter for measuring a flow rate of the recovered water.   The water injector for injecting water into the borehole of the assembly of boreholes according to claim 3, 4 or 5, wherein a pressurized water acquisition device is provided in the injection line and the recovery line.   The water injector according to any one of claims 3 to 6, wherein a stop valve is provided in the at least one recovery line.   The water injector according to any one of claims 3 to 7, wherein the injection pump of the injection line extracts water coming from the recovery line so that the water circulates in a closed circuit.   The water injector according to any one of claims 3 to 8, further comprising a precipitation tank that performs a function of containing water from the recovery line.   The water injector according to claim 9, further comprising an aeration tank to which water coming from the precipitation tank is supplied.   The water injector according to claim 10, wherein the injection pump extracts water from the aeration tank.   The water injector according to claim 10 or 11, wherein the aeration tank is provided with means for concentrating oxygen content of water.   The water injector according to any one of claims 10 to 12, further comprising a booster line for supplying water to the aeration tank.   The water injector according to any one of claims 3 to 13, comprising a plurality of recovery lines connected to respective boreholes of a plurality of surrounding boreholes for recovering water. A method for testing crack closure in a rock provided with an assembly of boreholes according to claim 1 or 2 related to the water injector according to any one of claims 3-14,
First, determining the characteristics of each of the rock, the injected water, and the naturally occurring water in the rock during the first stage before injecting water into the main borehole;
Second, after the water injection step, determining the characteristic again. 15. A method for testing crack closure in a rock provided with an assembly of boreholes according to claim 1 or 2 in relation to a water injector according to claim 14, comprising variations of at least one of the following parameters: A method comprising the step of monitoring.
-Injection pressure into the main borehole;
-The flow rate collected in the surrounding borehole;
-The pressure in the recovery line, and-the physicochemical and biological properties of the water (water, gas dissolved in the water, bacterial content) circulating in the system during or after the long water injection phase

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