AU2014202119B2 - Method for testing connectivity between vertical formations while drilling - Google Patents

Abstract

Provided is a method for testing connectivity between vertical formation while drilling. The method for testing the connectivity between the vertical formations while drilling in a fornation structure including a cap rock constituted by 5 impermeable rocks through which a fluid is impermeable and upper and lower reservoirs that are respectively disposed on upper and lower portion of the cap rock and constituted by permeable rocks through which the fluid is permeable includes an equipment preparation process of preparing a drill pipe including a double pipe constituted by an inner pipe and an outer pipe disposed. to surround the inner pipe, a 10 bhit rotatably coupled to a lower end of the double pipe to drill the ground, an expandable first packer spaced upward from the bit and fixedly disposed on an outer circumferential surface of the double pipe, a second packer disposed on the double pipe to seal a space between the outer circumferential surface and an inner wall of a drill hole, and a pressure sensor disposed on the double pipe between the first packer 15 and the second packer, a drilling process of allowing the drill pipe to dig the ground so that a lower end of the drill pipe and the first packer are respectively disposed in the lower reservoir and the cap rock, wherein mud is supplied through the outer pipe, and the mud and rock pieces are collected through the inner pie when the drill pipe digs the ground, a sealing process of expanding the first and second packers to seal a 20 measurement space in which the pressure sensor is disposed in a state where the digging of the drill pipe is stopped, and a measuring process of injecting the fluid into the lower reservoir through the outer pipe and sensing a change in pressure within the measurement space through the pressure sensor in a state where an inlet of the inner pipe is closed. x~ 9 92 Ix x x -- ' x x x x 7 y x x 7xx0

Description

METHOD FOR TESTING CONNECTIVITY BETWEEN VERTICAL FORMATIONS WHILE DRILLING CROSS-REFERENCE TO RELATED APPLICATIONS 5 [0001] This patent application claims priority to Korean Patent Application No. 10-2013-004915, filed on May 02, 2013, the entire contents of which are hereby incorporated by reference. BACKGROUND [0002] The present disclosure relates to a method for testing connectivity test 10 between vertical formations while drilling, and more particularly, to a method for testing connectivity between vertical formations while a drilling operation is performed in a formation structure in which a fluid-permeable formation and a fluid non-permeable formation are alternately stacked on each other. [0003] While greenhouse gases that cause global warming are diverse and 15 include methane, Freon gas, and carbon monoxide, carbon dioxide accounts for about 80% of all greenhouse gases. Because carbon dioxide can be regulated, it is the focus of the greenhouse gas problem. [0004] Carbon Capture & Storage (CCS) technology has recently been viewed with optimism as a technology for reducing carbon dioxide. According to 20 the International Energy Agency (IEA), by the year 2050, about 9.2 billion tons (or 19% of the total amount of carbon dioxide to be reduced per year) may need to be processed through CCS technology. While there are only about four CCS projects in operation around the world that have been substantiated and are commercial-scale 1 projects, about 300 projects are currently being planned, and there are estimates that ,500 or more projects will be needed in 2050, [0005] Underground storage technology (in the storage field of CCS) is one for storing carbon dioxide collected from power plants and the like semi-permanently 5 in the cors of structures underground or under the seabed, and oil fields, gas fields, aquifers, coal layers, and the like are the main sites for storage according to the geological environment, The most important conditions Bor deciding on a storage site are that the site must be one that is at least 800 meters, the reservoir rock must have a high porosity and penetration ratio, and a cap rock must exist at the top of the 10 reservoir rock so that injected carbon dioxide does not escape above ground, Also, the cap rock must ensure sealability because if cracks develop in the cap rock, the carbon dioxide stored in the reservoir rock would escape above ground through the cracks in the cap rock. [0006] A site for carbon dioxide storage is first selected through a geological 15 survey, and after a drill well is formed, the cap rock layer of the drill well is checked for cracks. The Korean Patent No. 0999030, for which the present applicant filed an application and registered the patent, discloses a method for monitoring changes in pressure during injection following drilling, in a state in which all transport and injection equipment has been finalized from the carbon dioxide collecting equipment 20 to the injection site, [0007] In the past, the process of excavating the drill well and the process of detecting cracks in the stratum were separated. Thus, when changes in pressure were monitored during the injection process to determine the possibility of leakage from the upper layer, and injection was stopped according to such a, determination, all 25 work and expended time would be rendered pointless 2 [0007a] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. 5 [0007b] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it 10 existed before the priority date of each claim of this application. SUMMARY [0008] The present disclosure provides a method for testing connectivity between vertical formations while drilling, which is capable of testing the 15 connectivity between the vertical formations while a drill well is formed through drilling. [0009] Some embodiments relate to a method for testing connectivity between vertical formations while drilling in a formation structure including a cap rock constituted by impermeable rocks through which a fluid is impermeable and 20 upper and lower reservoirs that are respectively disposed on upper and lower portion of the cap rock and constituted by permeable rocks through which the fluid is permeable, the method including: an equipment preparation process of preparing a drill pipe including a double pipe constituted by an inner pipe and an outer pipe disposed to surround the inner pipe, a bit rotatably coupled to a lower end of the 25 double pipe to drill the ground, an expandable first packer spaced upward from the 3 bit and fixedly disposed on an outer circumferential surface of the double pipe, a second packer disposed on the double pipe to seal a space between the outer circumferential surface and an inner wall of a drill hole, and a pressure sensor disposed on the double pipe between the first packer and the second packer; a 5 drilling process of allowing the drill pipe to dig the ground so that a lower end of the drill pipe and the first packer are respectively disposed in the lower reservoir and the cap rock, wherein mud is supplied through the outer pipe, and the mud and rock pieces are collected through the inner pipe when the drill pipe digs the ground; a sealing process of expanding the first and second packers to seal a measurement 10 space, in which the pressure sensor is disposed, when the drill pipe is in a state where digging has stopped; and a measuring process of injecting the fluid into the lower reservoir through the outer pipe and sensing a change in pressure within the measurement space through the pressure sensor in a state where an inlet of the inner pipe is closed. 15 [0010] In some embodiments, the pressure sensor may be disposed at the same depth as the upper reservoir. [0011] In other embodiments, the mud may include a clay base mud, and the fluid may include water or gas. [0012] In still other embodiments, the second packer may be vertically 20 movably disposed along the double pipe. Particularly, the second packer may include a piston that is closely attached and fitted between an outer surface of the double pipe and drill-hole wall, and the second packer may be vertically movable by an oil pressure that is applied between the outer circumferential surface of the double pipe and the inner wall of the drill hole through an upper portion of the piston. 4 [0013] In even other embodiments, when the measurement space increases in pressure after the fluid is injected into the lower reservoir, a fluid leakage region may be detected by using a time point at which the injection of the fluid into the lower 5 reservoir starts and a time point at which the measurement space increases in pressure. [0014] In yet other embodiments, when the measurement space decreases in pressure after the injection of the fluid into the lower reservoir is stopped, a fluid leakage region may be detected by using a time point at which the injection of the 10 fluid into the lower reservoir is stopped and a time point at which the upper reservoir decreases in pressure. 4a [0015] In further embodiments, a distance form the pressure sensor to a fluid leakage region may be detected by using an amplitude in pressure change within the upper reservoir. [0016] In still farther embodiments, the cap rock and the reservoirs may be 5 alternately stacked again downward from the lower reservoir in the formation structure, and after the measuring process is performed, the drilling process, the sealing process, and the measuring process may be repeatedly performed while the drill pipe digs the ground. 10 BRIEF DESCRYiPT ION OF THE DRAWINGS [0017] The accompanying drawings are included to provide a further understanding of the present invention, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present invention and, together with the description, serve to explain principles of the present 15 invention. In the drawings: [0018] FIG, 1 is a schematic flowchart of a method for testing connectivity between vertical formations while drilling according to an embodiment of the present invention: [0019] FIG 2 is a schematic cross-sectional view for explaining a method for 20 forming a, drill well in the ground by a drill pipe and testing connectivity between vertical formations according to the present invention; and [0020] FIG. 3 is a schematic enlarged view of a region A of FIG. 2. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 5 [0021] A method for testing connectivity between vertical formations while drilling according to the present invention may be performed together with a method for testing salability of a cap rock while drilling a gas injection well(drill well) in Carbon Capture & Storage (CCS) that is a carbon dioxide storage system. 5 [0022] However., the present invention is not restrictively applied to only the CCS fields, That is, the present invention may be applied to all drilling methods with respect to compressed air energy storage (CAES) and oil and underground water productions [0023] Flereinafter, techniques for storing gases such as carbon dioxide in 10 underground geological formations in the CCS fields, for example, a method for testing connectivity between vertical formations while drilling according to an embodiment of the present invention will be described in more detail with reference to the accompany drawings. [0024] F.i C. 1 is a schematic flowchart of a method for testing connectivity 15 between vertical formations while drilling according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view for explaining a method for foring a drill well in the ground by a drill pipe and testing connectivity between vertical formations according to the present invention. [0026] The method for testing the connectivity between the vertical 20 formations while drilling according to an embodiment of the Present invention is to test connectivity between vertical formations while drilling so as to store gases such as carbon dioxide in the underground formations of land or undersea. Thus, a fonation structure having a specific pattern may be needed, That is, the present invention may be applied to a geological formation structure in which reservoirs 1A 25 and 12 and a cap rock 20 are alternately stacked. Here, even if the reservoirs I1 and 6 12 and the cap rock 20 are not alternately stacked, the present invention may be applied to a formation structure in which at least one cap rock is disposed, and then, reservoirs are disposed on each of upper and lower portions of the cap rock [0026] First, the reservoirs 11 and 12 and the cap rock 20 will be described, 5 [0027] The reservoirs 11 and 12 represent formations constituted *by rocks having porosity and water permeability. Examples of the reservoirs i1 and 12 may include sedimentary rocks formed by sand, sandstone, arkose, or the like, Since each of the reservoirs I1 and 12 has a plurality of pores, natural gases or underground water may be filled into the pores. Thus, when a pressure is applied to the reservoirs 10 11 and 12. the natural gases or underground water may move along the reservoirs 11 and 12. [0028] According to the CCS technologies, the reservoirs 11 and 12 may provide places in which carbon dioxide is injected and stored. lere, although the reservoirs 11 and 12 may be developed newly, oilfields or gas fields that are 15 previously developed may be utilized as reservoirs. Also, aquifers in which underground water is filled into pores of rocks may be used as reservoirs. [0029] Explaining a principle for storing carbon dioxide in more detail, the fine pores within the reservoirs 11 and 12 constituted by porous rocks have been saturated with hydrocarbon such as oil or natural gases or flud such as water. Thus, 20 when a gas such as carbon dioxide is injected into the reservoirs 11 and 12 at a high pressure, the gas may push the fluid within the pores and then be stored in the pores while being filled into the pores of the reservoirs 11 and 12. Also, when the reservoirs 11 and 12 are located at about 800 mi depth of underground, gases may be injected at a high pressure and then stored in the reservoirs I and 12, 7 [0030] The cap rock 20 may be disposed on the upper or lower portion of each of the reservoirs 11 and 12 to trap the fluid in the reservoirs II and 12. Thus, the cap rock 20 may be generally constituted by impermeable rocks having very low porosity and water permeability. In general, a shale formation may be used as the 5 cap rock 20. [0031] The present invention provides a method for testing the connectivity between the vertical formations while a drill well for injecting carbon dioxide is fbrined. [0032] To perform the embodiment of the present invention, a drill pipe 10 hav ing a special shape is needed, [0033] Referring to FIG. 2, a drill pipe 100 according to the present invention includes a double pipe 60 and a bit 70 An existing drill pipe has been provided in a single pipe type. That is, the existing drill pipe has a structure in which a bit is coupled to a lower end of the drill pipe. However, the drill pipe according to the 15 present invention is different from that according to the related art in that the drill pipe is not provided in a single pipe type, but provided in a double pipe type. [0034] The double pipe 60 includes an inner pipe 40 and an outer pipe 50, The inner pipe 40 may be inserted into the outer pipe 50 to forn a double pipe structure on the whole. That is, the inside of the inner pipe 40 may serve as a first 20 flow path 61 through which a fluid flows. Also, a second flow path 62 through which a fluid flows may be defined between an inner circumference of the outer pipe 50 and an outer circumference of the inner pipe 40. [0035] Also, a bit 70 is rotatably coupled to a lower end of the double pipe 60. The bit 70 crushes rocks of the ground while rotating together with the drip pipe to 25 allow the drip pipe to dig the rocks. 8 [00361 Also, the drill pipe 100 used in the present invention includes a first packer 80 and a second packer 90. The first packer 80 is spaced a predetermined distance upward from the lower end of the double pipe 60 to which the bit 70 is coupled and then is fixedly coupled to an outer circumferential surface of the double 5 pipe 60. [0037] As illustrated in FIG, 3, the first packer 80 includes a body part 81 and an expansion part 82. The body part 81 has a pipe shape. Also, upper and lower ends of the body part 81 are pipe-jointed on the outer pipe 50. In the current embodiment, the body part 81 of the first packer 80 may be screw-coupled. The 10 expansion part 82 may be formed of an elastically expandable material and be coupled to an outer circumferential surface of the body part 81. A space part 83 may be defined between an inner circumferential surface of the expansion part 82 and the outer circumferential surface of the body part 81. Also, an inflow hole 84 may be defined in the body part 81 to inject a fluid into the space part 83. A fluid injection 15 pipe 85 disposed along the inside of the double pipe 60 may be connected to the inflow hole 84, As a result, a fluid may be introduced into or discharged from the space part 83. When the fluid is injected, the expansion part 82 is expanded and then closely attached to an inner wall of a drill well w. [0038] The second packer 90 is disposed on an upper end of the first packer 20 80 to vertically move along the double pipe 60. In the current embodiment, the second packer 90 may have a piston shape. The second packer 90 may have a ring shape and be fitted onto the outer circumferential surface of the double pipe 60 and closely attached to the inner wall of the drill well w, Thus, the second packer 90 may be vertically slid. In the current embodiment, a casing c is installed on an upper 25 portion of the drill well w. The second packer 90 may move within a range in which 9 the casing c is installed. However, the second packer 90 does not always move within the range in which the casing c is installed. For example, the second packer 90 may move to a lower portion of the drill well w. [0039] In the current embodiment, the second packer 90 moves by a 5 hydraulic system. That is, since the drill well w is blocked by a cover s, a sealed space 31 is defined between the second packer 90 and the cover s. Here the space 31 may serve as the inside of a cylinder. [0040] When a pump 91 operates to inject a fluid into the space 31 through a fluid injection line 91 to apply a hydraulic pressure in a state where mud supplied 10 while drilling is filled into a lower space (i.e., a space between an outer circumferential pipe and a drill-hole wall) of the second packer 90, the second packer 90 is slid downward. On the other hand, when the fluid is collected to release the hydraulic pressure, the second packer 90 moves upwardly. [0041] A first pressure sensor 41 is disposed on an outer wall of the double 15 pipe 60 between the first packer 80 and the second packer 90. Also, a second pressure sensor 42 is disposed on the outer wall of the double pipe 60 inder the first packer 80. [0042] Non-described reference symbol r in FIG. 2 may represent a mud circulation system for supplying mud through the double pipe 60 and separating and 20 circulating the collected mud and rock pieces. [0043] After the drill pipe 100 including the above-described constitutions is prepared (an equipment preparation process), drilling and testing according to the present invention are performed at the same time, [0044] In the drilling press, the bit rotates in a state where the drill pipe 25 100 stands up to dig the ground g, thereby verticaly forming a drill well w. In the 10 mud circulation system r, the mud is supplied toward a lower end of the bit 70 through the second. flow path 62. When rocks are crushed while supplying the mud, rock pieces are generated. The mud and rock pieces are collected into the mud circulation system r through the first flow path 61 5 [0046] Although the mud and rock pieces are introduced into a space between the double pipe 60 and an inner wall of the drill well w, since the second packer 90 disposed on an upper portion of the drill well w blocks the discharge path defined between the drill well w and the double pipe 60, all the mud and rock pieces may be collected into the mud circulation system r through the first flow path 61. 10 After the rock pieces and mud are separated from each other in the mud circulation system r, the mud is supplied again into the drill well w. Although the second packer 90 covers the space between the drill well. w and the double pipe 60 in the drilling process, the first packer 80 may be maintained in a state in which the first packer80 is not expanded, 15 [0046] In the drilling process, the drill pipe 100 passes through the upper reservoir 11 and the cap rock 20 to stop the drilling when the drill pipe 100 reaches the lower reservoir 12. In the state where the drilling is stopped, the bit 70 is disposed in the lower reservoir 12, and the first packer 80 is disposed in the cap rock 20, Alternatively, the first packer 80 may be disposed at a boundary between the cap 20 rock 20 and the lower reservoir 12. Here, the important thing is that an upper space of the first packer 80, particularly, a test space t sealed between the first packer 80 and the second packer 20 has not to be connected to the lower reservoir 12. [0047] Also, the first pressure sensor 41 has to be disposed within the test space t. Since the test space t is sealed to have the sane pressuret the pressure within 11 the test space t is not changed according to a position of the first pressure sensor 41. However, the test space t may be defined at the same depth as the upper reservoir II, (0048] As described above, in the state where the drilling process is temporarily stopped, a sealing process for testing is performed. The first packer 80 is 5 expanded to seal a space between the inner wall of the drill well w and the outer circumferential surface of the double pipe 60. Since the second packer 90 seals the space between the double pipe 60 and the inner wall of the drill well 2 always at the upper portion of the drill well w, the sealed test space t may be defined between the first packer 80 and the second packer 90. Also, an upper portion of the inner pipe 40 10 is covered to lose the first flow path 61. [0049] When the sealing process is finished as described above, a measuring process is performed. [0050] In the measuring process, a fluid is injected through the second flow path 62 in a state where the supply of the mud is stopped. Water that does not have a 15 bad influence on underground environments may be used as the fluid. [0051] The fluid is discharged through a lower end of the drill pipe 100 and then is introduced into the lower reservoir 12. Here, the second. pressure sensor 42 measures a pressure of a lower space b defined under the first packer 80, [0052] if cracks do not occur in the cap rock 20 disposed on the lower 20 reservoir 12, or the lower reservoir 12 and the upper reservoir 11 are not connected to each other even though the cracks occur, the test space t defined above the first packer SO may not be changed in pressure due to the introduction of the fluid. [0053] However, if cracks 21 occur in the cap rock 20, or a plurality of pores are provided in the cap rock 20, the cap rock 20 may not seal the lower reservoir 12. 25 In this case. a pressure may be transmitted into the upper reservoir 11 through the 12 cap rock 20 by the fluid that is injected into the lower reservoir 12 at a high pressure. in more detail, the pores within the upper and lower reservoirs 11 and 12 and the pores or cracks within the cap rock 20 may be saturated with water or gases, In this state, when the high-pressure fluid is injected into the lower reservoir 12, existig 5 fluids within the pores may successively receive the pressure to increase a pressure within the upper reservoir 12. After a predetermined time elapses from a time point at which the fluid is injected, the first pressure sensor 80 measures a change in pressure within the test space t to test sealability of the cap rock 20! [0054] If the pressure is changed within an available range, it is seen that the 10 cap rock 20 connects the lower reservoir 12 to the upper reservoir 11. If a change in pressure does not occur or is less, the sealability of the cap rock 20 may be tested. [0055] If the cap rock 20 is not secured in sealability, it may be difficult to inject and store carbon dioxide into the lower reservoir 12., Thus, it may be previously determined whether the corresponding formation is suitable for storing 15 the carbon dioxide in the drilling process, [0056] As described above, the method for testing a change in pressure due to the injection of the fluid may be useful in that the test result is confirmed immediately. That is, a pressure may be quickly propagated into the whole upper reservoir 11 without a flow of a fluid (a fluid such as hydrocarbon or water that is 20 saturated within the injected gas or pores). That is, the change in pressure within the upper reservoir I I due to the introduction of the fluid may be amost immediately detected when compared to the actual flow time of the fluid. Thus, the change in pressure may be useful as a factor for testing connectivity between vertical formations. 13 (0057] As described above, after the sealability or connectivity of the cap rock 20 is tested, the drilling process is performed. again. That is, after the first packer 80 is contracted, the first flow path 61 is opened, and then the mud is supplied again through the second flow path 62 Then, the drill pipe 100 may dig up to the 5 lower reservoir 12 disposed at a position lower than the present position. Also, the sealing process and the measuring process as described above are performed. Through the above-described method, the drilling and testing may be performed at the same time up to the depth that is determined in the basic geological investigation, [0058] -lereinafter, application examples of the method for testing the 10 connectivity between the vertical formations while drilling will be described. [0059] First, according to the present invention, a region in which a gas leaks from the cap rock 20 or a region in which the sealability is not maintained may be measured through an interrelationship between changes in pressure within the upper reservoir 11. due to the injection of the fluid. That is, when the region in which the 15 gas leaks is close to the first pressure sensor 41, a pressure transmission time may be relatively short when compared to that the region in which the gas leaks is far away from the first pressure sensor 41, On the other hand, if the gas leaking region is far away from the pressure sensor, the pressure transmission time may be relatively long [0060] In this point, the first pressure sensor 41 may measure a time from a 20 time point at which the gas is injected into the lower reservoir 12 to a time point at which a pressure of the upper reservoir 11 increases to reversely track a leakage occurrence distance by using the measured times. Here, a leakage occurrence region may be estimated along a concentric circle with respect to a center point of the first pressure sensor 41. 14 [0061] However, if the first packer 80 does not completely seal the space between the inner wall of the drill well w and the double pipe 60, an increase in pressure within the test space I may be measured immediately after the fluid is injected into the lower reservoir 12 n this case,. since it does not matter in the 5 sealability of the cap rock 20, a pressure may be measured again after the first packer 80 is contracted and then expanded again. [0062] However, the region in which the salability is not secured may be predicted through a time from the fluid injection time point to a pressure increase time point in the upper reservoir 11. There are many variables for quantifying an 10 interrelationship between the distance and pressure change time points The pressure change time point may be changed according to the porosity and water permeability of the upper reservoir 1, boundary conditions between vertical formations the fluid injection pressure, and the like., [0063] When a predetermined time elapses after the fluid is injected, a 15 normal state at which a pressure is not changed according to a time may become. That is, even though the cracks occurs in the cap rock 20, when the pressure of the upper reservoir 11 increases at the time point at which the fluid is injected, the pressure may be constantly maintained without changing in pressure according to a time. 20 [0064] While maintainingI the above-described normal state, if the tipper reservoir II increases in pressure suddenly. it may be determined that a new fluid leaks. Here, an occurrence of the release of the normal state may be because new cracks occur in the cap rock 20. [0065] H-owever, a pressure may be changed within a predetermined range 25 even though the normal state is maintained after the injection of the fluid into the 15 lower reservoir 12 starts. Thus, in the present invention, a change in pressure may be filtered within a predetermined range, and also, it may be determined that the new cracks occur only when the change in pressure exceeds a predetermined range. [0066] Also, when the injection of the fluid into the lower reservoir 12 is 5 stopped, the normal state may be released to reduce an amount of fluid injected into an upper permeable formation 30. Thus, a gas leakage occurrence region may be analogized by using an interrelationship between the time point at which the injection of the gas is stopped and the time point at which the pressure within the upper permeable formation 30 drops 10 [0067] Since the time point at which the pressure drop is detected is proportional to a distance from the first pressure sensor 41 to a place at which the gas leakage occurs, a radius around the center point of the first pressure sensor 41 may be extended as time goes. Thus, the leakage region may be predicted by using the concentric circle region. 15 [0068] Alternatively, the fluid leakage region may be predicted by using an amplitude in pressure change in addition to the time point at which the change in pressure is detected, That is. although the fluid is injected at the same pressure, if the fluid leakage occurrence region is close to the first pressure sensor 41, the upper reservoir 1 1 may be significantly changed in pressure when compared that the fluid. 20 leakage occurrence region is far away from the first pressure sensor 41. Since the pressure is transmitted in all directions, if the pressure is transmitted from a long distance, a pressure loss may increase when compared that the pressure is transmitted. from a short distance. This is done because the pressure loss is involved. due to influences of surrounding conditions in the pressure transmission path. As described 25 above, the place (a region in which the scailability of the cap rock is lost) at which the 16 leakage of the fluid occurs may be predicted and determined by using the time at which the change in pressure within the upper reservoir II is detected and the amplitude in pressure change. However, although the accurate quantitative determination in position and distance may be possible when the surrounding 5 conditions are considered, the foundation in quantitative measurement may be obtained in tie present invention, [0069] So far, although the second packer is fitted between the casing and the drill pipe to vertically move by an oil pressure, the present invention is not limited to the structure of the second packer For example, the second packer may have the 10 same structure as the first packer. [0070] Alternatively, a rail may be vertically disposed on the upper portion of the drill pipe, and the second packer having the ring shape may be coupled to the rail. Then, the second packer may vertically move along the rail by a gear that converts a rotation motion of a motor into a linear motion, 15 [0071] According to the present invention, since the connectivity between the vertical formations is tested while driving, th.e sealability of the cap rock, which is an important technical factor in the carbon dioxide storage technologies, may be accurately measured. [0072] Also, although the tentative business promotion exists because the 20 connectivity test with respect to the cap rock is performed in the injection process after the drilling is completed in the related art, the present invention may enhance the economic feasibility in the CCS technology. [0073] According to the present invention, since the connectivity test between the vertical formations is performed while drilling to immediately confirm 17 whether a target drill well is used for the gas storage formation, the reliable solution with respect to the possible leakage of carbon dioxide later may be suggested. (0074] Also, the region in which the sealability of the cap rock is not secured may be estimated by using a time interval from the fluid injection tine point or fluid 5 injection stopping time point to the time at which the upper reservoir is changed in pressure or the amplitude in pressure change within the upper reservoir. [0075] The description of the present invention is intended to be illustrative, and those with ordinary skill in. the technical field of the present invention pertains will be understood that the present invention can be carried out in other specific 10 forms without changing the technical idea or essential features. Hence, the real protective scope of the present invention shall be determined by the technical scope of the accompanying claims. 18

Claims (10)

1. A method for testing connectivity between vertical formations while drilling in a formation structure comprising a cap rock constituted by impermeable rocks through which a fluid is impermeable and upper and lower reservoirs that are 5 respectively disposed on upper and lower portion of the cap rock and constituted by permeable rocks through which the fluid is permeable, the method comprising: an equipment preparation process of preparing a drill pipe comprising a double pipe constituted by an inner pipe and an outer pipe disposed to surround the inner pipe, a bit rotatably coupled to a lower end of the double pipe to drill the 10 ground, an expandable first packer spaced upward from the bit and fixedly disposed on an outer circumferential surface of the double pipe, a second packer disposed on the double pipe to seal a space between the outer circumferential surface and an inner wall of a drill hole, and a pressure sensor disposed on the double pipe between the first packer and the second packer; 15 a drilling process of allowing the drill pipe to dig the ground so that a lower end of the drill pipe and the first packer are respectively disposed in the lower reservoir and the cap rock, wherein mud is supplied through the outer pipe, and the mud and rock pieces are collected through the inner pipe when the drill pipe digs the ground; 20 a sealing process using the first and second packers to seal a measurement space, in which the pressure sensor is disposed, when the drill pipe is in a state where digging has stopped; and 19 a measuring process of injecting the fluid into the lower reservoir through the outer pipe and sensing a change in pressure within the measurement space through the pressure sensor in a state where an inlet of the inner pipe is closed. 5

2. The method of claim 1, wherein the pressure sensor is disposed at the same depth as the upper reservoir.

3. The method of any one of the preceding claims, wherein the mud comprises a clay base mud, and the fluid comprises water or gas. 10

4. The method of any one of the preceding claims, wherein the second packer is vertically movably disposed along the double pipe.

5. The method of claim 4, wherein the second packer comprises a piston 15 that is closely attached and fitted between an outer surface of the double pipe and drill-hole wall, and the second packer is vertically movable by an oil pressure that is applied between the outer circumferential surface of the double pipe and the inner wall of the drill hole through an upper portion of the piston. 20

6. The method of any one of the preceding claims, wherein, when the measurement space increases in pressure after the fluid is injected into the lower reservoir, a fluid leakage region is detected by using interval from a time point at which the injection of the fluid into the lower reservoir starts to a time point at which 25 the measurement space increases in pressure. 20

7. The method of any one of the preceding claims, wherein, when the measurement space decreases in pressure after the injection of the fluid into the lower reservoir is stopped, a fluid leakage region is detected by using interval from a 5 time point at which the injection of the fluid into the lower reservoir is stopped to a time point at which the upper reservoir decreases in pressure.

8. The method of any one of the preceding claims, wherein a distance from the pressure sensor to a fluid leakage region is detected by using an amplitude 10 in pressure change within the upper reservoir.

9. The method of any one of the preceding claims, wherein the cap rock and the reservoirs are alternately stacked again downward from the lower reservoir in the formation structure. 15

10. The method of claim 9, whereinafter the measuring process is performed, the drilling process, the sealing process, and the measuring process are repeatedly performed in sequence. 20 21