함수율 변화에 따른 포항 지열 시추코어의 전기비저항 (Electrical Resistivity Versus Water Contents of Core Samples from a Geothermal Borehole in Pohang, Korea)

서지정보

· 발행기관 : 한국자원공학회
· 수록지 정보 : 한국자원공학회지 / 45권 / 5호 / 526 ~ 535페이지
· 저자명 : 이상규, 이태종

초록

As an effort for precise measurement of electrical resistivity of a rock or soil sample, basic physical properties of rock samples, such as water content, porosity, and dry density have been measured based on the standard test method suggested by Korean Society for Rock Mechanics and ISRM, and discussed about the temporal variation of resistivity and water content of the rock sample during the measurement. Conventional 4-electrode array can cause errors in resistivity measurement due to the fact that the water in the filter papers infiltrates to the rock samples. Instead, we suggest a 2-electrode array with appropriate load, which can give rather stable results by compensating resultant contact resistance. Keeping the sample in water for several hours is necessary to get fully saturated rock sample, otherwise the air in the pore space cannot be fully replaced by the water. As experiment time elapses, the water on the surface or pore space of the core sample evaporates (decrease of relative water content), which causes severe increase of measured electrical resistivity. For a core sample from deep geothermal well in Pohang, Korea, for example, the resistivity increase 22 times from 205 ohm-m to 4,444 ohm-m, when relative water content decrease from 99.6% to 89.3%, respectively.

영어초록

As an effort for precise measurement of electrical resistivity of a rock or soil sample, basic physical properties of rock samples, such as water content, porosity, and dry density have been measured based on the standard test method suggested by Korean Society for Rock Mechanics and ISRM, and discussed about the temporal variation of resistivity and water content of the rock sample during the measurement. Conventional 4-electrode array can cause errors in resistivity measurement due to the fact that the water in the filter papers infiltrates to the rock samples. Instead, we suggest a 2-electrode array with appropriate load, which can give rather stable results by compensating resultant contact resistance. Keeping the sample in water for several hours is necessary to get fully saturated rock sample, otherwise the air in the pore space cannot be fully replaced by the water. As experiment time elapses, the water on the surface or pore space of the core sample evaporates (decrease of relative water content), which causes severe increase of measured electrical resistivity. For a core sample from deep geothermal well in Pohang, Korea, for example, the resistivity increase 22 times from 205 ohm-m to 4,444 ohm-m, when relative water content decrease from 99.6% to 89.3%, respectively.

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