US 12,442,948 B1
Borehole-to-surface near-source transient electromagnetic high-precision exploration method
Guoqiang Xue, Beijing (CN); Weiying Chen, Beijing (CN); Junjie Xue, Beijing (CN); Yulian Zhu, Beijing (CN); and Pengfei Lv, Beijing (CN)
Assigned to Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing (CN)
Filed by Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing (CN)
Filed on Jun. 14, 2025, as Appl. No. 19/238,389.
Claims priority of application No. 202510366840.8 (CN), filed on Mar. 26, 2025.
Int. Cl. G01V 3/38 (2006.01); G01V 3/20 (2006.01); G01V 3/26 (2006.01)
CPC G01V 3/38 (2013.01) [G01V 3/20 (2013.01); G01V 3/26 (2013.01)] 2 Claims
OG exemplary drawing
 
1. A borehole-to-surface near-source transient electromagnetic high-precision exploration method, comprising:
step 1: preparing data acquisition in a manner of surface-based fixed receiving and in-borehole movable transmitting, comprising:
deploying a plurality of receivers on a surface along a survey line at intervals of 50 meters, placing a movable transmitting electrode in a borehole at one of positions including three positions of B1, B2 and B3, and placing a fixed transmitting electrode A0 at a head location of the borehole on the surface;
step 2: transmitting a bipolar rectangular zero-crossing step current with an intensity of 40 amperes (A) to a periphery of the borehole through the fixed transmitting electrode A0 and the movable transmitting electrode at the position B3, and observing and recording electric field component data in electromagnetic component ExAB3(t) through the plurality of receivers deployed along the survey line on the surface;
step 3: moving the movable transmitting electrode in the borehole from the position B3 to the position B2, transmitting the bipolar rectangular zero-crossing step current with the intensity of 40 A to the periphery of the borehole through the fixed transmitting electrode A0 and the movable transmitting electrode at the position B2, and observing and recording electric field component data in electromagnetic component ExAB2(t) through the plurality of receivers deployed along the survey line on the surface;
step 4: moving the movable transmitting electrode in the borehole from the position B2 to the position B1, transmitting the bipolar rectangular zero-crossing step current with the intensity of 40 A to the periphery of the borehole through the fixed transmitting electrode A0 and the movable transmitting electrode at the position B1, and observing and recording electric field component data in electromagnetic component ExAB1(t) through the plurality of receivers deployed along the survey line on the surface; and
step 5: determining apparent resistivity values of a target formation based on the electric field component data in the electromagnetic component ExAB3(t), the electric field component data in the electromagnetic component ExAB2(t) and the electric field component data in the electromagnetic component ExAB1(t), and inferring, based on the apparent resistivity values of the target formation, oil-bearing zones.