Method for underground in-situ extraction of hydrocarbon compound in oil shale

The invention relates to a method for the underground in-situ extraction of a hydrocarbon compound in an oil shale, which comprises the following steps: arranging at least one working well and one production well in an enclosed working region where the hydrocarbon compound in the oil shale is extracted, communicating the bottoms among the working wells by directional drilling after a drilling well enters an oil shale ore layer, injecting water and inert gas water vapor into the working well to form a near-critical water microenvironment, cracking the oil shale into organic compounds with different chain lengths to form an oil-water mixture, lifting the oil-water mixture to the ground through the production well, and obtaining the hydrocarbon compound through an oil-water separating system. The heat utilization ratio is improved through a multi-well integrated heat circulating system, the extraction ratio of hydrocarbon substances is greatly improved through repeated oil-water separating and circulating processes, and the technical process is shortened. A water micro-pool is formed after an oil shale layer is overflowed by water, the cracking of the oil shale can be realized within3 to 5 hours after a near-critical state is reached, and more energy sources and time are saved than an underground dry distillation method.