关键词: 油页岩, 原位干馏, 原位注蒸汽中试, 原油采收率, 适用性分析

Abstract: Oil shale is an important strategic resource with huge reserves in China, and it is also an internationally recognized alternative energy source for crude oil. It has been fully proved that in-situ retorting of oil shale is the only feasible technical solution to realize its large-scale industrial development. Taiyuan University of Technology obtained an invention patent authorization of oil shale in-situ steam injection (MTI) for oil and gas productionin in 2010. Based on the principle of MTI technology, a pilot test of in-situ steam injection for oil and gas production was carried out on large-size oil shale specimens, and the applicability of multi-mode oil shale in-situ retorting technology was also analyzed. The results show that:(1) In the process of oil shale in-situ multi-well hydraulic fracturing, the maximum water injection pressure is only 41% of the in-situ stress, and the fracture initiation and propagation pressure is low. (2) The steam convection heat transfer method has high heat transfer efficiency, organic matter pyrolyzes quickly, and steam carrying oil and gas comes quickly from the production well. Meanwhile, by opening or closing the drilling valves of the well group, the flow and direction of steam can be adjusted in real time, and the target heating pyrolysis area of the oil shale can be flexibly controlled to realize the scientific deployment of steam. (3) During the normal operation of in-situ steam injection into oil shale, the steam injection pressure is only about 1/4 of the self weight stress, and the long-term operation load of steam boiler is low. (4) The land subsidence caused by in-situ pyrolysis of oil shale is very small, resulting in little harm to the geological environment. (5) The recovery oil content of the steam injection pyrolysis area is more than 95%, and the overall oil recovery rate reaches 67.3%, which has fully proved that the in-situ steam injection pyrolysis of oil shale by MTI technology can achieve high oil recovery. (6) The proportion of light oil products in the obtained shale oil is 72.51%; the proportion of H₂ in pyrolysis gas is absolutely dominant, and its volume content is as high as 68.87%. (7) The pyrolysis of the top and bottom oil shale in the steam injection pyrolysis area is insufficient, and the fracture development is not obvious, which has become a good anti-seepage and thermal insulation layer. (8) Compared with other oil shale in-situ thermal recovery technologies, MTI technology has obvious advantages in technical process and cost saving, and broad prospects in commercial development and application.

Key words: oil shale, in-situ retorting, pilot test of in-situ steam injection, oil recovery, applicability analysis