Oil shale in-situ mining technology is to directly heat the underground oil shale to crack it underground to generate oil and gas, which is extracted through production wells. This process has advantages for the development of medium-deep oil shale (more than 300m deep); in addition, because this process does not require open-pit and mine mining, there is no accumulation of a large amount of oil shale waste, very few by-products, and very little water consumption. This process is currently a technology focused on research and development by major international oil companies.
Currently, in terms of in-situ mining technology research, U.S. Shell’s ICP frozen wall technology, Exxon-Mobil’s ElectrofracTM horizontal well conductive medium heating technology, and Diamond Energy’s EGL closed-circuit circulation technology are at the world’s leading level. Among them, Shell's ICP frozen wall technology is relatively mature. It is a patented technology developed by Shell with huge investment in mining oil shale and other unconventional resources. It is especially useful for the development of deep oil shale. The basic principle of ICP technology for oil shale mining is to heat and crack the oil shale deposits underground to convert them into high-quality oil or gas, and then extract the oil and gas separately through relevant channels; these high-quality After the oil (gas) is collected from the ground and processed, it can produce naphtha, kerosene and other refined oil products. Its advantage is that it improves the efficiency of resource development and utilization and reduces the damage to the ecological environment during the mining process, that is, it takes less land, no tailings waste, no air pollution, less groundwater pollution, and minimizes the generation of harmful by-products. Although this technology has not yet been fully commercialized, key process, equipment and other technical issues have been solved, and commercial demonstrations have been carried out in Colorado, USA and Alberta, Canada.
The research on in-situ oil shale mining in China has just started, and there is a lack of basic theoretical research and process technology research. In terms of theoretical and technical process research, it is basically in the initial stage.
Among the in-situ mining technologies, heating technology is the most critical. According to the heating method, in-situ mining heating technology can be divided into three types, namely electric heating technology, steam heating technology and radiation heating technology, with electric heating technology being more mature.
(1) Electric heating technology: The technology is mature and easy to control, but the heating speed is slow, easy to cause a large loss of heat, high cost, low pressure of oil and gas generated, and difficult to exploit.
(2) Steam heating technology: The heating speed is fast, and due to the effect of fluid pressure, the cracks generated will generally not close, and the produced oil and gas are easy to exploit; during the heating process, the fluid flow rate is too fast, and it is easy to A short circuit is formed in which the fluid flows out of the formation with only a small amount of heat exchange with the oil shale.
(3) Radiant heating technology: The heat generated has strong penetrating power and fast heating speed; but the technology is difficult and the cost is high.