Oil & Gas Geology ›› 2022, Vol. 43 ›› Issue (2): 286-296.doi: 10.11743/ogg20220204

• Petroleum Geology • Previous Articles     Next Articles

Progress in shale reservoir upgrading through in-situ heating

Guohui Chen1,2,3(), Shu Jiang1,2,3, Chun Li1,2,3, Sisi Li1,2,3, Peng Peng1,2,3, Lan Mo1,2,3, Yuying Zhang1,2,3, Luchuan Zhang1,2,3, Tianyu Zhang1,2,3   

  1. 1.Key Laboratory of Tectonics and Petroleum Resources,Ministry of Education,China University of Geosciences (Wuhan),Wuhan,Hubei 430074,China
    2.Key Laboratory of Theory and Technology of Petroleum Exploration and Development,China University of Geosciences (Wuhan),Wuhan,Hubei 430074,China
    3.School of Earth Resources,China University of Geosciences (Wuhan),Wuhan,Hubei 430074,China
  • Received:2020-10-09 Revised:2022-01-20 Online:2022-04-01 Published:2022-03-11

Abstract:

Non-marine oil shale is abundant in China but most of it is not economically accessible due to its low maturity, low API gravity, high viscosity, low-pressure formation fluid as well as low porosity and permeability. In-situ heating technology has been used to improve the recovery rate of the oil and proven quite effective in improving the shale reservoir properties. Based on previous studies on shale pore evolution and reservoir property improvement through in-situ heating of oil shale, this study clarifies that the improvement of shale reservoir properties through heating is realized by both the pore evolution and the thermal cracking. Pore evolution is mainly facilitated by organic matter cracking, inorganic mineral transformation, mineral dissolution and recrystallization. Thermal cracking is mainly induced by thermal stress and hydrocarbon generation supercharging. Despite the insights gained from previous studies on pore evolution pattern of shale of different maturity and on thermal cracking in sandstone and granite, challenge remains in further revealing the effect of reservoir improvement in the in-situ heating process of shale because of the complex mineral composition in shale that leads to a more complex pore evolution process, which is further complicated by pore formation, acid product dissolution and supercharging effect associated with organic matter decomposition. It is therefore suggested that further research be carried out separately on each different effect to reveal the mechanisms and establish models, so as to effectively predict the temporal and spatial evolution of the entire pore and permeability enhancement effect during the in-situ heating process.

Key words: pore evolution, thermal cracking, thermal stress, EOR, in-situ heating, oil shale

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