Energy evolution during in-situ conversion of low-maturity shales

Low-maturity shale is one of the most promising resources for transitioning from traditional fossil fuels to clean energy. Here we established a mathematical model that conforms to the physical process of in-situ conversion and constructed a large-scale semi-open three-dimensional reservoir system close to reality. The results show that: (i) The power function can characterize the relationship between reservoir temperature and heating time. (ii) When the kerogen in the target area is completely converted, the energy ratio of the target area periphery is the largest (54.9 %), followed by the target area (28.9 %), the outer cap layer (9.7 %), the inner cap layer (4.0 %), the chemical reaction heat of target area (2.42 %), and the chemical reaction heat of target area periphery (0.08 %). (iii) As the heating temperature increases, energy ratios of the target area periphery and the outer cap layer decrease, while energy ratios of the target area and the chemical reaction heat in the target area periphery increase, and the energy loss decreases. (iv) The cap layer with small thermal conductivity, and the reservoir with large kerogen content and high permeability should be selected as much as possible and the target area should be large to reduce energy loss.