关键词: 深部, 煤系气, 多层合采, 产层组合判识模型, 经济评价, 临兴西区块

Abstract: The deep coal-measure gas production layer is characterized by large span, various types of superposed reservoirs and strong interlayer heterogeneity, and the combined layer development faces serious interlayer interference. Therefore, it is urgent to establish a scientific identification method system of coal-measure gas production layer combinations to support the economic and efficient co-exploration and co-mining of coal-measure gas. This study focuses on the coal and sandstone beds of Benxi-Shanxi formations in west block of Linxing area, Ordos Basin. The basic principles of coal-measure gas production layer combination are proposed by taking into account the productivity effect and economic efficiency. Then a mathematical model of production layer combination identification has been established to determine the lower limit of production and thickness of production layer that can realize the economic benefits. The paper proposes a research approach to analyze the feasibility of coalbed methane joint production layer combinations by converting coalbed methane production capacity to the thickness of the production layer and proposes the correction coefficients for the key parameters of multi-layer co-production, thus forming a simple and reliable co-production evaluation system. The results show that in the study area, the single well production satisfying the economic limit is 9.858 2×10⁶ m³, and the coal and sandstone production layer thicknesses that can satisfy the economic requirement are 4.34 m and 6.45 m, respectively. Considering the sensitivity of the single well production capacity, the production layer thickness, permeability, gas content and reservoir pressure correction coefficients have been introduced, thus building an identification system for the coal-measure gas co-production layer combination. Taking Well L-01 as an example, seven types of optimal production layer combinations are divided, two of which are suitable for co-production. The simulation results of coal-measure gas layer development are consistent with the production layer combination identification results, which verifies the reliability of the production layer combination identification model. The feasibility of coal-measure gas co-production can be evaluated using the parameters of production layer thickness, permeability, gas content and reservoir pressure after the production capacity is converted to the production layer thickness, which can simply and effectively guide the co-production of multiple coal-measures.

Key words: deep, coal-measure gas, multi-layer co-production, production layer combination identification model, economic evaluation, west block of Linxing area