深部煤系气合采产层组合判识方法及效果评价

Identification method of deep coal-measure gas co-production layer combinations and its effect evaluation

深部煤系气产层具有跨度大、多种类型储层叠置且层间非均质性强等特点。合层开发层间干扰问题严重,亟需建立科学的煤系气产层组合判识方法以支撑煤系气经济高效共探共采。以鄂尔多斯盆地临兴西区块本溪组—山西组煤层和砂岩层为例,考虑产层组合的产能效果与经济性,提出了煤系气产层组合的基本原则,建立了产层组合判识的数学模型,确定了满足经济效益的产量下限及产层厚度;提出了将煤系气产能转换成产层厚度并以此分析煤系气合采产层组合的研究思路,提出了多层合采关键参数的校正系数,形成了简单、可靠的合采评价体系。研究结果显示,研究区满足经济极限的单井产量为9.8582×10^(6)m^(3),煤层、砂岩层满足经济要求的产层厚度分别为4.34 m和6.45 m。考虑到单井产能的敏感性,引入了产层厚度、渗透率、含气量以及储层压力的校正系数,由此构建了煤系气合采产层组合判识体系。以L-01井为例,划分出7种最优产层组合,指出2个产层组合适宜合采,其煤系气合层开发模拟结果与产层组合判识结果一致,验证了产层组合判识模型的可靠性。煤系气合采产层组合判识体系可通过产层厚度、渗透率、含气量和储层压力等参数,将产能转换为产层厚度后进行合采可行性评价,简单有效地指导煤系多产层合采开发。

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 9.8582×106 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.