松藻矿区多煤层合采储层压降特征及启示

Characteristics and revelation of pressure drop of reservoir during combined CBM production of multi-coal seams in Songzao mining area

西南地区晚二叠世龙潭组煤层气勘探开发取得较好的成效,该层位弱含水性制约着煤层气的排采。为揭示多煤层合采条件下煤储层的压降特征,以平面径向渗流理论为指导,利用松藻矿区Q1井地质工程数据,基于井底流压、套压、日产水量、日产气量数据的综合分析,建立了纵向上不同储层的井底流压数学模型,并分析不同储层的压降特征。研究表明:M_6、M_7、M_8煤层的初始产气时间分别为45 d、162 d、217 d;储层压力和渗透率控制储层供液能力,导致压降效果随层位的降低而降低;储层临界解吸压力相差较大(4.07 MPa)和日产水量低(0.23 m^3)影响多煤层的合采效果。加强选层综合研究、产水特征分析和注水时机研究,开展递进排采相关工艺设备研发和工程探索是弱含水煤层群合采的重要工作方向。

Coalbed methane exploration and development of Late Permian Longtan Formation in Southwest China has achieved good results,and weak aquifer in this region restricts the drainage of coalbed methane.In order to reveal the pressure drop characteristics of different reservoirs in the coal seam group,based on the plane radial seepage theory,using the geological engineering data of well Q1 in Songzao mining area,based on the comprehensive analysis of the bottom hole flow pressure,the set pressure,the daily water production and the daily gas output data,the mathematical model of the bottom hole flow pressure of different reservoirs was established vertically,and the pressure drop of different reservoirs features was analyzed.The results show that the initial gas production time of coal seams M6,M7 and M8 was 45 d,162 d and 217 d.The reservoir pressure and permeability controlled the reservoir feeding capacity,leading to the decrease of pressure drop effect as the layer lowered,and the critical desorption pressure of the reservoir(4.07 MPa)and the low water production(0.23 m3)affected the combined CBM extraction effect of multiple coal seams.It is an important work direction to strengthen the comprehensive study of the selected layers,the analysis of the characteristics of water production and the study of the timing of water injection,to carry out research and development of progressive production-related process equipment and engineering exploration.