四川盆地页岩气水平井高产的地质主控因素

四川盆地长宁—威远国家级页岩气示范区目前已转入大规模开发阶段,在考虑同等工程技术因素的前提下,寻找影响该区页岩气水平井高产的主控地质因素便成了研究的重点。为此,从分析该示范区目的层下志留统龙马溪组的沉积背景入手,结合区内三维地震资料、取心井地质及测井资料,开展水平井小层划分与对比,筛选影响页岩气井产能的储层关键参数,进行储层分类综合评价。结果表明,Ⅰ类储层钻遇率的高低直接影响着气井高产与否,具体到长宁—威远示范区的海相页岩气藏而言,靶体位置及龙一_1~1小层钻遇长度是决定气井是否高产的主控地质因素。基于上述研究成果,提出了该区页岩气高产水平井的地质模式,有效地指导了钻井作业,提高了页岩气水平井的产量,推动了页岩气规模效益开发。

Main geological factors controlling high production of horizontal shale gas wells in the Sichuan Basin

The Changning–Weiyuan national shale gas demonstration area in the Sichuan Basin is currently at the stage of large-scale development. Without considering engineering and technology factors, the research focuses on the main geological factors controlling the high production of horizontal shale gas wells in this area. In this paper, the sedimentary setting of the Lower Silurian Longmaxi Fm in the target layer of the study area was firstly analyzed. Then, based on the 3D seismic data of the study area and the geological and logging data of coring wells, layers in horizontal wells were divided and correlated. Finally, the key reservoir parameters affecting the productivity of shale gas wells were selected and the reservoirs were classified and evaluated comprehensively. Results indicate that the drilling ratio of Type Ⅰ reservoirs has a direct effect on the high production of gas wells. As for the marine shale gas reservoirs in the Changning–Weiyuan area, target location and drilling length of Long Ⅰ₁¹ sublayer are the main geological factors controlling the high production of gas wells. Based on these study results, a geological mode of high-production horizontal shale gas wells in this area was proposed. This model can guide the drilling operation effectively, improve the production rate of horizontal shale gas wells and promote scale and economic development of shale gas.