鄂尔多斯盆地延安气田南部岩溶古地貌分级识别及有利区预测

延安气田南部地区古地貌研究程度较差,难以满足精细勘探要求。综合利用钻井、测井、录井、二维地震资料,对延安气田南部下古生界奥陶系顶部风化壳岩溶古地貌进行精细恢复,结合钻井试气成果,明确了岩溶古地貌对气藏分布的控制作用,并划分有利目标区。研究结果表明:研究区划分为西部岩溶台地、中部岩溶斜坡以及东部岩溶盆地3个二级古地貌单元,在二级古地貌单元上进一步分级识别出三级古地貌单元;沟槽两翼及高地洼地转换地岩溶作用强烈,储层物性较好,为最有利目标区,沟槽、洼地以及远离沟槽处物性较差。具体优选吴起志丹部分地区、甘泉地区、西南部黄陵富县西地区为有利岩溶储层区。该研究可有效提高钻井成功率,为后期气田增储上产提供有力支撑。

Classification and Identification of Karst Palaeogeomorphology and Prediction of Favorable Areas in Southern Yan'an Gas Field,Ordos Basin

The research degree of paleogeomorphology in the southern Yan'an gas field is poor, which is difficult to meet the requirements of fine exploration. By comprehensive utilization of drilling, well logging, mud logging and 2D seismic data, the karst palaeo-geomorphology of weathering crust on the top of Lower Paleozoic Ordovician in the southern Yan'an gas field was finely restored. Combined with the results of drilling and gas testing, the control effect of karst palaeo-geomorphology on gas reservoir distribution was clarified, and favorable target areas were divided. The results show that: (1) The study area can be divided into three secondary palaeo-geomorphological units: the western karst platform, the central karst slope and the eastern karst basin, and the third-order palaeo-geomorphic units were further identified on the secondary palaeo-geomorphic units; (2) The two flanks of grooves and the transition area between highland and depression have strong karstification and better reservoir physical properties, which are the most favorable target areas; (3) The physical properties of groove, depression and there locations far away from groove are worse. Specifically, some areas of Wuqi County and Zhidan County, Ganquan County, and the western Fuxian County and Huangling County in southwest were selected as favorable karst reservoir areas. This study can effectively improve the success rate of drilling and provide strong support for increasing reserves and production in the later stage of gas fields.