准噶尔盆地滴南凸起西段梧桐沟组成藏条件及勘探实践

Reservoir‑Forming Conditions and Exploration Practices of Wutonggou Formation in Western Dinan Swell,Junggar Basin

准噶尔盆地滴南凸起烃源岩条件优越,古生界发育石炭系滴水泉组、松喀尔苏组和二叠系平地泉组3套优质烃源岩,具有良好的供烃能力。通过成藏条件、地震储集层预测及地质综合分析认为,二叠系梧桐沟组作为石炭系顶部不整合面之上的第一套沉积岩储盖组合,以海西运动末期断裂及石炭系顶部不整合面为输导体系,以上部100多米厚高位体系域泥岩为区域盖层,可近源运移形成较大规模油气藏。在凸起西段发育水进体系域砂体,为建设性三角洲沉积,具有叠合连片成藏特征;在凸起斜坡区及凹陷区发育低位体系域砂体,砂体平面规模大,厚度大,但物性较差,坡积体或冲积扇扇中等物性较好的沉积体可形成低孔、低渗、低丰度块状油气藏。目前,梧桐沟组已发现气藏依然有扩边潜力,在斜坡区及凹陷区仍有可能发现新气藏。

Superior conditions in the Dinan swell help develop three sets of hydrocarbon source rocks including Paleozoic Carboniferous Dishuiquan formation,Songkaersu formation and Permian Pingdiquan formation,which have good hydrocarbon supply capacity.Comprehensive analysis of accumulation conditions,seismic reservoir prediction and regional geology shows that large near‑source oil and gas reservoirs could be developed in the Permian Wutonggou formation.This is the first set of sedimentary reservoir‑cap assemblage above the unconformity in the Carboniferous top,whose transport system is composed of late Hercynian faults and the unconformity in the Carboniferous top,and the regional caprock composed of the upper 100‑meter‑thick mudstone is developed in the high‑stand system tract.In the western section of the swell,transgressive sand bodies are constructive delta deposits,with the characteristics of superimposed and continuous accumulation.In the swell slope and sag areas,large and thick sand bodies of low‑stand system tract are developed,but with poor physical properties.Sedimentary bodies with good physical properties such as slope deposits or alluvial fans and mid‑fans can form massive oil and gas reservoirs with low porosity,low permeability and low abundance.The potential around the gas reservoirs that have been discovered in the Wutonggou formation is still large,and new gas reservoirs may be discovered in the slope and sag areas.