玛湖凹陷及周缘石炭系储层与流体相态预测

玛湖凹陷及周缘下二叠统-石炭系发育一系列继承性构造圈闭，埋深普遍超过6000 m，成藏条件优越。通过优选，选择最为有利的达1井背斜作为油气勘探的突破口。石炭系是否发育有效储层，圈闭流体相态及油气成藏模式是什么，是达1井背斜石炭系构造圈闭勘探能否获得成功亟待解决的关键问题。在单井资料匮乏的情况下，通过重磁电等资料与已钻井资料标定，认为达1井背斜石炭系发育中基性火山岩风化壳储层，储层物性相对较差；根据玛湖地区烃源岩演化阶段、地震层速度、浅层试油等资料预测达1井背斜为气藏；通过构造演化及烃源岩分析，认为达1井背斜为源边多期不整合侧向运聚成藏。综合储层、流体相态、成藏条件及埋深等因素，分析认为，达1井背斜具备优越的油气成藏条件，有望获得重大突破并发现规模大气田。

Prediction of Reservoir and Fluid Phase of the Mahu Sag and Surrounding Carboniferous Reservoir

A series of inherited structural traps with excellent reservoir formation conditions developed at a depth of >6 000 m in the Mahu Sag, surrounding Carboniferous system, and deep layers of the Lower Permian system. Through optimized selection, we chose the Da-1 Well anticline as the oil-gas exploration breakthrough point. The exploration of the Da-1 Well anticline Carboniferous structural trap might be the key to success in answering crucial questions such as whether a Carboniferous system can develop into an effective reservoir or what the formation patterns are for fluid phase traps and oil-gas reservoirs. Although a single well provides insufficient data based on the calibration of gravity-magnetic-electric data with drilling data, we consider the Da-1 Well anticline to be a developing basic volcanic weathering crust reservoir with relatively poor physical properties. The Da-1 Well anticline was predicted to be a gas reservoir based on the data on the evolutionary stages of the hydrocarbon source rock in the Mahu Area, seismic horizon velocity, and shallow well testing. Based on the structural evolution and hydrocarbon analysis, we consider the Da-1 Well anticline to be a side-of-source, multi-stage unconformity, lateral migration reservoir formation. After combining all factors, such as reservoir and fluid phase factors and reservoir-forming conditions and depth, the analyses confirm that the Da-1 Well anticline has advantageous conditions and high potential for reservoir formation, promising high-yielding gas flow and the exploration of a large gas field.