江汉盐湖盆地盐间泥质白云岩油藏地质特征与实践

Geological Characteristics and Practice for Intersalt Argillaceous Dolomites Reservoir in the Qianjiang Depression of Jianghan Salt Lake Basin

江汉盆地潜江组沉积时期受北部单向物源、古气候频繁交替、高盐度、强蒸发环境影响,沉积了一套最厚达6 000m的盐系地层,纵向上发育了193个盐韵律层,盐韵律主要由盐岩地层与盐间泥质白云岩层组成,平面上分布面积1 800km2,占潜江凹陷面积的71%,盐间泥质白云岩既是生油岩又是储油岩,其生成的油气由于上下盐岩封隔形成众多层状盐间泥质白云岩非常规油藏。截止目前,在该地层中见到了丰富的油气显示,且有多口井获工业油流,展现出良好的勘探开发前景。充分利用大量的钻井、测井、分析化验等资料,按照非常规油藏思路,从沉积、烃源、含油性、储集条件、成藏模式等方面详细阐述了油藏的地质特征,明确了"甜点区"受白云岩岩相、烃源、储集、含油性"四元"控制,其中烃源是基础,含油性和储集条件是关键因素。

Influenced by northern monodirectional provenance,frequently alternating palaeoclimate,high salinity and strong evaporation environment,a set of 6 000 mthick saliferous rhythmic sequences with sandstone and mudstone deposited during the period of Qianjiang Formation sedimentation.The saliferous rhythmic sequences mainly consist of salt and intersalt argillaceous dolomites and cover 1 800km2 area,accounting for 71 percent of the total Qianjiang Depression.Being regarded as both source rock and reservoir rock,the argillaceous dolomites generated hydrocarbons which were sealed by interlayered salts and formed multi-layered unconventional oil reservoirs.Until now,abundant hydrocarbon shows have been observed in the intersalt argillaceous dolomites and the commercial oil flow has been obtained from dozens of wells,showing favorable shale oil exploration and development potential in the depression.The geological characteristics on sedimentary facies,source rocks,oil-bearing properties,reservoirs and hydrocarbon accumulation pattern are analyzed by using data from drilling,well logging and core experiment.The＂sweet spot＂is controlled by four factors,including dolomite facies,source rocks,reservoir characteristics and oil-bearing properties.Source rock is the basic factor,reservoir characteristics and oil-bearing properties are critical.