珠江口盆地恩平凹陷断裂控藏研究

The Study on Fault Controlling Petroleum Accumulation in Enping Sag of Pearl River Mouth Basin

珠江口盆地恩平凹陷油气成藏与断裂活动关系密切,其断裂控藏特征值得重视。通过恩平凹陷293条断裂的类型划分、20口已钻井的控圈/控运断裂活动性能刻画、47个断裂圈闭的泥岩涂抹封堵性能计算,分析了断裂类型、活动性能、封堵性能与油气成藏的定量关系,明确了研究区不同构造带的断裂控藏规律。研究发现,恩平凹陷发育6种类型断裂,深部断裂和深浅沟通断裂最为发育;5Ma以来的断裂活动强度是恩平凹陷中浅层油气规模成藏的关键,当5Ma以来活动速率大于5.6m/Ma时,有利于中浅层规模成藏;恩平凹陷断裂泥比率SGR(累积泥岩厚度与垂直断距比值)封堵临界值约为0.32,低SGR值可以封堵稠油;弧形断裂控制恩平凹陷北部断阶带的油气成藏;深层古近系是恩平凹陷未来的勘探潜力方向。

The hydrocarbon accumulation is closely related to the fault activities in Enping Sag of Pearl River Mouth Basin,and the characteristics of fault controlling petroleum accumulation are worthy of attention.Through the classification of 293 fractures,the activity performance characterization of circle-controlling fault/transport-controlling fault of 20 wells drilled,and the calculation of mudstone coating sealing performance of 47 fault traps in Enping Sag,the quantitative relationship between the fracture type,the activity performance,the plugging property and the hydrocarbon accumulation was analyzed,and the law of the fault controlling hydrocarbon accumulation in different tectonic belts in the study area was clarified.It is found that there are 6 types of faults in Enping Sag,among which deep faults and deep-shallow communication faults are the most developed.The fault activity intensity since 5Ma is the key to the large scale hydrocarbon accumulation in the middle-shallow layer of Enping Sag;when the activity rate since 5Ma is greater than 5.6m/Ma,it is conducive to the large scale reservoir formation in the middle-shallow layer;the plugging critical value of fracture mud ratio SGR(the ratio of cumulative mudstone thickness to vertical fault distance)in Enping Sag is about 0.32,and low SGR can block heavy oil;Arc-shaped fractures control the hydrocarbon accumulation in the northern step-fault zone of Enping Sag;the deep paleogene is the future exploration potential direction of Enping Sag.