大型凹陷斜坡带油气成藏模式--以三肇凹陷葡萄花油层为例

Hydrocarbon Accumulation Model of Big Depression Ramp Area——As Putaohua Reservoir in the Sanzhao Depression

利用4079口测井曲线、10口井岩心,结合开发井初期产能数据,对松辽盆地三肇凹陷葡萄花油层烃源岩埋藏史、古构造演化史、油气运聚场、储层沉积特征和油水分布规律等油气成藏主控因素进行了综合分析。认识如下:葡萄花油层油气主要来自下伏青山口组二+三段源岩,油气初始运移时期为嫩江组末期,成藏关键时期为明水组末期;总结出葡萄花油层顶面古构造演化的4个阶段,油气运移时期向凹陷中心倾没的大型鼻状构造轴线为古油气主要运移方向,油气运移方向呈"旋转式"变化,即嫩江组末期的北西向转变为明水组末期的近东西向;葡萄花油层为单一北部物源,发育河控浅水三角洲沉积成因的大量密集且水下延伸较远的分流河道砂体,北西向展布的河道砂体与断层组合构成了油气侧向运移的优势通道。开发井初期产能数据和圈闭精细解剖表明,油水分布受局部构造控制,单一圈闭内具有统一的油水界面。在以上研究基础上,总结出三肇凹陷葡萄花油层2种成藏模式:继承性鼻状构造控油和凹陷平缓斜坡区反向正断层下降盘泥岩遮挡成藏模式;并在研究区刻画出101个有利钻井圈闭,预测新增石油储量2800×104t,为三肇凹陷葡萄花油层下一步的勘探与开发提供了依据。

Using 4 079 log curves, 10 well cores, as well as the initial deliverability data of production wells, the authors comprehensively analyze the chief factors that control hydrocarbon accumulation in Putaohua reservoirs of the Sanzhao depression in the Songliao Basin, including the buried history of the source rocks, the palaeotectonics evolution history, the n]igration and accumulation field of hydrocarbon, the reservoir sedimentary character and oil-water distribution rule. The scenario is thought as the follows：the hydrocarbon of the Putaohua reservoir was derived from the underlying source rocks of the Ⅱ ＋Ⅲ segment of the Qingshankou Group, the initial migration period of hydrocarbon began from the final stage of the Nenjiang Group, the key stage of hydrocarbon accumulation was at the end of the Mingshui Group; the Putaohua reservoir top has undergone four stages of Daleotectonics evolution, and the major hydrocarbon migration direction was along the axis of some large nose structure that dumps to depression center, some hydrocarbon migration direction seems to be ＂rotating＂, namely, they was in northwest direction at the end of the Nenjiang Group, became near east-west at the end of Mingshui Group; The Putaohua reservoir is identified as the single northern source, with well development of distributary channel sand bodies that controlled by shallow water delta dominated river sediment and that are intensively located and have long extension. The combination of these channel sand bodies arranged in northwest direction and faults makes up the most favorable passageways for hydrocarbon lateral migration; initial deliverability data of production wells and detailed analysis of reservoir traps indicate that oil-water distribution is controlled by local structures, and a single trap has a unified oil-water interface. Based on above research, 2 types of accumulation mode are recognized in the Putaohua reservoir in the Sanzhao depression：inheritance nose structure accumulation mode and the overlying mudstone shielding of the reverse normal fault down-throwing block in depression gentle slope. Under the guidance of these accumulation models, 101 favorable drilling traps containing 2 800 × 10^4 t reserves are forecasted. This forecast could direct the next step of exploration and development of the Putaohua reservoir in the Sanzhao depression.