分析测井相预测歧50断块沙三段低电阻率油层

Prediction of low-resistivity zones in Sha-3 Member of the Q50 fault block based on logging-facies analysis

歧50断块是大港油田南大港构造带的富含油断块,主要含油层系沙三段发育岩性油藏且存在低电阻率油层,可划分为5套砂体单元,测井曲线对其沉积特征有清晰反映。高束缚水成因的低电阻率油层的主要特点是具有双组孔隙系统,其形成与沉积微相关系密切,砂体的坝体边部水动力变弱且不稳定,形成薄互层的岩性结构,导致储集层微观孔隙结构复杂化,具备形成低电阻率油层的地质条件;而砂坝主体的岩性结构与孔隙结构相对简单,油层电阻率较高。根据测井相准确认识砂体沉积微相的平面分布规律,有助于预测低电阻率油层分布。歧50-10井的3个小层因泥质含量高而电阻率较低被解释为干层,用此方法进行分析,认为它们具有低电阻率油层的特征,试油获得较高产量。通过测井相分析预测低电阻率油层分布,对老油田的进一步挖潜具有实际意义。

The Q50 Block is a block rich in petroleum located in the east of the South Dagang structure in the Dagang Oilfield. The lithologic oil pools with low-resistivity are developed in the Sha-3 pay zone, which can be subdivided into 5 sandstone units. Their sedimentary characteristics could be clearly reflected by logging curves. The low-resistivity oil zones, which formed of high irreducible water saturation, exist in the edge of the bar with weak and unstable water dynamics and have thin interbedded lithologic structure and dual-pore system. However, the high resistivity oil zones mostly formed in the host bar with simple lithologic and pore structure. The distribution of low-resistivity oil zones could be predicted by exact cognition of sedimentary micro-facies. This method is applied to analyze 3 dry layers with high shale content and low resistivity in the Well Qi 50-10, and the amount of oil and gas is significantly enhanced by the formation testing, suggesting that the logging-facies analysis would be important for exploiting some developed oil fields.