彩南油田低阻油气层测井沉积模式及其成因分析

Cainan Oilfield logging Logging deposition model of low resistivity reservoirs and its causes

在彩南油田低阻油气层定义为电阻增大率(油层电阻率与水层电阻率之比)小于2的油气层,其油水层的测井信息差异小,含油饱和度小于50%,试油时却产纯油气,投产后含水上升速度很快,且该区具有高阻水层和低阻油层同时存在的现象。根据该区低阻油气层测井曲线响应特征,可以总结出低能相带、正韵律、反韵律、齿状低幅四种测井沉积模式。其成因是由于岩石不动水饱和度高、地层水矿化度高、盐水泥浆侵入影响大、构造幅度低、油层厚度薄、原油密度和粘度较小和油水关系复杂,其核心机理为岩石颗粒表面的水膜厚,油层厚度薄,油水分异作用差或无分异造成油气层电阻率降低。

In the Cainan oilfield low-resistivity hydrocarbon layer is defined as that the enlargement rate of the layer resistivity(the ratio of hydrocarbon & water resistivity) is less than two,the deviation of log information between oil or water layer is little,although the oil saturation is lower than 50 percent,it produce pure oil or gas during testing well.After putting into production,the rate of water content increases rapidly,and in this area there is the phenomenon that the high resistivity water layers and the low resistivity oil layers exist at the same time.According to logging response characteristics of low resistivity layers,the logging depositional models can be summarized as the following four: Low-energy facies,positive rhythm,reverse rhythm,dentate low-amplitude.Their genesis causes are due to high saturation of immovable water in rock,high salinity of formation water,deep invasion of brine mud,low structure amplitude,thin thickness of oil layer,low density and viscosity of crude oil,complex relationship of oil & water.And its core mechanisms are that the surface of rock particles has thick water film,the thickness of oil layer is thin and the oil-water differentiation is poor or no seperation,which result in descend of resistivity of hydrocarbon layers.