成像测井技术在柴达木盆地藻灰岩储层评价中的应用

青海油田尕斯库勒下干柴沟组上段油藏的储层以藻灰岩为主,非均质性强,物性变化大,其储集空间类型主要有原生孔隙、次生孔隙和裂缝。常规测井难以进行有效储层划分和流体性质识别。微电阻率成像测井(FMI)技术具有分辨率高、携带大量地质信息的优势,能较好地识别、区分和评价藻灰岩、粉砂岩、石灰岩储层。藻灰岩储层FMI图像呈絮状或云朵状,外部边界不平直,内部构造不均匀,层理无规律,局部有溶蚀现象;泥质粉砂岩与钙质粉砂岩的FMI图像为亮黄色、棕黄色条带;而石灰岩、泥灰岩为白色、亮黄色及黑白相间的条带。张开缝或高导缝在FMI图像上显示为暗色的正弦曲线,高阻缝的FMI图像显示为亮黄色—白色的正弦曲线。裂缝越发育,储层渗透性越好。溶蚀孔主要表现为沿裂缝的局部溶蚀扩大,在裂缝特征不明显时,多为分散的星点状或串珠状暗色斑点,这种特征越明显,储层孔隙性就越好。

Application of FMI Imagine Technique in Evaluating Algae Limestone Reservoir in Qaidam Basin

The reservoir lithology of upper Xiaganchaigou oil reservoir in Gasikule area of Qinghai Oilfield dominates in alga limestone, with strong anisotropism and change of physical property.The storage space types include primary porosity, secondary porosity and fracture. Due to FMI technique having the advantages of high- resolution and a lot of geological information, it can be used to recognize, differentiate and evaluate alga limestone, siltstone and limestone reservoirs. The FMI image of alga limestone reservoir features in floc or cloud-like, outer boundary being not straight, asymmetry internal structure, disorder bedding, local dissolution; The FMI image ofsiltstone reservoir and calcareous siltstone features in bright-yellow, brown-yellow strip; and The FMI image of limestone and marlite features in white,bright-yellow and white black interbedded strips. Open fracture and highly conductive fracture show as dark sinusoidal curve on the FMI image, and high resistivity fracture shows as bright- yellow and white sinusoidal curve on the FMI image. More developed fractures, better permeability of reservoir has.The dissolution fracture shows as locally enlarging along the fracture, dispersed stellar or beaded dark spot on the FMI image.