Relationship Between Sedimentary Microfacies and Oil-bearing Characteristic of Chang3 Oil Reservoir in Huachi Oilfield

The sedimentary microfacies and oil bearing characteristic of Hua 152 wellblock are comprehensively analyzed. It is held that the sedimentary facies of Chang3 oil reservoir in the well block is a branch of Wuqi Huachi delta front subfacies. According to its lithology, electric property and/or sedimentary structural characteristics, the oil reservoir can be divided into four sedimentary units. Each unit is subdivided into five sedimentary microfacies of subaqueous channel, debouch bar, raised bank, interdistributary depression, and interdistributary bay. Each sedimentary microfacies has itself unique feature and sedimentary space distribution law. Analysis of these features and laws shows that Chang3 sandstone reservoir is a complex superposition composed of subaqueous distributary channel sandbody, debouch bar sandbody, etc. They constitute a typical constructive digitate delta front sandbody. This sandbody is a typical representative of the upper reservoirs of Yanchang Formation, Eerduosi Basin, and it is also main sandbody to form the oil reservoir.