GENG Bin¹, YAN Hua¹, ZHOU Dezhi¹, CHENG Ziyan¹, KANG Yuanyong¹, HAN Lianbin¹, HU Xingzhong²

1. Exploration and Development Research Institute, Shengli Oilfield Company, SINOPEC, Dongying 257015, Shandong Province, China;

2. Oil and Gas Exploration Administration Center, Shengli Oilfield Company, SINOPEC, Dongying 257001, Shandong Province, China

Abstract: The selection of rock resistivity parameters in Archie’s formula is important during the logging interpretation of oil saturation. However, the influence of the occurrence states of oil and water in reservoirs is rarely considered. Their occurrence states in the shallow heavy oil reservoirs of unconsolidated sandstone are different from that in the conventional oil reservoirs. The pore water in the form of “isolated water droplets” is separated by oil, which makes it difficult to form a conductive network. As a result, the oil saturation of heavy oil reservoirs interpreted by Archie’s formula is higher than the actual one. Therefore, it is necessary to optimize and correct the saturation interpreted by logging data. In this study, the heavy oil reservoir of Guantao Formation in Zhanhua Sag, Jiyang Depression is selected as the research object to illustrate that the main factor influencing the occurrence of “isolated water droplets” in pores is the pore structure. Then, the oil saturation analyzed by oil-based mud coring is taken as the standard. The correction value of the initial interpretation ranges from 4.1% to 5.4% with an average of 5% by such methods as CT scanning, Archie’s formula, calculation of oil column height by capillary pressure or water cut equation. The results provide a basis for the interpretation and correction of the oil saturation in heavy oil reservoirs, and provide a method for the oil saturation correction of shallow heavy oil reservoirs of unconsolidated sandstone.