RESEARCH AND APPLICATION OF CORING TECHNOLOGY FOR HIGH TEMPERATURE UNCONSOLIDATED SANDSTONE FORMATI ON: A CASE STUDY OF BLOCK ZH4 IN SHENGLI OILFIELD, CHINA

摘要

Shengli Oilfield is one of the early oilfields to carry out the field test of the in-situ combustion. For further clarify the development effect of in situ combustion and determine the combustion characteristics and other important data, it is necessary to ana- Iyze and test the core after in situ combustion. However, because of the great effect of in situ combustion on formation transformation, the formation becomes high temperature unconsolidated sandstone. The conventional coring technology is not applicable. Based on the difficulty of coring in high temperature unconsolidated sandstone, the coring technology for high temperature unconsolidated sandstone is established by improving the design of coring tools and optimizing drilling parameters, and the effectiveness of this technology is proved by practice. The results show that the difficulty of coring in high temperature unconsolidated sandstone includes two aspects. Firstly, high temperature formation will thicken the sealing fluid and increase the difficulty of core entering the cylinder. Secondly, unconsolidated sandstone is easy to break in the process of drilling and coring, resulting in low core recovery rate. And with the comprehensive use of the improved high temperature resistant sealing fluid, the coring tool for unconsolidated sandstone and the optimization design of drilling parameters, the average core recovery rate of high temperature unconsolidated sandstone can reach 86.44%, which is about 54.23% higher than that of conventional coring. This study can provide a good basis for efficient development of unconsolidated sandstone reservoirs.