Mechanism Analysis and Prediction of Lost Circulation in Igneous Formation: A Case Study from B Oilfield, Bohai Bay Basin, China

Abstract

Abstract Volcanic reservoirs are gradually becoming an important target for exploration and development in Bohai Bay, China. At the same time, the igneous formation is more prone to lost circulation than the conventional sedimentary formation. On the one hand, there is a lack of understanding of the mechanism of drilling fluid leakage in igneous formation; on the other hand, there is a lack of measured data on the leakage pressure of igneous formation. As a result, the risk prompt for well leakage in igneous formation before drilling is insufficient, and there is a lack of targeted plugging measures in case of well leakage during drilling, resulting in the original formation being polluted by mud and even abandoned by the project, which restricts the effectiveness of exploration and development of the oilfield. In response to the above problems, firstly, innovatively carry out research on the loss mechanism of igneous rock to help drilling engineering professionals formulate specific plugging measures for special lithological formations. Then summarize the igneous rock leakage laws of different lithofacies, and quantitatively evaluate the pressure bearing capacity of different lithofacies. Finally, the fine identification and characterization of pre-drilling igneous facies are carried out based on the difference of seismic reflection characteristics. Comprehensively apply the above research results to quantitatively predict the risk of lost circulation before drilling in B oilfield in Bohai Bay Basin to avoid lost circulation accidents.