Wellbore stability mechanism of igneous rock in Shunbei block

Abstract

Shunbei area is located in the belt structural of the northern margin of the shuntuogole low uplift. The proven oil reserves of the adjacent blocks are 142.93 million tons, which has the potential of exploration and development. In the igneous strata of Shunbei block, there are many complicated conditions, such as wellbore collapse, stucking pipe and so on, which seriously restrict the exploration and development speed and benefit of the block. In order to solve this problem, firstly, the composition, microstructure, mechanical properties and other parameters of igneous rock intrusion in Shunbei block are determined through laboratory experiments. The experimental results show that the igneous rock intrusion in Shunbei block does not contain expansive clay minerals, has weak hydration ability, and has developed micro fractures. Thirdly, the wellbore stability model considering fractures is established, and the influencing factors of wellbore instability are analyzed by combining the mechanical properties of igneous rocks, porosity and permeability characteristics, and in-situ stress state. The results show that the micro fractures and weak surfaces have a controlling effect on wellbore stability. The longer the immersion time is, the deeper the drilling fluid invasion depth is, and the higher the wellbore collapse pressure is. Finally, according to the microstructure and physicochemical properties of igneous intrusions, the main points of drilling fluid technology are determined, that is, the anti sloughing drilling fluid technology is mainly strong plugging. In this paper, through the analysis of the rock characteristics of igneous rocks and the main controlling factors of wellbore instability mechanism in Shunbei block by using the method of mechano-chemical synthesis, the clear main controlling factors of wellbore stability are of positive significance for ensuring the safe well construction, shortening the drilling cycle, reducing the drilling cost and improving the development efficiency in Shunbei block.