Increasing the strength of wells walls during drilling and abnormal operating conditions
Authors:   Institute of Strategic Research of the Republic of Bashkortostan, CHIZHOV Alexandеr , MUKHAMETSHIN Vyacheslav ,   Ufa State Petroleum Technological University, KULESHOVA Lyubov ,   Ufa State Petroleum Technological University, SAFIULLINA Albina ,   Ufa State Petroleum Technological University
Published: July 2022

Introduction. The current stage of well construction is characterized by the complication of drilling conditions and casing of exploratory and production wells. The increase in the complexity of mining conditions is associated with both geological and man-made factors. The drilling technologies used in these conditions are not always efficient enough and do not provide the required level of drilling quality and well casing tightness. In this regard, there is a need to conduct research aimed at studying the non-stationarity of the hydrodynamic conditions of drilling, the possibility of controlling and managing these processes and changing the properties of drilling fluids. Purpose of research. Determination of the parameters of the strength of the walls of wells during drilling in difficult mining conditions of exploited oil fields. Methods of research. Theoretical and experimental studies of wall strength parameters are based on the principles of a systematic approach to solving complex engineering and scientific problems. The system approach used includes information support, organization and management of technological drilling processes. The controllable strength and insulation parameters of the formed screen are revealed, the regulation of which ensures the achievement of the goals of work on strengthening the walls of the well. Research results and discussion. Based on the results of the research, a method is proposed for strengthening the walls of the well in the process of deepening its bottomhole. To test the method, a site was selected that meets the requirements of the complexity of mining conditions: the eastern outskirts of the East European platform; the sedimentary cover is represented by various rocks, including fractured, weakly stable ones; The field currently in production is at an advanced stage of development. The wells planned for construction are reserve, designed to regulate the oil recovery system. The drilling of directional wells with a horizontal ending in these conditions was accompanied by a number of complications: screes, landslides, oil and gas shows. The cavernousness values in the considered interval reached 2.0-2.2 units. Moreover, water shows and intense losses of the drilling fluid were noted. An analysis of the results of field tests of the proposed technology showed that the strength and stability of the borehole walls increased significantly (cavernousness ratio decreased to 1.0–1.09 units). Oil and gas shows and losses of drilling fluid were not observed, or they were extremely short-lived. In addition, the labor intensity of the drilling process has decreased due to the exclusion of technological operations to eliminate complications and change drilling fluids of various types. A decrease in the cost of drilling fluids and a reduction in the construction time of the well as a whole was noted. Conclusions. The conducted studies confirmed the correctness of the approach to solving the set scientific problems, methodically based on systemic principles. Indicators characterizing the effectiveness of methods for strengthening the walls of wells under construction have been identified. It was determined that as a result of field tests, the stability and tightness of the walls of 9 experimental wells increased. This made it possible to exclude loss of drilling fluid, gas, oil and water intrusions in the process of penetrating permeable rocks. The proposed technical and technological solutions allow us to successfully solve the set scientific and technical problems, which are recommended to be tested in the conditions of fields in other regions of Russia and abroad.