Successful Application of a New Generation of Clay Inhibitor Polymers While Drilling a Deep Exploration Well in the Astrakhan Region

Abstract

This paper presents the results of laboratory studies and field application of a drilling fluid based on a new generation of polymer inhibitors. The summarized results of the application confirm the effectiveness of the new polymer type used. The body of the article is devoted to the experience of using an innovative drilling fluid system for drilling an exploration well in the Astrakhan gas condensate field. One of the features of the Astrakhan gas condensate field is a number of intervals of possible complications: lost circulation zones, prone to clay swelling and caving, and presence of salts and hydrogen sulfide in the reservoir. One of the solutions for ensuring trouble-free drilling in such conditions is using an oil-based drilling fluid (OBM). However, OBM is often avoided when drilling exploratory wells due to environmental and technological limitations. In this connection, the project team carried out work on selection and development of a water-based drilling fluid formulation, which would ensure the most trouble-free and cost-effective drilling operations. Considering these studies, a drilling fluid was selected based on a new generation of inhibitor polymers. The key feature of the proposed formulation is the use of a new polar inhibitor polymer. The selected formulation showed the best laboratory test results after which it was approved for application. The main risk of using the new drilling fluid formulation was lack of filed experience in using this system in similar geological conditions. At the same time, laboratory tests showed that the proposed alternative mud formulations did not provide the required level of contamination resistance and inhibiting ability. Over the period from April to September of 2020, the exploration well was successfully drilled at the Astrakhan gas condensate field using the selected drilling fluid based on a new polymer type. Using the same drilling fluid type, four intervals - from the surface pipe to the production liner, - were drilled.