SPECIFICS OF WELL KILLING TECHNOLOGY DURING WELL SERVICE OPERATION IN COMPLICATED CONDITIONS

The process of the well killing operations in the oil and gas condensate field in Volga-Ural province is complicated due to several conditions like fractured carbonate reservoir, abnormally low reservoir pressure, high gas-oil ratio, high hydrogen sulfide content, acid fracturing, and hydrochloric acid treatments requirement. During the well killing process, significant gas breakthroughs and fluid loss are observed in this field, which requires significant usage of blocking compositions (up to 50-100 m3 per single well) and increases the well service costs. The aim of this work was to increase the well killing efficiency during well service by studying the mechanisms that take place near the wellbore zone during this process. The application of statistical and multifactor analysis of well-killing processes were conducted from 2018 to 2019, which allowed highlighting the main reasons for the low success of these works. The calculation results showed that the stress state near the well significantly differs from the regional stress field and varies depending on the generated pressure in the well, which in turn affects the activity of fractures near the wellbore. The revealed mechanisms that take place near the wellbore zone coupled with the laboratory and pilot tests of the blocking compositions can be used to improve the well service operations at the oil and gas condensate field in the Volga-Ural province. In this work, it was concluded that it is important to use the geomechanical approach to increase the well killing efficiency in combination with a complex of laboratory rheological and filtration tests of blocking compositions.