ENSURING THE SEALING OF GAS WELLS EQUIPPED WITH LINER

Abstract

The current problem of fountain safety, which affects the further well operation, namely the problem of their sealing, is considered. Traditional and modern technologies used to ensure the sealing of gas wells (including offshore wells), equipped with liners that simultaneously cover gas and water layers, are analysed. The issue of mandatory testing of casing strings in two ways is considered in more detail: pressing after lowering and cementing of the liner; lowering the level of the working fluid in the wellbore. These tests are intended to detect the fact of the well sealing and its suitability for further operation, or to detect the sealing fact and at the same time collect data for the analysis of the further action plan to overcome the consequences of such sealing. The sequence of testing casing strings using vaporizer-type coiled tubing installation that consumes liquefied nitrogen is considered. Schemes of well tying during tests of the production casing are presented. The peculiarities of the pressing process when nitrogen is injected into the annular space and into the tubing are noted. As a result of calculating of nitrogen injection pressure (the permissible value of which was 80 % of the testing pressure of the production casing) and the permissible pressure in the casing pipes, a comparative graph was constructed. The analysis of the received data confirmed the feasibility of pressing using a coiled tubing unit when pumping liquid into the tubing, as a result of exceeding the permissible pressure value at a depth of 3500 m. The need to use an operational packer, which was installed in the pipeline at the level between the head of the liner and the productive horizon, was determined. The necessity of perforating the liner through the inner space of the tubing using a hydraulic sandblasting perforator was confirmed.