Research and Application of Special Completion Technology in Complex Wellbore Conditions of Ultra-Deep Carbonate Reservoirs

The oil and gas resources over 6000 m in Tarim Basin account for 83.2% and 63.9% of the total oil and gas resources in China’s ultra-deep reservoirs respectively, and the prospect of exploration and development is very broad, and the development depth of deep reservoirs is gradually moving from 8000 m to 9000 m. Carbonate reservoirs are characterized by pressure sensitivity, small safe density range, easy well blowout and well leakage, and high risk of well control, etc. Influenced by the occasional development of salt paste layer in the upper strata, the difficulty of capping layer jamming, the difficulty of reservoir tracking in the target layer, the unsmooth borehole trajectory, and the serious pressure of drilling tools, the engineering geological conditions are extremely complicated, which brings great challenges to the later completion operations. In order to solve the problems of technical casing deformation, unsealed formations prone to collapse, difficult access to the tubular column and inability to carry out conventional completions, we carried out wellbore integrity evaluation and mechanical verification of the tubular column, proposed special completion techniques centered on clean completion, use of thick-walled drilling tools, access to liner tubulars for bare-hole section completion, combination of drill pipe and tubulars for oil recovery slope and soft stratification modification, optimized the structure of the completion tubular column and established standardized operation procedures. It establishes a standardized operation process. This process is capable of establishing oil and gas passages under complex wellbore conditions and provides a new idea for completion engineering of similar wells.