FORMATION DAMAGE CONTROL TECHNOLOGY FOR TIGHT GAS SANDSTONE RESERVOIRS IN WESTERN SICHUAN BASIN: DEVELOPMENTS AND CHALLENGES

Tight gas sandstone reservoirs in western Sichuan Basin are characterized with low energy, complex in macro- and micro-structures, and extreme sensitivity to environmental variations. Being congenitally deficient and liable to impairments, the damages of these reservoirs are very difficult to remove completely. With the above considerations, this work initiated from effective protection of natural fractures during drilling and completion. In the light of temporary shielding principles, a technical system of drilling-completion-stimulation for vertical wells, accompanied by methods of predicting fracture parameters close to bore-hole, and by core lab evaluations on sensitivity and working fluids damage, has been formed. The practices contribute an insight into the strategy that damage control and reservoir stimulation can be integrated for gas production from these reservoirs. Based on the discussion on technical, economical and environmental situations, this paper suggests that new and improved technology should be developed in order to cope with more complicated geologic situations such as deep tight gas reservoirs and abnormally low pressure gas reservoirs. It is also pointed out that environmental protection should be an especial concern in the research and application of formation damage control technology in drilling and completion operations.