Multi–cycle CO_2 huff and puff matching technology and parameter evaluation for horizontal wells in heavy oil reservoirs with bottom water drive——by taking HZ block of Subei oilfield as an example

Aiming at the problem that horizontal wells in heavy oil reservoir with bottom water drive of Subei oilfield are prone to produce water cones and are always in a state of low production and low efficiency after the production enters the ultra–high water cut stage, the CO_2 huff and puff is an effective measure to improve the production of low-efficiency heavy oil horizontal wells. Therefore, the horizontal wells in HZ block are selected to carry out CO_2 huff and puff test, and the reasonable parameters and matching technology of CO_2 huff and puff are studied, and the factors affecting the effect of CO_2 huff and puff are analyzed. The results show that the main factors affecting the effect of multi-cycle CO_2 huff and puff in horizontal wells include the selection of horizontal wells, CO_2 injection volume, gas injection intensity, injection speed, injection pressure, well closure time and oil production intensity, etc. Adding CO_2 corrosion inhibitor, injecting CO_2 into fixed string and using pumps to produce oil are the matching technology.