Optimal Design Of Well Pattern By CO₂ Flooding In Low Permeability Reservoir Of ZQ

With the improvement of oil & gas exploration and development in China, high-permeability reservoirs gradually entered into the high water-cut stage. At the same time, low permeability reservoir is taking an increasing proportion and has become a vital supplier of oil & gas reserves. Although water injection is a mature displacement method, it is subjected to certain restrictions in low permeability reservoirs. While CO2 flooding is more advantageous in low permeability reservoir since CO2 encounters less resistance during seepage and gets miscible with oil easily, reduces oil viscosity and hence decreases residual oil saturation. What is more, gas channeling is not easy to occur in low permeability reservoir.Firstly, based on literature research on well patterns suitable for low permeability reservoir development with CO2 flooding at home and abroad, this paper analyzed the advantage of using horizontal wells in low permeability reservoirs and its adaptability to ZQ low permeability reservoir according to its geological characteristics. Secondly, corresponding to ZQ reservoir with CO2 flooding, the author obtained reasonable well spacing ranges by reservoir engineering and economic evaluation, and optimized well patterns and the involved parameters, such as the length and direction of horizontal well, the number and length of artificial fractures, well spacing and row spacing, based on numerical simulation. Then, on this basis, the thesis optimized gas injection parameters, such as injection amount, injection rate, reservoir pressure, etc. Finally, the author arranged wells for the geological model of the targeted block with the above mentioned result and compared the dynamic performance of different development methods in order to testify the adaptability of CO2 injection.