The Optimal Design Theory and Method of Balanced Gas Injection for Horizontal Wells in Heavy Oil Reservoirs

According to unbalanced steam injection in in horizontal wells, this paper studies the structure of the balanced steam injection devices (BSID) and the improvement effect of the unbalanced steam injection. Firstly, the structure of the BSID is designed, and then an optimization model is established to study the optimization method of structural parameters. Finally, the optimization model is verified by numerical simulation software. The research shows that the optimization model of BSID established in this paper can effectively complete the calculation of the parameters related to the steam injection process. The maximum relative error is 1.11% of the steam quality in the gas injection tube compared with CMG model. According to the analysis of the calculation results of the steam injection using the BSID and steam injection in the conventional tube in A well group in Liaohe Oilfield, it can be determined that the pressure in the annulus of the conventional tube decreases sequentially from the “toe” to the “heel”. While the annular pressure using the BSID fluctuates with the physical properties of the formation, which demonstrates that the pressure in the high-permeability section is low and the pressure in the low-permeability section is high. The higher daily oil rate and cumulative oil could be acquired when BSID are installed, and the faster oil recovery rate, the higher recovery efficiency, a better development effect are emerged in production.