The application of N_2 huff and puff for IOR in fracture-vuggy carbonate reservoir

摘要

In Tahe Oilfield, Tarim Basin, NW China, although the carbonate reservoir displays poor porosity and permeability in matrix, the fractured-vuggy system distributes in a random, discreet and discontinuous way, which could yield high oil rates once the fractured-vuggy system is connected by production wells. The fractured-vuggy carbonate reservoirs consist a group of large caves which are inter-connected with high permeable fractures. Due to the lack of powerful and suitable IOR (Improved Oil Recovery) strategies, the depletion recovery is usually applied at the beginning for a fractured-vuggy carbonate reservoir. During the depletion process, the elastic energy of the cave formation starts to decrease, which will cause insufficient liquid supply. Then, the water was injected to improve the oil recovery when the energy (pressure) is the main reason for the insufficient production performance of the well. However, if the high water cut is the main reason, alternative IOR techniques such as the N-2 huff and puff method could be utilized. This paper mainly researches the application of N-2 huff and puff in a fracture-vuggy carbonate reservoir, where the critical parameters for designing the N-2 huff and puff process are proposed. In addition, the proposed method is applied to Well SX to serve as a practical example. Based on the three-dimensional (3D) quantitative sculpture geological model and the dynamic production analysis, the critical parameters for N-2 huff and puff are obtained by numerical simulation. In addition, the obtained parameters are validated by the field data, which proves that the proposed method can be applied to design the critical parameters for simulating the N-2 huff and puff process in a fractured-vuggy carbonate reservoir.