The use of Horizontal well has been increasing very rapidly throughout the oil industry and its applicability is now extended to the secondary and tertiary recovery processes. In this paper, a study on mature oil field case has been made to assess the technical feasibility of miscible gas injection using horizontal wells and to investigate the impact of gas injection horizontal wells on ultimate oil recovery. A reservoir model using 3-D compositional equation of state simulator is built to carry out different development scenarios to optimize the field development and increase the oil recovery using miscible gas injection process. The model is used to investigate the impact of using different combinations of horizontal and vertical injection and production wells on the performance of the process. The impact of alternative development scenarios on oil recovery, plateau oil production rate, and fluid saturation distribution are evaluated. The results show that the use of horizontal gas injection wells resulted in increase in cumulative oil recovery and gives better sweep efficiency.

A sensitivity study is also presented in this paper to evaluate the parameters that affect the performance of the horizontal well pattern used in miscible gas injection process. The study emphasized on the horizontal permeability, permeability anisotropy, horizontal well length. From the simulation results, the model is found to be most sensitive to permeability anisotropy followed by horizontal permeability then to horizontal well Length. Thus it is recommended that these parameters must be properly estimated prior to use in simulating miscible gas injection process using horizontal well pattern.

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