Transient analysis of horizontal wells with multiple fractures in sour gas reservoirs

Abstract

Due to the decrease of reservoir pressure, the elemental sulfur deposits in sour gas reservoirs, leading to the reduction in the reservoir porosity and permeability. It can also impact the transient pressure and rate behavior of gas wells, which is always reflected in pressure and flow rate type curves. However, few studies focus on transient analysis of multi-fractured horizontal wells affected by sulfur deposition. Therefore, the objective of this work is to develop a comprehensive model to analyze the transient pressure and flow rate of multi-fractured horizontal wells in sour gas reservoirs. Pseudo-time function and pseudo-pressure function are derived and the point source method is applied in this model. Then the proposed model is validated against analytical solutions and real production data. Furthermore, sensitivity analysis for pressure and rate type curves was conducted. Results show that the pressure type curves can be divided into six stages. The reservoir with higher H2S concentration will result in more sulfur deposition, which requires larger pressure difference to maintain a constant rate in the late time. Fracture properties impact flow rate in the early production time, and increasing fracture conductivity and fracture number is helpful to reduce the generation of sulfur deposition. For a smaller reservoir, larger pressure difference is essential to stabilize constant production rate, which means more sulfur deposition will be produced in the reservoir. During the development of sour gas reservoir, it is important to control flow rate to reduce pressure depletion for decrease amount of sulfur deposition. This paper reveals the impacts of sulfur deposition on type curves and provides a comprehensive transient analysis for multi-fractured horizontal wells in the development of sour gas reservoirs.