Optimal Selection of Shale Gas Processing and NGL Recovery Plant from Multiperiod Simulation

Abstract

The advent of unconventional oil and gas has resulted in a plethora of shale gas production, and it has been predicted to increase from 1 in 2000 to 40% in 2035 of the total US domestic gas produced. Since shale gas is both industrially economical and environmentally clean compared to oil or coal as a resource, many studies are focused on developing technologies to monetize shale gas. However, one of the key challenges in utilizing shale gas is its varied flow rate and uncertain compositional behavior. The flow rate of a shale gas well dwindles over a period of time, and the composition differs from well to well in the same shale play. This provides a challenge in designing a plant of optimum capacity for shale gas processing and natural gas liquids (NGL) recovery. In this study, the periodic variation in feed flow rate is addressed while designing shale gas processing and NGL recovery plant. Different shale gas flow rates as obtained from average shale gas rate declination curve of a shale play over the period of well life is used for the design of five different plants with varied capacities. The corresponding economics of different plants are compared to find optimal plant capacity. The base case scenario is further improved through incorporation of heat integration and optimization of individual units of the process using pinch and sensitivity analyses, respectively. Economic analysis of the optimum plant size is also performed with a constant feed flow rate over its entire life. From the economic analysis of various period studies, it is observed that the optimum plant design with highest ROI percentage has more than minimum ROI requirement both with declining and constant flow rate case, implying that the proposed processing plant is economically viable to implement. Finally, environmental impact of the base case and improved design is also discussed.