A Global Search Algorithm for Determining Water Influx in Naturally Fractured Reservoirs

Abstract

The determination of water influx in naturally fractured reservoirs is always a significant and difficult task in gas reservoir engineering. To improve this situation, this paper presents a new global search algorithm to determine water influx in the naturally fractured gas reservoirs. In the methodology, a dimensionless water influx derivative curve is first introduced in this paper. It is used to identify flow regimes of water invasion by combining with the water influx characteristic curve. Following that, a sensitivity analysis is performed to study the impacts of key factors on flow regimes. Finally, based on the sensitivity study and material balance equation, a global search algorithm is proposed to obtain water influx. Results show that there are two steps in the dimensionless water influx curve and a “V-shape” in the derivative curve. The smaller the aquifer and gas reservoir radius ratio is, the earlier and more obvious the “V-shape” appears. The smaller the storativity ratio is, the earlier the “V-shape” appears. The smaller the interporosity flow coefficient is, the more obvious the “V-shape” is. Results of the field application demonstrate the method applicability, which provide a good reference for further work about determination of water influx.

Physical Simulation Experimental Technology and Mechanism of Water Invasion in Fractured-Porous Gas Reservoir: A Review

“…China's annual natural gas output has exceeded 100 million tons of oil equivalent, and natural gas consumption has grown at an average annual rate of 12% in the past decade, playing a significant role in the country's transition to low-carbon energy [1][2][3][4][5][6][7][8][9][10]. Proven reserves of aqueous gas reservoirs account for more than 50% of conventional natural gas in China, which is the core area of natural gas development to increase production [11].…”