Study on Early Warning and Controlling of Water Invasion in Gas Reservoirs

Abstract

AbstractWarning and controlling the water invasion in water-driving gas reservoirs is significant because water invasion will seriously hamper well productivity and gas recovery. Unfortunately, there are few comprehensive methodologies to control water invasion. In this paper, firstly, a water invasion model of reservoir scale is established and verified. Then a new workflow for Warning and controlling the water invasion is developed by the numerical simulation method in this paper. This paper takes the water-gas ratio corresponding to the turning point of the water invasion rate as the water invasion identification signal. Then, the method of water control after water invasion is studied by turning off the perforation of the primary water production. Finally, the optimal water control scheme is obtained by comparing water and gas production.The results show that the reserve accuracy of the established water invasion model is 99%, and the model has a good pressure-fitting result. After studying the warning method of water invasion, it is found that the water-gas ratio of about 10-2 m3/104m3 is the signal of water breakthrough under the well produced at fixed production. The water-gas ratio in the range of 10-3 to 10-2 m3/104m3 signals water breakthrough in the well producing at a fixed pressure. The water-gas ratio as a signal of water breakthrough will increase with the increase of gas production rate and decrease with the fixed bottom hole pressure increase. The water-gas ratio chart of the early warning under the different producing models is drawn in this paper for applications in the field. A study of the water control method found that there will be a success in controlling the water cut after closing the perforation of the primary water production. Water production has been reduced by 90.9%, and gas production has been reduced by only 9.7% after using the technique in the field.