Pilot Test Shows Promising Technology for Gas Drilling

Abstract

Young Technology Showcase Gas drilling has been widely promoted and applied in China in recent years. The cuttings-carrying media usually consist of air, nitrogen, and natural gas. Air is commonly used because of its free availability. However, the mixture of air and natural gas in a borehole can cause fire and explosion. Although the downhole fire problem is prevented with nitrogen or natural gas, other issues arise, such as costly nitrogen generation, restrictions to the use of natural gas, resource waste, and environmental concerns. The current gas drilling practice of handling gas returned from the borehole is to discharge it to the atmosphere directly. If the gas can be recycled in the same way as drilling mud, the energy consumption and drilling cost can be greatly reduced. The recycling system can also allow the produced gas from the reservoir to be compressed and transported to the gas gathering system in the field. The overall efficiency of gas drilling will be improved significantly. The gas recycling system (GRS) has been investigated at the China University of Petroleum, Beijing (CUPB), for several years. A systematic research and development group at the CUPB carried out a comprehensive study including an integration design, technological process investigation, cuttings transport analysis, separation and filter equipment selection, and control system design. To verify the feasibility of the new system and technology, CUPB recently conducted an open-loop field test at Sinopec Group’s Dayi 101 well in the Sichuan province in western China. The result of the test is very promising. It proved the feasibility of the innovative technology. System Description The general idea of the GRS is to separate gas effectively from the gas-liquid-solid mixtures returned from the well and reinject the gas back into the well. At the same time, cuttings and fluids are discharged after the separation. During the natural gas drilling process, the separated gas can be released to the gas gathering system in the field. The integrated design of the process is illustrated in Fig. 1.