Performance Analysis of Horizontal Wells for Underground Gas Storage in Depleted Gas Fields

Abstract

Abstract Underground gas storage is a common activitity in countries with major transport and distribution gas pipeline infrastructures, which allows to efficiently resolving demand seasonality problems. The first ever underground gas storage project in Turkey is being carried out in the KM field with injection and withdrawal operations. Optimization of gas storage field was enabled by an improved reservoir and geologic description, including the evaluation of deliverability and storage capacity in the reservoir. Based on available information and those generated by simulation model, KM field is the best candidate for underground gas storage. The KM offshore natural gas field was discovere in 1988 located about 3 km off the shore of Silivri in the Marmara sea. The field was initially planned to be developed with 3 wells, but recently 2 additional wells were added during the development of the field hence increasing the depletion rate. In this study, after gathering necessary reservoir, fluid, production and pressure data, IMEX (CMG) simulation program was used for history matching of depletion of the field. Reservoir performance after history matching using depletion scenario was predicted and depletion last for 4 years. In 2005, 5 ERD wells were drilled in KM field from onshore drilling site location for gas storage application. Five scenarios were developed for forecasting of injection and withdrawal performance of the reservoir. These scenarios were used 5 newly drilled horizontal wells with combination of existing vertical wells. With a predetermined injection rate of 65 MMscf/day was set for all the wells and among all scenarios, 5 horizontal - 5 vertical injectors and producers was the most successful in hamdling the gas inventory and he injection period was 5 months and production period was 7 months, respectively. After the determination of the well configuration, the optimum injection rate for the entire field was obtained as 65 MMscf/day by using horizontal gas injection wells. The total produced gas volume until 2012 was estimated as 394 Bscf with this optimum gas injection where the maximum average reservoir pressure was 1901 psi and cushion gas pressure was 1270 psi by withdrawal. Introduction Undeground gas storage (UGS) is defined as the storage in reservoirs of porous rock, salt formations and aquifers, at various depths beneath the surface of the earth of large quantities of natural gas not to native to these reservoirs in order to support the natural gas demand in domestic, commercial, industrial, or space heating which is the most critical case and reason for storage especially in cold winter months. The strong trend towards increasing the number of UGS facilities, which is currently seen in countries with sharp weather differences in winter and summer, is related to the fact that this operating tool is the most adequate, economical, safe and environment-friendly technological means that the industry has to store large volumes of gas ready to be marketed. In 2000, there were 602 underground storage sites world-wide with a working gas volume capacity of 310 bcm and a maximum daily output around 4.46 bcm/day. Underground gas storge projects have been operated successfully in the U.S. for almost 90 years and today, 450 projects store approximately 139 million metric tones of natural gas in 30 states. The majority of storage facilities are in depleted oil and gas reservoirs, but 51 are in brine filled aquifers and 40 in salt caverns [1,2,3]. Horizontal drilling appeared in the 1950's in some areas of oil production, with commercial success. This technique is now generally used all over the world in oil and gas fiels. The application of this technique to UGS is starting slowly with only a few successful horizontal gas storage wells having come on stream. Indeed, in 2000, out of some 10,000 storage wells in the 600 UGS facilities in the world, only less than 100 were horizontal wells. At the same time, at least more than 100 new horizontal wells were planned, pointing out the fast growth in the use of this technique to increase maximum deliverability [4].