The Development of a Major Gas-Condensate Field

Abstract

Abstract A major grass-root gas project has been recently implemented to develop two condensate reservoirs in a field onshore Abu Dhabi. The project facilities comprise of a gas gathering system, a processing plant for condensate recovery and an injection system to recycle the lean gas back to the reservoir. This paper addresses the basic design concepts and describes the surface facilities. The paper also outlines the project implementation strategy as well as the commissioning and start up experience. Introduction According to the Oil & Gas Journal [1] and the US Department of Energy [2], the United Arab Emirates (UAE) has the fourth largest natural gas reserves in the world after Russia, Iran and Qatar. Most of these gas reserves are located in the Emirate of Abu Dhabi. The past few years have seen Abu Dhabi embark on a massive investment program to develop its gas sector. One of these developments is a major grass root gas project, which has been recently implemented in Asab field (figure 1). The field is one of the largest onshore oil fields of Abu Dhabi and is located 225 km south of Abu Dhabi City. It was discovered in 1963 and oil production began in 1974 [3]. The field also contains two large gas condensate reservoirs. These are zone "F" and zone "G" reservoirs, which are parts of the Thamama Group of Eastern Abu Dhabi, which is an Early Cretaceous platform carbonate sequence [4]. Project Description The project facilities include a gas gathering system, a central gas processing plant, an injection system and a condensate export pipeline (figure 2). These are described below. The Gas Gathering System The layout of the project facilities is shown in figure 3. There are 29 producing wells of which 17 wells are completed in Zone "F". The remaining 12 wells are completed in Zone "G". All the wells are completed as a single horizontal producer with a 5 1/2 inch completion string. Each well has a dedicated flowline, which transfers the fluids to one of the four Gas Remote Stations. The wellhead piping and flowline up to and including the production manifold are designed for the WHCIP (wellhead closing-in pressure) of 253 barg. The flowlines are either 6 or 8 inch in diameter. The well fluids are highly corrosive and contain up to 3.7 Mole % H2S and 4.3 Mole% CO2. Corrosion inhibition facilities are provided at each wellhead. The main function of the gas remote station is to gather well fluids from the producing wells in the vicinity, while allowing the wells to be tested. Each of the four gas remote stations contains the same equipment. The facilities at the gas remote stations include : an inlet manifold, three-phase test separator, air cooler heat exchanger and a pig launcher. Utilities and offsite facilities include : corrosion inhibition facilities, flare and burn pits, diesel system for the standby generator, instrument air, as well as potable water systems.