Evaluation of Remaining Gas Reserves Using the Material Balance Method for Planning Gas Field Development

The “CJ” field is a gas field located in the South Sumatra Basin with a reservoir located in the Basalt Telisa Limestone (BTL) formation. This gas field consists of 3 wells namely Well GTA-1, GTA-2, and GTA-3 which produced from 1951 to 1991. In 1991 the three wells were suspended and will be reopened in 2021 due to requests from buyers for 10 years. The research method used is to collect data consisting of data on reservoir, production, and physical properties of the gas. The next step is to calculate the value of the gas formation volume factor and Z-factor with various pressures. Next, determine the type of drive mechanism using the Cole Plot method. After knowing the type of drive mechanism, you can determine the current OGIP value using the material balance method. If the OGIP value is known, the next calculation is the Recovery Factor (RF), Ultimate Recovery (UR) and finally the value of Remaining Reserve (RR). Based on the calculation, the current OGIP value obtained by the material balance method with P / Z vs GP plots is 83.46 BSCF, Recovery Factor of 80.223%, Ultimate Recovery of 66.96 BSCF, and remaining gas reserve 15.45 BSCF. From these results, the maximum reserve value that can be produced to the surface for 10 years is 4.2325 MMSCFD. So that "CJ" Field is able to supply gas every day of 4.2325 MMSCFD or less than 4.2325 MMSCFD for 10 years.