Perpustakaan Digital ITB

In the last decades, injection of brines with modified ionic composition has been developed to improve oil recovery. Low Salinity Water Injection (LSWI) is one of the most prominent Enhanced Oil Recovery (EOR) method which can increase oil recovery better than that of other conventional chemical EOR methods. As a result of further studies of LSWI, an idea of combining it with other EOR technique was generated. One of the Idea is to combine LSWI with gas injection which is known as Low Salinity Water Alternating Gas (LSWAG) Injection. Applying Water Alternating Gas (WAG) in LSWI process means to inject both low salinity water and gas to the reservoir in order to improve the oil recovery. The presence of flue gas produced during production process leads to the idea of utilizing the produced hydrocarbon gas to be used for injection as pure carbon dioxide (CO2) gas is considered costly. In this study, the author proposes the idea of modelling Low Salinity Water Alternating Hydrocarbon Gas (Hydrocarbon-LSWAG) injection using compositional model to identify the effects of Hydrocarbon-LSWAG injection operational parameters and to propose the most optimum Hydrocarbon-LSWAG injection scenario to be applied in the sandstone reservoir at “B” Structure in “S” Field, South Sumatera Province, Indonesia. Reservoir simulations and production forecasts were done using CMG GEMTM Simulator during 15 years of production period starting from 1st January 2021 until 1st January 2036 with preliminary work using CMG WINPROPTM for generating the reservoir fluid compositional model. Series of sensitivity analysis was conducted in this study to identify the effects of operational parameters in modelling Hydrocarbon-LSWAG injection and to determine the most optimum Hydrocarbon-LSWAG injection scenario to be applied in “B” Structure in “S” Field to gain promising oil recovery using two injector wells. Water salinity, number of cycle and gas-water injection duration ratio were varied in order to observe the effects of those parameters to oil recovery factor. The result of this study shows that injection using lower water salinity of 1,800 ppm results in higher oil recovery compared to water salinity of 3,600 ppm. The recovery factor results in higher value when the LSWI duration is longer than the hydrocarbon gas injection, in this case, with 1:2 ratio of gas-water injection. Furthermore, the findings of this study also show that the increasing number of Hydrocarbon-LSWAG injection cycle is neither directly or inversely proportional to the improvement of oil recovery. The most optimum Hydrocarbon-LSWAG scenario to be applied in “B” Structure of “S” Field is by injecting hydrocarbon gas of 2.5 MMSCFD alternating with low salinity water injection of 1000 BPD with salt concentration of 1,800 ppm by applying one time of Hydrocarbon-LSWAG cycle per year with gas-water injection duration ratio of 1:2 which results in 60.01% of oil recovery factor. Therefore, Hydrocarbon-LSWAG is suggested to be applied in “B” Structure of “S” Field for further field development.