Designing Optimum Injection Parameters With Low Salinity Water Injection in Sandstone Reservoir for Tangai Structure At Sukananti Field

Abstract

Waterflood has become the most successful and widely practiced method in the oilfield because its ability to increase oil recovery from the reservoir, also its simplicity and low cost to increase the recovery factor, especially in Indonesia. However, EOR method, after the IOR process is completed it is essential to obtain higher oil recovery by using alkaline, surfactant, polymer, steam, CO2, heat energy, or other methods that will encourage oil discharge, change wettability, swelling effect, including other mechanisms that will lead to increased oil recovery from the reservoir. But in Indonesia, some EOR method have not been executed because of its feasibility and high cost to implement EOR. Low Salinity Water Injection can serve as an alternative to the EOR method and has become a topic in current important research in the oil and gas industry. This comes after the publication of research that Low Salinity Water Injection can increase oil gain up to 10-20% through coreflood and pilot experiments in the field. The advantages of Low Salinity Water Injection are expected to be used as a feasible solution of the EOR method in Indonesia.

For determining potential of the real field case in Indonesia, this study will presents a design of optimum injection parameters in Sandstone Reservoir of Tangai structure in Sukananti field. Basic mechanisms theory which has been proposed by researchers implemented to compositional reservoir simulator model using GEMTM (CMG Ltd.) simulator. This field is categorized as light-medium oil with PVT fluid model constructed using WINPROP (CMG Ltd.). The study to obtain the optimum design has been done by using two types of water, namely formation water and low salinity water (1782 ppm) in order to obtain optimal oil recovery and optimal residual oil saturation.

The results of this study indicate that Low Salinity Water Injection is more suitable for the EOR method compared to secondary recovery. This is due to the difference in mechanisms described in several mechanisms such as the MIE and Electrical Double Layer Expansion which will cause the oil particles to be detached from the clay. In this study, it was found that the greater the rate and pressure of the injection, the higher the oil recovery. Interwell tests conducted on this field have resulted, i.e. an increase in cumulative oil production up to 11% compared to the use of conventional waterflood.