Predicting of Oil Water Contact Level using Material Balance Modeling of a Multi-tank Reservoir

Nowadays, the increase in water production becomes a problem in the oil and gas industry. Besides being a problem, it also becomes extra energy to produce oil and gas. OWC is one of the keys for water production determination for each layer. If the perforation at production well is at OWC or below OWC, the production will be 100% water. In general, the log is used to determine OWC. Besides with log, tank modeling from the material balance equation is also used to determine OWC. WH field located 15 km from Bangko Field in Riau. This primary field has high water production with 97% water cut. Before tank modeling starts, each layer needs to be analyzed based on its reserves, production cumulative and remaining reserves to determine the productive layer, which can be developed in the future. Prediction can be done when history matching and calibration process for both historical data and simulated data by software. Prediction ends in August 2021, which is the end of development contract in WH field. From the results, it can be determined that from C sand, the OOWC and COWC are at 2922 ft and 2883 ft with the cumulative oil production is 6.78 MMSTB. From E sand also can be determined the OOWC at 2368 ft and COWC at 2325 ft with the cumulative oil production is 14.57 MMSTB. From K sand, the OOWC is at 2002 ft and COWC at 1911 ft with the cumulative oil production is 13.5 MMSTB. L sand the OOWC is at 2243 ft and COWC at 2191 ft with the cumulative oil production is 29.17 MMSTB. From the analysis, K sand has the most significant OWC movement, which is 91 ft and it is also validated with the current log data. This sand needs more care to maintain water production.