INJECTION MANAGEMENT AT DARAJAT FIELD, INDONESIA: IMPACT OF MOVING INFIELD INJECTION TO EDGEFIELD

Abstract

Power plant condensate has been injected back into the reservoir since the Darajat Field started commercial generation in 1994. For almost 20 years, condensate was injected infield as the injectors were located in the central portion of the field. Although infield condensate injection provides pressure support to the reservoir it has also resulted to reservoir cooling, which led to steam condensation and high production decline, and wellbore scaling. To combat these negative impacts of injection, condensate injection was moved to the northern edge of the field in 2012.
As expected, fieldwide production decline went down as a result of edgefield injection. About four years after edgefield injection, reservoir boiling in the central portion of the field is more prevalent as evidenced by increasing superheat, production of more Injection Derived Steam (IDS), and the deuterium (2H) and boron contents of most central production wells. Edgefield condensate injectate appears to move deep in the reservoir as indicated by microearthquake (MEQ) swarms. To date, edgefield injection has not had any detrimental impact to the Darajat reservoir. A time-lapse of gravity response shows a decline in the net-mass produced in northeast Darajat since the implementation of edgefield injection suggesting a mass balance condition due to support from the peripheral injection.