Water Flood Management of the Mishrif Reservoir, Rumaila Field, Southern Iraq

Abstract

The Rumaila field in southern Iraq is a super-giant oil field and contains multiple, stacked, world-class reservoirs. The Mishrif carbonate formation is one of the largest and least-developed Rumaila reservoirs and is a key focus of the Rumaila Operating Organization (ROO) work activities and budget. . At the start of production in 1973, Mishrif well rates were high with average rates exceeding 10,000 bbl/day. Today, after production of only 3% of the STOIIP, reservoir pressure has fallen significantly to the point that many wells have ceased to flow and active wells are flowing only 1,000-3,000 bbl/day. This pressure declined and the absence of any significant water production, suggests the absence of an active aquifer. Material balance work supports this position. The challenge to improving recovery from this reservoir lies in increasing reservoir pressure and mobilising additional oil. A major waterflood expansion project has been planned in order to increase and maintain pressure above the Mishrif bubble point pressure. The full-field water injection project began April 7, 2013 in the first phase of this massive development project. Water injection commenced in 2010 into the Mishrif in three trial areas in the north part of the field. The past three years of trial area operation have yielded encouraging results to water injection in the Mishrif. The first stage of the water injection expansion project involves treatment of water at the Qarmat Ali plant in Basra and then delivery through large pipelines to the existing Cluster Pump Stations (CPS) in north Rumaila. Conversions of producers to injectors are planned in order to convert the field from an existing line drive injection pattern to an inverted 9-spot with a 5-spot pattern ultimately planned. In addition, the wellwork plan includes the installation of larger tubing, packers and high-pressure wellheads. The injection process is under continuous surveillance to monitor the reservoir response to water injection. Reservoir pressure is being monitored in numerous wells both before and during water injection. Water quality is monitored at the CPS facilities and at each injection well to ensure appropriate quality injected water is injected into the reservoir. Individual injection well rates are measured weekly and integrated asset models are updated to improve the allocation of injection water. Produced water samples are taken in wet wells to ascertain water injection breakthrough. It will take some time before the water injection is expected to impact the pressure in the entire Mishrif formation. Significant steps are being taken by ROO to progress and improve production from the Mishrif reservoir in the near future.