The Greater Burgan Field, operated by Kuwait Oil Company (KOC), is the largest clastic and overall the second largest oilfield in the world. First discovered in 1938, with production from 1946, production to date has relied on primary recovery methods. In recent years secondary and enhanced recovery techniques have been investigated with water flood now at an advanced state of implementation. The first such water flood project is in the Upper Cretaceous (Cenomanian) Wara Formation, one of the main producing reservoirs within the Greater Burgan complex where production has been accompanied by falling reservoir pressure. The Wara Formation comprises multiple sandstone units deposited in a fluvial-tidal coastal system. The reservoir exhibits a considerable degree of permeability heterogeneity, which poses significant challenges to the implementation of waterflood. The highly complex nature of the reservoir necessitate for implementation of suitable strategies from an early stage of waterflood to ensure better volumetric sweep and ultimate recovery. Several initiatives/studies, including sector model simulation, were undertaken to formulate strategies and evaluate the waterflood performance in this multilayered reservoir. This paper summarizes results of the studies and strategies:• Issues related to vertical sweep and lessons from pilot study.• Strategies for improving vertical sweep.• Evaluation of strategies by using sector model simulation to improve recovery.• Well completion strategies and candidate selection criteria.
The Wara reservoir has been producing for over 60 years and its pressure has slowly decreased over the years, now below saturation pressure in some structurally-high areas where gas cap has increased in size compared to very small initial gas caps in these areas. A peripheral, water injection project is being considered to maintain the pressure above bubble point and improve oil recovery from the flank areas. However, limited information is available concerning Wara reservoir heterogeneity. Shut-in of all Wara producers provided an "once-in-a-lifetime" opportunity to carry out a fieldwide pressure data acquisition campaign. Over a period of six months (Nov. 2006-May 2007, 127 static bottom-hole pressure (SBHP) surveys, 26 pressure buildup (PBU) tests (including buildup tests for 2 active wells of the interference test program) and 3 interference tests were conducted. Each interference test involved one active well and 3-6 observation wells. This paper describes a systematic methodology to select wells to test on a fieldwide basis, test design exercise, data acquisition program execution, and observations and conclusions reached from this data set.Over the duration of the campaign, an increasing pressure trend was observed in almost all wells slated for PBU and interference tests. This observation was made possible due to multiple SBHP recordings in these wells. The linearlyincreasing pressure trend had to be taken into account in the analyses of the buildup tests to avoid interpreting wrong boundary conditions. Wellbore dynamics also initially affected some pressure buildup tests and were later circumvented by the use of a downhole shut-in tool (DHST) to limit the phase segregation effect. The transient analyses revealed different flow regimes, from infinite-acting radial flow, to dual-layer and radial composite with or without sealing faults. From the SBHP data, maps have been made to assist in identifying compartments. One interference test showed anisotropy which could be critical in the implementation of a water injection project. Overall, the interpretation of the data from this extensive data acquisition campaign has shed light on reservoir heterogeneities that have been integrated with changes made in a fullfield, "Wara only", history-matched simulation model.
Stimulating water injectors successfully is critical to any waterflood and to successfully stimulate wells it is important to understand what technology works and what does not. An effective method of evaluating stimulation efficency is by monitoring the long term performance of the water injectors and how injection pressure and temperature varies over time.
The primary source of injection water for Greater Burgan is produced water, which is collected through an extensive gathering system. Because this gathering system is so large, the resulting fluids drop to atmospheric temperature before they are available for injection. Average daily temperatures in Kuwait vary by more than 60°F annually. All of the injection wells are injecting above fracturing pressures and these temperature swings impact the size of fractures leading to observed changes in rate of up to 40%. These effects must be understood to evaluate the impact of injection fluid temperature upon stimulation.
Monitoring this surface injection data has allowed the team to select a successful stimulation method for the injectors and added significantly to the field's injection rate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.