Design Considerations For Dome's David Alkali/Polymer Flood

Abstract An alkali/polymer flood has been designed for the David Lloydminster ‘A’ pool in east central Alberta. The David Lloydminster ‘A’ pool was originally under waterflood from November 1978 to March 1986 and approximately 30% OO1P has been recovered. Laboratory tests were initially done which showed incremental oil recovery through the use of 2% wt caustic. Further laboratory test done by Surtek Inc. of Golden, Colorado showed increased oil recovery through the use of alkali in conjunction with polymer and surfactant. This paper presents the results of the lab tests as well as the facility design for an alkali/polymer injection system. The progression of the process from straight caustic injection to sodium carbonate/ polymer to sodium carbonate/polymer/surfactant will also be described. Introduction The David alkali/polymer project is located in Sections 2 and 11–41-3-W4M approximately 100 km south of Lloydminster, Alberta. The pool is in the Lloydminster formation, which is an unconsolidated (partially cemented) sand of the Upper Cretaceous period, located at a depth of about 750 m KB. The average net pay is 3.2 m with an initial oil saturation of 73%. Porosity average 29% and the OOIP is 1.35 million m3? Reservoir fluid properties and other reservoir data are shown in Table 1. Initially the David Lloydminster ‘A’ pool was under primary operations from 1969 to 1978 and approximately 6.3% of the OOIP was recovered. In 1978, a waterflood scheme was initiated and continued until March 1986, when the infill drill program was completed and 50ft water injection began. Figures 1 and 2 show the production history for the project. In December 1983, Dome Petroleum submitted an application to the ERCD for an Enhanced Recovery Scheme which involved injection of a 2 wt % caustic (NaOH), 0.5 PV slug and Infill drilling 22 wells. A 0.1 PV slug of soft water (preflush) was to be injected to condition the reservoir prior to caustic injection. A post flush of 0.2 PV of soft water was also to be injected and a total project life of six years was anticipated. In August 1984, Dome Petroleum received approval from the ERCB to proceed with the experimental scheme. As a result of falling oil prices the economics of the project were reviewed and it was decided to drill only 13 of the proposed 22 wells. Figure 3 shows the pattern arrangement indicating the original 12 wells and the new infill wells. Drilling of the infill wells began in December 1985 and was finished in January 1986. Well 13D-2 was cored for further lab studies. Flowlining of the project and construction of the soft water facilities and battery expansion were completed in February 1986. In March 1986 the soft water injection began at a rate of 630 m3/d into the seven injection wells. Voidage replacement ratio for the project was approximately one. Encouraging results from chemical/polymer lab studies done on Dome's Cessford and Grand Forks projects as well as finding from other papers(l,2,3) led to further investigations on the David Lloydminster ‘A’ pool.