Alkali / Surfactant / Polymer at VLA 6/9/21 Field in Maracaibo Lake: Experimental Results and Pilot Project Design

Abstract

The VLA 6/9/21 Field is a waterflooded light crude oil reservoir located in Maracaibo Lake, West Venezuela. In the last two years PDVSA E & P has developed Integrated Laboratory Fields (ILF) as a strategy to evaluate new technologies and EOR methods in order to improve light and medium oil recoveryfactors. Alkali/Surfactant/Polymer (ASP) is one of the chemical flooding technologies that has recently been evaluated in Venezuela. The objetive of this study is to describe the followed methodology to develop ASP formulas, describe the pilot test planned for this year and also to determine whether ASP technology can produce incremental oil in the Eocene C-4Unit of VLA 6/9/21 Field economically. The study was performed at reservoir temperature of 90°C with dead crude oil and rock sandstones from the oil producing zone located in the pilot area. Several ASP formulas were developed for the VLA 6/9/21 Field with comercial petroleum sulfonates. Each ASP solution gave interfacial tension (IFT) values below 9×10-3 dynes/cm. Rheologic studies with polyacrylami depolymers using different additives indicate that the solution viscosity can be mantained over the time at least 2 cp above the crude oil viscosity (2,5 cP) atreservoir temperature. Surfactants, alkali and polymer retention were below 0,08 mg/g rock. Incremental oil recoveries were higher than waterflood, obtaining recoveries between 22 and 39% OOIP for 0,3 PV ASP and 0,15 PV polymer injection in reservoir cores. The positive results of this laboratory study provided an ASP formula for a pilot test supported with the injection of oil partitioning tracers before and after the chemical additives as part of one ofthe ILF of PDVSA E & P. Introduction PDVSA´s light oilfields in Lake Maracaibo have been under exploitation formore than four decades. To date, the expected recovery factor is only 29% ofthe OOIP. As these resources approach maturity, it has been realized tha timproving recovery will demand the earliest use of many technologies, provenand new, in an integrated manner and tailored to solve specific regional problems. The Integrated Field Laboratory (IFL) philosophy is one of PDVSA´s main technology strategies designed to accomplish these goals. Three Field Laboratories are being developed in the Maracaibo Lake Basin: one for heavy oils and two for light oils: shallow and deep reservoirs. Lagomar´s VLA-6/9/21 area was selected as representative of a large numberof shallow (less than 10000´) light oil reservoirs in the Maracaibo Lake basinwith similar reservoir characteristics, currently under water injection and atan advance stage of depletion. Resent characterization studies indicate that there exists a large volume of reserves not contacted in the VLA-6/9/21 area which need new strategies of exploitation to bring them to production. Venezuela has over 50000 MMSTB of oil currently in place in reservoirs with similar condition [1]. The area selected for the IFL has an approximate aerial extension of 10Km2. It is confined between two major sealing faults to the Southand West and the OWC to the East. To the North, an arbitrary line (Figure 1)limits it. There are six overlying reservoirs in the IFL´s area: Basal la Rosa,C-4, C-5, C-6-S/M, C-6-I and C-7. Most of the remaining reserves are concentrated in the three uppermost reservoirs, which were selected for the multi-reservoir water injection project.

Potential for Non-thermal Chemical Augmented Waterflood for Producing Viscous Oils

“…Vargo et al (1999), Wang et al (1999), Manrique et al (2000) and many other researchers have also reported successful ASP field tests. Gao and Gao (2010) documented the test results of different ASP flooding at Karamay, Daqing and Shengli fields.…”

Global sensitivity analysis of Alkali–Surfactant–Polymer enhanced oil recovery processes

“…• If we could eliminate the uncertainty of one or more of the input variables which ones should be chosen (variable selection for maximum uncertainty reduction)? Previously reported works using reservoir numerical simulation have been limited to local sensitivity analyses (Wu, 1996;Zhijian et al, 1998;Manrique et al, 2000;Qi et al, 2000;Hernández et al, 2001) and global but discrete analyses -factorial designs (Delshad et al, 2005). The latter approach given its discrete nature may hide the true nature of the process behavior or may require an unaffordable amount of experiments.…”

An Efficient Response Surface Approach for the Optimization of ASP Flooding Processes: ASP Pilot Project LL-03 Reservoir

“…Traditional approaches for the optimization of ASP flooding processes have been limited to a trial and error method or local sensitivity analysis using reservoir numerical simulation [6][7][8][9][10] , where formal optimization is seldom used because of the computationally expensive objective function evaluations (i.e., numerical reservoir simulator model). The surrogate-based optimization approach has been shown to be useful in the sensitivity analysis and optimization of computationally expensive simulation-based models in the aerospace [11][12][13] , automotive 14,15 , and oil industries [16][17][18][19] .…”