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 recovery factors. 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-4 Unit 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 9x10−3 dynes/cm. Rheologic studies with polyacrylamide polymers 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) at reservoir 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 of the ILF of PDVSA E & P.
