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

摘要

The VLA 6/9/21 Field is a waterflooded light crude oilreservoir located in Maracaibo Lake, West Venezuela. In thelast two years PDVSA E & P has developed IntegratedLaboratory Fields (ILF) as a strategy to evaluate newtechnologies and EOR methods in order to improve light andmedium oil recovery factors. Alkali/Surfactant/Polymer (ASP)is one of the chemical flooding technologies that has recentlybeen evaluated in Venezuela.The objetive of this study is to describe the followedmethodology to develop ASP formulas, describe the pilot testplanned for this year and also to determine whether ASPtechnology can produce incremental oil in the Eocene C-4Unit of VLA 6/9/21 Field economically. The study wasperformed at reservoir temperature of 90°C with dead crudeoil and rock sandstones from the oil producing zone located inthe pilot area.Several ASP formulas were developed for the VLA 6/9/21Field with comercial petroleum sulfonates. Each ASP solutiongave interfacial tension (IFT) values below 9x10-3 dynes/cm.Rheologic studies with polyacrylamide polymers usingdifferent additives indicate that the solution viscosity can bemantained over the time at least 2 cp above the crude oilviscosity (2,5 cP) at reservoir temperature. Surfactants, alkaliand 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 PVASP and 0,15 PV polymer injection in reservoir cores. Thepositive results of this laboratory study provided an ASPformula for a pilot test supported with the injection of oilpartitioning tracers before and after the chemical additives aspart of one of the ILF of PDVSA E & P.