Optimization of a CO2 flood design Wesson Field - west Texas

摘要

The Denver Unit of Wasson Field, located in Gaines and Yoakum Counties in westTexas, produces oil from the San Andres dolomite at a depth of 5,000 ft. Wasson Field ispart of the Permian Basin and is one of the largest petroleum-producing basins in theUnited States.This research used a modeling approach to optimize the existing carbon dioxide (CO2)flood in section 48 of the Denver Unit by improving the oil sweep efficiency of miscibleCO2 floods and enhancing the conformance control.A full compositional simulation model using a detailed geologic characterization wasbuilt to optimize the injection pattern of section 48 of Denver Unit. The model is aquarter of an inverted nine-spot and covers 20 acres in San Andres Formation of WassonField. The Peng-Robinson equation of state (EOS) was chosen to describe the phasebehavior during the CO2 flooding. An existenting geologic description was used toconstruct the simulation grid. Simulation layers represent actual flow units and resemblethe large variation of reservoir properties. A 34-year history match was performed tovalidate the model. Several sensitivity runs were made to improve the CO2 sweepefficiency and increase the oil recovery.During this study I found that the optimum CO2 injection rate for San Andres Formationin the section 48 of the Denver Unit is approximately 300 res bbl (762 Mscf/D) ofcarbon dioxide. Simulation results also indicate that a water-alternating-gas (WAG) ratioof 1:1 along with an ultimate CO2 slug of 100% hydrocarbon pore volume (HCPV) willallow an incremental oil recovery of 18%. The additional recovery increases to 34% if apolymer is injected as a conformance control agent during the course of the WAGprocess at a ratio of 1:1. According to the results, a pattern reconfiguration change fromthe typical Denver Unit inverted nine spot to staggered line drive would represent anincremental oil recovery of 26%.