Computer Simulation of Rock-Water Interactions During Water Flood of the San Andres Formation, New Mexico

S. E. Sommer

Rock-water reactions in reservoirs leading to scale production, porosity modification, and mineral alteration may be simulated with PC and mainframe computer models. Chemical computer simulation has been utilized to evaluate the effect of water and rock composition, pressure, temperature, porosity, and reactivity on scaling in the reservoir and well bore for a San Andres waterflood. Results demonstrate that the primary source of scale components is the injected waters, with 5 to 25% of mineralization derived from reservoir components. Rock-water reactions can account for a maximum increase in porosity of 1 to 1.5% with porosity increasing near the injector and decreasing near the producer, but with an irregular distribution. The porosity alteration is the result of anhydr te and carbonate dissolution and gypsum and calcite precipitation. The pressure gradient between injector and producer and the fluid composition are the major causitive factors in gypsum scale production, with pressure controlling spatial distribution. Evaluation of chemical and physical parameters by computer simulation demonstrates the interplay of factors that contribute to scaling and porosity modification and suggests alternative operating procedures for reservoir management.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.