Geochemical Modeling of Scale Formation, and Formation Damage during Production from Sulfate and Carbonate Mineral-Bearing Reservoirs
MACGOWAN, DONALD B., THOMAS L. DUNN, and RONALD C. SURDAM, University of Wyoming, Laramie, WY
The physical and chemical processes that affect reservoir fluids during production can be modeled by methodologies similar to those used for modeling clastic diagenesis. That these processes may result in formation damage and scale formation make them of interest to production geologists and engineers. Pathway modeling, based upon a series of critical divides, predicts which reactions are likely to occur between formation, production tubing, and reservoir fluids. Thermodynamic equilibria modeling calculates direction and magnitude of possible reactions. Integration of these approaches with observations of patterns of scale formation, production line, and formation damage yield a model capable of predicting the magnitude and direction of reactions that may produce negative impacts on r servoir production.
Critical divides characterizing these processes in carbonate and sulfate mineral-bearing reservoirs include: (1) presence or absence of sulfate-bearing minerals within the production volume; (2) presence of iron within production line or formation; (3) ratio of concentration of bicarbonate to hydrogen sulfide; (4) capacity of aqueous and solid phases to buffer formation fluid pH; and (5) magnitude of pressure and temperature drops during production. The model qualitatively predicts: (1) likelihood of sulfide, sulfate, or carbonate mineral precipitation during production; (2) souring of the reservoir; and (3) corrosion of production tubing. These predictions are based upon geochemical pathways which aqueous and solid reactants take, chemical equilibria between reactants, and reservoir eochemical conditions. The model has been developed from production histories for Weber Sandstone reservoirs, Colorado and Wyoming, and has been applied to examples of reservoir production from Tensleep and Minnelusa reservoirs in Wyoming.
AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)