Abstract: Steam-Induced Alteration of Mineralogy and Permeability in Kaolinitic, Siderite-Bearing Sandstones

David C. Keith, Wendy J. Harrison, Richard F. Wendlandt, Alden B. Carpenter, Eric J. Daniels, Gregory S. Orton

Laboratory experiments using mixtures of quartz sand, kaolinite, and crushed siderite were performed in a high-temperature/high-pressure permeameter to determine how reservoir mineralogy and permeability are affected in steamflood enhanced oil recovery operations. Cores of "artificial sediments" were prepared in shrink-fit Teflon tubes and subjected to temperatures ranging from 150 to 250°C. At 250°C, influent fluid compositions simulated either a residual liquid phase (pH 11-12), derived from incomplete vaporization of water during steam generation, or low salinity vapor-phase steam condensate (pH 6-7). In experiments below 250°C, an intermediate composition influent was used to simulate steam generator feedwater.

Below 175°C, there was no apparent reaction over the time span of the experiments (up to three days), although there was a permeability loss probably associated with fines migration. At approximately 175°C, siderite grains developed a thin coating of smectite. In subsequent higher temperature experiments, this smectite coating became progressively more prevalent, extending into pore spaces and onto quartz grains, reducing permeability drastically. In siderite-free experiments, no expandable clay was produced, but in experiments using only quartz and siderite, an iron-rich expandable clay was produced at high temperature. Although expandable clays are the primary authigenic phase responsible for permeability damage, other phases produced that contributed to permeability decli e include magnetite, analcime, chlorite, K-feldspar, and illite. Experiments performed at irreducible oil saturation showed no apparent influence of hydrocarbons on these inorganic reactions.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994