--> Cyclic-Steam-Induced Diagenesis in Potter Sand Midway-Sunset Field, California, by D. A. Pennell and R. A. Horton, Jr.; #90986 (1994).

Datapages, Inc.Print this page

Abstract: Cyclic-Steam-Induced Diagenesis in Potter Sand Midway-Sunset Field, California

Dawne A. Pennell, Robert A. Horton, Jr.

Steam injection is widely used in hydrocarbon extraction, yet, little has been published regarding its mineralogic effect on reservoir properties. This study documents the diagenetic effect of cyclic steam injection into the Potter sand (Miocene) at Midway-Sunset field. Thin section and x-ray diffraction analyses of a pre-5 team and post-steam well were compared. Samples were chosen from correlative sands within highest (215°F) and lowest (98°F) reservoir temperature zones at depths ranging from 401-1026 feet.

Results indicate significant mineralogic and textural changes occurred as a result of cyclic steam injection. These were accompanied by a 5.7% drop in average thin section intergranular porosity. Included are: (1) increased grain dissolution resulting in a QFL ratio shift from lithic arenite toward feldspathic litharenite composition and loss of sulfate minerals; (2) changes in percentages and mineralogy of the clay fraction including a large drop in kaolinite abundance, loss of chlorite, a slight decrease of clay-sized mica, and changes in mixed-layered illite/smectite composition; (3) an overall increase in relative percentages of clay (coatings, bridges and pore filling cements), pseudomatrix and framework grain alteration was observed. This increase appears related to smectite (ab ent in pre-steam samples) formation in the steamed zone; 4) increased trace levels of calcite cement and pyrite; 5) decreased intergranular porosity (from 25.4% to 19.7%) overshadowing an increase in dissolution-induced intragranular porosity. Permeability and pore size geometry were not evaluated, but the net loss in porosity suggests permeability may have been affected as well.

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