Use of Scanning Electron Microscopy to Detect Parameters for Reservoir Evaluation
Michael G. Waddell, Paul B. Basan
Scanning electron microscopy (SEM) is a technique that permits a more detailed observation than thin-section studies for evaluating hydrocarbon reservoirs. This technique provides valuable data about textural conditions that may control log response and the reservoir's potential for damage, and it helps evaluate reactions from introduced fluids. Logs respond to many conditions that can mislead interpreters about potential well productivity. Disintegration of labile grains as well as development of pore- and grain-lining clays may produce erroneously high, movable water saturation. The breakdown of grains and pore fill create abundant microscopy, whereas pore-lining clays create high surface-area pores that effectively hold water.
Formation damage can occur from mechanisms that are not related to the minerals. SEM is an important tool for identifying potential damaging conditions. Loosely attached mineral particles present a situation where they can break free and migrate into regions near a well bore. Clay-lined pores are especially sensitive to ionic changes of pore water, which may lead to clay dispersion and migration. SEM also is used to evaluate rock-fluid compatibility. Compatibility studies require before flow and after flow SEM evaluation to establish which fluids are compatible before treatment and to determine which fluids may have created damage. Several causes of damage have been documented, including new mineral growth in pores, damage from crystallization of solids, and polymer residue.
AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.