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Porosity of Accumulation Stage: An Important Basis for Evaluating Reservoirs

Desheng Ye, Shuhui Liu, Weiyuan Hu

Present porosity of surface rock and core samples has commonly been considered by petroleum geologists as one of the main parameters for evaluating hydrocarbon reservoirs in the exploration of hydrocarbons. The porosity of reservoir rocks evolves during geological history through several stages, including various diagenetic stages.

Our research on diagenesis, hydrocarbon reservoirs, and the relationship between them shows that although the present porosity of surface rock and core samples reflects, to some degree, reservoir behavior, it cannot precisely reflect the full view of reservoir behavior. This is especially true for rock samples which do not contain hydrocarbons and rock samples of an old geologic age and a complex geological history. The writers propose that only "porosity of accumulation stage" can be used to evaluate reservoir behavior correctly. The porosity of accumulation stage is the porosity of reservoir rocks when source beds were in their peak period of generating hydrocarbons (i.e., the main hydrocarbon migration and accumulation period). The porosity of accumulation stage is primarily contro led by some minerals and certain rock fabrics in a special diagenetic stage. To determine the porosity of accumulation stage, detailed diagenetic research must be undertaken. Thus, we can understand the history of diagenesis (including the history of porosity evolution), the history of hydrocarbon evolution (including hydrocarbon generation, migration, accumulation, and destruction), and especially the relationship between the history of porosity evolution and the history of hydrocarbon evolution.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.