--> ABSTRACT: Model Experiments on the Origin of Tar Mats and Viscous Oil Barriers in Petroleum Reservoirs, by A. Wilhelms, S. R. Larter; #91003 (1990).

Datapages, Inc.Print this page

ABSTRACT: Model Experiments on the Origin of Tar Mats and Viscous Oil Barriers in Petroleum Reservoirs

A. Wilhelms, S. R. Larter

Tar-mat and viscous oil occurrence in petroleum reservoirs can have significance both to the explorationist, in terms of affecting the formulation of viable geological models, and to the production engineer, in terms of assessment of barriers and simulated models of production. Despite a widespread appreciation of their significance to the oil industry, our models of viscous oil formation and tar-mat genesis are inadequate. Traditionally, tar mats in reservoirs below their critical points are often thought to be associated with catastrophic reservoir events, such as gas injection, biodegradation, reservoir maturation, etc. However, recent studies by our group have shown that small tar mats may form as a result of far more subtle mechanisms involving, among others, in-rese voir mixing of petroleums of slightly different maturity.

We have developed a coupled experimental-field study approach to tar-mat architecture, with a view to developing a strategy for recognizing mechanisms of tar-mat formation in data from a given reservoir. Such conclusions cannot be reliably obtained at this time by conventional geochemical analysis. We have used a set of model tar-mat precipitation experiments and a novel analytical methodology (pyrolysis-gas chromatography, gel permeation chromatography, and automated TLC-FID methods) to develop a set of criteria for field recognition of precipitating mechanisms from real tar mats. We discuss the geological applicability of this type of study.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990