ABSTRACT: Spatial Variability of Formation Waters in the Western Canadian Sedimentary Basin

FREEMAN, JAMES T., RAUSH RAKHIT, and PHIL ESSLINGER, Rakhit Petroleum Consulting Ltd., Calgary, Alberta, Canada, and HUGH ABERCROMBlE, GSC, Calgary Alberta, Canada

Natural variations in the compositions of formation waters in sedimentary basins result from differences in the depositional pore water chemistry and natural evolutionary changes induced by diagenesis, mixing with meteoric water and water derived from other formations, rock-water interactions, and geochemical reactions related to the incursion of meteoric waters during uplift. It is difficult, however, to utilize the composition of water samples recovered during oil and gas operations to distinguish inherent local or regional chemistry variations unless rigorous screening methodologies are employed to aid in the identification of contaminated fluld analyses.

In this study, the entire database of formation water chemistry analyses for the Alberta and British Columbia portions of the Western Canada sedimentary basin have been entered into digital computer files. These data were then screened for various types of contamination. It was found that empirical methods, employing ionic ratio scatterplots and other fluld characteristics, assisted in the establishment of mixing lines between contaminated samples and samples of formation waters.

Validated formation water chemistries were then mapped for various hydrostratigraphic sequences throughout the basin. Spatial

compositional trends iliustrate regional flow patterns that may have widespread implications for interpreting fluid flow regimes and hydrocarbon accumulation within the basin. In particular, these data indicate that a considerable quantity of recharge occurs in the basinal interior, as well as along the margins, suggesting that flow in the basin occurs largely in regional and intermediate scale topographically induced flow systems, rather than in singular large-scale cross-basinal flow systems

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)