Print this pageSpatial variations of stable isotopes and solute chemistry in basinal brines have been used to determine the origin and evolution of formation waters and to infer regional patterns of fluid flow and dominant diagenetic processes active in sedimentary basins. However, the genetic mechanisms and compositional controls on the development of saline waters in deep formations have yet to be completely resolved. In the Williston Basin, Canada/USA, there is the opportunity to sample these deep formation waters as newly completed wells continue to provide current data. Preliminary results of a regional, 75 well sampling program initiated in the Paleozoic formations, show the presence of chemically distinct Ca-Cl brines, as well as oxygen and deuterium signatures characteristic of each formation. These distinctive isotopic ratios are helpful in assigning fluid origin. Isotopic distributions will be mapped to track the direction and duration of fluid migration as well as cross-formational mixing. Furthermore, an investigation of the source and type of salinity will look at evaporative concentration endmembers to assist in the determination of the most viable brine formation process. Geochemical controls on major ion chemistry will be modelled to establish which chemical mechanisms dominate in the evolution of these brines. Chemical and isotopic tracers not only provide evidence for deep fluid flow, but also document fluid migration patterns that are important in the exploration and exploitation of economic resources found within the Williston Basin.
AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid