01996nab a2200205 4500 20260520000321.0 260224s2016 xxu ing Inglés Chemical and isotopic changes in Williston Basin brines during long-term oil production An example from the Poplar dome, Montana oct. 2016 12/12/2016 ; 12/12/2016 13 p. ; 1619-1632 Transcripción del resumen del autor: Brine samples were collected from 30 conventional oil wells producing mostly from the Charles Formation of the Madison Group in the East and Northwest Poplar oil fields on the Fort Peck Indian Reservation, Montana. Dissolved concentrations of major ions, trace metals, Sr isotopes, and stable isotopes (oxygen and hydrogen) were analyzed to compare with a brine contaminant that affected groundwater northeast of the town of Poplar. Two groups of brine compositions, designated group I and group II, are identified on the basis of chemistry and 87Sr/86Sr ratios. The solute chemistry and Sr isotopic composition of group I brines are consistent with long-term residency in Mississippian carbonate rocks, and brines similar to these contaminated the groundwater. Group II brines probably resided in clastic rocks younger than the Mississippian limestones before moving into the Poplar dome to replenish the long-term fluid extraction from the Charles Formation. Collapse of strata at the crest of the Poplar dome resulting from dissolution of Charles salt in the early Paleogene probably developed pathways for the ingress of group II brines from overlying clastic aquifers into the Charles reservoir. Such changes in brine chemistry associated with long-term oil production may be a widespread phenomenon in the Williston Basin. 10 AAPG Bulletin 100 ARTICULO Peterman, Zell 55996 Thamke, Joanna 55997 189948 189948 0 0 0 0 257767 BAAB BAAB 2026-03-06 200062195 0 200062195 2026-03-06 00:20:05 2026-03-06 ARTICULO