The state of Kansas generated an estimated 614 million barrels of produced water (PW) in 2020 as a byproduct of oil and gas extraction. Reinjection of this high salinity water into active oil sites could both improve oil recovery and reduce the volume of PW that must be disposed of by other means. However, few studies have investigated the geochemical compatibility of the PW with the host oil reservoir.<br/>This study evaluates the geochemical feasibility of using low salinity PW to enhance oil recovery in a geologic formation with significantly higher salinity and to serve as a means of PW management. PW from the Arbuckle geologic formation (~20,000 mg/L TDS) was combined with PW from the Lansing-Kansas City (LKC) formation (~ 200,000 mg/L TDS) in specified ratios to examine brine compatibility and precipitation potential. Bulk static experiments were performed with mixed PWs in the presence of ground LKC rock (primarily limestone) to estimate precipitation and dissolution in the subsurface. Changes in solution cation composition were measured through ICP-OES to indicate the presence of reactions between carbonate solids and dissolved salts. Single phase coreflooding using only PW was performed on LKC limestone to evaluate the dynamic changes to the brine composition and rock structure due to dissolution, ionic exchange or precipitation. Multiphase coreflooding, with crude oil and PW present in LKC rock, was used to investigate the effect of crude oil on same reaction processes. It is expected that; dissolution reactions will be slower in the single and multiphase corefloods compared to bulk static experiments due to smaller exposed surface area and the presence of carboxylic material forming complexes with the brine ions. Insight gained in this work would elucidate the geochemical reactions at the crude-oil-brine-rock interface and would highlight the potential reuse of low salinity PW for oil recovery purposes.

Geochemical evaluation of brine exchange between Kansas Arbuckle and Lansing-Kansas City formations as a means of produced water management

ACS Fall 2021

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