Impacts of Rock-brine Interactions on Sandstone Properties in Lower Miocene Sediments, Southwest Louisiana

Abstract

Reinjection of cooled geothermal fluid is an essential part of geothermal reservoir management, and has been discussed in many recent reservoir studies. Geothermal fluid reinjection can improve heat recovery and maintain pressure. Reinjection may have unfavorable consequences, such as calcite and silica scaling in production and surface facilities. However, the impact of brine-rock interactions on reservoir properties has not been addressed as fully for reinjection. In this paper, interactions between geothermal fluid and reservoir rocks in the West Hackberry field, Cameron Parish, Louisiana are examined using geochemical modeling. The Hackberry Field comprises Miocene sediments on the flank of a salt dome. These sandstones are variably cemented with calcite, pyrite, and pyrrhotite. The field is 1.4-2.1 km deep, with initial temperature and pressures ranging from 65 to 75 °C and 15 to 27 MPa, respectively. The brine is cooled down to the estimated output temperature of power plant and re-equilibrated. Then, reinjected brine-rock interactions with declining reservoir temperature are simulated, and the effects on reservoir properties like porosity and permeability are investigated. Geochemical reactions between different sampled brine and reservoir rock compositions have been modeled as the reservoir is chilled.