Exposure to Phosphate-based Completion Brine under HPHT Laboratory Conditions Causes Significant Gas Permeability Reduction in Sandstone Cores

High-density potassium phosphate and potassium/cesium formate brines were tested in an advanced core flood test rig for their<br>compatibility with low-permeability sandstone containing simulated formation water under HPHT conditions. The tests were<br>carried out at a temperature of 175oC (347 oF) and pore pressure of 5,800 psi. Compatibility was determined by comparing the<br>relative gas permeability of the cores before and after exposure to the brines under HPHT conditions.