Experimental Evaluation of Hydrochloric Acid Treatment on Sandstone Reservoir Properties

Matrix acidizing is a popular stimulation method in oil and gas well that increases the permeability of sandstone reservoirs by dissolving minerals that block pore spaces. The success of this process is dependent on the mineral composition of the rock and the type of acid used. In this work the effects of HCl on sandstones from Sitakundo were studied in the laboratory. Pre and post acidize analysis is performed to observe alteration in porosity, permeability and uniaxial compressive strength (UCS). A significant enhancement in porosity from 11-13 to 22-25% and more than 70% permeability increase were achieved, ensuring an effective dissolution of minerals and an enhancement of porous structure. This implies that the UCS was reduced by 14% approximately as a result of mechanical weakening consequent to the dissolution of cementing materials. These results underline the two fold effect of acidizing - increasing flow capacity while decreasing rock strength and open avenues to more optimized acid treatment design for effective & stable reservoir stimulation.