Relative intensity ratio (RIR) method was used to determine the quantitative mineralogy of rock samples that were analyzed by X-ray powder diffraction (XRD). A total of more than 700 samples were tested from wells as deep as 7600 ft located at various carbonate reservoir locations in Arabian Peninsula. Pure mineral samples obtained from the same reservoir were employed as standards to determine relative intensity factors used in the calculations. The rock mineral was mainly composed of calcite, dolomite and anhydrite along with smaller quantities of quartz. (c) 2007 Elsevier B.V. All rights reserved.