Paper Title
Alteration of Physicochemical Properties of Northeastern Thailand Permian Limestone after Dissolving with Hydrochloric Acid

In limestone stimulation, hydrochloric acid (HCl) is most commonly used to improve permeability and porosity near the wellbore. This study focuses on variations in the chemical and physical properties of northeastern Thailand Permian limestone after dissolving it with various concentrations of HCl. In the Permian Saraburi Group, the Pha Nok Khoa, Nam Mahoran, and Khao Khad Formations were collected from Loie and Nakhon Ratchasima. Samples of limestone were soaked at room temperature for 24 hours in 5, 10, 15, and 20% HCl concentrations. X-ray fluorescence (XRF) and X-ray diffraction (XRD) analysis were performed on the limestone samples to determine their mineral and elemental composition. Based on test results, the contents of calcite (CaCO3), lime (CaO), and quartz (SiO2) were directly proportional to the amount of porosity and the rate of dissolution of the limestone matrix. The Porosimeter and Scanning Electron Microscope (SEM) were also used to analyze the amount of porosity and morphology of the rock matrix microstructure. Results of the research indicated that the most physical property alteration to be dissolved with HCl was Pha Nok Khao, Khao Khad, and Nam Mahoran Formation, respectively. Micropore size and quantity increased with HCl concentration increment and 15% of HCl concentration was suitable for matrix acidizing of northeastern Thailand Permian limestone. Keywords - Acidizing stimulation, Porosity, Carbonate reservoir, Petrography.