Kinetic Rate Expressions for Reactions of Selected Minerals with HCl and HF Mixtures

Abstract

This paper was prepared for the Oilfield Chemistry Symposium of the Society of Petroleum Engineers of AIME, to be held in Denver, Colo., May 24–25, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract The chemical kinetics of solid-liquid reactions were studied for different mud acid-mineral systems in a rotating disk apparatus. The minerals studied included calcite, dolomite, microcline, and albite. The kinetic rate equations, regimes of diffusion and reaction control, and possible mechanisms of dissolution are presented for these various minerals. At temperatures above 100 degrees C, the rotating disk rate data show that the rate of reaction of HCl with dolomite is controlled by the mass transport of HCl to the dolomite surface. The HCl-dolomite reaction becomes surface reaction controlled at temperatures below 100 degrees C. At the conditions existing in petroleum reservoirs, the HCl-calcite reaction can be considered controlled exclusively by mass transport of HCl. The feldspar-mud acid reaction rate results reveal that the dissolution of feldspars is surface reaction rate limited and depends on both the HF and HCl concentrations in the mud acid. Introduction Acid stimulation of oil and gas reservoirs is concerned with the application of acids and acid mixtures to dissolve porous and non-porous minerals. It has great utility in enhancing the productivity of oil reservoirs through increasing the permeability of the formation by the permeability of the formation by the processes of matrix and fracture processes of matrix and fracture acidization. In matrix acidization, acid such as hydrochloric acid or a mud acid (HCl and HF) is forced to flow within the pore structure of the rock matrix. The reservoir rock characteristics are altered as the acid reacts with the clays and minerals present. In fracture acidization, the present. In fracture acidization, the acid is forced to flow along hydraulically induced fractures.