Experimental study of alcoholic retarded acid systems for high temperature gas wells acidizing process

Matrix acidizing treatments are applied to gas wells to remove near-wellbore permeability impairment (formation damage). This work relates to the use of some alcoholic components as a retarding agent in gas field acidizing operations to reduce rate of calcium carbonate (dolomite MgCa(CO3)2) dissolution by acid. The retarding agent is feasible to “retard” acid formulations and slow down their reaction rates to allow deeper penetration of live acid or preferential creation of large wormholes through any near-wellbore damage. In this study, two new alcoholic retarding acid systems (RE 1, RE 2) are presented. RE 2 is stable up to 75 °C, highly retarded compared to the straight acid. Laboratory data comparing alcoholic retarding acid with commercial retarding acid (F-98) and straight acid are shown at temperatures ranging up to 75 °C. Moreover, results show that RE 1 is a proper retarding agent for low temperature and deep gas well acidizing. Reaction rates of RE 1 and RE 2 (acid systems) with dolomite MgCa(CO3)2 are slower than the reaction rate of commercial retarding acid system (F-98) at low and high temperatures. Experiments are conducted in a rotating disk instrument to measure dissolution rates of dolomite rock samples in retarding acid systems and straight acid. A rotating disk system is used at 30-75 °C under a pressure of 8 MPa and rotational speeds up to 1200 rpm.