Dynamic Etching Tests And Their Use In Planning Acid Treatments

Abstract

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for Oklahoma Regional Meeting of the Society of Petroleum Engineers of AIME, to be held in Stillwater, Okla., Oct. 25, 1968. 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 request 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 discussion 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 satisfactory stimulation of oil and gas producing wells by "Fracture Acidizing" is dependent upon development of adequate flow capacity in naturally occurring or induced fractures of sufficient areal extent. The flow capacity is either obtained or improved through the action of the acid on the exposed fracture faces. The type and quantity of acid used in a treatment greatly influences the pattern and degree of etching. Consequently, the type of etch affects the fracture flow capacity. Dynamic acid etching tests can be used to determine the feasibility of an acid treatment, and the type acid and the contact time necessary to produce a conductive fracture. produce a conductive fracture Introduction The first wells stimulated with hydrochloric acid were treated by dumping small quantities of acid down the well. These treatments were interstitial and improved the natural permeability near the well bore only. Later, when acid inhibitors were developed and pumping equipment was improved, acid was pumping equipment was improved, acid was injected at higher rates and pressures, and consequently larger volumes were used. At this time, acid reaction time, fluid efficiency and pump rate were used in designing acid stimulation treatments. For years, these factors were used, and are still being used, to calculate the surface area of created fractures. It was assumed that a conductive fracture would be created by hydrochloric acid in limestone and dolomite formations. Of course, this is not always true.