Optimum matrix acidizing: How much does it impact the productivity

Abstract

Formation damage is one of the big challenges for oil and gas oilfields development. Several types of formation damage most likely exist during the entire life of producing wells. Formation damage can occur during the drilling or coring operations, well completion, work-over and production. The most important problems that affect formation during drilling operations are mud filtrate and fines invasion. There are different damage mechanisms affect reservoirs for instance pore blocking by solids, clay swelling and dispersion and liquid block which all reduce effective permeability to hydrocarbons. The reduction in production and an excessive build up pressure in injection wells indicate the formation. Many techniques are developed to remove the formation damage and to improve the productivity of wells. Matrix acidizing is one of these method which depend on injecting acids into the formation below fracturing pressure to eliminate the damage around the well. In this study, comprehensive design procedures for the acid treatment have been introduced. The procedures include the determination of the damage type and the mineralogy of the formation. Accordingly, the selection of the appropriate acid for the treatment and the optimum volume of injected acid are explained in the study. Additionally, the research presents several models for the pre-flush volume and the main acid volume based on the radius of the damaged zone and the height of the formation. New technique has been proposed for determining the final permeability improvement ratio based on current and proposed productivity index. It has been found the pre-flush volume increase as the carbonate percentage in the formation increases while the main acid volume conversely proportional with the clay content in the formation.