Evaluation of a Systematic Approach to Matrix Acidizing on an Oil Producing Well

All wells are susceptible to formation damage to some degree, ranging from relatively minor loss of productivity to plugging of specific zones. Formation damage could simply be referred to as a term used to emphasize reduced current production. Acidizing is a well stimulate technique where acids are primarily used to remove or cure damage around wellbore caused by drilling, completion, production and work over operations in order to improve production. In matrix acidizing, acid is used to remove the damage near the wellbore. This removal of severe plugging in sandstone, limestone or dolomite by matrix acidizing process can lead to large increase in well productivity. It is expected that matrix acid treatment should remove flow restrictions near the wellbore and allow the well to produce at an undamaged rate. However, the production rate after treatment is sometimes lower than predicted or in extreme cases without any improvement at all. This study evaluates matrix acidizing operations in oil producing wells with a view to identifying causes of acidizing failures and developed a systematic approach to matrix acidizing that will eliminate failures and greatly enhance the performance of acidized oil wells. Discussions have been centered on the fundamentals of formation damage and acidizing, review of existing literature on the subject and matrix models. In treated wells studied, stimulation ratios from productivity indices were almost equal to or greater than 2 ( 2) and always greater than stimulations ratios from production rates, showing that the treatments were positive in reducing or curing damage around the wellbore but the stimulation ratios from the two parameters (productivity index and production rate) were not the same as a result of flow restrictions. Since all treated intervals in the different wells studied showed positive response to damage reduction, it could be concluded that acidizing if properly executed will reduce or cure damage around the wellbore and improve productivity.