Identification of formation scales and design of compatible matrix acidizing fluid system

Abstract

Low productivity caused by formation damage during drilling process or low permeability resulting from scale formation is a problem in the oil industry. Designing and pumping of acid fluid systems to enhance productivity has been the usual amelioration approach. However, lack of proper identification of scale types, poorly designed treatment fluid and inability to use best practice in laboratory pilot tests, before job execution had resulted to poor stimulation targets and in some cases compound initial formation problems due to incompatibility of recommended treatment and formation fluids. This study was conducted to identify different formation scales, design compatible matrix acidizing fluid systems with formation fluids for effective scale removal and enhanced productivity for low permeable and damaged formations. Test results indicated that the main constituents of the scale were iron oxide, calcium carbonate and iron carbonate, typical of sandstone and carbonate reservoirs. Though 15% HCl was faster than 7.5% HCL in dissolving the scales, 7.5% HCl with corrosion inhibitors should be used for field application to avoid intense corrosion of pipes. The emulsion break and compatibility tests also indicated an effective treatment fluid system which had 100% separation within 10 minutes at the test temperatures. The fluid systems as indicated in this work had been successfully implemented in the field for stimulation operations in the Niger Delta of Nigeria.

Keyword: Formation scales, crude oil, matrix acidizing fluids, wellbore, formation pressure

International Journal of Natural and Applied Sciences, 5(4): 329-333, 2009