New Approach to Chemical Diversion Using Biodegradable Particulates and Fibers in Matrix Acidizing: Kuwait Case Studies

Abstract

Heterogeneity across the producing interval is typical in oil and gas wells; it is rare to find uniform production distribution or fluid injection across a substantially long interval. Hence, diversion during matrix acidizing is critical, especially if the downhole pressure and/or temperature are high. In two Kuwait Jurassic fields, two wells were completed in an over 100 ft producing interval across a carbonate reservoir. Reservoir temperature is 280°F, and the estimated reservoir pressure is 11,000 psi. Multiple matrix acidizing trials to enhance well productivity have been performed with conventional diversion techniques and, as indicated by the surface pressure response, were not effective. This requires an adequately engineered near wellbore diversion system that can overcome the challenge of these bottomhole conditions and form a uniform production distribution across a substantially long heterogeneous interval. A new methodology was applied in two Jurassic wells that combined a multimodal blend of biodegradable particulates and fibers as a chemical diverter, and emulsified acids as main fluids for a matrix stimulation. In each diversion stage, the change in surface pressure ranged from 800 to 1,000 psi after the diversion pill hit the perforation tunnel. Moreover, a clear signature of diversion was demonstrated in the instantaneous shutin pressures. In another Kuwait field, the diversion pill was tested by using injectivity logging tests to monitor the changes in injectivity across the perforated interval during an acid fracturing treatment in comparison to the earlier injection profile. A remarkable change in injection was observed and a total of 80% change in the injection profile was quantified from before and after the diversion. The diversion pill is relatively small in volume and is easy and safe to handle. Fibers help to maintain the carrying capacity and allow safe landing of the biodegradable material to the formation face. Only a few barrels are required to plug the opened or stimulated interval, and the method allows the following stimulation stage to treat the subsequent interval. The first well revealed a 330% and 110% production increase in gas and oil rates, respectively. The production was set as one of the highest producers in the field. The second well yielded a 320% increase in total production, which set the highest record for the field. The new method is proved to be highly effective in terms of wellbore coverage, and highest production records in the field after matrix acidizing treatments.