Engineered Solution to Reduce the Impact of Lost Circulation During Cementing in South Iraq Field, Iraq

Abstract

Abstract Curing lost circulation, one of the greatest contributors to drilling non-productive time (NPT), may impair the final well construction process, including securing production casing/liner and ensuring zonal isolation between target formations. This problem was faced in the South Iraq oil field, where conventional practices were to cure losses in a highly heterogeneous reservoir carbonate formation (vugs, fractures) before proceeding with the cementing operation ensuring the well integrity during the production phase. As Common field operational practices dictated that whenever losses were encountered, drilling was stopped to cure the losses (Dreger, 2014 1), often by spotting acid-soluble cement plugs before drilling ahead. The time spent on curing losses encountered while drilling plays an important role in the total well construction and delivery. This paper presents how engineered solutions were applied in the design and execution phase of cementing operation by running production casing under losses but still achieving well integrity and zonal isolation. The foundation of the proposed engineering and operational approach is the characterization of the wellbore with the caliper and formation image logs for better understanding of fractures and estimation of fracture volume (Arshad, Umar, 2015 2). The results and information were shared with cementing team as redesigning the cement slurry formulation was the key objective. To overcome the challenge, innovative solution for the problem, which was the implementation of dispersible inert fibers mixed in specified concentration conventional spacer and had the capability of plugging fractures of 5 mm successfully. Synergy effect of degradable fiber in spacer and fibrous mesh material in the slurry strengthened the loss zone and enabled to achieve top of cement.