Curing Total Losses Via Placement of Aggressive Cement Recipe Through Sacrificial Fiberglass Pipe

Abstract

Drilling across severely fractured formations results in losses of circulation that are almost impossible to cure. In the cases under study, offset wells showed a struggle to regain returns even after spending 33% of the well construction time, pumping more than 15 conventional and non-conventional loss circulation plugs (5,000 bbl of slurry). The objective of this paper is to describe the methodology developed to recover returns from a total losses scenario and demonstrate its effectiveness. After encountering losses, a mud cap is pumped through the annulus to maintain well control as per local requirements. However, the mud cap contaminates any cement plug placed to regain circulation. That can be mitigated by spotting a vast amount of fast-setting slurry which increases the risk of stuck pipe if the job is performed with conventional cement stinger. The risk of a stuck pipe can be mitigated by utilizing a sacrificial fiberglass pipe to spot a large volume of slurry across the loss zone. The cement setting time can be accelerated by pumping silicate spacer which will flash set when it reacts with the slurry. In the extreme cases of cavernous formations, gravel solids can be used to create a base where loss circulation plug is spotted. After filling the loss zone with gravel, conventional cement is placed on top of it and wait till it is set. The mixture of gravel and cement is then drilled which can smear the wellbore wall and fill the caverns. The paper introduces the utilization of sacrificial fiberglass pipe to be able to pump a higher volume of cement slurry with flash setting silicate spacer that improves the possibility of curing losses and mitigating stuck pipe risk. In addition, it shows how smearing the wellbore with gravel can enhance the chances to cure the most challenging downhole mud losses.