Successfully Curing Dynamic Losses in a Highly Fractured Reservoir Section by Using an Engineered Self-Degradable Lost Circulation Material in a Field Trial in Middle East

Abstract

Abstract Lost circulation of drilling fluids costs the oil and gas industry about $1 Billion USD per year, with the Middle East and North Africa (MENA) region accounting for most of such lost circulation events. Within MENA, these observed losses are due to the prevalence of natural fractures, especially in carbonate reservoirs. In a worst-case scenario, if not mitigated, lost circulation could lead to well control challenges, wellbore instability issues and potential loss of downhole tools and equipment. The challenge in MENA is further complicated by high-temperature reservoir sections, which may cause thermal instability of typically used polymeric lost circulation materials (LCMs). In this case study, we used a geomechanics-based approach to create bridging and sealing at the fracture aperture using a bi-particle self-degradable lost circulation fluid system. The effectiveness of the system was assessed by considering interactions between particles and slurry fluid, with respect to the wellbore profile. The analysis was performed using an analytical model dictated by fluid density, viscosity, flow rate, and travel distance of LCM slurry, with the aim of minimizing issues related to dispersion and interface instabilities. This paper discusses the results of our first successful field trial job in Iraq. The well had earlier experienced total losses amounting to 167,250 barrels (bbl), with the 6″ reservoir section only accounting for 9,050 bbl of the observed losses prior to using the bi-particulate self-degradable LCM system. This holistic geomechanics-based approach of designing LCM helped in curing losses in the highly faulted and fractured reservoir section. A 20-bbl pill of the bi-particulate system was pumped at 4.2 bpm and 51 psi via an open-ended pipe then displaced with 110 bbl. of water at 4.2 bpm and 81 psi at a depth of 9317 ft. The operator subsequently filled the string with 87 gpm and then increased flow in successive steps upto 250 gpm and observed no dynamic losses, allowing the well to be drilled ahead successfully. The LCM system was effectively able to stop the losses, allowing the hole section to be drilled successfully, after several attempts using traditional methods. For the case study highlighted in this paper, the approach and LCM system was successfully able to prevent dynamic losses in the reservoir section without damaging the formation, hence confirming the viability of this technology and material. This model can be applied across the globe where similar challenges present themselves. This paper will provide an insight into ideas revolving around degradable LCM materials, as part of our commitment to make the industry cleaner and greener and minimize unwanted environmental impact.