Successful Application of Engineered Loss Control Solution thru Drill Bits and Coil Tubing in a Naturally Fractured Limestone and High-Temperature Ultra Low-Pressure Sandstone
Authors: Ahmad Syed Hamza , Khokhar Saad Yousuf , Anwar Rameez , Yousuf Arif , Rehman Aziz Ur , Asad Abdul , Saeed Muhammad Salman , Noor Sameer Mustafa , Nazir Irfan 
Published: August 2023

Loss circulation has been a serious concern for drilling and workover operations, especially in depleting brownfields, leading to huge financial and time losses. In addition to the loss of expensive drilling/completion fluid, it also causes several other drilling problems including wellbore stability and stuck drill strings which themselves require additional resources and time for the continuation of operations safely.

Extensive research has been performed by engineers since the advent of modern drilling techniques, however, LCM (loss circulation materials) in practice today still have operational and technical limitations. Commonly used materials are loaded with solids to plug off the formation limiting their application via drilling strings (especially with advanced BHAs containing directional drilling and MWD tools). Similar challenges are common during rigless workover operations using coiled tubing (CT) for well intervention solutions. To address the challenges related to solid-laden fluid pumping, a temperature-activated anionic polymer is formulated when combined with a carboxylate complex cross-linking agent, it produces a rubber-like ringing gel structure. It works by entering the porous media and permanently reducing permeability while improving the wellbore stability by strengthening the formation, instead of simply plugging the sand face as in conventional LCM and Cement Plug Solutions. In addition to being a solids-free solution, the product is also in-soluble with acid, making it more robust for workover operations.

This paper presents two case studies of the successful application of engineered LCM solutions in drilling and workover operations. In Case A, the product was deployed via drill bit where the string got stuck due to total losses and coarse CaCO3 could not be pumped via drill string to cure losses creating the risk of losing the string downhole. Polymer-based LCM (non-acid soluble) was pumped via drill string to effectively seal off the fractures in a naturally fractured loss zone, reinforced with Bond Enhancer to increase structure robustness to sustain hydrostatic column thus allowing successful resumption of circulation in the first attempt eventually leading to release the stuck drill string. In another case, the product was designed and placed via Coil Tubing (CT) to seal off a High-Temperature Ultra-low Pressure depleted sandstone formation to sustain ~ 3500 psi differential pressure to safely perforate the deeper zone and allowing the operator to add reserves while avoiding rig workover.

This approach highlights the ‘limitations of application’ of conventional Loss control material. The methodology adopted to overcome conduit and BHA challenges in drilling and rigless operations provide a new area of opportunities for designing ringing gels to meet desired isolation objectives within present operational limitations.