Particulate lost circulation materials (LCM) that work for severe-to-total losses are difficult, if not impossible, to find. Solutions that are effective for lower loss rates do not perform well at higher loss rates. Many LCM formulations have been used to treat severe losses, but their design and use has been more trial and error based mostly upon successful case histories. This paper describes the development of a combination of materials that is used in conjunction with other Engineered, Composite Solutions (ECS) to further enhance their performance.
A novel combination of swelling materials, retarder, and fibers with a large aspect ratio is proposed as an activator that can be deployed with ECS typically available on the rig. The activator was designed and tested under conditions that qualitatively resemble severe lost circulation scenarios (large fractures). A shale swell meter was modified to qualitatively compare the swelling behaviour of different materials under different temperatures and retarder concentrations. A polyacrylamide-based swelling material was found to be sensitive to both temperature and retarder concentration. A newly sourced, potentially reservoir-friendly swelling material was found to be sensitive to temperature only. The activator-ECS combinations were tested for plugging capability with Permeability Plugging Apparatus (PPA) test equipment using different size tapered slots. Data from these modified PPA tests were used to determine the best combination of activator and ECS for plugging a particular-sized fracture simulated by the tapered slot.
Field applications of systems that led to this proposed approach are discussed along with laboratory data comparing the swelling behaviour of different materials as related to mixing and pumping times.