Abstract
Controlling severe to total lost circulation in naturally fractured vugular formations and rubble zones can be challenging. In such situations, conventional lost circulation materials (LCMs) might not be effective, and more difficult applications, such as gunks, reverse gunks, or cement, might fail as well. High fluid loss squeeze (HFLS) applications have been applied with mixed success. A new HFLS LCM containing a unique component has been developed and shows great potential as a dependable solution. This new HFLS LCM also shows potential for sealing induced fractures in shale or other formations of low permeability.
This paper discusses a laboratory investigation of a HFLS LCM to plug slotted discs of various sizes in a permeability plugging apparatus (PPA) test. Follow-up field applications that demonstrate its success are also discussed. The proposed HFLS LCM is a combination of particulates and a unique reticulated foam material that contributes to a rapid dewatering effect. The reticulated foam is the unique component, which forms a bridge on the face of large fractures. The particulates of the composition then plug the foam, forming a thick cake. Recommended practices for mixing and placement of HFLS LCM essential for successful applications are also discussed.
The HFLS LCM application was able to seal slotted discs up to 3000 μm. Supplementing the HFLS LCM with additional larger reticulated foam (medium) enabled the plugging of slotted discs up to 8000 μm. For plugging slotted discs from 8000 to 10 000 μm, the HFLS LCM was supplemented with medium and coarse reticulated foam. This plugging data, covering slotted disc sizes up to 10 mm, is the first of its kind and provides confidence in considering the HFLS LCM as a potential option for severe to total loss situations.
Three applications of HFLS LCM are discussed. The first application manages severe losses (in the range of 180 bbl/hr) in a naturally fractured shale formation in an unconventional reservoir in North America. The second application manages severe losses in naturally fractured, vugular formations in the Asia Pacific region. In both the cases, because high losses were expected, the HFLS LCM was stored on-site as a contingency LCM. As soon as losses were observed, an appropriate volume of the pill containing the HFLS LCM supplemented with additional amounts of reticulated foam LCM was pumped. Losses were cured, and the wells were drilled/cemented successfully.
