Abstract
High resiliency graphitic carbon lost circulation material (LCM) is one of several graphitic materials that achieve varied success. Effectively controlling loss of circulation (LC) is more than just selecting LCM and requires an engineered approach. Particulate LCM like ground marble, graphitic carbon and cellulosic fibres have been widely used but careful consideration should be given to how these materials are combined based on fracture types. Induced fractures created when the equivalent circulating density (ECD) exceeds the formation fracture gradient or during wellbore strengthening applications, could be "pressure-sensitive" as reported in fracture closure studies (Dupriest 2005). Resilient graphitic carbon (RGC) has many unique properties (Whitfill 2003) that can be exploited in lost circulation scenarios.
Laboratory methods developed to characterize the resiliency of different graphitic carbons are presented, and the lack of resiliency of other LCM is demonstrated. RGC also imparts resiliency to other LCM combinations (Kumar 2010). Resiliency associated with RGC can be enhanced in an LCM combination that exhibits a granular nature, rather than forming a solid plug. RGC also imparts crush resistance to other more brittle LCM and can help reduce attrition, thereby retaining particle size for effective wellbore strengthening, while also acting as a solid lubricant.
RGC is manufactured in a proprietary two-stage furnace process that produces 99.9% carbon content. It is conductive material with no magnetic properties, so it does not interfere with logging tools (e.g., density and neutron) and other downhole equipment. RGC is suitable for use in reservoir sections because it is completely inert and may be combined with acid-soluble ground marble to allow flow back.
The paper includes field and laboratory data that validate RGC characteristics related to resiliency, lubricity, resistance to attrition, and compatibility with downhole tools, making it a versatile material for most LCM combinations for LC control and wellbore strengthening applications.
