Acid-Soluble Lost Circulation Material for Use in Large, Naturally Fractured Formations and Reservoirs

Abstract

Abstract Lost circulation is an extremely difficult challenge to overcome in areas with large natural fractures. Few lost circulation materials (LCMs) are capableoftreatingsuch zones where severe to total losses occur, particularlyin the reservoir sections. Particulate-based LCMs are commonly used to help mitigate losses but mightnot contain the proper particle size distribution (PSD) or acid-solubility characteristicsfor useful application in production zones. This paper discusses a novel particulate-based LCMthat is an engineered composite solution (ECS) with a multimodal PSD comprised of acid-soluble components. The multimodal PSD provides the necessary particle sizes to seal a range of fracture widths, including large fractures where total losses canoccur. The acid solubility of the LCM can enable proper removal to help prevent hindering well production. Laboratory results are explained todemonstrate the potential effectiveness of the LCM forsealing large natural fractures. Acid solubility in a reservoir or production zone is important. LCMs used in these zones have tobe removed to permit maximum formation production. For large natural fractures, large particulates are necessaryto effectively mitigate losses. TheECS was designed to include particulates and fibers of various sizes and shapes to plug large-width fractures while retaining the ability to plug smaller- to intermediate-width fractures. This blend can plug laboratory simulated fractures up to 5,000micronsin width.When supplemented with an additional chip particulate, it can plug fractures up to 7,000 microns. The acid-soluble component of this blend is degradable in both 10% hydrochloric (HCl) and 10% formic acids. This paperdiscusses product specifications, such as PSD, recommended treatments, and laboratory performance test results, including acidizing treatment of anLCM plug contaminated with invert emulsion fluid.