LCM (Lost Circulation Material)

LCM selection follows the bridging ratio principle — the D50 (median particle size) of the LCM should be approximately 1/3 the average pore throat or fracture width of the loss zone. Graded blends covering fine, medium, and coarse particles provide a cascading seal across a range of fracture widths.

LCM materials are classified by shape: granular (CaCO₃, nutshell — bridges across pore throats), flake (mica, graphite flake — covers fracture surfaces), and fibrous (Fibro Seal, rice husk — forms interlocked fibrous mats). Effective LCM blends combine all three types in optimised proportions to seal loss zones with different geometries.

Yes. LCM is designed to be compatible with drilling fluids including weighted muds. However, high LCM concentrations can affect mud viscosity and density. LCM should be added at concentrations sufficient to seal the loss zone (typically 20–50 ppb for moderate losses, up to 150 ppb for severe losses) while monitoring mud properties.

Preventive LCM treatment adds LCM to the drilling fluid before entering known loss-prone formations to pre-seal potential pathways. Corrective treatment is applied after losses have begun, typically at higher concentrations or using specialised LCM pills pumped to the loss zone. Both strategies use the same materials but with different concentrations and application methods.

Fibro Seal uses fibrous material that physically weaves across the fracture opening to create a structurally interlocked mat, rather than simply filling pore spaces. This mat provides superior bridging in wide fractures where granular material would fall into the void, and also provides a foundation for subsequent granular material to create a composite, high-strength seal.