Few events on a drilling rig generate more concern, and more cost, than the moment when drilling fluid stops returning to surface. Lost circulation, the partial or total disappearance of mud into the formation, is one of the leading causes of non-productive time in drilling operations, with direct consequences on well stability, safety, and the overall economics of the project.
Controlling losses requires more than simply pumping a bag of bridging material. It requires understanding what kind of loss is occurring, why, and selecting an LCM (Lost Circulation Material) strategy that matches the formation, the fluid system, and the operational constraints.
Understanding the four severity levels
Industry practice classifies fluid losses into four broad severity levels, each with different operational implications and treatment strategies:
- Seepage losses (typically below 10 bbl/h): minor losses through micro-pores or small fractures, often manageable through fine bridging materials added directly to the active mud system.
- Partial losses (approximately 10–50 bbl/h): mud is still returning to surface but at reduced rate. The formation is taking fluid through pores or small fractures, and a more structured LCM treatment is required.
- Severe losses (50+ bbl/h): most of the fluid pumped downhole is being lost into the formation. Higher-concentration LCM pills with coarser particle size are typically needed, often combined with multiple LCM families.
- Total losses: no returns at the flowline. This typically points to natural or induced fractures, vugs, or highly permeable formations, and may require specialised remedial techniques such as cement plugs or cross-linked pills.
Correctly identifying the severity level and the geological cause behind it is the first step in deciding which LCM family to deploy.
The main families of LCM
Lost circulation materials are generally grouped into four functional families, each with distinct mechanical behaviour and field of application:
- Granular materials (such as sized calcium carbonate or graphite) provide effective bridging across pore throats and small fractures, with the additional benefit of being acid-soluble in the case of calcium carbonate.
- Fibrous materials form a deformable mat that adapts to irregular fracture geometries. Synthetic and mineral fibers, available in different size ranges, are particularly effective at bridging openings that granular materials alone cannot seal.
- Flake materials (such as mica or cellophane) overlap onto formation surfaces creating a low-permeability barrier, often used in combination with other LCM types.
- Blends and engineered systems combine particles of different shapes and sizes to deliver multi-mode bridging generally the most effective approach in fractured or heterogeneous formations.
Why acid-soluble fibers matter in reservoir sections
Among fibrous LCMs, acid-soluble mineral fibers deserve particular attention when drilling through reservoir sections. The reason is straightforward: any LCM left in the near-wellbore area can compromise productivity if not properly removed. Conventional fibers may require mechanical or specialised cleanup operations; acid-soluble fibers, on the other hand, can be efficiently removed using standard hydrochloric acid washes or filter cake breakers minimising formation damage and protecting future well productivity.
Typical performance benchmarks for high-quality acid-soluble mineral fibers include solubility above 85% in 6 mol/L HCl solution, compatibility with both water-based and non-aqueous fluid systems, and availability in multiple particle size ranges (fine, medium, coarse) to address different fracture sizes. Recommended dosing typically ranges from 5–15 ppb when added directly to the active mud, and 15–30 ppb when deployed as part of a dedicated LCM pill.
G&G DESMAC LCM portfolio
Through its Industrial Materials & Chemicals Supply business unit, G&G DESMAC supplies a range of lost circulation materials suitable for different operational scenarios, including:
- Synthetic fibers (fine and coarse) for use as auxiliary LCM and as sweep agents during sidetrack operations, supporting downhole cuttings removal and improving the success rate of complex treatments.
- Acid-soluble extrusion-spun mineral fibers in fine, medium and coarse grades, designed for seepage, partial and total losses control particularly suitable for production reservoirs where cleanup performance is critical.
- Oleophilic hydrophobic flocculent fibers for sealing fractures in the 0.5–3 mm range a specialised solution that can replace traditional wooden fibers, nut shell or sized carbonate LCMs in selected applications.
All products are non-toxic, environmentally friendly, asbestos-free, and compatible with both water-based and oil-based mud systems.
Matching the product to the problem
Effective lost circulation control is rarely the result of a single product. It is the result of a strategy: an accurate diagnosis of the loss mechanism, the selection of compatible LCM families in the right particle size distribution, and proper concentration and pumping schedule. The right partner is one that can supply not just the materials, but the technical understanding to deploy them effectively.
G&G DESMAC supports operators, drilling contractors and service companies in developing the right LCM strategy for each well combining product supply with technical expertise across drilling fluid management, well integrity and reservoir protection.
Facing lost circulation challenges on your next well?
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