Mr. Erik Milito - The House Committee on Natural Resources ...

72 API STANDARD 65-2
C.3.7 Lost Circulation Materials and Systems
C.3.7.1 General
<strong>The</strong>re are a wide variety of lost circulation materials available to deal with the most severe types of lost circulation.
<strong>The</strong>re is no universal treatment available to cure all types of lost circulation. LCM can range from fine to coarse
particulate materials, fibers, cements, reactant pills and acid soluble particulates. <strong>The</strong> type of material should be
matched with the severity of the lost circulation encountered.
C.3.7.2 Seepage Losses
<strong>The</strong> most common type of lost circulation materials for seepage losses are the fine cellulosic fibers and fine granular
types of additives. <strong>The</strong> most commonly used granular material is calcium carbonate. Another widely used technique
is to pump the fine seepage loss additives as a sweep while drilling the seepage loss zone.
C.3.7.3 Partial Losses
<strong>The</strong> most commonly used materials for this type of loss circulation are granular- and flake-type products that have
particles sizes larger than those used to deal with seepage losses. <strong>The</strong>se can include mica, nut shells, and medium to
coarse calcium carbonate, graphitic materials and coarse cellulosic fibers. <strong>The</strong>se additives can be added to the
drilling fluid system as a continuous treatment or can be spotted as a sweep across the suspected loss zone.
C.3.7.4 Severe Losses
Materials commonly used for severe losses are granular and flake type products that have larger particle sizes than
those used to deal with partial losses. As the severity of the loss becomes greater than the preceding two types of
losses, coarser sizes of the same additives should be used for bridging, but some of the finer particles can be
included. <strong>The</strong>se additives can be added to the drilling fluid system as a continuous treatment or they can be spotted
as a sweep across the suspected loss zone.
C.3.7.5 Complete Losses
<strong>The</strong> types of additives and procedures used to deal with complete losses are generally different than those required
for the preceding types of lost circulation. <strong>The</strong>se types of losses generally occur in formations with leakoff flow paths
larger than the diameter of most bridging particles. Large fracture openings and vugs usually account for these
massive losses. <strong>The</strong>se openings are not effectively sealed with the cellulosic and granular type of products described
above. Reactive pills and agglomerating-type LCM materials are used under these circumstances. Some of these
include:
— high filtration squeezes allowing for rapid loss of the carrier fluid resulting in a solid plug forming in the formation
opening;
— hydration type systems where a very active material such as powdered clay or mixtures of clays and polymers in
an inert carrier reacts with the drilling fluid to form a rubbery type of plug;
— chemical systems where special resins or polymers and catalysts react to form a semi-solid plug;
— mixtures of the above systems with cement to create highly viscous and hard setting plugs;
— special, highly thixotropic cement slurries squeezed into the zone or left in the wellbore as a plug;
— large volumes of these materials for cavernous loss zones or special squeeze cements such as foamed cement;
— silicate-base gels with and without cement;