The invention is a well-treating process for plugging a permeable subterranean earth formation. It is particularly suited for plugging earth formations located behind sand or gravel packs, or behind a section of cemented or grouted casing along which there is fluid communication through or behind the cement or the grout.
The value of plugging permeable subterranean earth formations and numerous methods for doing so have long been known. For example, plugging procedures (using cements, plastics, etc.) were described in the 1946 edition of "Petroleum Production Engineering Oilfield Development" by L. C. Uren, published by the McGraw Hill Book Company, Inc. More recently, the value of plugging such formations by forming a relatively impermeable sheath within the first few inches of the formations was described (in the J. H. Thomeer U.S. Pat. No. 3,830,299, discussed below).
Numerous procedures have been developed for injecting suspensions of solid or substantially solid particles into permeable subterranean formations to form relatively deeply penetrating, or shallowly penetrating, deposits of permeability-reducing materials within the formations. For example, U.S. Pat. No. 3,749,171 relates to injecting suspended particles and teaches that where the largest particle size is less than the median pore size of a reservoir formation, most of the suspension will flow through the formation for a considerable distance. U.S. Pat. No. 3,762,475 relates to injecting a suspension of starch granules and teaches that suitable sizes and concentrations include sizes of 4-6 microns in diameter and concentrations of 1,000-5,000 parts per million. U.S. Pat. No. 3,785,438 relates to first injecting a suspension of bridging particles of an oil-soluble resin material and then injecting a suspension of a colloidal additive, e.g., a lignosulfate complexed with a trivalent cation and divalent base, to seal the filter cake formed by the bridging particles. U.S. Pat. No. 3,827,498 relates to forming suspensions of particles to be used as diverting agents and teaches that about 75% of a batch of particles having a maximum diameter of 44 microns will pass through a borehole gravel pack of grains of 20-40 standard mesh size.
The J. H. Thomeer U.S. Pat. No. 3,830,299 relates to adjusting the permeability profile of a subterranean reservoir interval by forming a shallow plug within the first few inches of all of the permeable formations and then perforating at selected depths to provide selected rates of flows at those depths. It teaches that in an earth formation having a permeability of about 50 millidarcies and a mean pore size of about 20 microns, significant plugging within the first few inches is provided by injecting a suspension of particles of which about 5 parts are generally less than 12 microns in diameter and about 1 part are primarily within the 1-10 micron range.