METHODS FOR USING ADDITIVES CONTAINING MICROGELS FOR CONTROLLING FLUID LOSS Russian patent published in 2013 - IPC C09K8/512 E21B21/14 E21B43/22 

FIELD: oil and gas industry.

SUBSTANCE: mud solution containing an aqueous fluid and an additive to control fluid loss, containing at least one polymer microgel comprising a reaction product prepared by a polymerisation reaction of a polymer or a copolymer and a crosslinking agent, wherein the polymer or copolymer comprises at least one unit of at least one compound from a group of: polybutylene succinate, polybutylene succinate-co-adipate, polyhydroxy-butyrate-valerate, polyhydroxy-butyrate-covalerate, polyester amides, polyethylene terephthalates, sulphonated polyethylene terephthalate, polypropylene, aliphatic aromatic copolyester, chitins, chitosans, proteins, aliphatic polyesters, poly(hydroxyester ethers), poly(hydroxybutyrates), poly(anhydrides), poly(orthoesters), poly(amino acids), poly(phosphazenes), a copolymer thereof, a homopolymer thereof, a tetrapolymer thereof, and any derivative thereof. The method involves: preparing an aqueous compound for well treatment and containing the above additive, introducing the compound into a downhole formation, thereby allowing the additive to flow into a filter cake on the surface inside the downhole formation, allowing the filter cake to degrade, and extracting hydrocarbons from the formations. The method involves preparing the above mud solution, introducing it into the downhole formation, allowing the additive to flow into the filter cake on the surface inside the downhole formation, allowing the filter cake to degrade, and extracting hydrocarbons from the formation. The method involves preparing a filter thickener containing the above aqueous fluid and the additive, placing the thickener into the downhole formation with gravel packed filtration and a portion of the downhole formation. The invention is developed in the secondary claims.

EFFECT: more effective control of the fluid loss, reduced residual injury.

22 cl, 2 dwg, 1 tbl, 13 ex