COMBINED METHOD FOR SELECTIVE AND TOTAL SEALING POROUS LAYERS

摘要

Two-rotage method of sealing porous oilfield strata, in the vicinity of prodn. and injector wells, corrects unfavourable flows (as formation of channels, cones and fingers), reactivates severed strata, and storage areas and improves oil to water ratios in the extracted fluid, so concns. of water are diminished in obtd. oil or gas. The first stage comprises continuous or cyclic injection of a fluid mixt. contg. a water soluble low mol. wt. anionic polymer, pref. - a partially hydrolysed acrylamide at a 0.1-50 (1:5)g/l concn. - and an alkaline-pref. sodium-silicate at a concn. of 1-200 g/l (5-50 g/l), expressed as silica. The order to gel or crosslink the fluid injected in the first stage a second stage fluid is applied. This is of low pH and comprises a low mol.wt. pref. quat.-ammonium contg, cationic linear polymer at 0.1-50 g/l (1-5 g/l)concn., and an inorganic divalent, pref. - calcium salt of the same concn.