Abstract: A process is described for reducing the production of water in oil wells which comprises the injection into the formation around the well of an aqueous solution of one or more polymers selected from those having general formula (I), wherein: n ranges from 0.70 to 0.98; m ranges from 0.30 to 0.02; n+m=1; X1 and X2, the same or different, are selected from H and CH3; R1, R2, R3, the same or different, are selected from C1–C10 monofunctional hydrocarbyl groups; and x ranges from 2 to 5.

Abstract: A process is described for reducing the production of water in oil wells which comprises the injection into the formation around the well of an aqueous solution of one or more polymers selected from those having general formula (1) [] wherein: n ranges from 0.70 to 0.98; m ranges from 0.30 to 0.02; n+m=1; X1 and X2, the same or different, are selected from H an CH3; R1, R2, R3, the same or different, are selected from C1-C10 monofunctional hydrocarbyl groups; x ranges from 2 to 5.

Abstract: A process is described for reducing the production of water in oil wells, with temperatures of up to (90° C.), which comprises the injection in the formation around the well of an aqueous solution of one or more polymers selected from those having general formula (I) wherein: n ranges from (0.40) to (0.70), preferably from (0.5) to (0.65); m ranges from (0.15) to (0.65), preferably from (0.3) to (0.5); p ranges from (0.02) to (0.20), preferably from (0.05) to (0.

Abstract: A process is described for reducing the production of water in oil wells which comprises the injection into the formation around the well of an aqueous solution of one or more polymers selected from those having general formula (1) [ ] wherein: n ranges from 0.70 to 0.98; m ranges from 0.30 to 0.02; n+m=1; X1 and X2, the same or different, are selected from H an CH3; R1, R2, R3, the same or different, are selected from C1-C10 monofunctional hydrocarbyl groups; x ranges from 2 to 5.

Abstract: A process is described for reducing the production of water in oil wells, with temperatures of up to (90° C.), which comprises the injection in the formation around the well of an aqueous solution of one or more polymers selected from those having general formula (I) wherein: n ranges from (0.40) to (0.70), preferably from (0.5) to (0.65); m ranges from (0.15) to (0.65), preferably from (0.3) to (0.5); p ranges from (0.02) to (0.20), preferably from (0.05) to (0.10); n+m+p=1; x1 is selected from H and CH3; R1, R2 the same or different, are selected from C1-C10 monofunctional hydrocarbyl groups.

Abstract: Disclosed is a process for preparing aqueous, clay-based muds, not aggressive to layer clays, which process comprises a first step in which clay is treated with an aqueous solution containing the necessary amount of dispersant to fluidify the mud; a second step, of separation of so treated clay from the aqueous solution containing any not adsorbed dispersant, and finally, a step of re-dispersion of so treated clay in water, in order to formulate the mud.

Abstract: Aqueous drilling muds are disclosed which contain, as fluidifier agent, one or more complexes, which may be either pre-formed or produced in situ, selected from:tetravalent zirconium and one or more organic acids, or their salts, having the general formula (I) ##STR1## wherein R.sub.1 and R.sub.2, which may be the same or different from each other, represent --H, --COOH, --CH.sub.3, --CH.sub.2 COOH, --CH(OH)COOH;aluminum citrate.

Abstract: Aqueous drilling muds effective at high temperature containing complexes, preformed or formed in situ, of tetravalent zirconium with one or more organic acids, or relative salts, of general formula (I) ##STR1## where R.sub.1 and R.sub.2, which can be the same or different, represent --H, --COOH, --CH.sub.3, --CH.sub.2 COOH or --CH(OH)COOH, or R.sub.1 and R.sub.2 jointly represent an oxo group (.dbd.O).

Abstract: The permeability of high-permeability zones in a oil reservoir can be reduced by using a gellable aqueous composition with delayed gelation. The composition comprises:a) water;b) a high-molecular weight natural or synthetic water-soluble polymer cross-linkable by means of Cr.sup.3+ ions;c) a water-soluble inorganic Cr.sup.

Abstract: The permeability of high-permeability zones in a oil reservoir can be reduced by using a gellable aqueous composition with delayed gelation.The composition comprises:a) water;b) a high-molecular weight natural or synthetic water-soluble polymer cross-linkable by means of Cr.sup.3+ ions;c) a water-soluble inorganic Cr.sup.

Abstract: A gellable aqueous compositions able to reduce the permeability of high-permeability zones in an oil reservoir is a aqueous solution containing metered quantities of:a) a water-soluble organic polymer cross-linkable by the effect of a polyvalent metal ion cross-linking agent;b) a Cr(III) ion cross-linking agent; andc) a ligand for the cross-linking agent chosen from water-soluble organic alpha-hydroxy acids and alpha-amino acids.

Abstract: A method for reducing the permeability of a high-permeability zone in a high-temperature oil reservoir comprises:preparing a gellable polymeric aqueous solution, operating on the surface under controlled conditions;injecting said gellable solution into the oil reservoir through a well;moving the solution through the reservoir until it reaches and substantially fills the high-permeability zone to be treated; andgelling the solution in situ with consequent lowering of the permeability in said high-permeability zone, and is essentially characterized in that the gellable solution is an aqueous solution containing a Cr(III) ion cross-linking agent and a water-soluble organic polymer cross-linkable by the effect of said cross-linking agent, said solution being free or substantially free of ligands for the cross-linking agent and having a pH adjusted to a value within the range of 1.5 to 5.5, depending on the desired gelling time.

Abstract: A gellable aqueous composition particularly suitable for reducing the permeability of high-permeability zones in an oil reservoir is an aqueous solution comprising:a) a water-soluble organic polymer cross-linkable by the effect of a polyvalent metal ion cross-linking agent;b) a Cr(III) ion cross-linking agent;c) a buffer agent free or subtantially free of ligand characteristics towards the cross-linking agent, and chosen from organic bases and aromatic carboxylic or sulphonic acids;the solution pH being adjusted to a value within the range of about 2 to about 7.

Abstract: When used as occlusion agents or to cause fractures in a petroleum reservoir, polymer gels crosslinked with polyvalent metal ions can be removed by the use of special complexing agents.