Abstract: There is disclosed a method of separating a mixture (e.g. dispersion) of oil and water into oil-rich and water-rich phases, the method comprising the steps: (i) selecting a mixture which comprises oil recovered from a subterranean formation and a treatment formulation, wherein said treatment formulation was added to the oil in order to facilitate its recovery and/or mobility, wherein said treatment formulation has an Interfacial Tension (IFT), measured against a sample of said oil in the range 2 to 20 mN/m; (ii) directing said mixture to a separation means; and (iii) in the absence of a chemical demulsifier, heating the mixture until separation is effected at least partially under gravity. Preferably the IFT is in the range 9 to 12 mN/m. The mixture of oil and water may be formed by treating oil in a subterranean formation.

Abstract: A treatment formulation for use in enhanced oil recovery is described which includes a dispersing polymer which may be a partly hydrolyzed polyvinyl alcohol and a displacing polymer which may be a partially hydrolysed polyacrylamide.

Abstract: An oil well includes a wellbore (2), below ground level (4), which extends to an oil reservoir (6). The wellbore includes a casing (8) within which is arranged a progressing cavity pump (PCP) 10 which includes an inlet (12) at its lower end and is connected at its upper end to production tube (14). An annulus (16) is defined between the pump (10)/tube (14) and the casing (8). The annulus communicates with the reservoir and includes a head (20) of reservoir fluid. A water based formulation which comprises an optionally cross-linked polyvinylalcohol can be poured down the annulus (16) and pass under gravity to the reservoir (6), immediately upstream of inlet (12). The formulation may improve the performance and efficiency of the pump (10) due to its ability to increase the mobility of the oil in the reservoir immediately upstream of the pump (10) and/or enhance the ability of the oil to enter the pump inlet.

Abstract: Method of improving performance or efficiency of a wellbore pump associated with a wellbore and/or for increasing the rate of production of reservoir fluid from a reservoir, in which a wellbore pump is arranged to pump wellbore fluid within the wellbore to a surface. The method includes (a) selecting a wellbore which includes an associated wellbore pump associated with a production tube and arranged within a casing. An annulus is defined between the casing and the pump/production tube, the annulus including reservoir fluid which has a hydrostatic head which is at least 15 m above the level of an inlet of the wellbore pump, and (b) contacting a reservoir fluid in the annulus upstream of an inlet of the wellbore pump with a treatment formulation. The treatment formulation has a first polymeric material which includes —O— moieties pendent from a polymeric backbone thereof, and the first polymeric material is optionally cross-linked.

Abstract: Wax-containing crude oils are treated with polyvinyl alcohol, which is optionally cross-linked, to improve the mobility of the oil and thereby facilitate its transport between its point of production and a point downstream thereof.

Abstract: An additive for a water-based mud drilling fluid or for drill-in fluids comprises a 0.5 wt % solution of 87-89 mole % hydrolysed polyvinylalcohol, having a weight average molecular weight of about 20,000. Use of the additive may reduce susceptibility of a wellbore to blockages, reduce accumulation of accretions between a drill string and wellbore casing, reduce bit-balling and facilitate separation of undesirable insoluble solids from a drilling fluid returned to the surface.

Abstract: A method of treating crude oil which comprises contacting the oil with a treatment fluid formulation comprising a polymeric material which comprises vinylalcohol repeat units, wherein said polymeric material is of a type which has a weight average molecular weight in the range 5,000 to 50,000 and/or wherein the viscosity of a 4 wt % aqueous solution of the polymeric material at 2° C. is in the range 1.5-7 cP. The oil may be contacted with the treatment fluid formulation underground by, for example, injection of the fluid formulation into an injection well or production well and the mobility of the oil contacted thereby is significantly improved.

Abstract: A method of recovering oil from a subterranean formation which includes an association production well involves contacting oil in the formation with a treatment fluid formulation which includes polyvinylalcohol and collecting oil which is being contacted with said treatment fluid formulation by said production well. Use of the polyvinylalcohol, optionally in combination with other materials, facilitates recovery of oil from subterranean formation, particularly those involving medium or high viscosity oils.

Abstract: A method of recovering oil from a subterranean formation which includes an association production well involves contacting oil in the formation with a treatment fluid formulation which includes polyvinylalcohol and collecting oil which is being contacted with said treatment fluid formulation by said production well. Use of the polyvinylalcohol, optionally in combination with other materials, facilities recovery of oil from subterranean formation, particularly those involving medium or high viscosity oils.

Abstract: An oil well includes a wellbore (2), below ground level (4), which extends to an oil reservoir (6). The wellbore includes a casing (8) within which is arranged a progressing cavity pump (PCP) 10 which includes an inlet (12) at its lower end and is connected at its upper end to production tube (14). An annulus (16) is defined between the pump (10)/tube (14) and the casing (8). The annulus communicates with the reservoir and includes a head (20) of reservoir fluid. A water based formulation which comprises an optionally cross-linked polyvinylalcohol can be poured down the annulus (16) and pass under gravity to the reservoir (6), immediately upstream of inlet (12). The formulation may improve the performance and efficiency of the pump (10) due to its ability to increase the mobility of the oil in the reservoir immediately upstream of the pump (10) and/or enhance the ability of the oil to enter the pump inlet.

Abstract: Wax-containing crude oils are treated with polyvinyl alcohol, which is optionally cross-linked, to improve the mobility of the oil and thereby facilitate its transport between its point of production and a point downstream thereof.