1. A pumpable well treatment composition comprising a hydratable polyvinyl alcohol in an aqueous fluid, wherein the amount of polyvinyl alcohol in the well treatment composition is between from about 50 pounds to about 1,200 pounds per 1,000 gallons of aqueous fluid and further wherein at least one of the following conditions prevail:
(a) the aqueous fluid further comprises at least one delayed viscosification agent;
(b) the aqueous fluid further comprises at least one delayed crosslinking agent; or
(c) the polyvinyl alcohol is at least greater than or equal to 95 percent hydrolyzed.
2. The well treatment composition of claim 1, wherein the aqueous fluid further comprises at least one delayed viscosification agent.
3. The well treatment composition of claim 1, wherein the aqueous fluid further comprises at least one delayed crosslinking agent.
4. The well treatment composition of claim 1, wherein the polyvinyl alcohol is at least greater than or equal to 95 percent hydrolyzed.
5. The well treatment composition of claim 2, wherein the delayed viscosification agent is selected from the group consisting of an inorganic salt, sorbitol, boric acid and citric acid.
6. The well treatment composition of claim 3, wherein the aqueous fluid further comprises a crosslinking delaying agent.
7. The well treatment composition of claim 6, wherein the crosslinking delaying agent is encapsulated.
8. The well treatment composition of claim 3, wherein the at least one delayed crosslinking agent contains boron.
9. The well treatment composition of claim 1, further comprising a weight modifying agent.
10. The well treatment composition of claim 1, wherein the density of the composition is between from about 6 to about 23 ppg.
11. A method of treating a well in communication with a subterranean formation which comprises:
(a) introducing the pumpable well treatment composition of claim 1 into the well;
(b) increasing the viscosity of the well treatment composition; and
(c) forming a fluid-impermeable barrier within the formation or within the wellbore from the composition resulting from step (b) and thereby reducing the permeability of the formation, mitigating loss of fluid into the formation andor reducing fluid communication within the wellbore.
12. The method of claim 11, wherein the composition resulting from step (b) is a filter cake.
13. The method of claim 11, wherein the well treatment composition of step (a) is introduced into the well in the form of a loss circulation pill.
14. The method of claim 11, wherein the well treatment composition contains at least one delayed crosslinking agent and further wherein the increase in viscosity in step (b) is attributable to the presence of the delayed crosslinking agent.
15. The method of claim 11, wherein the well treatment composition introduced into the well contains a delayed viscosification agent and further wherein the increase in viscosity in step (b) is attributable to hydration of the polyvinyl alcohol.
16. The method of claim 11, wherein the well treatment composition contains a polyvinyl alcohol which is at least greater than or equal to 95 percent hydrolyzed and further wherein the increase in viscosity in step (b) is attributable to hydration of the polyvinyl alcohol.
17. The method of claim 11, wherein the well treatment composition of step (a) is prepared on location.
18. A method for reducing the loss of fluids into flow passages of a subterranean formation during well drilling, completion, or workover operations which comprises introducing into the flow passages an effective amount of the well treatment composition of claim 1 and then viscosifying the well treatment composition, thereby reducing the loss of fluids into the flow passages upon resuming of the well drilling, completion or workover operation.
19. A method for reducing the loss of fluids into flow passages of a subterranean formation during well drilling, completion or workover operations, the fluids being selected from the group consisting of drilling fluids, completion fluids and workover fluids, the method comprising:
(a) introducing the pumpable well treatment composition of claim 1 into the flow passages of the formation;
(b) increasing the viscosity of the well treatment composition and thereby reducing the loss of fluid upon resuming the well drilling, completion or workover operation.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
There is claimed:
1. A current andor voltage transformer comprising at least one primary circuit P and one secondary circuit S, which comprises m elementary windings each having Ni turns, m and Ni being integer numbers, and i lying between 1 and a predetermined integer number n, said groups of elementary windings being capable of being associated in series andor in parallel in such a way as to produce a particular configuration from among a plurality of distinct configurations of primary circuits P and of secondary circuits S each of said configurations corresponding to previously fixed electrical and magnetic parameters.
2. The transformer claimed in claim 1, wherein the electrical andor magnetic parameters of said transformer are configurable through choice of the number and of the mode of association of the elementary windings.
3. The transformer claimed in claim 2, wherein the number of turns of each group of elementary windings is determined through choice of the number of elementary windings of this group, of the number of turns of each elementary winding and of the mode of association of these elementary windings.
4. The transformer claimed in claim 3, wherein the number of turns of a group of elementary windings of the transformer lies between Inf and Ni depending on the tailored configuration.
5. The transformer claimed in claim 1, wherein the resistance of each group of windings is configured through the number of elementary windings of this group, the resistance of each elementary winding and through the nature of the various connections between these elementary windings.
6. A power supply, which comprises a configurable transformer in accordance with claim 1.
7. An induction coil which comprises m elementary windings each having Ni turns, m and Ni being integer numbers, and i lying between 1 and a predetermined integer number n, said groups of elementary windings being capable of being associated in series andor in parallel in such a way as to constitute a main winding having previously fixed electrical and magnetic parameters.
8. The induction coil claimed in claim 7, wherein the electrical andor magnetic parameters of the main winding are configurable through choice of the number and of the mode of association of the elementary windings.