Spacer composition and method of use
AssigneeThe Dow Chemical Company
InventorsThomas J. Griffin, Jr., Larry K. Moran
Life of this patent
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Abstract
A composition comprising water, a water soluble alkali metal silicate, and a water soluble metal compound capable of releasing a multivalent metal cation to react with the soluble silicate to form a pumpable gel is employed as a spacer for displacing a drilling mud from a borehole, particularly immediately preceding injection of a fluid, such as a cement slurry, containing compounds capable of detrimentally reacting with the mud. Optionally, the composition may contain one or more of: a water dispersible cellulose compound and an inert particulate which cooperate to provide fluid loss control; a chelating agent for polyvalent metal cations; a weighting material; a material to minimize lost circulation, and a salt to stabilize fresh water sensitive sandstones and shales.
Claims58
In a method for injecting a fluid into a borehole containing a drilling mud, wherein the fluid is not compatible with the mud, and wherein injection of the fluid is preceded by injection of a spacer composition compatible with both the mud and the fluid, the improvement comprising:
- injecting a sufficient quantity of said spacer to separate said mud and said fluid, said spacer comprising
- (a) water
- (b) a water soluble alkali metal silicate;
- and
- (c) a water soluble metal compound capable of releasing a multivalent metal cation to react with the water soluble silicate;
- said components (a)-(c) being provided in amounts effective to form an aqueous pumpable gel.
In a well treating method for displacing drilling mud from a borehole having a conduit therein so that fluid may be injected down the inside of said conduit and back to the surface via the annulus surrounding said conduit, or vice versa, the improvement which comprises displacing said mud with an aqueous pumpable gel prepared from components including
- (a) water
- (b) a water soluble alkali metal silicate;
- and
- (c) a water soluble metal compound capable of releasing a multivalent metal cation to react with the water soluble silicate;
- said components (a)-(c) being provided in amounts effective to form a pumpable gel which does not react with the mud to form an unpumpable mass.
In a method for cementing a conduit in a borehole containing a drilling mud wherein at least part of the mud is displaced from the borehole by a spacer fluid and the cement is circulated into position immediately following the spacer fluid, the improvement which comprises:
- employing as the spacer fluid, a pumpable gel prepared from components including
- (a) water;
- (b) a water soluble alkali metal silicate;
- and
- (c) a water soluble metal compound capable of releasing a multivalent metal cation to react with the water soluble silicate;
- said components (a)-(c) being provided in amounts effective to form a pumpable gel which does not react with either the mud or the cement to form an unpumpable mass.
In a method for acidizing or fracturing a formation penetrated by a borehole initially containing a drilling mud, wherein a casing is cemented into position within said borehole prior to said acidizing or fracturing step, the improvement which comprises:
- (a) temporarily positioning said casing in said mud-containing borehole;
- (b) providing a spacer comprised of water, a water soluble alkali metal silicate, and a water soluble metal compound capable of releasing a multivalent metal cation to react with the water soluble silicate, said spacer components being provided in amounts effective to form a pumpable gel;
- (c) displacing at least a portion of said mud from said borehole with said spacer;
- (d) injecting a cement slurry into said borehole immediately following said spacer and circulating said slurry into position;
- (e) permitting said slurry to set, thereby permanently cementing said casing into position;
- and
- (f) thereafter carrying out said acidizing or fracturing step;
- the quantity of spacer employed being sufficient to separate said mud from said cement.
An aqueous fluid composition suitable for use as a spacer in treating wells comprising:
- (a) water, and effective amounts of
- (b) a water soluble alkali metal silicate,
- (c) a water soluble metal compound capable of releasing a multivalent metal cation to react with the water soluble silicate to form a pumpable gel, and
- (d) a water dispersible cellulose compound and an inert particulate which together impart fluid loss control to said composition.
A blend of solids suitable for use as an additive to water to form an aqueous spacer for treating wells, said blend comprising:
- (a) from about 0.1 to about 5 parts by weight a water soluble alkali metal silicate;
- (b) a water soluble metal compound capable of releasing a multivalent metal cation to react with the water soluble silicate, in an amount sufficient to release from about 30 to about 130 percent of the molar equivalents of the polyvalent metal cation stoichiometrically required to react with the alkali metal silicate;
- (c) from about 0.5 to about 1.5 parts by weight a water dispersible cellulose compound;
- and
- (d) from about 1 to about 100 parts an inert particulate which, when said blend is added to water in an effective amount, cooperates with said cellulose compound to impart fluid loss control to said spacer.
Dependencies are inferred from the claim text.