Delayed release breakers in gelled hydrocarbons
OwnerDavid B. Acker, Fati Malekahmadiinventors
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Abstract
Granules composed of a particulate breaker chemical dispersed in a wax matrix are used in fracturing operations to break hydrocarbon liquids gelled with salts of alkyl phosphate esters. The wax granules are solid at surface temperature and melt or disperse in the hydrocarbon liquid at formation temperature releasing the breaker chemical to react with gelling agent.
Claims16
In the method of fracturing a subterranean formation wherein a hydrocarbon liquid gelled with a pH sensitive alkyl phosphate ester gelling agent is pumped from the surface down a wellbore and into the formation, the improvement wherein the hydrocarbon liquid has dispersed therein granules comprising:
- (a) from about 40 to about 90 weight % of a matrix of a substantially oil-insoluble Fischer-Tropsch wax;
- and
- (b) from about 10 to about 60 weight % of a powdered acid or powdered base breaker chemical dispersed in the wax matrix,
- the temperature of the subterranean formation being sufficiently high to cause the breaker chemical to be released from the wax matrix.
A method of fracturing a subterranean formation with an oil-based fracturing fluid which comprises:
- (a) gelling a liquid by adding an alkyl phosphate ester gelling agent to the hydrocarbon liquid;
- (b) adding an aluminum compound to the liquid hydrocarbon to react with the gelling agent and form a salt of the alkyl phosphate ester which gels the hydrocarbon liquid;
- (c) adding a proppant to the gelled hydrocarbon which is carried into and placed in the fracture by the gelled hydrocarbon fluid;
- (d) adding free flowing granules having an average particle size of 8 mesh or smaller to the hydrocarbon liquid, said granules comprising from 65 to 80 wt. % of a substantially oil-insoluble Fischer-Tropsch wax matrix having a melting point between about 175° F. and about 230° F., said matrix having dispersed therein 20 to 35 wt. % of a powdered base compound capable of breaking the gelled structure of a salt of an alkyl phosphate ester, said wax releasing the base compound at formation temperature;
- (e) pumping the gelled hydrocarbon liquid containing the granules into the formation at a rate and pressure sufficient to form a fracture therein;
- and
- (f) shutting the well whereby the temperature of the formation causes part or all of the wax to release the base compound to react with the salt of the alkyl phosphate ester to reduce the viscosity of the gelled hydrocarbon liquid.
Dependencies are inferred from the claim text.