(iii) a water-soluble polymer having at least one functional group that can be crosslinked with aluminum(III); 

(iv) a water-soluble aluminum carboxylate; and 

(iv) a complexation agent for calcium ions; 

wherein the pH of the treatment fluid is less than the pH required for the aluminum to crosslink the polymer to form a crosslinked gel. 

According to another embodiment of the invention, a method of treating a zone of a subterranean carbonate forma› tion penetrated by a wellbore is provided, the method includ- ing the steps of: 

(a) forming a treatment fluid comprising: 

(i) water; 

(ii) a strong acid; 

(iii) a water-soluble polymer having at least one functional group that can be crosslinked with aluminum(III); 

(iv) a water-soluble aluminum carboxylate; and 

(v) a complexation agent for calcium ions; 

wherein the pH of the treatment fluid is less than the pH required for the aluminum to crosslink the polymer to form a crosslinked gel; 

(b) introducing the treatment fluid through the well bore into the zone; and 

( c) allowing time for the strong acid in the treatment fluid to spend in the formation such that the pH of the fluid increases sufficiently for the aluminum to crosslink the poly› mer, thereby forming a crosslinked gel in the zone. 

The method can be used in acidizing treatments, including, for example, in acid fracturing or matrix acidizing. 

Preferably, the method includes the step of allowing time for the strong acid and any other acids in the previously› introduced treatment fluid to spend against the formation such that the pH increases sufficiently to break the crosslinked gel. 

Although the methods have been described here for, and are most typically used for, hydrocarbon production, they may also be used in storage wells and injection wells, and for production of other fluids, such as water or brine. 

These and other aspects of the invention will be apparent to one skilled in the art upon reading the following detailed description. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof will be described in detail and shown by way of example. It should be understood, however, that it is not intended to limit the invention to the particular forms dis- closed, but, on the contrary, the invention is to cover all modifications and alternatives falling within the spirit and scope of the invention as expressed in the appended claims. 

## DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS 

Interpretation 

The words or terms used herein have their plain, ordinary meaning in the field of this disclosure, except to the extent explicitly and clearly defined in this disclosure. 

If there is any conflict in the usages ofa word or term in this disclosure and one or more patent(s) or other documents that 60 may be incorporated by reference, the definitions that are consistent with this specification should be adopted. 

The words "comprising," "containing," "including," "hav› ing," and all granimatical variations thereof are intended to have an open, non-limiting meaning. For example, a compo- sition comprising a component does not exclude it from hav› ing additional components, an apparatus comprising a part 

## Definitions and Usages 

does not exclude it from having additional parts, and a method having a step does not exclude it having additional steps. When such terms are used, the compositions, apparatuses, and methods that "consist essentially of’ or "consist of’ the specified components, parts, and steps are specifically included and disclosed. 

The indefinite articles "a" or "an" mean one or more than one of the component, part, or step that the article introduces. 

Whenever a numerical range of degree or measurement with a lower limit and an upper limit is disclosed, any number and any range falling within the range is also intended to be specifically disclosed. For example, every range of values (in the form "from a to b," or "from about a to about b," or "from about a to b," "from approximately a to b," and any similar expressions, where "a" and "b" represent numerical values of degree or measurement) is to be understood to set forth every number and range encompassed within the broader range of values. 

Terms such as "first," "second," "third," etc. are assigned arbitrarily and are merely intended to differentiate between two or more components, parts, or steps that are otherwise similar or corresponding in nature, structure, function, or action. For example, the words "first" and "second" serve no other purpose and are not part of the name or description of the following name or descriptive terms. The mere use of the term "first" does not require that there be any "second" simi› lar or corresponding component, part, or step. Similarly, the mere use of the word "second" does not require that there by any "first" or "third" similar or corresponding component, part, or step. Further, it is to be understood that the mere use of the term "first" does not require that the element or step be the very first in any sequence, but merely that it is at least one of the elements or steps. Similarly, the mere use of the terms "first" and "second" does not necessarily require any sequence. Accordingly, the mere use of such terms does not exclude intervening elements or steps between the "first" and "second" elements or steps, etc. 

## Oil and Gas Reservoirs 

In the context of production from a well, oil and gas are understood to refer to crude oil and natural gas. Oil and gas are naturally occurring hydrocarbons in certain subterranean formations. 

A "subterranean formation" is a body of rock that has sufficiently distinctive characteristics and is sufficiently con› tinuous for geologists to describe, map, and name it. A sub› terranean formation having a sufficient porosity and perme- ability to store and transmit fluids is sometimes referred to as a "reservoir." A subterranean formation containing oil or gas may be located under land or under the seabed off shore. Oil and gas reservoirs are typically located in the range of a few hundred feet ( shallow reservoirs) to a few tens of thousands of feet (ultra-deep reservoirs) below the surface of the land or seabed. 

Sandstone, Carbonate, and Other Formations 

Reservoirs can be of various rock materials. 

As used herein, a subterranean formation having at least 50% by weight of inorganic siliceous materials ( e.g., sand› stone) is referred to as a "sandstone formation." 

Limestone is essentially calcium carbonate. Dolomite is essentially a combination of calcium carbonate and magne› sium carbonate, wherein at least 50% of the cations are mag› nesium. As used herein, a carbonate formation is at least 50% by weight calcium carbonate, magnesium carbonate, or a combination thereof. 

## Well Terms 

A "well" includes a wellhead and at least one wellbore from the wellhead penetrating the earth. The "wellhead" is 

