Earth boring – well treating – and oil field chemistry – Well treating – Contains organic component
Reexamination Certificate
2000-05-26
2004-05-18
Tucker, Philip C. (Department: 1712)
Earth boring, well treating, and oil field chemistry
Well treating
Contains organic component
C507S209000, C507S271000, C507S266000, C507S267000, C507S922000, C166S308400
Reexamination Certificate
active
06737386
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to fracturing fluids and, more particularly, but not by way of limitation, to an aqueous based zirconium (IV) crosslinked guar fracturing fluid and a method of making and use therefor, suitable to the purposes of hydraulically fracturing subterranean formations having static bottom-hole temperatures greater than about 250° F.
2. Description of the Related Art
An aqueous based crosslinked polygalactomannan fluid is typically used to perform a hydraulic fracturing treatment of a hydrocarbon bearing reservoir when the static bottom-hole temperature of a well exceeds approximately 250° F.
One type of aqueous based crosslinked polygalactomannan fluid that might be used in high temperature wells are borate crosslinked guar fluids, where the pH of the crosslinked fluid under treating conditions ranges from about 8.5 to about 12. Typical borate crosslinked guar fluids include, but are not limited to, those described in U.S. Pat. No. 5,145,590 (Dawson), U.S. Pat. No. 5,445,223 (Nelson et al), and in “Chemistry & Rheology of Borate-Crosslinked Fluids at Temperatures to 300° F., P.C. Harris, J. Petroleum Technology, March 1993, pp. 264-269.
A second type of aqueous based crosslinked polygalactomannan fluid that might be used in fracturing high temperature wells are titanium (IV) or zirconium (IV) crosslinked derivatized guar fluids where the pH of the crosslinked fluid under treating conditions may range from about 3.5 to about 11. Typical derivatized guar polymers suitable to formulate a titanium (IV) or a zirconium (IV) crosslinked derivatized guar fluid include but are not limited to, alkyl-derivatives, such as hydroxypropyl guar (HPG), carboxyalkyl-derivatives, such as carboxymethyl guar (CMG), and carboxyalkyl-hydroxyalkyl-derivatives, such as carboxymethylhydroxypropyl guar (CMHPG). The guar used in the high temperature borate fracturing fluids is distinguishable from the derivatized guar used in the zirconium (IV) or titanium (IV) high temperature crosslinked fracturing fluid, in that guar for the borate crosslinked fluid is not subjected to a chemical treatment wherein some form of molecular substitution, such as alkylation, carboxylation or combinations thereof, has been performed to derivatize the guar. Typical titanium (IV) or zirconium (IV) crosslinked derivatized guar fluids include but are not limited to, those described in U.S. Pat. No. 3,888,312 (Tiner et al.), U.S. Pat. No. 4,534,870 (Williams), U.S. Pat. No. 4,686,052 (Baranet et al.), and U.S. Pat. No. 4,799,550 (Harris et al.)
In hydraulically fracturing a hydrocarbon bearing reservoir with an aqueous based crosslinked guar or derivatized guar fracturing fluid, it is often necessary that the aqueous based crosslinked guar or derivatized guar fracturing fluid exhibit more than an hour of stability. Those of ordinary skill in the art generally regard stability as a minimum viscosity achieved based upon an agreed rheological test method for an agreed period of time. The agreed rheological test method may be one proposed by the American Petroleum Institute (API) or an adaptation of an API method as proposed by a petroleum production company or its hydraulic fracturing service provider. Alternatively, the agreed rheological test method may be a novel method proposed and mutually agreed upon by the participants in the hydraulic fracturing fluid evaluation and may follow a regime based upon anticipated field conditions.
A borate crosslinked guar fracturing fluid is typically used when bottom-hole temperatures (BHT's) of a well do not exceed about 325° F. and where more than an hour of stability is necessary. A borate crosslinked guar fracturing fluid is generally made more stable by raising the pH of the fracturing fluid, increasing the borate concentration, or increasing the guar concentration in solution. A problem experienced in stabilizing the high temperature borate crosslinked fracturing fluid by raising the pH of the fluid, increasing the borate concentration, or increasing the guar concentration in solution is that pH, borate concentration, or guar concentration can be excessive, any of which may render the fracturing fluid unsuitable for use in the intended hydraulic fracturing treatment of a hydrocarbon bearing reservoir. Increasing chemical constituent loading to accommodate wells with higher BHT's is also more costly.
A zirconium (IV) crosslinked derivatized guar fracturing fluid is typically used when the BHT of a well does not exceed about 400° F. and where more than an hour of stability is necessary. A zirconium (IV) crosslinked derivatized guar fracturing fluid is generally made more stable by raising the pH of the fracturing fluid, increasing the zirconium (IV) concentration, or increasing the derivatized guar concentration in solution. A problem experienced in stabilizing the high temperature zirconium (IV) crosslinked fracturing fluid by raising the pH of the fluid, increasing the zirconium (IV) concentration, or increasing the derivatized guar concentration in solution is that pH, zirconium (IV) concentration, or derivatized guar concentration can be excessive, any of which may render the fracturing fluid unsuitable for use in the intended hydraulic fracturing treatment of a hydrocarbon bearing reservoir. Likewise, as is the case of borate crosslinked fluids, increasing chemical constituent loading to accommodate wells with higher BHT's is also more costly.
A zirconium (IV) crosslinked derivatized guar fracturing fluid provides certain advantages over a borate crosslinked guar fracturing fluid, especially when BHT of a well exceeds about 325° F. At BHT's less than about 250° F., a zirconium (IV) crosslinked derivatized guar fracturing fluid is usable at a pH of less than about 8.5, which is particularly advantageous if carbon dioxide comprises a portion of the fracturing fluid because the pH of the fracturing fluid may be as low as 3.5. Also, at BHT's greater than about 250° F., and certainly as BHT's increase above about 325° F., it is much easier and less costly to delay the gelation of a zirconium (IV) crosslinked derivatized guar fracturing fluid than a borate crosslinked guar fracturing fluid.
Although a zirconium (IV) crosslinked derivatized guar fracturing fluid provides certain operational advantages over a borate crosslinked guar fracturing fluid, a borate crosslinked guar fracturing fluid provides the advantage that it employs guar, which is less costly and more readily available than derivatized guar, and borate crosslinked guar fracturing fluids have historically been shown to operate to temperatures approximately 50° F. higher than zirconium (IV) crosslinked guar fracturing fluids. Consequently, a zirconium (IV) crosslinked guar fracturing fluid is typically not suitable for hydraulic fracturing treatments where the BHT of a well exceeds about 275° F. In those instances where a zirconium (IV) crosslinked guar fracturing fluid may be utilized where the BHT of a well exceeds 275° F., the zirconium (IV) crosslinked guar fracturing fluid requires guar loadings in excess of 50 pounds of guar per 1000 gallons of make-up water and may often require as much as 80 pounds of guar per 1000 gallons of make-up water before a stable fracturing fluid is achieved. When such guar loadings are necessary, derivatized guar is utilized because, although it is more expensive, the derivatized guar requires considerably lower loading levels, and by virtue of the lower polymer loading, the spent fracturing fluid is easier to recover following the fracturing treatment.
Brannon et aL (U.S. Pat. No. 4,801,389) describe partially successful attempts to develop a zirconium (IV) crosslinked guar fracturing fluid for high temperature applications. Brannon et al. teaches to a fracturing fluid pH of about 8 to about 10. Any greater pH in this method tends to accelerate the crosslink rate thereby negating the benefit of delayed crosslinking on the subsequent rheological performance reported for the cross
Matthews Lester E.
Moorhouse Ralph
Benchmark Research and Technology Inc.
Makay Christopher L.
Tucker Philip C.
LandOfFree
Aqueous based zirconium (IV) crosslinked guar fracturing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Aqueous based zirconium (IV) crosslinked guar fracturing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aqueous based zirconium (IV) crosslinked guar fracturing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3202131