US4848468A
Expired / Lapsed
US
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Enhanced hydraulic fracturing of a shallow subsurface formation
Assignee: ExxonMobil Oil Corp
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Filing: 1987-12-22
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Granted: 1989-07-18
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Expires: 2007-12-22
Abstract
Abstract A method for extending a vertical fracture formed in a formation having original in-situ stresses that favor the propagation of a horizontal fracture. In this method, a subsurface formation having original in-situ stresses that favor the propagation of a horizontal fracture is penetrated by a cased borehole which is perforated at a pair of spaced-apart intervals to form separate pairs of perforations. Fracturing fluid is initially pumped down said cased borehole and out one of said sets of perforations to form the originally favored horizontal fracture. The propagation of this horizontal fracture changes the in-situ stresses so as to favor the propagation of a vertical fracture. Said horizontal fracture is extended by placing a chemical blowing agent and surfactant into the fracturing fluid. Gas released by decomposition of said agent causes foam to be generated along with an increase in pressure thereby extending the horizontal fracture. Thereafter, while maintaining pressure on said horizontal fracture, fracturing fluid is pumped down said cased borehole and out of the other of said sets of perforations to form the newly favored vertical fracture.
Inventors
- 👤 Randy D. Hazlett
- 👤 Duane C. Uhri
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 16:48
CPC Classifications
E; E21; E21B; E21B43/00; E21B43/25; E21B43/26
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
178 words
A method for enhancing the propagation of a vertical hydraulic fracture in an earth formation surrounding a borehole where the original in-situ stresses favor a horizontal fracture, comprising: (a) supplying a slug of fracturing fluid containing water, a chemical blowing agent, and a surfactant into said formation at a first depth within said borehole which surfactant and blowing agent are contained in said slug in an amount sufficient to generate fracturing pressure after propagating a horizontal hydraulic fracture; (b) supplying additional fracturing fluid at said first depth thereby fracturing said formation and propagating a horizontal fracture which places said slug a desired distance from said well; (c) causing said chemical blowing agent to decompose and liberate gas sufficient to form a foam thereby extending said propagated horizontal fracture further into the formation; and (d) supplying fracturing fluid to said formation at a second depth within said borehole, while maintaining pressure in said horizontal fracture, thereby propagating a vertical fracture to an extended distance as favored by the in-situ stresses as altered by the propagating of said horizontal fracture.
Claim 2
Independent Claim
178 words
A method for enhancing the propagation of a vertical hydraulic fracture in an earth formation surrounding a borehole where the original in-situ stresses favor a horizontal fracture, comprising: (a) supplying a slug of fracturing fluid containing water, a chemical blowing agent, and a surfactant into said formation at a first depth within said borehole which surfactant and blowing agent are contained in said slug in an amount sufficient to generate fracturing pressure after propagating a horizontal hydraulic fracture; (b) supplying additional fracturing fluid at said first depth thereby fracturing said formation and propagating a horizontal fracture which places said slug a desired distance from said well; (c) causing said chemical blowing agent to decompose and liberate gas sufficient to form a foam thereby extending said propagated horizontal fracture further into the formation; and (d) supplying fracturing fluid to said formation at a second depth within said borehole, while maintaining pressure in said horizontal fracture, thereby propagating a vertical fracture to an extended distance as favored by the in-situ stresses as altered by the propagating of said horizontal fracture.
Claim 3
Dependent Claim
46 words
The method as recited in claim 1 where after step (c) a slug containing water, said blowing agent and surfactant in increased amounts is injected into said formation at said first depth thereby further extending said horizontal fracture and allowing further propagation of said vertical fracture.
Claim 4
Dependent Claim
32 words
The method as recited in claim 1 where in step (d) an aqueous slug containing said blowing agent and surfactant is injected into the second depth thereby extending the propagated vertical fracture.
Claim 5
Dependent Claim
20 words
The method as recited in claim 1 where said water comprises fresh water, formation brine, sea water, or brackish water.
Claim 6
Dependent Claim
20 words
The method as recited in claim 1 where said chemical blowing agent is dinitrosopentamethylenetetramine which decomposes to release nitrogen gas.
Claim 7
Dependent Claim
14 words
The method as recited in claim 1 where said chemical blowing agent is azodicarbonamide.
Claim 8
Dependent Claim
21 words
The method as recited in claim 1 where said chemical blowing agent is azodicarbonamide where decomposition is accelerated by alkali carbonates.
Claim 9
Dependent Claim
28 words
The method as recited in claim 1 wherein said chemical blowing agent is the sodium salt of azodicarboxylic acid which upon decomposition liberates nitrogen and carbon dioxide gases.
Claim 10
Dependent Claim
15 words
The method as recited in claim 1 where said chemical blowing agent is p,p'-oxybis(benzenesulfonyl hydrazide).
Claim 11
Dependent Claim
29 words
The method as recited in claim 1 where said chemical blowing agent is sodium hydrogen carbonate and p-toluene sulfonyl hydrazide which decompose to release nitrogen and carbon dioxide gases.
Claim 12
Dependent Claim
35 words
The method as recited in claim 1 where said aqueous slug contains therein a pH adjustor, an accelerator, or an inhibitor sufficient to provide for variable propagation distances within said formation prior to foam generation.
Claim 13
Independent Claim
146 words
A method for enhancing the propagation of a vertical hydraulic fracture in an earth formation surrounding a borehole where the original in-situ stresses favor a horizontal fracture comprising: (a) supplying a fracturing fluid containing water, a chemical blowing agent, and a surfactant into said formation at a first depth within said borehole which surfactant and blowing agent are in said fluid in an amount sufficient to generate fracturing pressure after propagating a horizontal fracture; (b) causing said chemical blowing agent to decompose and liberate gas sufficient to form a foam thereby extending said propagated horizontal fracture further into said formation; and (c) supplying fracturing fluid to said formation at a second depth within said borehole, while maintaining pressure in said horizontal fracture, thereby propagating a vertical fracture to an extended distance as favored by the in-situ stresses as altered by the propagating of said horizontal fracture.
Claim 14
Independent Claim
146 words
A method for enhancing the propagation of a vertical hydraulic fracture in an earth formation surrounding a borehole where the original in-situ stresses favor a horizontal fracture comprising: (a) supplying a fracturing fluid containing water, a chemical blowing agent, and a surfactant into said formation at a first depth within said borehole which surfactant and blowing agent are in said fluid in an amount sufficient to generate fracturing pressure after propagating a horizontal fracture; (b) causing said chemical blowing agent to decompose and liberate gas sufficient to form a foam thereby extending said propagated horizontal fracture further into said formation; and (c) supplying fracturing fluid to said formation at a second depth within said borehole, while maintaining pressure in said horizontal fracture, thereby propagating a vertical fracture to an extended distance as favored by the in-situ stresses as altered by the propagating of said horizontal fracture.
Claim 15
Dependent Claim
32 words
The method as recited in claim 12 where in step (c) an aqueous slug containing said blowing agent and surfactant is injected into said second depth thereby extending the propagated vertical fracture.
Claim 16
Dependent Claim
20 words
The method as recited in claim 12 where said water comprises fresh water, formation brine, sea water, or brackish water.
Claim 17
Dependent Claim
20 words
The method as recited in claim 12 where said chemical blowing agent is dinitrosopentamethylenetetramine which decomposes to release nitrogen gas.
Claim 18
Dependent Claim
29 words
The method as recited in claim 12 where said chemical blowing agent is sodium hydrogen carbonate and p-toluene sulfonyl hydrazide which decompose to release carbon dioxide and nitrogen gases.
Claim 19
Dependent Claim
14 words
The method as recited in claim 12 where said chemical blowing agent is azodicarbonamide.
Claim 20
Dependent Claim
21 words
The method as recited in claim 12 where said chemical blowing agent is azodicarbonamide where decomposition is accelerated by alkali carbonates.
Claim 21
Dependent Claim
28 words
The method as recited in claim 12 where said chemical blowing agent is the sodium salt of azodicarboxylic acid which upon decomposition liberates nitrogen and carbon dioxide gases.
Claim 22
Dependent Claim
15 words
The method as recited in claim 12 where said chemical blowing agent is p,p'-oxybis(benzenesulfonyl hydrazide).
Claim 23
Dependent Claim
35 words
The method as recited in claim 12 where said aqueous slug contains therein a pH adjustor, an accelerator, or an inhibitor sufficient to provide for variable propagation distances within said formation prior to foam generation.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-07-17 | 1993-01-16 | 1993-07-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-07-17 | 1997-01-16 | 1997-07-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-07-17 | 2001-01-16 | 2001-07-18 | $7700.00 | Window Closed / Lapsed |