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PROCESS FOR HYDRAULIC FRACTURING WITH pH CONTROL

a hydraulic fracturing and control technology, applied in the direction of fluid removal, survey, borehole/well accessories, etc., can solve the problems of increasing the pumping pressure during the fracturing, and affecting the performance of organic polymer friction reducers such as anioni

Inactive Publication Date: 2013-08-15
THE CHEMOURS CO FC LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention is about a process for hydraulic fracturing, which involves using water in large volumes. By controlling the pH, the fracturing process can create water that can be flowed back and produced, which can include metal salts, hydrocarbons, and other additives that can interfere with the performance of friction reducers. Proppant, such as sand, is used to keep the fracture open after treatment, and the fracturing fluid may include other components such as polymers, breaking agents, scale inhibitors, corrosion inhibitors, and other substances. The process involves combining water, proppant, an oxidizing biocide, and a friction reducer in a single step or multiple steps, and can involve treating the water with other components before combining it with proppant and friction reducer. Frac tanks are commonly used as a source of water, and the process can involve blending and mixing the friction reducer, proppant, and biocide or biocide mixture in a device like a ribbon mixer. Overall, the invention provides a way to manage the pH and other components in the fracturing process to create high-quality water that can be flowed back and produced.

Problems solved by technology

Problems have been encountered in the performance of organic polymer friction reducers such as anionic polyacrylamide polymers (either hydrolyzed to produce acid functionality or copolymerized with acrylic acid).
It has been theorized that use of oxidizing biocides in combination with these polymers causes the polymers to degrade and therefore increasing pumping pressure is necessary during the fracturing operations.
However, many non-oxidizing biocides are not acceptable due to environmental concerns and low efficacy.
At low pH, protonation of the polyacrylamide friction reducers can inhibit its ability to hydrate and unwind rapidly, thus, reducing its friction-reducing ability.
Because of the shortage of fresh water and the cost of treatment and / or disposal of produced water it is desirable to re-use at least a portion of the produced water in subsequent hydraulic fracturing treatments; however, the presence of contaminants, which include oxidizable, acid-producing metal ions, such as soluble Fe2+ and Mn2+, also negatively affects performance of the friction reducers.

Method used

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  • PROCESS FOR HYDRAULIC FRACTURING WITH pH CONTROL

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0039]This example provides the results of friction loop tests which demonstrate the effect of pH on friction reduction of various friction reducing polymers.

[0040]Friction loop tests were carried out at Stim-Lab, Inc. located in Duncan, Okla., using a standard apparatus known to those skilled in the art. For each test, approximately 9 gallons of test fluid was circulated at 10 gallons / minute (approx. Reynolds number of 75,000). The friction reduction was calculated from the pressure drop across a precise length of the test loop.

[0041]The water used to prepare the test fluids was a blend of 40% produced water from the Marcellus shale formation and 60% surface water collected from a location in Pennsylvania. The unadjusted pH of the water was 5.8. For tests run at lower pH, the water was acidified with sulfuric acid. In some cases the acidified water was also treated to contain about 10 mg / L residual ClO2. The test temperature was about 24° C. (75° F.).

[0042]For each test, a baseline...

example 2

[0044]This example demonstrates the pH lowering effect of oxidizing biocide in combination with divalent iron.

[0045]Unbuffered deionized water was adjusted to a pH of 6.0-6.2 with 1N NaOH or HCl as needed. Samples 2B and 2C were prepared from this water and 99.5% iron(II) heptahydrate so that the added Fe2+ content was 25 and 50 mg / L, respectively. Sample 2A was a control sample and contained no added iron. To each of samples 2A-2C, 30 mg / L ClO2 was applied, after which the pH and residual ClO2 was measured about 30 minutes later. Results, which were gathered at ambient laboratory temperatures of about 20-22 C, are summarized in the following table.

Fe2+pHpHClO2 mg / LClO2 mg / LSamplemg / Linitialfinalappliedresidual2A06.186.243028.52B256.103.613018.12C506.103.33014.5

[0046]Control sample 2A, without Fe2+, shows no substantial change in pH with addition of ClO2 and substantially no consumption of ClO2 (the applied and residual amount is substantially the same). In contrast, ClO2 addition t...

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Abstract

A process for hydraulic fracturing including the steps of (a) providing a fracturing fluid by combining water, proppant, an oxidizing biocide, and a friction reducer; (b) introducing the fracturing fluid into a well; and (c) controlling the pH of the fracturing fluid to a pH of at least about 4.5.

Description

FIELD OF THE INVENTION[0001]The present invention relates to the stimulation of the production of subterranean hydrocarbon formations or stimulation of fluid injection into subterranean formations in a hydraulic fracturing process. More particularly, the present invention relates to an improved process for hydraulic fracturing in which performance of additives, in particular, friction reducers, is enhanced.BACKGROUND OF THE INVENTION[0002]The production of oil and natural gas from an underground well (subterranean formation) can be stimulated by a technique called hydraulic fracturing in which a fracturing fluid is introduced into an oil or gas well via a conduit, such as tubing or casing, at a flow rate and a pressure to create, reopen and / or extend a fracture into the well, allowing access to the oil or gas within the formation.[0003]The fracturing fluid is typically a water based solution and may comprise components such as suspended proppants (e.g., sand, bauxite); biocides to i...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): E21B43/26E21B47/00
CPCE21B43/26C09K8/62E21B47/00
Inventor TUFANO, THOMAS PETERVORE, ROY DEANEHRHART, RAYMOND
Owner THE CHEMOURS CO FC LLC
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