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Viscosity reduction of viscoelastic surfactant based fluids

A surfactant and viscoelastic technology, which is used in the treatment of underground formations and oil wells and gas wells, can solve problems such as fractured viscoelastic solutions, fluid viscosity effects, etc.

Inactive Publication Date: 2005-10-05
SCHLUMBERGER TECH LTD BV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The fracture method discussed by Rose cannot be used to fracture viscoelastic solutions down a well and appears to have a direct effect on the viscosity of the fluid

Method used

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  • Viscosity reduction of viscoelastic surfactant based fluids
  • Viscosity reduction of viscoelastic surfactant based fluids
  • Viscosity reduction of viscoelastic surfactant based fluids

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0055] Embodiment 1: adding alcohol

[0056] The viscosity of an aqueous solution comprising a viscoelastic surfactant composed of a long chain quaternary ammonium salt is reduced in viscosity by adding an alcohol. figure 1 The effect of the addition of various alcohols on the fluid rheological properties of a general viscoelastic surfactant-like gel composition containing 3% by weight of causticylmethylbis(2-hydroxyethyl)ammonium chloride ( EMHAC), 1 wt% isopropanol and 3 wt% ammonium chloride.

[0057] All alcohols tested significantly reduced viscosity at low shear rates, with efficiency increasing with chain length (from C 1 to C 5 ).

[0058]Using shorter chain length alcohols (especially methanol and ethanol), at higher shear rates, the fluid viscosity was essentially the same as the measured viscosity of the control fluid without alcohol. It is believed that most fracturing fluids are subjected to about 20 to 150 seconds of fracture creation -1 The addition of alc...

Embodiment 2

[0060] Example 2: adding ether

[0061] This method relies on the use of an ester (R'COOR") which has a minor effect on the rheological properties of the viscoelastic gel, but at concentrations greater than or equal to the critical concentration required to break the gel , can be decomposed to generate alcohol (R"OH), where R' and R" are aromatic, saturated or unsaturated hydrocarbon chains.

[0062]

[0063] Since some organic acids are also effective at breaking down gels containing VES (see Example 3), the addition of ether can be quite effective, provided the hydrolysis occurs at the right time. Similar effects can also be obtained by using suitable dibasic or tribasic esters.

[0064] image 3 The effect of adding various methyl diesters to Gel B as defined in Example 1 is shown. In contrast to the more hydrophobic diesters (dimethyl glutarate, dimethyl adipate, dimethyldiethyl malonate, and dimethyl azelate), when added at 3-4 wt% The more hydrophilic esters (...

Embodiment 3

[0066] Embodiment 3: add organic acid salt

[0067] Some organic acids are effective breakers. Acids can be provided encapsulated or as salts. Then, under acidic conditions, the following reaction was carried out.

[0068]

[0069] The salt can be chosen so that RCOO - Has little or no effect as an effective counterion in viscoelastic gels.

[0070] Salicylate Anion / Salicylic Acid:

[0071]

[0072] Adipate Anion / Adipic Acid:

[0073]

[0074] Tertiary carboxylate anion / tertiary carboxylic acid:

[0075] Glutarate anion / glutaric acid:

[0076] In this example, the pH of the initial fluid is greater than the pK of the carboxylic acid a , so RCOO - The concentration is greater than the concentration of RCOOH. At the right time, lower pH conditions are generated so that the concentration of RCOOH increases and becomes greater than RCOO - concentration. As described in Example 1, lower pH conditions can be generated by hydrolysis of es...

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PUM

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Abstract

Methods and compositions are disclosed for controlled addition of components that decrease the viscosity of the viscoelastic surfactant fluids or for controlled changes in the electrolyte concentration or composition of the viscoelastic surfactant fluids. One aspect of the invention relates to the use of internal breakers with a delayed activation. Another aspect of the invention relates to the use of precursors that release a breaking system such as alcohol by a process such as melting, slow dissolution, reaction with a compound present in the fluid or added to the fluid during or after the step of injecting, rupture of an encapsulating coating and de-adsorption of a breaking agent absorbed into solid particles. In another aspect of the invention, alcohols are included in a pad to reduce the low-shear viscosity and reduce the resistance to flow of the treatment fluids during a desired phase of the treatment.

Description

field of invention [0001] The present invention relates to compositions and methods for reducing the viscosity of viscoelastic surfactant (VES) fluids, particularly for treating subterranean formations and oil and gas wells. Background technique [0002] Viscoelastic surfactant fluids are generally prepared by mixing appropriate amounts of suitable surfactants, such as anionic, cationic, nonionic and zwitterionic surfactants. The viscosity of a viscoelastic surfactant fluid is due to the three-dimensional structure formed by the components in the fluid. When the concentration of surfactant in a viscoelastic fluid significantly exceeds a critical concentration, and in most cases, in the presence of electrolytes, the surfactant molecules aggregate into substances such as those that interact to form a network that exhibits elasticity micelles. In the remainder of this specification, the term "micelle" will be used as a generic term for organized interacting species. [0003]...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C09K8/536C09K8/62C09K8/68C09K8/70C09K8/74C09K8/92
CPCC09K2208/26C09K8/92C09K8/536C09K8/706C09K8/68C09K8/74C09K2208/30Y10S507/921C09K8/805C09K8/62E21B43/25
Inventor 杰西·李埃里克·纳尔逊
Owner SCHLUMBERGER TECH LTD BV