Polyvinyl Alcohol Diverting Agent for Hydraulic Fracturing
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Solution Overview
Problem
Conventional diverting agents used in hydraulic fracturing, such as polyglycolic acid or polylactic acid, are water-insoluble and have inadequate filling retention time, leading to inefficient fracture growth and generation of new fractures due to insufficient durability and prolonged removal times.
Innovation Solution
A diverting agent comprising a polyvinyl alcohol-based resin with specific properties, including a slope of 80 or less in a cumulative dehydration amount plot against the square root of time, ensuring effective filling and easy water-soluble properties for removal, is developed. This agent is combined with guar gum and pressurized to achieve optimal dehydration and filling properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If water-insoluble resins such as polyglycolic acid or polylactic acid are used as diverting agents, then the diverting agent can maintain shape for a certain period, but the removal time becomes prolonged and filling retention time is inadequate
Solution Approach 1:
The patent changes the solubility parameter of the diverting agent from water-insoluble (conventional polyglycolic acid or polylactic acid) to water-soluble (polyvinyl alcohol-based resin). This parameter change enables the diverting agent to be easily removed after serving its filling function, thereby reducing removal time while maintaining adequate filling retention time during the hydraulic fracturing process.
2Reliability
If conventional diverting agents are used, then they can be introduced into fractures, but they do not provide sufficient durability for sustained fracture growth
Solution Approach 1:
The patent changes the material parameter from water-insoluble resins to water-soluble polyvinyl alcohol-based resin, which provides both durability during the fracturing process and easy removal afterward. This ensures reliable filling performance for sustained fracture growth while maintaining productivity through efficient removal.
3Stability of the object's composition
If water-insoluble resins are used as diverting agents, then they can maintain filling, but they cannot be easily removed after use
Solution Approach 1:
The patent changes the solubility parameter of the diverting agent material. By using polyvinyl alcohol-based resin instead of water-insoluble resins, the diverting agent achieves both filling stability during the hydraulic fracturing process and ease of removal afterward through water dissolution, eliminating the trade-off between stability and ease of removal.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The diverting agent provides improved durability and filling efficiency for fractures in hydraulic fracturing, allowing for sustained fracture growth and easy removal after use, enhancing the hydraulic fracturing process for natural gas and petroleum extraction.
Implementation Method 1
the mixed solution is dispersed at 30° C. for 60 minutes to obtain a dispersion liquid, the dispersion liquid is pressurized and dehydrated at a pressure of 1 MPa
Implementation Method 2
a water-soluble polyvinyl alcohol-based resin... easy removal after use
Data Source
AI summary
A diverting agent of the present invention contains a polyvinyl alcohol-based resin, wherein when the diverting agent is added to a 0.48 mass % aqueous solution of guar gum to prepare a mixed solution having a concentration of 12 mass %, a dispersion liquid obtained by dispersing the mixed solution at 30° C. for 60 minutes is pressurized and dehydrated at a pressure of 1 MPa using a pressure dehydration device including a drainage part having a slit having a width of 2 mm, and a regression line represented by an equation (A): y=ax+b (in the equation (A), y is a cumulative dehydration amount (g), x is a square root of a time (minutes) elapsed from start of pressurization, a and b are a slope and an intercept of the regression line, respectively, and 0<x≤2) is calculated by a least squares method from a scatter diagram plotted on a graph in which the square root x of the time is plotted on a horizontal axis and the cumulative dehydration amount y is plotted on a vertical axis, a slope a of the equation (A) satisfies a condition (B): a≤80.