Self-diverting Acidizing Fluid Viscosity and Diversion
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Solution Overview
Problem
Current acidizing methods for oil production, such as those involving sulfobetaine surfactants and viscoelastic compositions, face challenges in achieving effective viscosity enhancement and diversion of acid flow into low permeability zones, leading to inefficient stimulation treatments.
Innovation Solution
A method involving a gelling fluid composed of a gelling agent and a hydrophobically-modified associative polymer, which includes a water-insoluble part selected from alkyl or alkylaryl alcohol esters of acrylic or methacrylic acid, is injected into a wellbore at pressures below fracturing pressure, allowing the fluid to acidize the formation and self-divert into lower permeability zones, enhancing viscosity and acting as a delayed internal breaker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional acidizing methods using sulfobetaine surfactants and viscoelastic compositions are used, then acid flow diversion into low permeability zones is achieved, but viscosity enhancement is insufficient and treatment effectiveness is reduced
Solution Approach 1:
The patent combines hydrophobically-modified associative polymers with gelling agents to create a composite treatment fluid system. The polymer provides viscosity enhancement through hydrophobic associations, while the gelling agent contributes to gel structure formation. This composite approach achieves both sufficient viscosity enhancement and effective acid flow diversion into low permeability zones, resolving the contradiction between productivity and substance quantity.
Solution Approach 2:
The patent utilizes changes in fluid parameters including viscosity, gel strength, and breakdown characteristics. The treatment fluid is designed to exhibit specific rheological parameters that enable effective diversion while maintaining pumpability. By controlling parameters such as polymer concentration, gelling agent dosage, and fluid composition, the system achieves optimal balance between viscosity enhancement and diversion effectiveness.
2Productivity
If treatment fluid viscosity is increased to enhance diversion, then acid flow control improves, but fluid cleanup difficulty increases
Solution Approach 1:
The treatment fluid is designed with dynamic rheological properties that change over time. The fluid exhibits higher viscosity during the treatment phase to enable effective acid flow control and diversion. After treatment, the fluid undergoes breakdown or degradation, reducing viscosity and facilitating easy cleanup. This dynamic behavior resolves the contradiction between acid flow control and cleanup ease by providing high viscosity when needed and low viscosity when cleanup is required.
Solution Approach 2:
The patent incorporates breakdown mechanisms or degradation pathways in advance within the treatment fluid formulation. These pre-designed features ensure that after the fluid performs its diversion function, it automatically transitions to a lower viscosity state that is easier to remove from the formation. This beforehand cushioning approach prevents permanent high-viscosity residue, resolving the contradiction between acid flow control and cleanup ease.
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 method effectively increases viscosity, imparts viscoelastic properties, and self-diverts acid flow into low permeability zones, improving the effectiveness of acidizing treatments by maintaining initial fluid properties and reducing viscosity over time for easy cleanup.
Implementation Method 1
The gelling fluid includes a gelling agent and a hydrophobically-modified associative polymer
Implementation Method 2
allowing the treatment fluid to acidize the formation and self-divert into lower permeability zones, enhancing viscosity
Implementation Method 3
It includes injecting acid into the formation. The acid then reacts with soluble substances of the formation, creating pathways for oil conductivity
Data Source
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AI summary
A method of acidizing a formation penetrated by a wellbore that includes the steps of injecting into the wellbore at a pressure below formation fracturing pressure a treatment fluid that includes a gelling fluid including a gelling agent and a hydrophobically-modified associative polymer, and an aqueous acid; and allowing the treatment fluid to acidize the formation.