Crosslinked Xanthan Acidizing Fluids for Deep Penetration
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Solution Overview
Problem
Conventional acidizing fluids for subterranean formations face challenges such as limited deep penetration due to rapid spending and the undesirable residues left by synthetic polymers, which hinder effective permeability enhancement and require costly remedial operations.
Innovation Solution
The use of acidizing fluids comprising in-situ crosslinked spent acids and crosslinked live acids with derivatized xanthan, which acts as a gelling agent to enhance penetration and prevent residue formation, allowing for deeper fracture acidizing lengths and reduced fluid loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional acidizing fluids with high acid strength are used, then the acid can quickly react with formation materials near the well bore, but the acid becomes spent before achieving desirable deep penetration into the formation
Solution Approach 1:
The acidizing fluid is pre-gelled using crosslinked polymers before injection to control its flow and reaction characteristics. This preliminary gelling action allows the acid to maintain its reactive strength while moving deeper into the formation before the gel structure breaks down, enabling both rapid reaction and deep penetration.
Solution Approach 2:
The gel structure of the acidizing fluid is designed to be dynamic, maintaining its gel state during injection and initial flow to control penetration rate, then breaking down at the target depth to allow rapid acid reaction. This dynamic transition enables the fluid to adapt its properties during different stages of the acidizing process.
2Reliability
If synthetic polymers are used to gel acidizing fluids, then delayed gelation and temperature tolerance are achieved, but undesirable residues are left in the subterranean formation requiring costly remedial operations
Solution Approach 1:
The polymer structure is chemically modified by changing its parameters - specifically using partially hydrolyzed polyacrylonitrile with controlled degrees of hydrolysis and specific molecular weights. These parameter changes enable the polymer to maintain temperature tolerance while being completely degradable into harmless substances, eliminating residue formation.
Solution Approach 2:
The patent employs a disposable, fully degradable polymer gel system that performs its function temporarily during the acidizing process and then completely breaks down. This approach replaces persistent synthetic polymers with a short-lived, environmentally benign alternative that leaves no harmful residues.
3Ease of manufacture
If natural biopolymers are used in crosslinked gel acidizing applications, then degradability is achieved, but the polymers function at relatively low temperatures and have poor crosslinking ability
Solution Approach 1:
The patent creates a composite polymer system by combining partially hydrolyzed polyacrylonitrile chains with crosslinking agents to form a gel network. This composite structure integrates the degradability of natural polymer systems with the temperature tolerance and crosslinking capability of synthetic polymers, achieving both properties simultaneously.
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 acidizing fluids achieve deeper penetration and longer effective fracture lengths, reduce residue formation, and effectively stimulate production by dissolving damage and removing fines, while minimizing fluid loss and potential for costly clean-up operations.
Implementation Method 1
crosslinked acids comprising derivatized xanthan
Implementation Method 2
crosslinked live acids comprising derivatized xanthan, which acts as a gelling agent
Implementation Method 3
the acidic solution reacts with acid-soluble materials contained in the formation which results in an increase in the size of the pore spaces
Implementation Method 4
crosslinked oxidized xanthan
Data Source
AI summary
Many methods are provided herein including, in one embodiment, a method comprising: providing a fluid that comprises an acid, crosslinked oxidized xanthan, and optionally, a base fluid; placing the fluid in a well bore penetrating a subterranean formation; and allowing the fluid to acidize at least a portion of the formation or damage contained therein. In another embodiment, herein provided is a fluid for subterranean uses comprising an acid and crosslinked, oxidized xanthan.