Expandable Plugging Agent Micro-Capsule Design for Lost Circulation
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Solution Overview
Problem
Existing plugging agents, such as hydrolyzed polyacrylamide, face challenges in drilling operations due to high water absorption rates, large particle sizes, and inadequate strength, leading to compromised plugging effects in lost circulation situations, especially in large fractures and high-permeability formations.
Innovation Solution
A viscoelastic expandable plugging agent is developed through a polymerization reaction of acrylic acid, acrylamide, and acrylate, with a strength improving material and gelatinized colloid, using a cross-linking agent and initiating agent, which is encapsulated in micro-capsules for enhanced performance and stability in high-pressure and high-temperature environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If hydrolyzed polyacrylamide (HPAM) is used as plugging agent, then water absorption rate is high, but particle size becomes too large causing pumping difficulties and compromised plugging effect
Solution Approach 1:
The plugging agent is divided into multiple micro-capsules with diameter of 0.01-5mm, each containing cross-linked polymer beads. This segmentation allows the material to be pumped easily through drill string while maintaining high water absorption capacity, as the small capsule size reduces pumping resistance while the internal polymer structure retains water absorption functionality.
Solution Approach 2:
The structure employs a nested configuration where cross-linked polymer beads are enclosed within micro-capsule shells. The polymer beads (absorbing core) are nested inside the micro-capsule housing, creating a hierarchical structure that combines the water absorption capability of the polymer with the pumpability and controlled release properties of the capsule shell.
2Quantity of substance
If water-absorbent resin is used for plugging, then water absorption capacity is improved, but strength becomes insufficient for large fractures and high-permeability formations
Solution Approach 1:
The plugging agent combines multiple materials with complementary properties: water-absorbent polymer beads provide water absorption capacity, while the micro-capsule shell material (such as cellulose acetate, epoxy resin, or polyurethane) provides structural strength and fracture resistance. This composite structure enables the material to simultaneously achieve high water absorption and sufficient mechanical strength for plugging large fractures and high-permeability formations.
Solution Approach 2:
The cross-linking degree of the polymer beads is controlled at 10-90% to optimize the balance between water absorption capacity and structural strength. By adjusting the cross-linking parameter, the polymer network achieves adequate rigidity to maintain plugging strength while preserving sufficient porosity and hydrophilicity for water absorption functionality.
3Quantity of substance
If expandable polymers are used, then plugging effect is achieved through water absorption and expansion, but hydrocarbon absorption occurs simultaneously reducing effectiveness
Solution Approach 1:
The micro-capsule structure creates distinct functional zones: the inner polymer bead core is designed with hydrophilic properties for water absorption, while the outer capsule shell is engineered with hydrophobic characteristics that resist hydrocarbon absorption. This local quality differentiation ensures that the material selectively absorbs water while excluding hydrocarbons, preventing the harmful side effect of hydrocarbon uptake.
4Quantity of substance
If polymer gel system is used for plugging, then water absorption is achieved, but plugging strength in large fractures and high-permeability formations is insufficient
Solution Approach 1:
The polymer beads are pre-cross-linked and pre-formed with controlled pore structure and mechanical properties before being encapsulated in micro-capsules. This preliminary preparation ensures that the beads possess adequate structural strength and dimensional stability prior to deployment, enabling them to maintain plugging effectiveness in large fractures and high-permeability formations where post-absorption strength would be insufficient.
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 expandable plugging agent achieves a stable structure, high strength, and improved water absorption, salt resistance, and degradability, effectively reducing lost circulation issues and improving drilling efficiency with reduced handling time and cost.
Implementation Method 1
These three kinds of expandable polymers absorb water and expand after they enter into a leakage zone, and thereby plug up the leakage zone
Implementation Method 2
absorb water and expand after they enter into a leakage zone
Implementation Method 3
viscoelastic gel obtained through a polymerization reaction of first acrylic acid, acrylamide, acrylate, a strength improving material, and gelatinized colloid
Implementation Method 4
obtained through a polymerization reaction of first acrylic acid, acrylamide, acrylate, a strength improving material, and gelatinized colloid in the presence of a cross-linking agent
Data Source
AI summary
An expandable plugging agent is described. The expandable plugging agent is obtained through a polymerization reaction of acrylamide, a strength improving material, an acrylate, and gelatinized colloid, the acrylate is obtained through a neutralization reaction of an acidity neutralizer and acrylic acid, and the gelatinized colloid is obtained through a gelatinization reaction of starch in deionized water.