Thixotropic Gel Plugging Agent for High-Temperature Fracture Sealing
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Solution Overview
Problem
Conventional gel plugging agents face challenges in high-temperature and high-pressure environments, particularly in deep fractured formations, where they fail to provide adequate sealing and are ineffective in filling vertical fracture spaces, leading to drilling fluid loss and economic losses.
Innovation Solution
A high-temperature resistant, high-strength, and thixotropic gel plugging agent composed of acrylamide monomer, reactive polymer, organic polymer cross-linker, resin toughening agent, and encapsulated cross-linking regulator, which exhibits low apparent viscosity during shear flow for easy pumping and rapid viscosity increase for effective sealing, forming a complex network structure for enhanced temperature resistance and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional gel plugging agents are used in high-temperature formations, then the plugging agent can be injected into the formation, but the gel structure breaks down and loses plugging effectiveness at temperatures above 120°C
Solution Approach 1:
The patent uses composite cross-linking systems combining organic cross-linkers (MBAM, DDM) with inorganic cross-linkers (ZrOCl2, AlCl3) to create a dual-network gel structure. This composite approach allows the gel to maintain structural integrity at high temperatures up to 150°C while retaining plugging effectiveness, solving the contradiction between temperature resistance and plugging reliability
Solution Approach 2:
The patent modifies the cross-linking density and gel composition parameters to optimize high-temperature performance. By adjusting cross-linker ratios and concentrations, the gel structure is tuned to remain stable at elevated temperatures, preventing breakdown and maintaining effective plugging under high-temperature conditions
2Strength
If the gel plugging agent has high viscosity to provide strong sealing, then the sealing performance improves, but the gel solution becomes difficult to pump into the wellbore and leakage layers
Solution Approach 1:
The patent creates a dynamic gel system that transitions from low-viscosity sol state during pumping to high-viscosity gel state after injection. The gelation process is controlled to occur after the solution enters the formation, allowing easy pumpability during injection while achieving strong sealing once in place
Solution Approach 2:
The gel plugging agent is prepared in a liquid precursor state that can be easily pumped, and the gelation process is initiated after injection into the formation. This preliminary action allows the solution to be delivered to the target location before transforming into the high-strength gel structure needed for sealing
3Strength
If the gel plugging agent forms a strong gel structure for high-strength plugging, then the plugging strength improves, but the gel loses thixotropic properties and cannot easily fill vertical fracture spaces
Solution Approach 1:
The patent implements a time-dependent gelation process where the gel structure develops progressively after injection. The periodic transformation from sol to gel allows the solution to first flow into vertical fractures under gravity, then gradually build strength as gelation proceeds, maintaining both thixotropic flow and final plugging strength
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 gel plugging agent effectively prevents drilling fluid leakage by forming a strong, high-temperature resistant barrier in leakage layers, demonstrating excellent thixotropic properties, mechanical strength, and even filling of vertical fractures, thereby addressing the limitations of conventional agents.
Implementation Method 1
The gel solution shows a low apparent viscosity during the shear flow and is easy to be pumped into the wellbore and then into the leakage layers of the formation; after the pumping stops, the gel solution shows rapidly increased viscosity
Implementation Method 2
the organic polymer cross-linker and the reactive polymer; among them, the organic polymer cross-linker is a polymerizable macromolecular polymer with vinyl groups (CH2═CH) on its surface and can polymerize with the vinyl groups (CH2═CH) on the acrylamide monomer
Implementation Method 3
then, the gel solution gelates after cross-linking and solidifying and forms a high-temperature resistant and high-strength barrier in the leakage layers between the wellbore and the formation
Data Source
AI summary
A high-temperature resistant, high-strength, and thixotropic gel plugging agent is composed of 8-20% of acrylamide monomer, 0.05-0.5% of reactive polymer, 0.1-1.0% of organic polymer cross-linker, 3.0-8.0% of resin toughening agent, 1.0-5.0% of flow pattern regulator, 0.01-0.5% of cross-linking regulator by the weight in the water. The gel solution shows a low apparent viscosity during the shear flow and is easy to be pumped into the wellbore and then into the formation leakage layer; after the pumping stops, the gel solution shows rapidly increased viscosity and strong adhesive force, and form a high-strength barrier between the wellbore and the formation, preventing the drilling fluid from further leaking.