Salt-Responsive Polymer Drilling Fluid for High-Salt Reservoirs

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Solution Overview

Problem

Current polymer drilling fluids face challenges with poor rheological properties, insufficient salt resistance, and irreversible damage from high shearing rates, limiting their effectiveness in complex oil and gas reservoirs.

Innovation Solution

A saturated salt water drilling fluid with a salt response type intelligent polymer composition, including bentonite, NaOH, KCl, calcium carbonate, barite, supramolecular fluid loss additives, and shear-enhancing agents like xanthan gum or zwitterionic polyacrylamide, which maintains structure recovery and enhances salt resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If linear high molecular polymer treating agents are used to improve shearing and diluting characteristics, then shear enhancement is achieved, but high shearing rates break molecular chains causing irreversible damage

Engineering Contradiction:

Improveshear enhancementVSAvoidmolecular chain stability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The polymer molecule is divided into multiple segments connected by flexible bonds, forming a segmented structure that can bend and flex without breaking under high shear stress, thus maintaining molecular integrity while providing shear enhancement

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the molecular structure parameters by introducing flexible bonds and bulky side groups, transforming the polymer from a linear rigid structure to a flexible segmented structure that resists chain breaking under high shear rates

Inventive Principle:

Principle #35Parameter changes

2Reliability

If strong hydration groups (such as sulfonic acid groups) are introduced to improve salt resistance, then hydration dispersion is maintained in high-salt environment, but charge shielding effect of electrolyte ions limits salt pollution resistance

Engineering Contradiction:

Improvesalt resistanceVSAvoidcharge shielding effect

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent creates a composite polymer structure combining hydrophobic and hydrophilic segments, where the hydrophobic segments provide structural stability and the hydrophilic segments provide salt resistance, achieving enhanced performance against charge shielding effects

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different segments of the polymer molecule are designed with different local properties: hydrophobic segments for structural stability and hydrophilic segments for salt resistance, allowing the polymer to resist charge shielding effects through localized functional regions

Inventive Principle:

Principle #3Local quality

3Productivity

If conventional polymer drilling fluids are used to improve mechanical drilling speed, then some performance enhancement is achieved, but poor rheological properties and insufficient salt resistance limit effectiveness in complex reservoirs

Engineering Contradiction:

Improvemechanical drilling speedVSAvoidrheological property

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent employs composite polymer structures combining multiple functional segments that work synergistically to provide both excellent rheological properties and salt resistance, enabling effective drilling in complex high-salt reservoirs while maintaining high mechanical drilling speed

Inventive Principle:

Principle #40Composite materials

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 drilling fluid exhibits excellent salt response, self-assembly, and reservoir protection characteristics, with improved shear recovery, temperature resistance, and reduced fluid loss, facilitating efficient drilling in high-salt environments.

Implementation Method 1

the saturated salt water drilling fluid of salt response type intelligent polymer provided by the invention has excellent salt response characteristics and self-assembly characteristics

Methodology Applied

Scientific EffectSelf-assembly: Self-Assembly

Implementation Method 2

the structural unit A is a structural unit with hydrophobicity; the structural unit B is a structural unit with hydrophilicity

Methodology Applied

Scientific EffectHydrophobic interaction: Hydrophobe

Implementation Method 3

excellent salt response characteristics

Methodology Applied

Scientific EffectSalt response:

Data Source

PatentUS11453812B2Saturated salt water drilling fluid of salt response type intelligent polymer and preparation method thereof

Publication Date: 2022.09.27 CHINA UNIV OF PETROLEUM (BEIJING)

AI summary

The invention relates to the field of drilling fluid, in particular to a saturated salt water drilling fluid of salt response type intelligent polymer and preparation method thereof. The drilling fluid contains two or more of the following components stored in admixture or separately: bentonite, NaOH, KCl, calcium carbonate, barite, NaCl, supramolecular fluid loss additive, supramolecular shear-enhancing agent, plugging agent, coating agent and water. The drilling fluid provided by the invention has the characteristics of salt response and self-assembly, can keep rheological properties such as rapid recovery of the sheared structure, low extreme high shear rate viscosity, good shear dilution property and the like in a high-salt environment, has good fluid loss reduction performance, reservoir protection performance and debris dispersion inhibition performance, and has good temperature resistance and pollution resistance performance.