Clay-Free Drilling Fluid Viscosifiers With Starch and Acrylamide
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Solution Overview
Problem
The existing viscosifiers for water-based drilling fluids, such as xanthan gum, face supply inconsistencies and cost fluctuations, and alternative biopolymers like diutan gum are not ideal for high-temperature wellbores, while clay-based formulations pose issues in water-sensitive formations, leading to challenges in maintaining optimal viscosity and stability.
Innovation Solution
A synergistic combination of a cross-linked starch and a cross-linked acrylamide-based polymer is used as viscosifiers in a clay-free drilling fluid, creating a synergistic effect that enhances yield point and gel strength, providing improved suspension and pumpability without excessive viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If xanthan gum is used as a viscosifier, then viscosity and suspension capability are improved, but supply consistency and cost stability deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters by replacing xanthan gum with a synergistic combination of hydrolyzed starch and polyacrylamide polymer, thereby maintaining viscosity performance while eliminating supply and cost instability associated with xanthan gum
Solution Approach 2:
The patent uses a composite viscosifier system combining hydrolyzed starch and polyacrylamide polymer in specific proportions (0.5-5 lb/bbl starch and 0.1-2 lb/bbl polymer) to achieve reliable and consistent viscosity performance that is not dependent on single-material supply chains
2Reliability
If diutan gum is used as an alternative viscosifier, then supply consistency is improved, but performance in high-temperature wellbores deteriorates
Solution Approach 1:
The patent selects polymers with specific thermal stability parameters, using cross-linked starch and thermally stable polyacrylamide derivatives that maintain their viscosifying properties at high temperatures up to 200°F, unlike diutan gum which degrades
3Strength
If clay-based formulations are used, then viscosity is improved, but compatibility with water-sensitive formations deteriorates
Solution Approach 1:
The patent extracts and eliminates clay components from the drilling fluid formulation, replacing them with synthetic polymers that provide equivalent or superior viscosity without the harmful effects on water-sensitive formations
Solution Approach 2:
The patent uses soluble, biodegradable polymers that can be easily removed or degraded after serving their viscosifying function, unlike clay particles that can cause long-term formation damage
4Strength
If high viscosity is achieved for suspension, then drill cutting suspension is improved, but pumpability deteriorates
Solution Approach 1:
The patent creates a dynamic viscosity system where the fluid exhibits high viscosity at low shear rates (when stationary for suspension) but low viscosity at high shear rates (when pumped), achieved through the synergistic polymer combination and cross-linking structure
Solution Approach 2:
The patent adjusts the molecular weight, cross-linking density, and polymer concentration parameters to optimize the shear-thinning behavior, ensuring the fluid transitions between suspended and pumped states efficiently
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 synergistic viscosifiers achieve superior performance in maintaining viscosity and stability, enabling effective suspension and transport of drill cuttings while remaining pumpable, even in high-temperature conditions, thus overcoming the limitations of existing viscosifiers.
Implementation Method 1
the first viscosifier and the second viscosifier create a synergistic effect whereby a first test drilling fluid consisting of the base fluid, the first viscosifier, and the second viscosifier
Implementation Method 2
Viscosifiers can be added to drilling fluids to help suspend drill cuttings during an oil or gas drilling operation
Data Source
AI summary
A water-based drilling fluid can include a first and second viscosifier of a cross-linked starch and a cross-linked acrylamide-based polymer. The acrylamide-based polymer can be crosslinked and optionally include hydrophobic monomers. The viscosifiers create a synergistic effect that imparts desirable properties to the drilling fluid compared to using either of the viscosifiers alone. The viscosifiers can be used as an alternative to other types of viscosifiers such as xanthan gum.