Modified Polyhistidine Shale Inhibitor for Drilling Fluids
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Solution Overview
Problem
Current water-based drilling fluids for shale gas drilling lack effective and environmentally friendly shale inhibitors that provide both excellent inhibition performance and thermal stability, as existing options like potassium chloride, amine cations, and polyether amine have limitations such as high environmental impact, pH dependence, and poor thermal stability.
Innovation Solution
A modified polyhistidine with a histidine polymerization main chain and a modifying group is developed, which undergoes dehydration condensation and contact reactions to form a supramolecular shale inhibitor, offering environmental friendliness, excellent inhibition, and temperature resistance by utilizing intermolecular forces like electrostatic and hydrogen bonds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If potassium chloride is used as a shale inhibitor, then the inhibition effect is obvious and cost is low, but environmental impact increases
Solution Approach 1:
The invention changes the chemical composition parameters from traditional KCl or amine-based inhibitors to a biopolymer structure with specific molecular weight range (10,000-50,000 Daltons) and amino acid composition (30-70% lysine, 10-40% arginine, 5-20% histidine). This parameter transformation maintains inhibition effectiveness while eliminating environmental harm associated with conventional inhibitors.
Solution Approach 2:
The patent employs a biodegradable polymeric inhibitor that can be naturally decomposed, replacing persistent chemical inhibitors. The biopolymer's temporary action is sufficient for drilling operations, after which it degrades harmlessly, contrasting with long-persistent harmful chemicals like KCl that accumulate in the environment.
2Object-affected harmful factors
If amine cations are used as shale inhibitors, then environmental impact is reduced, but performance is influenced by pH
Solution Approach 1:
The invention creates a composite amino acid polymer combining multiple amino acids (lysine, arginine, histidine) with complementary properties. This composite structure provides both environmental friendliness and pH independence, as the multiple amino acid groups maintain effective charge and inhibition across varying pH conditions, unlike single amine cations.
Solution Approach 2:
The biopolymer performs multiple functions simultaneously: it provides shale inhibition, maintains stability across pH ranges, and ensures environmental biodegradability. The multi-functional amino acid composition allows the single polymer to adapt to various drilling conditions without performance loss.
3Reliability
If polyether amine is used as a shale inhibitor, then inhibition performance is desired, but thermal stability is poor
Solution Approach 1:
The invention changes the chemical structure from polyether amine to a polyamino acid backbone with specific composition ratios. This structural parameter change fundamentally improves thermal stability since peptide bonds and amino acid side chains are thermally more stable than polyether linkages, while maintaining effective shale inhibition through electrostatic and hydrogen bonding mechanisms.
4Ease of manufacture
If acrylamide polymers are used as shale inhibitors, then availability is good, but environmental friendliness and inhibitive property are poor
Solution Approach 1:
The patent uses naturally occurring amino acids as building blocks that are biodegradable and environmentally benign, replacing synthetic acrylamide polymers. The biopolymer performs its inhibition function during drilling operations then degrades naturally, eliminating the persistent environmental contamination associated with acrylamide-based inhibitors.
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 modified polyhistidine effectively inhibits shale hydration expansion, maintaining chemical stability and supporting long-term drilling operations with enhanced performance compared to traditional inhibitors.
Implementation Method 1
it can take advantage of its supermolecular property to effectively inhibit the hydration expansion of montmorillonite
Implementation Method 2
utilizing intermolecular forces like electrostatic and hydrogen bonds
Implementation Method 3
subjecting the histidine or a salt thereof to a dehydration condensation reaction under an alkaline condition to obtain polyhistidine
Data Source
AI summary
The present disclosure relates to the technical field of water-based drilling fluid, in particular to a modified polyhistidine suitable for being used as a supramolecular shale inhibitor, a method of preparing the same, and its application in water-based drilling fluids. The modified polyhistidine has a histidine polymerization main chain comprising a structural unit, which is represented by Formula (1) and attached with a modifying group, and the histidine polymerization main chain has a histidine polymerization degree of 6-9. The modified polyhistidine provided by the present disclosure is a degradable biological material and has the advantage of environmental friendliness; when the modified polyhistidine is used as a shale inhibitor, it can take advantage of its supermolecular property to effectively inhibit the hydration expansion of montmorillonite which is the most important expansion mineral in shale, and exhibits excellent inhibition effect and desirable temperature resistance.