Cysteine Protease Pretreatment for Bacterial Control in Fracturing Fluids
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Solution Overview
Problem
The use of plant-based polysaccharides in hydraulic fracturing fluids is hindered by premature viscosity loss due to bacterial degradation in oilfield produced water, which conventional bactericides fail to effectively prevent.
Innovation Solution
The application of cysteine proteases to pretreat produced water by inactivating bacteria, thereby preventing them from interacting with and degrading polysaccharides, using enzymes such as bromelain, papain, and ficain, which are commercially available and can be refined from natural sources, to maintain fluid viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bactericides are used to treat produced water, then bacterial growth is inhibited, but fluid viscosity is not effectively retained
Solution Approach 1:
The patent introduces cysteine proteases as an intermediary substance that specifically targets and degrades bacterial proteins. These enzymes act as a mediator between the produced water and the polysaccharide thickening agents, preventing direct bacterial degradation of the fluid while maintaining viscosity. The proteases selectively break down bacterial cell walls and proteins without affecting the polysaccharide structure, thus resolving the contradiction between bacterial control and viscosity retention.
2Stability of the object's composition
If polysaccharide thickeners are added to fracturing fluid, then viscosity and proppant transport capability are improved, but premature viscosity loss occurs due to bacterial degradation
Solution Approach 1:
The patent applies cysteine proteases to produced water before mixing with polysaccharide thickeners to pre-inactivate bacteria and their degradative enzymes. This preliminary treatment creates a protected environment that prevents subsequent bacterial attack on the polysaccharide molecules, thereby extending the operational lifespan of the fracturing fluid while maintaining its viscosity throughout the intended service period.
3Reliability
If high concentrations of bactericides are used to prevent viscosity loss, then bacterial activity is reduced, but fluid composition and performance are adversely affected
Solution Approach 1:
The patent changes the mechanism of bacterial control from chemical inhibition (bactericides) to enzymatic degradation (cysteine proteases). This parameter change in the control mechanism allows for effective bacterial suppression at lower concentrations that do not interfere with fluid performance. The enzymatic action specifically targets bacterial proteins without affecting the polysaccharide thickening agents or other fluid components, thus avoiding the harmful side effects associated with high-concentration bactericide use.
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
This method effectively prevents premature breakage of fracturing fluids by degrading bacterial proteins that attach to polysaccharides, ensuring stable viscosity and extending the lifespan of hydraulic fracturing fluids.
Implementation Method 1
adding a cysteine protease to said produced water; allowing said cysteine protease to inactivate said bacteria
Implementation Method 2
Possible enzymes come from a group of proteins known as cysteine endopeptidases such as bromelain, papain, calpain, and ficain
Data Source
AI summary
A produced water bacterial pretreatment method which includes a) optionally adjusting a pH and a temperature of a produced water containing bacteria; b) adding a cysteine protease to said produced water; c) allowing said cysteine protease to inactivate said bacteria, thus producing pretreated produced water; and d) introducing said pretreated produced water into a wellbore penetrating a subterranean formation is provided.