Invert Emulsion Fluid Density Control via Dissolved Salts
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Solution Overview
Problem
Existing wellbore fluids face challenges in controlling equivalent circulating density (ECD), which can lead to increased frictional pressure, restricted circulation rates, and potential formation damage due to high fluid pressures exceeding fracture pressures, especially in deep water wells and formations with small pore pressure and fracture gradient differences.
Innovation Solution
The development of an invert oil emulsion wellbore fluid comprising an oil phase, an emulsifier, and an internal phase with an alcohol and a salt dissolved in the alcohol, where the salt has a solubility greater than 3 g/100 ml at 23°C, reducing the need for weighting solids and thereby minimizing ECD, while maintaining desired thermal properties and hydraulic efficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If weighting solids are added to increase fluid density, then the equivalent circulating density (ECD) increases, but frictional pressure increases and formation damage risk increases
Solution Approach 1:
The patent changes the chemical composition parameters of the internal phase by using alcohols with specific molecular weights (500-5,000 Daltons) and incorporating salts (formates, acetates, phosphates, halides) with optimized concentrations. This chemical parameter modification increases the density of the internal phase, allowing for reduced weighting solids while maintaining desired ECD and reducing frictional pressure.
Solution Approach 2:
The patent creates a composite internal phase system combining alcohol base fluids with specific molecular weight ranges and dissolved salts. This composite material approach achieves enhanced density and thermal properties without relying solely on traditional weighting solids, thereby reducing ECD and frictional pressure while maintaining formation integrity.
2Quantity of substance
If weighting solids are added to increase fluid density, then the equivalent circulating density (ECD) increases, but circulation rate is restricted
Solution Approach 1:
By modifying the chemical composition parameters of the internal phase - specifically using alcohols within 500-5,000 Dalton molecular weight range and incorporating specific salt concentrations - the patent achieves increased internal phase density. This allows maintaining desired ECD with reduced weighting solids, thereby improving fluid rheology and enabling higher circulation rates.
3Reliability
If fluid pressure is increased to maintain formation integrity, then formation damage is prevented, but fracture risk increases
Solution Approach 1:
The patent modifies the chemical composition parameters of the internal phase by incorporating salts (formates, acetates, phosphates, halides) at optimized concentrations with alcohols of specific molecular weights. This increases the density of the internal phase, allowing precise control of ECD to maintain formation integrity while avoiding excessive pressures that could cause fractures.
4Temperature
If the internal phase uses high molecular weight polycyclic polyether polyol, then thermal properties are improved, but salt solubility decreases
Solution Approach 1:
The patent changes the molecular weight parameter of the alcohol to fall within 500-5,000 Daltons, which is significantly lower than high molecular weight polyols. This parameter change optimizes both thermal properties and salt solubility, allowing sufficient salt dissolution (formates, acetates, phosphates, halides) while maintaining adequate thermal characteristics for wellbore fluid applications.
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 invert oil emulsion wellbore fluid effectively reduces ECD, improves drilling hydraulics, and enhances thermal properties, allowing for safer and more efficient drilling and gravel pack operations by minimizing frictional pressure and maintaining formation integrity.
Implementation Method 1
an internal phase comprising an alcohol other than a polycyclic polyether polyol with a molecular weight in excess of 50,000 Daltons and a salt dissolved in the alcohol
Implementation Method 2
An invert emulsion is a complex heterogeneous fluid. Invert emulsions could be described as a polar fluid emulsified as the internal phase with a non-polar fluid as the continuous phase
Data Source
AI summary
A method of drilling and completing a wellbore in a subterranean formation comprises circulating an invert oil emulsion fluid in the subterranean formation; the invert oil emulsion fluid comprising an oil phase, an emulsifier, and an internal phase comprising an alcohol other than a polycyclicpolyetherpolyol with molecular weight in excess of 50,000 and a salt dissolved in the alcohol, wherein the alcohol and the salt are selected such that the salt has a solubility in the alcohol of greater than about 3 g/100 ml at 23° C.