Solids-Free Divalent Brine Drilling Fluid for High-Temperature Wells
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Solution Overview
Problem
Traditional drilling fluids for oil wells often cause damage to the productive formation by invading pores with insoluble solids and creating emulsions, leading to reduced permeability, especially at high temperatures and pressures, where existing polymers used to increase viscosity and control filtration lose effectiveness.
Innovation Solution
A solids-free fluid system using calcium chloride, calcium bromide, and zinc bromide brines with synthetic and biopolymers that are resistant to high temperatures, allowing for rapid hydration without prolonged stirring or heating, and containing additives that inhibit clay hydration and emulsion formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If traditional solids-containing drilling fluids are used to increase density and control pressure, then the fluid can effectively counter formation pressure, but the insoluble solids invade the productive formation and clog pores, reducing permeability and hydrocarbon production
Solution Approach 1:
The patent removes the harmful insoluble solids (barite, ilmenite, galena, iron oxide) from the drilling fluid system while retaining the essential function of density control. This is achieved by using only water-soluble divalent metal salts (CaCl2, CaBr2, ZnBr2) to achieve the required fluid density, thereby eliminating pore clogging and formation damage while maintaining pressure control capabilities
Solution Approach 2:
The patent creates a composite brine system combining multiple water-soluble divalent metal salts (calcium chloride, calcium bromide, zinc bromide) to achieve the required density and rheological properties. This composite approach allows the fluid to maintain high density for pressure control without incorporating insoluble weighting agents that cause formation damage
2Temperature
If traditional polymers are used to increase viscosity and control filtration at high temperatures, then the fluid can maintain rheological properties, but the polymers lose effectiveness at temperatures above 150°C and 200°C
Solution Approach 1:
The patent changes the chemical parameters of the polymer system by selecting specific polymers (polyanionic cellulose, polyacrylamide copolymers, xanthan gum) that maintain their viscosifying and filtration control properties at high temperatures up to 200°C. This parameter change in thermal stability allows the fluid to maintain effective rheological control in high-temperature wells where traditional polymers fail
3Ease of operation
If surfactants are used in drilling fluid formulation to reduce surface tension and improve flow, then the fluid can better lubricate and carry cuttings, but the surfactants interact with formation fluids to create difficult-to-remove emulsions that change formation wettability and restrict hydrocarbon flow
Solution Approach 1:
The patent applies surfactants selectively and in controlled amounts only where needed for lubrication and cuttings transport, while using divalent metal salts and polymer additives to provide the primary density and rheological control. This localized use of surfactants minimizes their interaction with formation fluids and reduces emulsion formation while maintaining operational effectiveness
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 system significantly reduces damage to the productive formation by maintaining high thermal stability, controlling rheological properties, and preventing emulsion formation, ensuring effective drilling and completion operations even at temperatures up to 200°C.
Implementation Method 1
uses mixtures of different salts of water-soluble divalent metals to provide the characteristics of density
Implementation Method 2
polymers and special additives to provide the system with the physicochemical properties that any fluid for drilling, completing and repairing wells requires
Implementation Method 3
providing lubrication and inhibiting hydration of any clays present in the productive formation pores
Implementation Method 4
certain types of surfactants... may interact with the formation fluids (water or crude oil) creating emulsions that are difficult to remove
Implementation Method 5
a bridging agent for controlling fluid losses
Data Source
AI summary
The present invention relates to the composition, preparation method and use of a solids-free drilling fluid system formulated with a mixture of divalent heavy brines, which is resistant to high pressures and high temperatures. The system has the special feature that it significantly reduces productive-formation permeability damage as it uses mixtures of different salts of water-soluble divalent metals to provide the features of density, polymers and special additives to provide the system with the physicochemical properties that any fluid for drilling, completing and repairing wells requires in order to fulfill the functions thereof and to provide heat resistance up to 200° C. A main feature of the present invention is that the composition that embeds the drilling/completing/repairing of oil wells fluid contains synthetic polymers and biopolymers that do not require large amounts of time, high shear speeds or heating for hydration thereof in divalent metal salt derived simple or binary brines.