Mineral Oil and Particulate Agents in VES Gelled Fluids
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Solution Overview
Problem
Viscoelastic surfactant (VES)-gelled fluids used in hydrocarbon recovery operations experience significant fluid loss into the reservoir matrix, reducing the efficiency of fracturing treatments and causing formation damage, as they do not form a filter cake and can plug pore throats.
Innovation Solution
Incorporating a combination of mineral oil with particulate fluid loss control agents such as alkaline earth metal oxides or transition metal oxides into VES-gelled aqueous fluids to reduce fluid leakage by forming a viscous micelle layer on the formation face, which limits further fluid leakoff without impairing the viscosity of the fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If VES-gelled fluids are used in hydrocarbon recovery operations, then the fluids exhibit excellent rheological properties and are less damaging to producing formations, but the fluids experience significant fluid loss into the reservoir matrix
Solution Approach 1:
The patent introduces particulate fluid loss control agents as intermediary substances that mediate between the VES-gelled fluid and the reservoir matrix. These particles form a filter cake barrier that prevents direct fluid loss into the formation while maintaining the beneficial non-damaging properties of VES fluids. The particulates act as a bridge that controls fluid loss without requiring the fluid to build a traditional polymer filter cake.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the VES fluid system by adding particulate agents with specific properties (size, concentration, composition). This changes the fluid's interaction with the reservoir matrix, enabling fluid loss control through filter cake formation rather than relying on the fluid's inherent viscosity alone. The parameter changes allow the fluid to maintain its excellent rheological properties while gaining fluid loss control capability.
2Object-affected harmful factors
If VES-gelled fluids do not form a filter cake, then the fluids leave no potentially damaging polymer cake residue, but the same property results in significantly higher fluid leakage into the reservoir matrix
Solution Approach 1:
The patent uses particulate fluid loss control agents as mediators that form the filter cake barrier instead of the VES polymer itself. This intermediary approach allows the fluid to control leakage without the polymer forming a damaging residue on the formation face. The particles perform the filter cake-building function while the VES fluid maintains its non-damaging characteristics.
Solution Approach 2:
The patent segments the filter cake formation function from the VES polymer by introducing separate particulate agents. Rather than relying on the polymer to form both the gelled structure and the filter cake, the system divides these functions: the VES provides rheological control and the particulates provide fluid loss control through filter cake formation. This segmentation resolves the contradiction between not forming a damaging polymer cake and controlling fluid leakage.
3Loss of substance
If particles are added to VES-gelled fluids to control fluid loss, then fluid loss is reduced, but the particles may plug pore throats and cause formation damage
Solution Approach 1:
The patent carefully controls critical parameters of the particulate agents including particle size, size distribution, concentration, and composition. By optimizing these parameters, the system achieves fluid loss control while minimizing the risk of pore throat plugging. The particle size is selected to be large enough to form an effective filter cake barrier but small enough to avoid severe plugging, and the concentration is optimized to provide sufficient filter cake without excessive particle loading that could cause damage.
Solution Approach 2:
The patent applies the concept of local quality by ensuring the particulate agents have specific properties suited for their location and function in the fluid system. The particles are designed with characteristics appropriate for forming a filter cake at the fracture face while considering the local conditions of the reservoir matrix. This localized optimization of particle properties helps achieve fluid loss control without causing pore throat plugging in the formation.
Data Source
AI summary
Fluids viscosified with viscoelastic surfactants (VESs) may have their fluid loss properties improved with the presence of at least one mineral oil in combination with at least one particulate fluid loss control agent that may be an alkaline earth metal oxides, alkaline earth metal hydroxides, transition metal oxides, transition metal hydroxides, and mixtures thereof. The mineral oil may initially be dispersed oil droplets in an internal, discontinuous phase of the fluid. In one non-limiting embodiment, the mineral oil is added to the fluid after it has been substantially gelled. The particulate fluid loss control agent may be added in any order relative to the VES and the mineral oil fluid loss control agent. The mineral oil may enhance the ability of a particulate fluid loss control agent to reduce fluid loss. The presence of the mineral oil may also eventually reduce the viscosity of the VES-gelled aqueous fluid.