Self-Balancing Mixing Control for Well Service Fluids
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Solution Overview
Problem
Control systems for mixing and pumping in hydrocarbon well bore servicing face challenges in maintaining desired mixture composition and flow rates due to supply constraints and limited instrumentation, particularly in monitoring flow rates of powdered solids like cement, which can lead to quality control issues and operational uncertainties.
Innovation Solution
A control system comprising multiple actuators and a logic circuit that adjusts the discharge rate of a mixture flow stream based on material supply constraints, ensuring the desired properties and flow rates are maintained by controlling the flow rates of individual materials and the discharge rate, even in the absence of accurate flow rate measurements for solids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If solids flow meters are installed to monitor flow rates of powdered solids like cement, then measurement precision is improved, but device complexity and ease of repair worsen due to difficulty in servicing and calibration
Solution Approach 1:
The patent extracts the flow rate monitoring function from complex solids flow meters and replaces it with a simplified approach using readily available water flow meters combined with logical inference. The control system infers solids flow rate from water flow rate measurements and mixture properties, eliminating the need for difficult-to-service solids flow meters while maintaining adequate measurement capability
Solution Approach 2:
The patent introduces water flow rate as an intermediary measurement to indirectly determine solids flow rate. By measuring water flow and using logical relationships based on mixture composition and density, the system derives solids flow information without directly measuring it, thus avoiding the complexity of solids flow meters
2Reliability
If multiple actuators and logic circuits are added to self-balance the mixing process in response to supply constraints, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements feedback control where the logic circuit continuously monitors water flow rate, mixture density, and supply constraint conditions, then adjusts the discharge rate actuator to maintain desired mixture properties. This closed-loop feedback mechanism improves reliability by automatically compensating for supply variations without requiring complex multi-actuator systems
Solution Approach 2:
The control system performs self-balancing by automatically detecting supply constraints and adjusting discharge rate to maintain quality specifications. The logic circuit uses inferred information from available measurements to make autonomous control decisions, reducing the need for additional actuators and complex control architecture
3Productivity
If flow rate of mixture discharge is maintained at desired rate despite material supply constraints, then productivity is improved, but manufacturing precision worsens due to potential composition deviations
Solution Approach 1:
The patent implements dynamic control where the discharge rate is adjusted in real-time based on detected supply constraints and inferred mixture composition. The logic circuit dynamically balances productivity and quality by modulating discharge rate to maintain desired composition while maximizing flow, rather than maintaining a fixed discharge rate that would compromise quality during supply variations
4Device complexity
If limited instrumentation is used without accurate solids flow rate measurement, then device complexity is reduced, but measurement precision and reliability worsen
Solution Approach 1:
The patent uses water flow rate measurement as an intermediary to indirectly determine solids flow rate and detect supply constraints. By measuring water flow and combining this with density measurements and logical inference, the system achieves reliable quality control with simple instrumentation, avoiding the need for complex solids flow meters while maintaining measurement accuracy
Data Source
AI summary
Systems for controlling the in-feed and discharge rates of materials flowing into and out of a mixing process where one priority is to achieve a target mixture flow rate from the mixing process and another priority can be to achieve a target value for a mixture property. Actuators can be operated to control material in-feed rates, the mixture composition, and discharge rate, and can maintain a hold-up of the mixture in the mixing process. A total flow rate controller provides a control signal to a controller acting on the discharge rate and a controller acting on the in-feed rates. The mixture discharge flow rate can be automatically reduced from its desired target when the commanded rate of at least one of the materials exceeds its available supply rate as inferred from an inability to maintain the targeted value for the mixture property.