Shear Stress Calculation for Drilling Fluids Without Viscometers
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Solution Overview
Problem
Conventional rotational viscometers fail to accurately measure shear stress at bottom-hole conditions due to memory retention, temperature and pressure variations, calibration errors, and limitations in measuring non-Newtonian behaviors of aqueous and non-aqueous drilling fluids, leading to unrealistic rheological data in drilling operations.
Innovation Solution
A system utilizing sensors and modules to calculate shear stress at any given shear rate for both aqueous and non-aqueous muds independently, without relying on rotational viscometer data, by detecting real-time drilling parameters and employing multivariate linear regression models to account for unique rheological behaviors of each mud type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rotational viscometer measurements are used to determine shear stress of drilling fluids, then rheological data can be obtained, but measurement accuracy deteriorates due to memory retention, temperature and pressure variations, and calibration errors
Solution Approach 1:
The patent replaces the mechanical rotational viscometer measurement system with a computational model that calculates shear stress using drilling parameters (flow rate, pump pressure, annular velocity) and fluid properties. This substitution eliminates mechanical measurement errors while maintaining the ability to determine rheological behavior under actual bottom-hole conditions.
Solution Approach 2:
The patent changes the approach from direct mechanical measurement to computational determination by transforming the measurement problem into a parameter-based calculation. By using readily available drilling parameters and fluid properties as inputs to mathematical models, the system achieves accurate shear stress determination without the limitations of rotational viscometers.
2Ease of operation
If a single rheological model is used for both aqueous and non-aqueous drilling fluids, then measurement simplicity is maintained, but measurement accuracy deteriorates due to ignoring fundamental structural differences between the two fluid types
Solution Approach 1:
The patent segments the drilling fluid population into two distinct categories (aqueous and non-aqueous) and applies separate rheological models to each. This segmentation recognizes that water-based and oil-based fluids have fundamentally different structures and flow behaviors, requiring different mathematical representations for accurate characterization.
Solution Approach 2:
The patent applies local quality by tailoring the rheological model selection to the specific type of drilling fluid being analyzed. Each fluid type receives a model appropriate to its characteristics, ensuring that the measurement approach is optimized for the local properties of the fluid rather than applying a one-size-fits-all method.
3Reliability
If laboratory viscometer measurements are performed under controlled conditions, then measurement consistency is achieved, but adaptability to actual bottom-hole conditions deteriorates
Solution Approach 1:
The patent introduces dynamics by making the shear stress calculation adaptable to varying bottom-hole conditions through the use of actual drilling parameters (flow rate, pump pressure, annular velocity) as inputs. The computational model dynamically adjusts to different operating conditions, unlike static laboratory measurements that are performed under fixed, controlled conditions.
Solution Approach 2:
The patent uses mathematical models and computational algorithms as intermediaries to bridge the gap between controlled laboratory measurements and actual bottom-hole conditions. These intermediaries transform readily available drilling data into accurate shear stress values that reflect real downhole environments, eliminating the need for complex high-temperature high-pressure laboratory testing.
Data Source
AI summary
A system and a method for calculation of a shear stress at any given shear rate for an aqueous and a non-aqueous mud separately at bottom hole conditions without using rotational viscometer data. The system includes one or more sensors to identify drilling parameters, and three key modules namely for calculating data constants, selecting shear rate, and calculating shear stress. The disclosed system and method significantly enhances the control and management of drilling fluids. The system's effectiveness is demonstrated through the encompassing of a wide spectrum of real-time drilling conditions, including fluid type, temperature, mud composition, and more. Employing specific formula constants for each mud type and accommodating varying shear rates, the system ensures precise calculations. Overall, this system is poised to revolutionize drilling fluid management and analysis.