Hydraulic Model Tuning via Surface String Weight
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Solution Overview
Problem
Current hydraulic models used to estimate downhole pressure during drilling are inaccurate, especially for dynamic pressure, due to their reliance on uncertain variables and non-Newtonian fluid rheology, leading to potential dangerous situations like loss and kick if not managed properly.
Innovation Solution
A system and method that indirectly measures downhole pressure using string weight measurements to tune hydraulic models, incorporating a load cell to measure string tension and a basic hydraulic model describing pressure loss gradients, which is robust against model errors, allowing for more accurate estimates of dynamic pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If hydraulic models are used to estimate downhole dynamic pressure, then direct pressure measurement equipment is avoided, but the estimation accuracy deteriorates due to uncertain variables and non-Newtonian fluid rheology
Solution Approach 1:
The patent introduces an intermediary measurement approach by using surface string weight measurements as a mediator to infer downhole dynamic pressure. Instead of directly measuring pressure downhole or relying solely on complex hydraulic models, the system measures the weight of the drill string at the surface, which changes in response to downhole pressure conditions. This intermediary measurement provides a more accurate indication of downhole pressure while avoiding the need for complex direct measurement equipment.
Solution Approach 2:
The system implements feedback by continuously monitoring surface string weight measurements and using these measurements to tune and calibrate the hydraulic model. The measured weight data provides feedback on the actual downhole pressure conditions, allowing the model parameters to be adjusted and optimized for better accuracy. This feedback loop enables the system to improve its pressure estimation accuracy over time while maintaining operational simplicity.
2Measurement precision
If direct pressure measurement methods (MWD tool with mud pulse telemetry or wired pipe) are used, then downhole pressure measurement accuracy is improved, but device complexity and operational constraints increase
Solution Approach 1:
The patent uses surface string weight as an intermediary measurement that indirectly reflects downhole pressure conditions without requiring complex downhole instrumentation. The weight measurement taken at the surface serves as a proxy for downhole pressure, eliminating the need for MWD tools with telemetry systems or wired pipe configurations, thereby significantly reducing device complexity while providing sufficient measurement accuracy for operational decision-making.
Solution Approach 2:
The invention extracts the pressure measurement function from the downhole environment and relocates it to the surface by measuring string weight. Instead of embedding complex measurement and communication equipment downhole, the system extracts the essential pressure information through surface-weight measurements, which can be obtained using simple, well-established weighing equipment already present on drilling rigs.
3Ease of manufacture
If hydraulic models with uncertain variables are used to estimate dynamic pressure, then equipment installation is simplified, but reliability deteriorates due to model errors and non-Newtonian fluid behavior
Solution Approach 1:
The system uses feedback from surface weight measurements to continuously tune and calibrate the hydraulic model parameters. By comparing predicted versus actual weight changes during drilling operations, the model can be adjusted to account for non-Newtonian fluid behavior and other uncertain variables, thereby improving reliability while maintaining the simplicity of the measurement system.
Solution Approach 2:
The invention addresses model reliability by dynamically adjusting model parameters based on observed weight measurements. Instead of relying on fixed model parameters that may not account for varying fluid rheology, the system changes model parameters in response to actual operational data, improving the reliability of pressure estimates while keeping the system simple and easy to implement.
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
Provides more accurate estimates of downhole pressure, reducing the risk of dangerous drilling conditions by improving the accuracy of hydraulic model predictions, even when direct pressure measurements are not available.
Implementation Method 1
The system and method may include an accurate load cell measuring the string tension (weight) at the top of the string
Implementation Method 2
a basic hydraulic model describing how the pressure loss gradient varies with the annulus geometry
Implementation Method 3
The hydrostatic pressure can be calculated with a relatively high accuracy from the density of mud in the well bore trajectory and the true vertical depth
Data Source
AI summary
Disclosed is a method and system for tuning a hydraulic model to be used for estimating down hole dynamic pressure as a function of flow rate includes:a) selecting a non-tuned hydraulic model estimating the relative magnitude of the pressure losses in various annulus sections of the well bore;b) applying the non-tuned hydraulic model to give a first order estimate of the pressure gradients and the shear stresses at the drill string;c) applying the same non-tuned model to estimate the flow lift area for two different flow rates, where the first flow rate is zero or much lower than the second flow rate being substantially equal to a typical flow rate obtained during drilling; andd) performing a model tuning test where the string is rotated off bottom while said two different flow rates are used to obtain corresponding string weights.