Managed Pressure Drilling Heave Compensation
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Solution Overview
Problem
Managed pressure drilling systems on floating drilling platforms face inaccuracies due to heave motion compensation, which changes the effective length of the drill string and fluid return line, affecting pressure measurements and calculations.
Innovation Solution
A method that involves pumping fluid at a determined rate into the drill string, measuring fluid pressure in the discharge line, and using hydraulic models and rheological properties to adjust wellbore pressure, accounting for changes in the platform's elevation, with a backpressure system controlled by time derivatives of pressure measurements to maintain a selected pressure value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If heave motion compensation is applied to maintain axial force on the drill bit during floating platform operations, then the stability of drilling operations is improved, but the accuracy of pressure measurements and calculations deteriorates due to changes in the effective length of the fluid return line
Solution Approach 1:
The system dynamically adjusts the measured pressure value based on the real-time change in length of the fluid discharge line caused by heave motion. The controller continuously monitors the platform's vertical displacement and modifies the pressure calculation accordingly, transforming a static pressure measurement system into a dynamic one that adapts to changing operational conditions.
Solution Approach 2:
The invention changes the parameter being measured by adjusting the measured pressure value to account for the variable length of the fluid discharge line. Instead of measuring pressure at a fixed reference point, the system modifies the pressure parameter based on the platform's elevation changes, ensuring accurate pressure control despite varying line lengths.
2Adaptability or versatility
If the length of the fluid discharge line is allowed to vary with platform elevation, then the adaptability of the drilling system to floating conditions is improved, but the reliability of pressure control deteriorates due to incorrect pressure inferences
Solution Approach 1:
The system employs feedback by continuously monitoring the actual pressure in the wellbore and comparing it with the setpoint pressure. The controller uses this feedback information, along with the measured change in fluid discharge line length, to automatically adjust the backpressure control valve and maintain accurate pressure control despite varying line lengths caused by platform heave motion.
Solution Approach 2:
The invention replaces direct mechanical pressure measurement at the wellbore with a calculated pressure value derived from surface pressure measurements and hydraulic modeling. This substitution allows the system to maintain reliable pressure control while adapting to varying discharge line lengths, as the calculated pressure accounts for the changing column height without requiring additional downhole sensors.
3Manufacturing precision
If backpressure control is used to maintain selected wellbore pressure, then the precision of pressure control is improved, but the complexity of the control system increases due to real-time adjustments for heave motion
Solution Approach 1:
The controller performs multiple functions: it monitors platform elevation, calculates the change in fluid discharge line length, measures surface pressure, determines the corrected wellbore pressure using hydraulic models, and controls the backpressure valve. By consolidating these functions into a single multi-functional control system, the invention achieves precise pressure control while minimizing the number of separate components required.
Solution Approach 2:
The invention introduces an intermediary calculation step that determines the change in length of the fluid discharge line based on platform elevation measurements. This intermediary value serves as a bridge between the physical heave motion and the pressure control mechanism, allowing the system to maintain precision without requiring direct mechanical coupling between the platform position sensors and the pressure control valve.
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
This approach ensures accurate wellbore pressure control, accounting for heave motion, thereby maintaining stable drilling operations on floating platforms by dynamically adjusting the backpressure system in real-time.
Implementation Method 1
using drilling fluid that is less dense than that needed to produce a hydrostatic fluid pressure sufficient to prevent fluid entry into the wellbore from permeable rock formations as a result of naturally-occurring fluid pressure
Implementation Method 2
pumping drilling fluid at a selected rate through a drill string to increase its equivalent hydrostatic pressure in the wellbore
Implementation Method 3
a backpressure system controlled by time derivatives of pressure measurements to maintain a selected pressure value
Data Source
AI summary
A method for maintaining pressure in a wellbore drilled from a drilling platform floating on a body of water includes the steps of pumping fluid at a determined flow rate into a drill string disposed in a wellbore and measuring fluid pressure within a fluid discharge line of fluid returning from the wellbore. The fluid discharge line has a variable length corresponding to an elevation of the floating platform above the bottom of the body of water. The wellbore pressure is determined at a selected depth in the wellbore or at a selected position along a drilling riser or variable length portion of the fluid discharge line using known parameters/methods. The determined wellbore pressure is adjusted for changes in length of the fluid discharge line corresponding to changes in the elevation of the floating platform relative to the bottom of the body of water. A backpressure system may be operated to maintain the adjusted determined wellbore pressure at a selected (or set point) value by applying backpressure to the wellbore.