Downhole Pressure Sensor TVD Determination
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Solution Overview
Problem
Current methods for determining true vertical depth (TVD) in wells are prone to errors due to intentional or unintentional wellbore curves, leading to inaccuracies that can be costly and dangerous, especially in high-pressure or gas formations, and require multiple survey stations accumulating errors over depth.
Innovation Solution
A method and apparatus using a pressure sensor positioned at a downhole location within a well, measuring pressure exerted by a fluid column, and applying hydrostatic equations, specifically Bernoulli's Equation, to calculate TVD, potentially using a single survey station to minimize errors and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple survey stations are used to calculate TVD, then the wellbore curvature can be accounted for, but measurement precision deteriorates due to error accumulation over depth
Solution Approach 1:
The patent replaces the mechanical surveying system (multiple survey stations with inclination and azimuth measurements) with a pressure-based measurement system. By using a pressure sensor to measure hydrostatic pressure at a single location, the system substitutes complex mechanical measurements with a simpler pressure measurement that directly yields TVD through hydrostatic equations, eliminating error accumulation inherent in multiple survey stations.
Solution Approach 2:
The patent extracts the TVD calculation from the complex multi-parameter surveying process and isolates it to a single pressure measurement. By taking out the TVD determination from the bundle of measurements (inclination, azimuth, multiple survey stations) and calculating it independently through pressure data, the system eliminates the error propagation that occurs when combining multiple measurements.
2Ease of operation
If conventional survey methods are used, then well placement can be determined, but harmful factors increase due to errors in high-pressure or gas formations
Solution Approach 1:
The patent replaces conventional mechanical surveying methods with a pressure-based measurement approach. By using pressure sensors to directly measure hydrostatic pressure, the system avoids the harmful errors associated with mechanical surveying in high-pressure or gas formations, while still enabling accurate well placement determination through the hydrostatic equation.
3Measurement precision
If pressure sensor measurement method is used, then measurement precision improves by reducing errors, but device complexity increases due to pressure sensor deployment requirements
Solution Approach 1:
The patent makes the pressure sensor deployment system multi-functional by using the same tubing string for both fluid circulation and pressure measurement. The tubing string serves dual purposes: as a medium for circulating fluid to establish hydrostatic pressure conditions and as a conduit for delivering the pressure sensor to the measurement location, thereby reducing overall system complexity despite the specialized pressure measurement capability.
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 allows for more accurate and reliable determination of TVD with reduced uncertainties, enhancing well placement, reservoir dimensioning, and resource recovery by minimizing errors associated with inclination, azimuth, and measured depth calculations.
Implementation Method 1
measuring, with the pressure sensor, a pressure exerted by the fluid column
Implementation Method 2
applying hydrostatic equations, specifically Bernoulli's Equation, to calculate TVD
Data Source
AI summary
A method of determining true vertical depth within a well penetrating a ground surface, the method including: positioning a pressure sensor at a downhole position within the well at the base of a fluid column extended from a ground surface to the pressure sensor; measuring, with the pressure sensor, a pressure exerted by the fluid column; and determining the true vertical depth (TVD) of the downhole position using the pressure measured by the pressure sensor. An apparatus for determining true vertical depth within a well, the apparatus including: a tubing string; a housing connected to the tubing string, the housing defining a chamber and having a port to the tubing string; a pressure sensor mounted to the housing and in fluid communication with the chamber.