Downhole Fluid Density Measurement for Vertical Distance Precision
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for measuring bulk density in boreholes using gravity measurements are limited by precision issues related to vertical distance calculations, particularly for large distances, due to factors like cable stretch, casing section variability, and inhomogeneous fluid density, leading to inaccuracies in bulk density calculations.
Innovation Solution
A method involving continuous fluid density measurements and differential pressure measurements is employed to calculate the vertical distance between two points in a borehole, using equations that account for varying fluid density and inclination, enabling more accurate bulk density calculations by averaging fluid density over the interval between measurement stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If vertical distance is calculated using cable stretch and casing section measurements, then the measurement can be obtained, but the precision deteriorates for large distances
Solution Approach 1:
The patent replaces mechanical measurement systems (cable stretch measurements, casing section variability) with a fluid pressure-based measurement system. By measuring fluid pressure at two different stations and using the pressure differential to calculate vertical distance, the system eliminates errors associated with mechanical cable stretch and casing section variations, thereby maintaining high precision even for large borehole separations.
Solution Approach 2:
The patent introduces fluid (drilling fluid or formation fluid) as an intermediary medium to transfer measurement information from the borehole environment to the measurement device. The fluid column acts as a mediator that transmits pressure information from different depths, allowing indirect measurement of vertical distance through pressure differential rather than direct mechanical measurement.
2Measurement precision
If bulk density calculation uses gravity measurements, then the bulk density can be determined, but the calculation becomes inaccurate when fluid density is inhomogeneous
Solution Approach 1:
The patent performs preliminary measurement of fluid density at multiple stations along the borehole before conducting the bulk density calculation. By measuring fluid density at various points (using the same pressure-based methodology), the system obtains accurate fluid density values that account for inhomogeneity, which are then used to correct or adjust the bulk density calculation from gravity measurements.
Solution Approach 2:
The patent uses fluid density measurements obtained through pressure differential measurements as feedback to improve the bulk density calculation. The measured fluid density values are fed back into the bulk density calculation process to compensate for inhomogeneity effects, thereby improving the overall accuracy of the formation evaluation.
3Measurement precision
If vertical distance measurement accounts for inclination, then the measurement accuracy improves, but the calculation complexity increases
Solution Approach 1:
The patent replaces complex geometric calculations involving inclination angles with a simpler fluid pressure-based measurement system. By measuring pressure differential in the fluid column and using the known relationship between pressure, density, and vertical height (ΔP = ρgΔh), the system directly obtains vertical distance without needing to perform complex trigonometric calculations based on inclination measurements.
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 enhances the accuracy of bulk density calculations by compensating for fluid density variations and inclination, providing precise vertical distance measurements even for large borehole separations, thus improving the reliability of reservoir evaluation in hydrocarbon exploration.
Implementation Method 1
a fluid density measurement device in the downhole tool measures a plurality of fluid density values of the fluid within the borehole between the first and second stations
Implementation Method 2
a pressure sensor in the downhole tool measures a fluid pressure value at a current depth of the downhole tool
Implementation Method 3
gravity measurements may be used to map out the vertical distribution of oil and gas in a borehole by enabling the calculation of the bulk density of an area adjacent to the downhole tool based in part on relatively minute gravity changes
Data Source
AI summary
A system and method for use in a downhole tool having a fluid density measurement device positioned therein are provided. In one example, the method includes deploying the downhole tool at a first station in a borehole. The downhole tool is moved from the first station to a second station in the borehole. A plurality of fluid density values of fluid within the borehole between the first and second stations are measured using the fluid density measurement device in the downhole tool. The plurality of fluid density values may represent a continuous log of fluid densities between the first and second stations.