Borehole Gravimeter Compaction Estimation
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Solution Overview
Problem
Current methods for measuring subsidence and compaction in subterranean formations are limited by the inaccuracy of wireline tools and the inability to operate below the surface for GPS-based measurements, and existing methods require invasive instruments or radioactive markers.
Innovation Solution
A method using a gravimeter to measure gravitational forces at multiple locations within a wellbore over time, comparing initial and later gravity values to estimate compaction and subsidence without invasive instruments or radioactive markers, considering changes in porosity and fluid density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wireline tools with multiple detectors are used to measure distance between markers, then measurement capability is provided, but the inherent elasticity of wireline reduces measurement accuracy
Solution Approach 1:
The patent replaces the mechanical wireline measurement system with a gravitational field-based measurement system. Instead of using physical detectors on elastic wireline to measure marker distances, the invention uses gravimeters to measure gravitational acceleration at different depths and calculates compaction from gravity differences. This substitution eliminates the elasticity problem inherent in mechanical wireline systems.
2Measurement precision
If GPS receivers are used to measure subsidence at the surface, then subsidence measurement is provided, but GPS cannot operate below the surface
Solution Approach 1:
The patent creates a universal measurement system using gravimeters that can operate both at the surface and below the surface in boreholes. The gravitational field measurement capability works across all depth ranges, eliminating the limitation where GPS only works at the surface. The system measures gravity at multiple depths and uses these measurements to calculate both surface subsidence and subsurface compaction.
3Reliability
If markers are implanted in the formation to detect subsidence and compaction, then detection capability is provided, but invasive instruments and radioactive markers are required
Solution Approach 1:
The patent extracts the measurement function from physical markers implanted in the formation and relocates it to gravitational field measurements taken at borehole locations. Instead of inserting radioactive bullets or physical markers into the formation, the system measures the gravitational field around the borehole and calculates compaction from changes in gravity differences. This removes the harmful invasive elements while maintaining detection reliability.
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
Enables accurate measurement of compaction and subsidence rates within the formation without surface contact or invasive tools, allowing for precise monitoring of formation changes over varying intervals.
Implementation Method 1
A method using a gravimeter to measure gravitational forces at multiple locations within a wellbore over time
Implementation Method 2
comparing initial and later gravity values to estimate compaction and subsidence
Data Source
Figure 1~2
Figure 3
Figure 4A~4B
AI summary
A method of estimating compaction of a subterranean formation (12) with gravity measurements. The free air gradient at surface (S) is measured and compared with gravity measured in a borehole (10) that intersects the formation (12). At a later point in time, values for gravity are re-measured, differences between the measured values at the initial point in time, and the later point in time are estimated. The differences are used to estimate the compaction. A gravimeter (20) can be used for measuring gravity, markers (221,222) in the formation (12) can be used in conjunction with the gravimeter (20).