X-Ray Reservoir Logging for Water-Oil Interface Detection
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Solution Overview
Problem
Current well logging techniques rely on radioactive isotopes for measuring formation density, which pose safety risks, regulatory challenges, and limitations in data acquisition speed due to attenuation by production liners, lacking a viable non-isotope based method for determining the water-oil interface and reservoir fluid ratios.
Innovation Solution
An x-ray based reservoir evaluation tool with a sonde section, x-ray source, radiation detectors, and electronics that illuminates the formation to measure density variations at the water-oil interface, compensates for production liner attenuation, and computes saturated formation density within the production interval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radioactive isotopes (such as Cesium-137) are used for measuring formation density, then gamma-ray fluence is sufficient for accurate measurement, but the amount of radiation is limited by regulation to 1.5 Ci which restricts logging speed
Solution Approach 1:
The patent changes the fundamental parameter of the radiation source from radioactive isotopes to an electronic x-ray generator. This allows control of x-ray tube current and voltage to adjust photon flux dynamically, enabling high-speed logging while maintaining measurement accuracy without being constrained by radioactive material regulations.
Solution Approach 2:
The patent replaces the mechanical/chemical radioactive decay system with an electronic x-ray generation system. The x-ray tube converts electrical energy directly into x-ray photons through electron bombardment of a target, providing a controllable, non-radioactive alternative that eliminates the inherent limitations of isotopic sources.
2Ease of manufacture
If radioactive isotopes are used for density logging, then gamma-rays are readily available for formation evaluation, but safety risks and regulatory challenges arise from handling and transporting radioactive materials
Solution Approach 1:
The patent extracts the harmful radioactive material component from the density logging system while retaining the useful function of gamma-ray generation for formation evaluation. The electronic x-ray source provides the necessary radiation without the safety and regulatory burdens of radioactive isotopes.
Solution Approach 2:
The patent employs an electronic x-ray tube that can be powered on and off as needed, replacing the long-lived radioactive isotope. This allows the system to be used only when necessary, eliminating ongoing safety concerns associated with transporting and handling radioactive materials.
3Reliability
If production liners are present in the wellbore, then well integrity is maintained, but they cause attenuation of gamma-rays reducing measurement quality
Solution Approach 1:
The patent changes the energy parameter of the x-ray beam by adjusting tube voltage to optimize penetration through the production liner. Higher energies are used when liner attenuation is significant, allowing the system to maintain measurement quality while the liner remains in place for well integrity.
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 and safe measurement of formation density at the water-oil interface without radioactive materials, improving data quality and operational efficiency by automating the detection of the interface and enhancing reservoir fluid ratio predictions.
Implementation Method 1
Compton scattering within the irradiated reservoir would result in returning gamma rays
Implementation Method 2
The number of Compton scattering collisions is related directly to the number of the electrons per unit volume, or electron density, within the formation
Data Source
AI summary
An x-ray-based reservoir evaluation tool for measurement variations in formation density anticipated at the water-oil interface of a reservoir is provided, the tool including at least: an internal length comprising a sonde section, wherein said sonde section further comprises an x-ray source; radiation measuring detectors; sonde-dependent electronics; and a plurality of tool logic electronics and PSUs. A method of using an x-ray based reservoir evaluation tool for measuring variations in formation density anticipated at the water-oil interface of a reservoir is also provided, the method including at least the following steps: using x-rays to illuminate the formation surrounding the cased borehole; uses detectors to directly measure the density of the formation; using detectors to directly measure the effects on the measurement from tool stand-off or production liner attenuation; and employing techniques for compensating for the production liner and liner-annular region when computing the saturated formation density within the production interval.