Downhole Fluid Dielectric Estimation Under Filtrate Contamination
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Solution Overview
Problem
Existing methods struggle to accurately estimate the dielectric properties of connate fluids in borehole drilling operations due to contamination from filtrate fluids, which complicates the interpretation of electrical logs and formation water salinity estimation.
Innovation Solution
A method and system for estimating dielectric properties of connate fluids by measuring a mixture of filtrate and connate fluids, adjusting the volume ratio, and comparing the measurements to reference profiles to determine the connate fluid's properties without separating the fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dielectric measurements are performed on downhole fluid mixture, then formation water evaluation can be conducted, but measurement precision deteriorates due to filtrate fluid contamination
Solution Approach 1:
The patent changes the volume ratio parameter of the fluid mixture by injecting additional filtrate fluid to create multiple measurements at different volume ratios. This allows the system to overcome the harmful effect of contamination by using parameter variation to extract accurate connate fluid properties through comparison with reference profiles.
Solution Approach 2:
The patent implements a feedback mechanism where measurements at different volume ratios are compared against reference profiles to iteratively estimate the dielectric properties of connate fluid. The system uses the measured data to refine the estimation until convergence, thereby overcoming the initial contamination effect.
2Measurement precision
If fluid separation is performed to obtain pure connate fluid, then measurement precision improves, but device complexity and operation difficulty increase
Solution Approach 1:
The patent extracts only the necessary information (dielectric properties of connate fluid) from the contaminated mixture without requiring physical separation of the fluids. By using dielectric measurements and reference profile comparison, the system obtains pure connate fluid properties while leaving the complex separation process unnecessary.
Solution Approach 2:
The patent introduces reference profiles as an intermediary between the contaminated measurements and the desired connate fluid properties. These reference profiles serve as a bridge that allows accurate estimation of pure connate fluid characteristics without requiring actual fluid purification.
3Measurement precision
If multiple measurements are performed at different volume ratios, then estimation accuracy of connate fluid properties improves, but loss of time increases due to additional filtrate injection and measurement cycles
Solution Approach 1:
The patent performs a limited number of measurements at different volume ratios - just enough to obtain accurate connate fluid properties through reference profile comparison, without excessive measurements that would unnecessarily extend the time required for the analysis.
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 estimation of connate fluid properties, such as salinity, without the need for fluid separation, improving the accuracy of formation water evaluation and reducing uncertainties in reservoir estimations.
Implementation Method 1
performing measurements of a dielectric property of the downhole fluid
Implementation Method 2
estimating the dielectric property by a mathematical model
Data Source
AI summary
A method of analyzing a downhole fluid includes performing measurements of a dielectric property of the downhole fluid, the downhole fluid including a mixture of a filtrate fluid circulated through a borehole and a connate fluid. The measurements include a first measurement of the downhole fluid, and one or more additional measurements, each additional measurement performed after an amount of the filtrate fluid is injected into the downhole fluid to change the volume ratio, each additional measurement performed when the downhole fluid has a different volume ratio. The method also includes acquiring a plurality of reference profiles of respective reference mixtures, the respective reference mixtures including a first fluid and a reference fluid, comparing the measurements to each reference profile, and estimating a value of the dielectric property of the connate fluid based on the comparing.