Integrated Well Logs for Uninvaded-Zone Water Saturation Estimation
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Solution Overview
Problem
Conventional methods for determining water saturation in the uninvaded zone of a formation require lengthy laboratory core measurements, which are not standardized and do not account for downhole conditions, leading to variations in measurement results and limited depth representation.
Innovation Solution
A method and system using well logging measurements at multiple depths to determine petrophysical parameters such as cementation and saturation exponents, along with water resistivity, to quantify water saturation in the uninvaded zone without external input or laboratory measurements, employing algorithms and physical models like Archie's and Waxman-Smith equations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laboratory core measurements are used to determine water saturation, then measurement precision may be improved, but measurement time and productivity deteriorate significantly
Solution Approach 1:
The patent replaces mechanical laboratory core measurements with electromagnetic well logging measurements taken during drilling operations. Multiple well logs (resistivity, neutron, density, sonic) are acquired in-situ and processed through petrophysical models to determine water saturation, eliminating the need for time-consuming laboratory analysis while maintaining measurement accuracy.
Solution Approach 2:
The patent performs water saturation measurements preliminarily during the drilling process itself, before laboratory core analysis would be conducted. By acquiring multiple well logs in real-time and processing them through automated algorithms, the measurement is completed upfront, eliminating subsequent laboratory processing time.
2Measurement precision
If laboratory core measurements are used, then detailed formation properties can be obtained, but the measurements do not represent downhole conditions and show limited depth representation
Solution Approach 1:
The patent allows the formation itself to provide the measurement data through well logging tools that interact directly with the formation in its natural downhole state. The formation's electrical, nuclear, and acoustic properties are measured in-situ, allowing the formation to 'self-report' its characteristics under actual downhole conditions rather than requiring extraction and laboratory analysis.
Solution Approach 2:
The patent transitions from limited-depth core sample analysis to multi-depth well logging measurements that sample the formation continuously over extended vertical intervals. Multiple logging tools measure different physical properties simultaneously, providing a multi-dimensional characterization of formation properties across various depths and radial distances from the wellbore.
3Productivity
If conventional well logging methods are used, then measurement speed is improved, but measurement precision and reliability deteriorate due to lack of multiple parameter integration
Solution Approach 1:
The patent merges multiple well logging measurements (resistivity, neutron porosity, density porosity, sonic transit time) into a unified petrophysical analysis framework. By integrating these complementary measurements and processing them through combined algorithms and physical models, the system achieves both rapid measurement and high precision water saturation determination that neither method could achieve alone.
Solution Approach 2:
The patent creates a composite measurement approach by combining data from multiple logging tools and measurement types. This composite methodology integrates electrical resistivity data with porosity measurements from neutron, density, and sonic tools, producing a more reliable and accurate water saturation estimate than any single measurement type could provide.
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
Efficiently quantifies water saturation in the uninvaded zone using well logging data, reducing reliance on laboratory measurements and providing accurate, consistent results across varying formation depths.
Implementation Method 1
obtain well log data, which includes resistivity, neutron, density and/or sonic measurements
Implementation Method 2
obtain well log data, which includes resistivity, neutron, density and/or sonic measurements
Implementation Method 3
obtain well log data, which includes resistivity, neutron, density and/or sonic measurements
Implementation Method 4
obtain well log data, which includes resistivity, neutron, density and/or sonic measurements
Implementation Method 5
The resistivity Rxo governs the electric current responses of the formation in the flushed zone, which is dominated by the electric conduction through the water that saturates the pore space of the flushed zone
Data Source
AI summary
Methods and systems are provided characterizing a formation traversed by a wellbore, wherein the formation includes at least a flushed zone and an uninvaded zone, which involve obtaining well log data based on plurality of different well log measurements of the formation at multiple depths in the wellbore. The well log data is used to a computational model that solves for a set of petrophysical parameters that characterize a portion of the formation corresponding to the multiple depths in the wellbore, wherein the set of petrophysical parameters include a cementation exponent, a saturation exponent, and a flushed zone water resistivity. The solved-for set of petrophysical parameters can be used to determine a value of water saturation of the uninvaded zone for the portion of the formation corresponding to the multiple depths in the wellbore.