Pressure Transient Analysis for Accurate Well Permeability Testing
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Solution Overview
Problem
Existing techniques for assessing hydrocarbon reservoir characteristics, such as permeability, are often unreliable and impractical due to their reliance on time-consuming and costly methods like laboratory assessments and well logging, and may provide inaccurate results depending on measurement conditions.
Innovation Solution
Conducting pressure transient tests, including build-up or draw-down tests, and analyzing bottomhole pressure data using time function superposition and derivative calculations to determine reservoir characteristics like permeability, enabling more accurate assessments through semi-log and log-log plots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laboratory assessment of rock samples or well logging is used to determine reservoir permeability, then permeability can be estimated, but the process becomes time-consuming and costly
Solution Approach 1:
The patent extracts the essential measurement function from complex laboratory and logging procedures by using simple pressure transient testing combined with derivative analysis. Instead of running logging tools along the wellbore or conducting laboratory core analysis, the method extracts permeability information directly from pressure measurements taken during well testing, eliminating the need for separate logging operations or core sample extraction.
Solution Approach 2:
The patent replaces mechanical and complex measurement systems (logging tools, laboratory equipment) with a simplified pressure measurement system. By substituting complex physical interventions with pressure transient testing and mathematical derivative analysis, the method achieves permeability determination without requiring sophisticated logging equipment or laboratory facilities.
2Ease of operation
If pressure measurements are taken during well testing to determine permeability, then the test procedure becomes simpler and data is more available, but the determinations may be inaccurate due to dependency on measurement conditions and processing methods
Solution Approach 1:
The patent transforms the analysis by changing from direct pressure measurement interpretation to derivative-based analysis. By calculating first and second derivatives of pressure with respect to time, the method transforms the measurement parameters to eliminate dependencies on specific measurement conditions and processing methods, thereby improving accuracy while maintaining operational simplicity.
Solution Approach 2:
The patent incorporates feedback mechanisms through iterative derivative calculations and trend analysis. The method uses the calculated derivatives to continuously refine permeability estimates by comparing observed pressure behavior with expected theoretical responses, allowing the system to self-correct for measurement condition variations and processing method differences.
3Reliability
If traditional pressure transient testing methods are used, then permeability can be determined from pressure trends, but the results are unreliable due to dependency on measurement conditions and processing methods
Solution Approach 1:
The patent segments the pressure transient analysis into distinct derivative orders (first derivative and second derivative). This segmentation allows each derivative level to address specific aspects of reservoir behavior independently, improving reliability by isolating different physical phenomena and reducing the impact of measurement condition dependencies on the overall results.
Data Source
AI summary
Techniques for developing a hydrocarbon reservoir that include: obtaining, by way of a downhole pressure sensor of a hydrocarbon well, pressure transient test data that reflects prior changes in the flow rates corresponding to measurements of bottomhole pressure across a given interval of time during pressure transient testing of the well, conducting, for the pressure data points, a time function superposition that includes application of a superposition time function to generate superposition times for the measurements of pressure across the interval, determining, based on the superposition times and corresponding measurements of pressure, first order derivative (FOD) values for the measurements of pressure across the interval, determining, based on the FOD values for the measurements of pressure, second order derivative (SOD) values for the measurements of pressure across the interval, and generating a log plot of the SOD values for the measurements of pressure across the interval of time.