Formation Pressure Testing with Drawdown-Buildup Flow Validation
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Solution Overview
Problem
Formation testing tools face challenges in low-mobility reservoirs due to long equilibration times, which increase rig time and risk of tool sticking, and existing pressure measurements are affected by fluid mobility and compressibility changes, leading to inaccurate data.
Innovation Solution
A system and method for obtaining representative formation pore pressure and mobility by performing a series of pressure pre-tests, analyzing pressure changes during drawdown and buildup periods using statistical analysis and denoising techniques, and ensuring the pressure drop during drawdown equals the total pressure increment during buildup to validate accurate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If formation testing tools are used in low-mobility reservoirs, then formation pore pressure and mobility can be measured, but equilibration time increases significantly
Solution Approach 1:
The patent applies preliminary action by performing a drawdown period before the buildup measurement. During the drawdown period, fluid is pumped from the formation to create a pressure difference, which accelerates the equilibration process. This preliminary action prepares the system for faster subsequent measurement during the buildup period, resolving the contradiction between measurement accuracy and time consumption in low-mobility reservoirs.
2Reliability
If prolonged equilibration is performed to ensure accurate measurements, then data quality improves, but rig time and risk of tool sticking increase
Solution Approach 1:
The drawdown period serves as a preliminary action that accelerates equilibration by creating a pressure gradient. This allows the buildup period to reach equilibrium faster, improving data quality while reducing the total time the tool must remain stationary, thereby reducing rig time and the risk of tool sticking.
Solution Approach 2:
The patent uses periodic action by alternating between drawdown (fluid removal) and buildup (fluid return) periods. This periodic pumping action creates repeated pressure cycles that accelerate the equilibration process compared to passive waiting, thus improving productivity without sacrificing data reliability.
3Measurement precision
If pressure measurements are taken during drawdown and buildup, then formation mobility can be calculated, but fluid mobility and compressibility changes affect measurement accuracy
Solution Approach 1:
The patent applies feedback by continuously monitoring pressure during both drawdown and buildup periods and using this information to calculate formation mobility. The system measures pressure at multiple time points and uses the pressure transient response to determine formation properties, compensating for fluid mobility and compressibility effects through mathematical analysis of the pressure data.
Solution Approach 2:
The patent changes parameters by performing measurements at different pressure conditions (drawdown and buildup phases). By analyzing pressure transients under varying pressure gradients and flow rates, the system can separate the effects of fluid mobility and compressibility from the formation properties, improving measurement accuracy through parameter variation and 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
This approach enhances the accuracy of formation pore pressure and mobility measurements by minimizing the influence of well operations and fluid mobility, reducing the need for prolonged equilibration times and improving data reliability.
Implementation Method 1
activating the pump, wherein a formation fluid is drawn in through the at least one probe into the at least one probe channel and the at least one fluid passageway by the pump and increasing pressure with the at least one fluid passageway
Implementation Method 2
measuring the pressure in the at least one fluid passageway by a pressure sensor
Implementation Method 3
activating the at least one stabilizer, wherein the at least one stabilizer is activated into a surface of the wellbore
Implementation Method 4
activating the at least one probe, wherein the at least one probe is activated into a mudcake, wherein the mudcake is disposed on the surface of the wellbore
Data Source
AI summary
Disclosed herein are systems and methods to obtain representative formation pore pressure and formation mobility from pressure measurements with a formation testing tool. One of the methods for performing a pressure test includes measuring the pressure in the fluid passageway by a pressure sensor, performing a pre-test with the pressure sensor, measuring the drawdown pressure, measuring the buildup pressure, performing another pre-test when the drawdown pressure is superior to the buildup pressure, and validating a formation flow when the drawdown pressure is equal to the buildup pressure, wherein a measured pressure obtained at an asymptote of a pressure curve after the buildup pressure corresponds to the formation pore pressure.