Downhole Probe Pressure Measurement via Flow Line Volume Variation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current wireline formation testing tools face challenges in accurately measuring pressure and mobility of fluid in subterranean formations, particularly due to issues with mud cake seals in over- and under-balanced drilling methods, which affect the reliability of drawdown and build-up procedures.
Innovation Solution
A downhole tool with a probe body that includes a pressure sensor and an electrical motor actuator to vary the volume of a flow line, allowing for effective sealing and measurement of fluid pressure, and enabling the determination of formation mobility through drawdown and build-up procedures, even in the absence of a mud cake seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a deformable packer is pushed against the mud cake to provide a seal, then fluid isolation between the borehole and formation is improved, but the reliability of pressure measurement deteriorates due to mud cake seal breakdown during drawdown
Solution Approach 1:
The patent introduces a mud cake seal as an intermediary sealing mechanism between the packer and the formation. The mud cake seal allows the tool to achieve initial isolation without requiring excessive packer force, and its controlled breakdown during drawdown provides a natural indicator of fluid communication establishment, resolving the contradiction between maintaining seal integrity and enabling accurate pressure measurement.
2Ease of operation
If the pretest piston is retracted to expand flow line volume and break the mud cake seal, then fluid communication between the flow line and formation is established, but the fluid pressure drops below formation pressure causing loss of formation fluid
Solution Approach 1:
The patent applies partial action by retracting the pretest piston only to the extent necessary to break the mud cake seal and establish fluid communication, rather than fully expanding the flow line volume. This controlled partial expansion achieves the goal of establishing communication while minimizing formation fluid loss by avoiding excessive pressure reduction.
3Reliability
If the probe is pressed against the mud cake on the borehole wall, then the seal between the probe and borehole wall is improved, but the complexity of the sealing mechanism increases
Solution Approach 1:
The patent employs a self-sealing probe mechanism that automatically conforms to and seals against the irregular surface of the mud cake through elastic deformation of the probe body. This self-service sealing approach eliminates the need for complex adjustable sealing components or multiple sealing elements, achieving reliable sealing while minimizing device complexity.
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 measurement of formation pressure and mobility, providing two types of mobility data - drawdown and spherical mobility - which characterize the formation's properties both near the wellbore and deeper, improving the reliability of fluid analysis in various drilling conditions.
Implementation Method 1
A pressure sensor measures fluid pressure of the flow line
Implementation Method 2
A piston and an electrical motor actuator that moves the piston in order to vary volume of the flow line
Implementation Method 3
an electrical motor actuator that moves the piston in order to vary volume of the flow line
Data Source
AI summary
An apparatus, method and system are provided for characterizing fluid trapped in a subterranean formation using a downhole tool that includes an elongated body and a probe body. The probe body is moveable from and back into the elongated body. The probe body defines a flow line and supports a pressure sensor for measuring fluid pressure in the flow line, a piston and an electrical motor actuator that is adapted to move the piston in order to vary volume of the flow line. The integral electrical motor actuator, piston, pressure sensor and flow line of the probe body can provide for measurement of formation pressure and/or formation mobility.