PDM Test Coupon for Downhole Condition Simulation
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Solution Overview
Problem
Conventional testing methods for subterranean positive displacement motors (PDMs) fail to accurately simulate downhole conditions, particularly cyclic loading stresses and elevated temperatures, and require large volumes of drilling fluid, making them costly and logistically challenging.
Innovation Solution
A miniaturized test apparatus using a partial length of a PDM power section test coupon within a sealed chamber, where the rotor and stator sections are independently rotatable, allowing for controlled differential rotation and braking torque application to simulate downhole conditions using a small volume of drilling fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ASTM immersion tests are used to evaluate PDM elastomer performance, then the testing procedure is simple and standardized, but the tests cannot accurately replicate cyclic loading stresses or elevated temperature and pressure conditions encountered in downhole service
Solution Approach 1:
The patent divides the full-scale PDM power section into a smaller test coupon containing essential components (rotor, stator, progressing cavity) that can be tested independently. This segmentation allows accurate simulation of downhole conditions without requiring complete PDM testing, thus improving reliability while controlling complexity.
Solution Approach 2:
The test apparatus is designed to perform multiple functions: it can apply cyclic loading stresses, maintain elevated temperatures and pressures, and simulate downhole environmental conditions all within a single integrated system. This multi-functionality improves simulation accuracy without proportionally increasing device complexity.
2Reliability
If flow loop testing is used to simulate downhole PDM service conditions, then comprehensive downhole environment simulation is achieved, but hundreds or thousands of gallons of drilling fluid are required making it costly and logistically challenging
Solution Approach 1:
The patent extracts only the essential power section components (rotor, stator, progressing cavity) from the complete PDM assembly to create a test coupon. This extraction eliminates the need for large volumes of drilling fluid while maintaining the ability to simulate downhole conditions, thus reducing fluid quantity from thousands of gallons to a minimal amount.
Solution Approach 2:
Instead of testing the complete PDM assembly with full-scale drilling fluid circulation, the patent uses a partial representation (test coupon) that contains only the necessary components to evaluate performance. This partial action achieves the essential testing objectives with dramatically reduced fluid requirements.
3Quantity of substance
If recirculating pump vessels are used to evaluate PDM performance, then less drilling fluid is required compared to flow loops, but the load ranges are limited which restricts the range of downhole environments that can be simulated
Solution Approach 1:
The test apparatus incorporates mechanisms to apply dynamic cyclic loading stresses to the test coupon, enabling simulation of varying downhole conditions. This dynamic capability allows the system to adapt to different loading scenarios and environmental conditions, improving versatility without requiring large fluid volumes.
Solution Approach 2:
The apparatus can vary testing parameters including temperature, pressure, and cyclic loading stresses to simulate different downhole environments. By changing these parameters, the system can evaluate PDM performance across a wide range of conditions while using minimal drilling fluid, thus improving adaptability without increasing fluid quantity.
4Reliability
If full-scale PDM dyno testing is performed, then complete downhole service simulation is achieved, but the specialized equipment and large drilling fluid volumes make it economically unviable for frequent testing
Solution Approach 1:
The patent creates a simplified copy (test coupon) of the full-scale PDM power section that retains the essential functional characteristics. This copy can be tested using a compact apparatus that is economically viable for frequent testing, while still providing reliable simulation of downhole conditions. The copy eliminates the need for expensive full-scale dyno equipment.
Solution Approach 2:
The test coupon serves as a disposable or reusable simplified representation of the PDM power section. Rather than investing in expensive full-scale testing equipment for frequent tests, the system uses inexpensive test coupons that can be quickly prepared and tested, making frequent evaluation economically viable while maintaining simulation accuracy.
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 simulation of downhole conditions, including temperature and stress loading, with significantly reduced fluid requirements, allowing for performance evaluation of PDM components in a laboratory or at a wellsite, and providing results that predict full-scale PDM performance without the need for large-scale equipment.
Implementation Method 1
the rotor and stator sections are independently rotatable, allowing for controlled differential rotation
Implementation Method 2
braking torque application to simulate downhole conditions
Implementation Method 3
accurate simulation of downhole conditions, including temperature and stress loading
Data Source
AI summary
A method for measuring load performance of a positive displacement motor (PDM) test coupon. The test coupon comprises a partial length of a PDM stage and is received inside a sealable test chamber. In some embodiments, the test coupon may be cut from a failed PDM stage. The test chamber is filled with test fluid. In some embodiments, the test fluid may be drilling fluid sampled from a live well. Rotation of the rotor on the test coupon actuates rotation of the stator. A braking torque is applied to the stator rotation, enabling evaluation of, for example, fatigue load performance of test coupon. Additional embodiments comprise the rotor axis and the stator axis being offset in order to simulate rotor/stator eccentricity in a full size PDM stage.