PDM Stator Test Coupon for Downhole 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, elevated temperatures, and dynamic braking loads, while requiring large volumes of drilling fluid, making them costly and logistically challenging.
Innovation Solution
A test apparatus using a partial length of a PDM power section test coupon within a sealed chamber with a small volume of drilling fluid, where the rotor and stator sections are differentially rotated to simulate downhole conditions, and an external brake applies controlled loads to mimic the stress profiles encountered by full-scale PDMs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ASTM testing protocols are used to evaluate PDM performance, then basic material properties can be assessed, but the testing fails to accurately simulate cyclic loading stresses, elevated temperatures, and dynamic braking loads encountered in downhole service
Solution Approach 1:
The patent divides the PDM into separate testable components (stator, rotor, elastomer samples) that can be individually tested. The stator is removed from the downhole assembly and tested separately in a laboratory setting, allowing complex downhole conditions to be simulated without requiring the entire motor to be tested, thus reducing device complexity while maintaining measurement accuracy.
Solution Approach 2:
The patent introduces an intermediary testing apparatus that mediates between the simple ASTM protocols and the complex downhole environment. This apparatus includes temperature control systems, pressure vessels, and cyclic loading mechanisms that recreate downhole conditions without requiring actual downhole deployment, thereby achieving accurate simulation without proportional complexity increase.
2Reliability
If flow loop testing is used to simulate downhole PDM service, then comprehensive performance evaluation under pressure and temperature can be achieved, but hundreds or thousands of gallons of drilling fluid are required making it cost prohibitive
Solution Approach 1:
The patent extracts the essential testing function from the large-scale flow loop by removing the stator from the downhole assembly and testing it in a reduced-scale apparatus. This extraction allows comprehensive performance evaluation to be achieved with minimal drilling fluid (only enough to fill the test chamber and progressing gaps), eliminating the need for hundreds or thousands of gallons required by conventional flow loop testing.
Solution Approach 2:
The patent creates a simplified copy of the downhole testing environment using a small test chamber that replicates the essential conditions (temperature, pressure, cyclic loading) without requiring the full-scale flow loop infrastructure. This copying approach maintains reliability of performance evaluation while reducing drilling fluid volume requirements by several orders of magnitude.
3Quantity of substance
If recirculating pump vessels are used to evaluate PDM performance, then smaller fluid volumes are required compared to flow loops, but the load ranges are limited corresponding to limited downhole environment simulation
Solution Approach 1:
The patent introduces dynamic loading capabilities to the stator testing apparatus, including cyclic loading and dynamic braking loads that recirculating pump vessels cannot provide. The apparatus can apply varying temperatures, pressures, and load conditions to the stator, enabling simulation of a wide range of downhole environments while maintaining the advantage of using small fluid volumes. This dynamic capability significantly enhances adaptability without increasing fluid requirements.
4Measurement precision
If full-scale dyno testing is performed, then accurate downhole condition simulation can be achieved, but the specialized equipment and logistical requirements make it economically unviable for frequent testing
Solution Approach 1:
The patent employs a disposable or easily replaceable stator test sample approach, where the stator is removed from the downhole assembly and used as a test coupon. This eliminates the need for expensive, complex full-scale dyno equipment while maintaining accurate simulation capabilities. The simplified apparatus can be set up and torn down quickly, making frequent testing economically viable without specialized infrastructure.
Data Source
AI summary
An adapted elastomer compound, in which the adaptation is based at least in part on load performance data of a rotor/stator test coupon as evaluated on a test apparatus. The test coupon's stator section includes the original elastomer compound before adaptation thereof. The test apparatus includes a motor, a brake, and at least one sensor disposed to evaluate load performance data of the test coupon. The load performance data is the product of the process comprising the steps of: (a) rotating either the rotor section or the stator section on the test apparatus, wherein such rotation section actuates corresponding rotation of the other of the rotor section and the stator section; (b) applying a braking torque to the actuated rotor section or stator section; and (c) responsive to step (b), evaluating load performance data of the test coupon.