Reliance’s ‘Cool Muscle’ delivers accurate tidal simulation
26 March 2013
In January 2013, a paper was published by two petroleum engineers from Curtin University (Australia) and Imperial College London (UK) which investigated how the action of tides can affect oil and water saturations in the capillary transition zone.
The capillary transition zone is an area where oil saturations in underground oil reservoirs change with height due to the combination of capillary and buoyancy forces. This can significantly influence the oil distribution in the reservoir and it is important to understand this in detail to design efficient oil recovery schemes. The paper investigated the influence of semi-diurnal lunar tides on this transition zone.
Stefan Iglauer and Ann Muggeridge constructed a model that would accurately mimic these sinusoidal changes in height and pressure. Three cylindrical columns, one metre high with a 100mm internal diameter were filled with sand and a varying change in air/water contact was applied for 90 days.
A reservoir was connected to the columns which moved up and down in a way that simulated the M2 semidiurnal lunar tide. This was made possible by mounting the reservoir on a platform attached to a linear slide which was in turn connected to Reliance’s Cool Muscle Motor.
It was the accuracy required to model an effective experiment which led the team to consider applying the Cool Muscle. Spotted in engineering publications and on the internet, the motor was viewed as an ideal choice for the experiment due to its ability to perform complex co-ordinated movement and use mathematical notation to induce motion.
A 50,000 count magnetic encoder, 32 bit RISC processor and vector drive amplifiers, provided the ultra-smooth operation and accuracy required to effectively mimic a lunar tide. It was noted that, in application, the accuracy of the stepper motor system was within the range of +/- 0.1%.
Reliance assisted the scientists by supplying the motor as a ready programmed unit. Using CoolWorks Lite 4.1.4, the motor/stepper was configured to reproduce the characteristics of a tidal sequence by programming 50,000 steps in each given period of 12 hours and 20 minutes; this mirrored the period from high to low tide.
A pressure change of 4,000 Pa was achieved to simulate comparable pressure changes expected with tides.
The experiment concluded that pressure changes do in fact influence the vertical saturation profile in addition to the expected saturation gradient predicted by assuming capillary – buoyancy force equilibrium.
Reliance’s willingness to supply an integrated, pre-programmed mechanism meant that the experiment could progress without the need to validate the test system. Reliance’s Cool Muscle worked so well in making this experiment a success that more units were purchased to be used in various other trials and studies throughout the institutions.
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