Rock Centrifuge Automation
The results of rock-fluid centrifuge tests can be used to calculate capillary pressure and relative permeability relationships for the reservoir sample tested. The data collection process of existing Beckman rock-fluid centrifuges can be automated with the addition of a computer controlled video camera and strobe light. The additional equipment includes a line video camera, special strobe light, synchronization encoding, electronic interfacing and a PC computer to control the test and take the data. This data collection system is modeled after the published work of Shell Development Corporation, Houston Texas USA.
The integrity of the Model 721 Automated Rock-Fluid Centrifuge is not compromised as the existing openings in the tub are used and no radical modification is required. The additional equipment should not interfere with maintenance contracts or warranties. Both Beckman J-6 and Ultra centrifuges can be modified.
The maximum data rate is one reading per revolution up to 600 RPM and then 10 readings per second. Core holders are read sequentially, 1 through 6. Centrifuge tests are normally conducted during speed ramp up, so the transient data is required.
The measured data reported are:
1) the rotor speed during the previous revolution,
2) the core holder number,
3) elapsed time, and
4) the number of camera pixels from the vial bottom to the interface enhancement. The video camera has 2048 pixels to view the vial, so that .05 mm resolution of the meniscus position is practical. The meniscus position is enhancement with a floating a black plastic washer.
Calibration of the vial volume and meniscus shape variation with speed are measured during a procedure, covering the speed range, before the sample test is conducted.