Determination of Capillary pressure & relative permeability curves

Transcription

1 Determination of Capillary pressure & relative permeability curves With Refrigerated Centrifuge Multi speed centrifuge experiments Introduction As the porous diaphragm method (see Vinci s CAPRI), the centrifuge method is a commonly used method for determining the capillary pressure properties of reservoir rocks. The procedure begins with a core sample which is placed in a centrifuge tube. The system is rotated at a number of different speeds selected to cover pressure differences between phases required for the particular cores. At each step, the rate of rotation is maintained constant until phase stabilization. Either Drainage or Imbibition experiments can be held as shown in the pictures below. Core saturated with the non-wetting fluid Wetting fluid Sample containment cup Calibrated receiving tube Non-wetting fluid VINCI TECHNOLOGIES Parc de l'ile, 27B rue du Port, 92022NANTERRE Phone: vincinet@vinci-technologies.com Centrifuge force Imbibition experiment VINCI TECHNOLOGIES Page 1

2 Refrigerated centrifuge (RC) The centrifuge technique for measuring relative permeability is a simple extension of the centrifuge technique for measuring capillary pressure. The RC is a refrigerated centrifuge enabling automatic determination of capillary pressure & relative permeability curves on six core sample. The fluid produced as a function of time for each rotational speed is analyzed to determine the relative permeability curves. Data collection is therefore no more complicated than for the capillary pressure case except that the frequency of data capture is greatly increased, particularly just after the speed of rotation has been changed. Custom designed core holders offer the ability to spin core plug samples. Each coreholder is equipped with a sample containment cup and a calibrated receiving tube. A unique feature is that Vinci s coreholder can accommodate either 1 or 1.5 diameter cores. The same coreholder can be used either for drainage of for imbibition experiments. VINCI TECHNOLOGIES Page 2

3 1mm wide Floating disc Lower end of the re tube Water / Gas Drainage experiment Drainage / Imbibition Core Holder / Amott cell Water Interface Gas Spontaneous Imbibition and drainage measurement are made using Amott cells The centrifuge is equipped with a high resolution digital camera system allowing measurement of displaced fluid volumes in each of the cells sequentially. Thanks to a 1360 x 1024 pixel resolution, the interface level is detected with an accuracy of less than 0.1 mm i.e cc for a 20 mm receiving tube. A unique feature of RC is the very important length of the centrifuges arms. Compared to some others centrifuge, RC can achieve important capillary pressure at relatively low rotational speed. Thanks to this particularity, the rotation speed is stable even for high capillary pressures and the interface detection remains perfect for any rotation speed. Dedicated software automatically detects the interface between the fluids and records the volume production. VINCI TECHNOLOGIES Page 3

4 Overburden core holder For overburden experiments, at reservoir conditions of pressure (5,000 psi), dedicated core holders can be provided. Confining pressure can be applied prior to the test using a manual pump. The great speed stability of RC and the accuracy of interface detection allows for high quality production curves. The loading mode is hydrostatic, therefore, axial and radial pressure are equivalent. The same core holder can be used both for drainage and imbibition test The same core holder can be used for 1 or 1.5 diameter cores. VINCI TECHNOLOGIES Page 4

5 Simulation package RC is provided with a dedicated simulation package. CYDAR includes a special module for centrifuge acquisition data. CYDAR automatically collects the production curve and calculates instant saturation and capillary pressure. For each experimental curve, CYDAR proposes 6 types of different fit (linear, splines, bi-exponential, etc.). Kr and Pc determination is made by numerical history matching. The modules allows for classical calculations (Hagoort, JBN, etc.) as well as accurate simulations. This simulation package has been developed in collaboration with core analysis specialists; it s customer friendly software accurate and powerful. CYDAR uses the most recent methods developed and tested in research laboratories and published in the proceedings of the Society of Core Analysis. VINCI TECHNOLOGIES Page 5

6 Technical Specifications Item Type / model / specification Number of Core Holder: 6 Core holder: Core Ø: 1 or 1.5 Core length: Up to 4 for atm. coreholder Up to 2.5 for overburden core holder Capillary pressure: Speed: Temperature: Larger radius: Accuracy on reading: Oil-water drainage: Oil-water imbibition: Air-water drainage: Air-water imbibition: Speed: Speed regulation: Speed ramp: From 5 to +90 C 26 cm 0.01cc 0.0 to 14.7 bar (0 to 213 psi) 0.0 to 15.9 bar ( 0 to 230 psi) 0.0 to 44.1 bar (1 to 639 psi) 0.1 to bar ( 1 to 690 psi) from 200 to 4,500 rpm ± 1 rpm Available VINCI TECHNOLOGIES Page 6