CODEN(USA): JSERBR Capillary Pressure Determination Using the Centrifuge Method
Journal of Scientific and Engineering Research
The centrifuge method of capillary pressure determination is a unique method of capillary pressure determination in the laboratory in that the core plug is spun at discrete rotational speed which necessitate a force which pushes out fluid from the pores of the rock sample. In this paper the method was carried out by preparing the cores and saturate them with brine and crude oil and spun at a rotation speed ranging from 500RPM to 3000RPM, an interval of 500RPM using a centrifuge and the
... ge and the displaced fluid Vcoll is collected in the test tube inserted in the core holder and the capillary pressure was determined. As seen in fig 6 through to fig. 9, saturation decreases as capillary pressure increases and vice versa. The effect of core length on capillary pressure is shown on fig.10.0 .The longer the length of the core the higher the capillary pressure. Advantages of the centrifuge method are that; it is a rapid approach, and a full drainage and imbibition cycle are being complete in a matter of days. Centrifuges can also be operated at elevated temperatures (up to 150°). Introduction The study of capillary pressure is relevant in the petroleum industry, since it is a major factor that controls the distribution of fluid in a reservoir rock. This study is aim to determine capillary pressure using the centrifuge method. The objective of this work is to determine the saturation of the core samples with respect to the measured capillary pressure. As defined by the petroleum dictionary, capillary pressure in a rock formation or core sample is the pressure of water or the contained fluid which causes it to rise or adhere to the surface of a small pore space than to larger one. Capillary pressure is grossly important in reservoir engineering studies since it a major factor controlling the distribution of fluid in the reservoir rock. The small pores in a reservoir rock are similar to capillary tubes and they usually contain two immiscible fluid phases in contact with each other. When two immiscible fluids are in contact with each other in a capillary tube, a clear interface exists between them. This interface is due to interfacial tension. The interface is a curved surface and the pressure on the concave side exceeds the pressure on the convex side. The resultant pressure difference existing on either side of the meniscus (concave or concave) gives rise to capillary pressure. In the presence of two immiscible fluids, one of them preferentially wets the tube surface and is called the "wetting" fluid, while the other is the "non-wetting" fluid . Mathematically and implicitly, the capillary pressure can be expressed as; P c = P nw-P w (1) Where P nw = pressure of non-wetting phase P w = pressure of wetting phase Although, there exist numerous techniques of obtaining capillary pressure such as the Laplace equation, the use of the interfacial tension correlation, the porous plate method, the mercury injection method etc. this research work deals exclusively on the use of the centrifuge method. The centrifuge method is increasingly favored for measuring capillary pressure; this is not to say it is as easy as the mercury method. The centrifuge measurements are much faster than the porous plate method .