Centrifuge Capillary Pressure: Method of the Center of Forces O. Jaimes O. Jaimes Ecopetrol-ICP Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, October 1991. Paper Number: SPE-22687-MS https://doi.org/10.2118/22687-MS Published: October 06 1991 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Jaimes, O. "Centrifuge Capillary Pressure: Method of the Center of Forces." Paper presented at the SPE Annual Technical Conference and Exhibition, Dallas, Texas, October 1991. doi: https://doi.org/10.2118/22687-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Annual Technical Conference and Exhibition Search Advanced Search AbstractShown that the commonly used methods of reduction of centrifuge capillary pressure data, based on the Hassler and Brunner theory, lead to double valued capillary pressure functions. To avoid this problem, an alternate equation with two methods of solution has been developed. This equation uses the concept of the center of forces to convert centrifuge data into capillary pressure curves. The proposed methods do not make assumptions about the form of the solution, nor do they use numerical differentiation of experimental data, and, lastly, they do not result in double valued capillary pressure curves. Several examples, including laboratory and analytical data with the computed capillary pressure curves, are presented along with a comparison of the results obtained using the new and several previously developed methods.INTRODUCTIONThe standard procedure for the laboratory determination of capillary pressure curves by the centrifuge method consists of filling a small sample with liquid, mounting it in the centrifuge as shown in Fig. 1, and measuring the volume of liquid Vdisp that is displaced from the sample in a series of increasing angular velocities Ï?. For each angular velocity the average saturation. S of liquid remaining in the sample and the distribution of capillary pressures Pc(r) are calculated according to the expressions:Equations 1 and 2In order to determine the capillary pressure curve it is not enough to know the average saturations in the core; it is also necessary to determine the distribution of saturations in the sample, so that one can relate one value of capillary pressure to one value of liquid saturation. However, in practice it is sufficient to calculate the capillary pressure and the liquid saturation just at one point in the sample for each value of the angular velocity. In the widely used Hassler and Brunner1 method, for example, the point selected is the top face of the sample, where the capillary pressure is, according to Eq. 2:Equation 3The corresponding liquid saturation S(z) is found from the solution of the equation:Equation 4where R is a geometric parameter equal to r1/r2.The previous equation is a Volterra integral equation of the first kind, whose numerical solution by some techniques may be unstable.2 However, it may be possible to approximate a solution by using any of the different methods developed since 1945, which include the solution of approximate equations and parametric techniques. Unfortunately, the approximate equations are valid only for limited ranges of variation of R and, in the majority of cases, require the use of numerical differentiation of experimental data. The parametric methods presuppose the form of the solution of Eq. 4 and use regression analysis techniques to adjust the parameters of the postulated solution, thus suffering from lack of generality.In this work we show that, regardless of the method we use, the solution of the Hassler and Brunner equation (Eq. 4) leads to double valued capillary pressure functions Pc(S). Keywords: axis, saturation profile, liquid saturation, upstream oil & gas, brunner theory, experiment, approximation, artificial intelligence, experimental data, sirr Subjects: Formation Evaluation & Management This content is only available via PDF. 1991. Society of Petroleum Engineers You can access this article if you purchase or spend a download.