A hybrid streamtube simulator using a semi-analytical method

A hybrid streamtube simulator is developed using a semi-analytical method. This hybrid simulator applies to steady-state, incompressible, two-phase, field scale problems, where the effects of gravity can be neglected. The underlying idea of the hybrid streamtube method is to decouple a large 3-D problem into multiple cross-sections along the areal streamtube bundles. Using the calculations of cross-sections, the areal recovery is computed. This method is based on the assumption that the effects of a changing mobility field can be accounted for by using fixed streamtube geometries with updated flowrates. In each cross-section the semi-analytical method is applied, which uses the single-phase pressure distribution and 1-D Buckley-Leverett solution along the streamtube. The distribution of pore volume along each streamtube is calculated by using the Time-Of-Flight method. This information and the pressure solution are used to calculate oil recovery by the semi-analytical method. Unlike previous hybrid methods, the developed simulator uses a streamtube method in each cross-section. Due to the simple calculations and small arrays the method developed shows very fast calculation speed compared to conventional finite difference simulator (ECLIPSE), a streamline simulator (3DSL) and another streamtube simulator (STUB3D). The developed simulator shows good agreement with other methods for an end-point mobility ratio range from 1 to 50. The hybrid streamtube method (HST) was faster than the updated streamline method (3DSL) by factors of 1 to 3 orders of magnitude, and the conventional finite difference method (ECLIPSE) by factors of more than 3 orders of magnitude.