Effect of heterogeneity on the performance of immiscible displacement with horizontal wells

A three-dimensional, finite difference, chemical flood simulator (UTCHEM) was used to study the performance of immiscible displacement with horizontal and vertical wells in several heterogeneous reservoirs. Three-dimensional heterogeneous permeability fields were generated geostatistically with Dykstra-Parsons coefficient and spatial correlation as characterizing parameters. A total of 21 permeability fields were generated to cover a wide range of Dykstra-Parsons coefficients and spatial correlations. Initially, simulations of immiscible displacement with two horizontal wells (one injector and one producer) were performed in all these permeable media. The effect of the amount of cross flow between producing layers on the flood performance was investigated. These results were then compared to those obtained with two vertical wells (one injector and one producer) for all the permeable media. Finally, investigations were carried out on a heterogeneous reservoir to study in detail the sensitivity of the displacement performance to the horizontal well length and to the ratio of horizontal to vertical permeability using various well combinations. These well combinations consisted of vertical injector-vertical producer, horizontal injector-horizontal producer, vertical injector-horizontal producer, and vertical producer-horizontal injector. Results show that the degree and the structure of the reservoir heterogeneity have a significant effect on the efficiency of immiscible displacements with horizontal wells. Long horizontal wells in highly heterogeneous reservoirs do not necessarily guarantee improved oil recovery.