A good understanding of the internal geometry of a reservoir is necessary for making realistic oil recovery forecasts. In answer to this need, software has been developed to generate 3D lithological images of a reservoir by using a geostatistical approach. Based on previous images, a petrophysical description is then previous images, a petrophysical description is then obtained on a geologic mesh scale. And to perform flow simulation, petrophysical parameters must then be scaled up to reservoir mesh scale. This paper shows an application of the complete procedure of processing from geostatistical imaging to fluid flow modeling.
When dealing with production forecasts in heterogeneous reservoirs, petroleum engineers are rapidly faced with the problem of the description of the internal geometry of reservoirs. Geostatistical methods are of great use in providing images of the reservoir. Therefore a complete procedure has been developed using three complementary software, including the 3D lithological and petrophysical description of the reservoir, the flow simulation, and the visualization of the results. This integrated data processing approach aims at making easier work dealing with several disciplines: geology, geostatistics, and reservoir engineering. And the software tools used for a reservoir study have to be efficiently connected to each other to help the different specialists to work together. Each step of this procedure is explained here, and an application example is described.
The main steps of the procedure are the following:
The geostatistical simulator, called HERESIM 3D, for HETEROGENEITIES-RESERVOIR-SIMULATION in 3 dimensions of space, leads to a petrophysical characterization of the reservoir. Its main feature is to establish the link between lithological and petrophysical well data and fluid flow reservoir petrophysical well data and fluid flow reservoir simulators, using conditional geostatistical simulations and petrophysical parameter scaling-up methods.
The second step is flow simulation, performed with a conventional flow simulator (SCORE).
Then, a graphic software is used to visualize the flow simulation results.
Data exchange between the 3 software is operated through files having a standard data structure.
All the reservoir characterization steps are performed on a work station connected to a network of other work stations and mainframe computers. And flow simulation can be performed either on the work station or on a mainframe computer.
The geostatistical simulator was developed to establish a link between the geologic model and fluid flow simulations. The main philosophy behind this software is that a correct reservoir characterization can be achieved only through a realistic geologic description.
The four main tasks of this modular software are reviewed below.