Reconciling Core Derived Permeabilities and Well Test Using A Fracture Network: A Field Case Example

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIt is a common observation that well test permeability values do not match with thickness weighted core permeability averages. This is not a surprise because of the differences in the measurement scales where, unlike well test measurements, core samples represent a very small portion of the reservoir around the well bore. In addition, the presence of fractures and/or high permeability channels will further enhance the difference between the two sources of data. Therefore, reservoir descriptions based on core measurements alone cannot honor well test results. They need to be modified properly without violating the underlying geological and geostatistical information.In this paper, we present a methodology to properly enhance permeability fields that also accounts for fracture distribution in the reservoir. The basic idea is that radial upscaling around a wellbore within a given investigation radius should match the permeability obtained from well tests. The enhancement is caused by two factors: microfractures, which cannot be explicitly represented in the reservoir description, and macro-fractures, which can be interpreted using 3-D seismic data. To account for these two different types of fractures, we calculate two different enhancement factors, one for the base level (microfractures) and one for the higher level (macro-fractures). The base level, after appropriate interpolation, is applied across the entire reservoir, whereas the higher level is applied only to locations where macro-fractures are interpreted from 3-D seismic data.The technique was successfully applied to a Middle Eastern carbonate reservoir. A significant correlation is observed between the enhancement required to match the well test data and the fracture density (macro-fractures obtained from 3-D seismic data) within a given investigation area. A correlation function is then obtained between the enhancement factor and the fracture density for a given grid block, which in turn is used to apply enhancement to interwell locations. Thus, the resulting permeability field did not only honor the well test results but also the fracture distribution and the underlying geological and geostatistical descriptions. In a later stage, a tensorial approach was used to upscale permeability to account for the anisotropy in permeability distribution. Using this approach, a proper anisotropy of permeability distribution, matching the fracture orientation, has been obtained.

Ranking and Upscaling of Geostatistical Reservoir Models by Use of Streamline Simulation: A Field Case Study

“…Fracture distribution was used in the data integration process to match the core-derived permeability with well test permeability. 10 A total of forty-eight realizations were generated considering four major type of uncertainties: structure (3 cases), spatial model (2 models), petrophysical properties (2 cases) and geostatistical realizations (4 cases). The matrix of case examined is shown in Table-1.…”

Fault and Fracture Corridors – How to Reduce the Structural Uncertainty for Reservoir Management Optimization

“…It may serve, as a guide for better modeling of permeability. 5 However, this information alone may not be enough to describe quantitatively the fracture system. For this reason, the hydraulic characterization of the fracture system, based on the well test and production data is required in order to get fracture properties that can be used to derive fracture porosity and fracture permeability.…”

Practical Approach in Modeling Naturally Fractured Reservoir: A Field Case Study

“…It may serve as a guide for better modeling of permeability. 1 However, this information alone may not be enough to quantitatively describe the fracture system. For this reason, the hydraulic characterization of the fracture system, based on the well test and production data is required in order to get fracture properties that can be used to derive fracture porosity and fracture permeability.…”

“…The results of Case-1 have been previously published in three technical papers. 1,2,3 It is presented here for convenience in order to maintain the integrity and continuity of the overall technique with respect to the new results (Case-2).…”