ABSTRACT

Reservoir continuity is an essential property for the characterization and development of heterogeneous reservoirs. Discontinuous permeable zones (e.g., sand bodies) are usually associated with highly continuous permeability barriers (e.g., shales) that cut through permeable zones. On the other hand, highly continuous, permeable areas often coexist with less continuous, low permeability rocks that are separated by the permeable areas. In terms of two phase spatial continuity, there is generally an opposite relationship between the two phases, i.e., one phase is more continuous, whereas the other phase is less continuous.

Variograms have been extensively used to quantify spatial distribution of certain parameters, such as permeability. They provide information on the similarities for various distances and are a type of size measurement for all the features within a region. They also provide directional measurements and can be used to quantify reservoir anisotropy. However, variograms cannot be used to examine a single phase. A variogram always characterizes an entire region, which may contain both continuous phases and discontinuous phases. Variograms lack the capability to distinguish such different phases, and therefore are not adequate for characterizing the continuity of a reservoir.

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