--> ABSTRACT: Eliminating Structural Influence in Three-Dimensional Ordinary Kriging of Borehole Data, by K. S. Hoffman, B. F. J. Kelly, and J. W. Neave; #91021 (2010)

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Eliminating Structural Influence in Three-Dimensional Ordinary Kriging of Borehole Data

HOFFMAN, KAREN S., Dynamic Graphics, Houston, TX; BRYCE F. J. KELLY; and JOHN W. NEAVE

Redevelopment of older fields requires accurate reservoir property models in order to maximize production. Collated co-kriging often provides the best model for reservoir characterization, but in older fields, 3-D seismic is often not available and the economics of redevelopment may not allow for a new 3-D survey. When borehole logs are the sole source of data, the 3-D distribution of properties estimated by kriging can be strongly influenced by data density and structural complexity.

The structural component within and between fault blocks is removed before kriging by transforming sample points into stratigraphic space. Grid node values estimated by kriging are then returned to their original structural position. This process is made easy, rapid, and precise due to the internal structural consistency of a three-dimensional geospatial model. Points which lie in wedge zones above or below faults are properly datumed through the use of this geospatial model rather than traditional 2-D grids and fault polygons. The resulting model thus reflects only existing stratigraphic influences, and not those which may be artificially introduced by ignoring the structural effect.

Estimates of reservoir properties produced by this methodology honor existing data and provide greater confidence in property distribution. Since redevelopment of older fields often involves marginal economics, it is important to obtain precise and believable reservoir models. Confidence can increase and risk decrease when utilizing this geospatial approach to eliminate structural influences in reservoir characterization models.

AAPG Search and Discovery Article #91021©1997 AAPG Annual Convention, Dallas, Texas.