Three-Dimensional Geological Modeling of Brazilian Reservoirs

Marco A. Moraes, Yeda Backheuser

A better understanding of the three-dimensional distribution of reservoir properties is a critical factor for improving recovery efficiency in Brazilian hydrocarbon fields. Workstation-based deterministic three-dimensional models, often complemented by stochastic models, are being introduced to aid exploitation efforts in onshore and offshore producing areas.

In onshore areas, data from closely spaced wells in mature oil fields are used to generate detailed three-dimensional models showing the distribution of well-log derived properties. In such models, flow units are inferred based on core vs. log property correlation, using multivariate analysis techniques. Each flow unit is characterized by specific permeability range, and its distribution is inferred based on well-log property interpolation. Such detailed models can be used for planning enhanced oil recovery operations, infill well locations, and better selection of completion intervals.

In offshore areas, well to well distances on the order of hundreds of meters or more lead to a different approach to reservoir modeling. Flow unit identification follows the procedures outlined above. Flow unit vertical distribution can also be determined at a very detailed scale. Their lateral distribution, however, due to the widely spaced wells, is represented by general trends. In this case, the relatively homogeneity of the massive sandstones that comprise most of the offshore reservoirs suggests that trend models are quite useful, especially for planning initial development strategies.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995