Exploration Geostatistics: Methods, Workflows, and Examples

By

 Jeffrey Yarus¹, Robert Ehrlich², Richard Chambers³

(1) Quantitative Geosciences, Houston, TX (2) Residuum Energy, Inc, Salt Lake City, (3) Quantitiative Geosciences, Broken Arrow,

 Exploration risks in mature basins can be reduced through analysis of pre-existing data. The integration of this data with the spatial component using a geostatistical approach can provide valuable insights for both close-in exploration as well as conventional exploration leads. Currently, far less attention has been paid to the use of spatial modeling over larger geographic scales such as those used to define exploration “leads” or “plays.” However just as geostatistical practice had to evolve when it moved from mining applications to reservoir studies, further evolution is needed to move to investigations that may involve hundreds to thousands of wells and more than 100,000 km2.

The data sets used are more varied, incorporating not only well, core, and seismic data from numerous fields, but also other forms such as gravity, magnetic and seismic data, as well as oil and water chemistry, pressures, decline curves, etc. Non-stationarity is the rule rather than the exception and efficient removal of this over large areas can be a problem. Furthermore, complex structural settings over large areas can also create modeling problems. For intracratonic basins such as those in the Middle East, the problem is minimized in that the tectonic style is dominated by intersecting far-field vertical wrench faults of relatively low vertical separation. With such a model in mind, an exploration geostatistical workflow overcoming these issues can be constructed.