Earth Model Complexity and Risk Description in Resource Exploration and Development

During the past 10 years, seismic imaging and analysis has expanded its role from structural exploration to reservoir description and property analysis. As experiences have developed, the description of the earth required to image and analyze the reservoirs has in many cases required significantly more complexity than anticipated. It is necessary to understand the range of earth complexity of the overburden to determine the accuracy of the seismic imaging, and the complexity of reservoir rocks to correctly risk quality and connectivity of flow compartments in oil and gas fields.

Seismic technology is a complex business. Historically, imaging and analysis tools have adopted or required simplifying assumptions in order to complete projects in a timely manner or simplify the descriptive analysis. Many of these assumptions are in widespread use today. Examples of this can be seen in seismic data processing applications that rely on a “flat earth” simplification, or reservoir analysis based solely on “bright spot” amplitude anomalies.

The difficulty facing earth scientists today is to understand, use and describe the right level of earth complexity for reservoir discovery and analysis. Using more complicated tools than necessary destroys project value by spending too much money and/or extending project time lines unnecessarily. However, using a tool that is too simple for a complex earth leads to a false sense of certainty and a commonly incorrect prediction (often wrong but never in doubt!).

In this talk, I’ll review case histories of structural imaging, stratigraphic imaging, velocity complexity, and prediction of reservoir, pore pressure, and fluid flow from a mixture of geological environments around the world. I’ll attempt to show the significance of earth complexity in the prediction analyses and the tools required handling it. Finally, I’ll cover an overview of connecting the earth complexity to resource and risk prediction in resource exploration and development.