The Pitfalls of Seismic Interpretation: How to Reduce Risk With Certainty

Abstract

The process of obtaining and processing seismic data is a lengthy, involved and expensive one. Indeed the continual reprocessing of seismic is commonly employed throughout the life cycle of a field, and in exploration often offered as a solution when the risks are unclear. The cellular model has become a primary objective in the assessment of a prospect and develops very early in the workflow, with investigations therein limited to adjusting properties of the rigid corner point grid created. In contrast, while the process of horizon identification is seen as an important one, the process of fault interpretation is a relatively short-lived step in the workflow and may lack the rigorous QC it requires. Furthermore it is rarely revisited once completed. Structural issues are regularly quoted in failed post-well analyses (note the recent DECC-OGA report “Exploration well failures in the North Sea”). In many cases this is one of the risks that can be largely mitigated - without the requirement of new seismic - and it is not an issue resolvable using uncertainty analysis or a corner point grid. With the application of a few fundamental principles relating to fault growth/interaction and the understanding that interpretation should be an iterative process rather than a one-off, interpreters (be they graduate explorationists or experienced geophysicists) can create far better realizations - even without “specialist” tools or experience. We present these fundamentals along with examples the recurring pitfalls of interpretation so that more common mistakes, once recognized, are not repeated. Only when a framework model is mechanically robust and defensible should it be cellularized and subject to further analysis, otherwise error is compounded at every derived step in the workflow and what is commonly regarded as a safeguard against error – uncertainty - is merely an exercise in attaining an accurate fallacy. Decisions made on the basis of such fallacies create unnecessary risks.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016