HOMEWOOD, PETER W., Elf Exploration Production, Pau, France

Abstract: Prediction and Correlation of Subsurface Lithologies: Best Practices for E&P

The prediction and correlation of lithologies in the subsurface are fundamental steps in E&P. The choice of appropriate stratigraphic concepts and rules to follow is helped by use of analogs, which are well documented modern or ancient case studies, commonly from outcrop. Traditional approaches have used biostratigraphic time units to constrain correlation and conventional facies models for a notion of distribution of lithologies within each time unit.

Recent developments of 3-D seismic and 3-D modeling have led to an abundance of sophisticated imaging of subsurface features and sometimes unprecedented views of subsurface geology. Calibration of such images is provided by core and logs where wells are available, but the prediction of lithologies between wells and the picking of relevant features on seismic both require an appropriate knowledge of stratigraphic process and product. Traditional methodology has proved to be insufficient in this context.

A consortium research program has validated the industrial use of recent theoretical developments in stratigraphy and has set up high-resolution stratigraphic models for a range of depositional environments of different geological ages to succeed standard facies models. Case studies were carried out on excellent 3-D outcrops and then were compared with subsurface data from adjacent oil or gas fields in equivalent strata.

A robust method has been established to provide appropriate stratigraphic rules with which to interpret sophisticated subsurface images to a satisfactory degree. This approach provides the greatest coherence between the results from analyses by different stratigraphic disciplines. It comprises a flow chart of the steps involved, running from theory, outcrop studies, and high-resolution stratigraphic models, to analogs and reference libraries for iteration with data from seismic and wells. 

AAPG Search and Discovery Article #90922©1998-1999 AAPG International Distinguished Lectures