Daniel M. Tetzlaff

Simulating clastic sedimentation

This book discusses a new computer methodology capable of simulating the erosion, transport and deposition of clastic sediment. It describes simulation models, a series of computer programs written in FORTRAN, representing geologic processes acting in three dimensions through geologic time. It also provides the theoretical and experimental foundations for the procedures used and a mathematical introduction to the components of the earths dynamic system involving running water.

Application of multipoint geostatistics to honor multiple attribute constraints applied to a deepwater outcrop analog, Tanqua Karoo Basin, South Africa

We have used a multipoint geostatistics algorithm called Snesim (Strebelle, 2000) to evaluate its applicability to reservoir modeling. To test the algorithm, we used a data from a deepwater reservoir analog from outcrops in the Tanqua Karoo Basin, South Africa. Our implementation demonstrated the ability of the algorithm to efficiently and faithfully reproduce the texture of geological facies while honoring a large number (127) hard data locations plus rotation and scaling fields and soft probability fields. We have used hand-drawn stationary training images with 3-5 facies to model the proximal to distal facies relationships seen in outcrop. The results show the ability to honor hard data, soft constraints, and complex geological relationships that vary over the reservoir grid.

Computer mapping of seismic reflectors in the coastal region of the National Petroleum Reserve in Alaska

This study deals with detailed mapping of sedimentary features within Torok Formation and Nanushuk Group in the northern part of the National Petroleum Reserve in Alsaka (NPRA). These Cretaceous units correspond to a single depositional regime of a large deltaic system. Seismic reflecting surfaces within the sequence are seen as sigmoidal traces in seismic sections. These horizons can be identified over long distances (up to 160 km) within individual seismic sections and can be correlated between intersecting sections. The study is centered in four different areas in which seismic information is relatively abundant and of good quality. One of the study areas is of special interest because of a large, now-filled ancient submarine canyon, Simpson Canyon. Reflection-time measurements were obtained by digitizing various horizons that were manually traced on seismic sections. Reflection-time measurements have been converted to depth values, corrected for postdepositional tilting, and portrayed as structure contour maps, perspective “fish-net” diagrams, and isopach maps prepared by computer. Computer mapping procedures are essential to obtain three-dimensional representations of reflecting surfaces. Because the northern NPRA has undergone little tectonic deformation since Cretaceous, horizons that have been mapped provide a close representation of submarine paleotopographic surfaces. A succession of these surfaces reveals progressive changes in the form of deltaic deposits from west to east, suggesting that energy of waves and currents increased as the delta prograded eastward. The succession of surfaces also suggests that Simpson Canyon was affected by at least two events of erosion and refilling.