Abstract: Quantitative Evaluation of 3D Seismic Data in an AVO Type II Environment

Currie, M. T.; Lancaster, S.; Redshaw, T. - BP; Areklett, E. - BP Norway

Quantitative analysis of 3D seismic data can be a powerful tool in reducing appraisal and development costs of fields where rock properties of the reservoirs allow application of appropriate techniques. Reduced numbers of appraisal wells, decreased time to first oil, and improved placement of development wells are benefits that may be derived from properly processed and interpreted data.

Many reservoirs along the West Africa margin display an AVO Type II seismic response. Extraction of meaningful quantitative parameters from such reservoirs is difficult because any given seismic response may represent numerous, and often conflicting, lithologic and/or fluid characteristics. Production of angle-limited 3D substacks is used to aid in the interpretation of such reservoirs. Long offset stacks are typically muted far below critical angles due to the introduction of undesirable phase and frequency effects if the farthest offsets are included in the stack. However, these are often the portions of a gather that will provide the necessary information to allow quantitative analysis.

Inability to compensate for non-hyperbolic moveout has been the limiting factor in the past. We have utilized a high order NMO processing technique to correct for this factor, thus allowing the use of the full range of offsets. Geologic consistency of reflectors and a single polarity seismic response for hydrocarbon-bearing sands are the results. Examples of processing and of resulting effects on the interpretation and evaluation of a major West Africa discovery will be shown.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil