Geopressure prediction using seismic data: Current status and the road ahead

Abstract

The subject of seismic detection of abnormally high‐pressured formations has received a great deal of attention in exploration and production geophysics because of increasing exploration and production activities in frontier areas (such as the deepwater) and a need to lower cost without compromising safety and environment, and manage risk and uncertainty associated with very expensive drilling. The purpose of this review is to capture the “best practice” in this highly specialized discipline and document it. Pressure prediction from seismic data is based on fundamentals of science, especially those of rock physics and seismic attribute analysis. Nonetheless, since the first seismic application in the 1960s, practitioners of the technology have relied increasingly on empiricism, and the fundamental limitations of the tools applied to detect such hazardous formations were lost. The most successful approach to seismic pressure prediction is one that combines a good understanding of rock properties of subsurface formations with the best practice for seismic velocity analysis appropriate for rock physics applications, not for stacking purposes. With the step change that the industry has seen in the application of the modern digital computing technology to solving large‐scale exploration and production problems using seismic data, the detection of pressured formations can now be made with more confidence and better resolution. The challenge of the future is to break the communication and the “language barrier” that still exists between the seismologists, the rock physicists, and the drilling community.

A simple derivation of the effective stress coefficient for seismic velocities in porous rocks

“…The effect of confining stress and pore pressure on seismic velocities is important for such geophysical applications as overpressure prediction from seismic data (Eaton, 1975;Dutta, 2002;Huffman, 2002;Sayers et al, 2002) and, more recently, for hydrocarbon production monitoring using timelapse seismic measurements (Tura and Lumley, 1999;Landrø, 2001). The dependence of seismic velocity on pressure has been confirmed for a variety of rocks by laboratory measurements of elastic wave velocities in samples with varying pressure in pore fluids (see, e.g., Wyllie et al, 1958;Todd and Simmons, 1972;Eberhart-Phillips et al, 1989;Prasad and Manghnani, 1997).…”

Glacially generated overpressure on the New England continental shelf: Integration of full‐waveform inversion and overpressure modeling

“…The velocity of a sedimentary rock in the subsurface is a function of many factors, including its depositional and burial history, lithology, texture, porosity, consolidation state, density, temperature, pore fluid type, and overpressure [Bowers, 1995;Dutta, 2002;Dvorkin and Nur, 2002;Huffman, 2002]. In considering the cause of the abrupt lateral change in seismic velocity exhibited by the bright spots, abrupt changes in most of these factors can be discounted.…”

“…We therefore assume that at a constant depth, observed velocity variations are most likely due to changes in effective stress, which are related to changes in overpressure and the bulk moduli of the materials [Carcione et al, 2003]. Dutta [2002] and Bowers [2002] showed that, at a given depth, deviations in observed seismic velocity from that predicted from a normal compaction trend could be used as an indicator of overpressure.…”

Multiples in Onshore Niger Delta from 3D prestack seismic data

“…According to Dutta (2002), secondary low velocity semblance plots represent optimum stacking velocities for multiples, but added that it has to be established not to be as a result of lithological changes or from abnormal pore pressure. Weiglein et al (2011) also proposed that interbed multiples can be generated by stronger subsurface reflectors regarded as multiple generators at any depth, more especially, the presence of geologic contacts of differing compactions on the footwall of main boundary faults.…”