What's new in exploration
Working with oil and gas R&D, l have concluded that these projects fall into two categories. The first are those projects that aim to develop technology, to increase our capabilities far beyond the realms of those currently possible. The second seeks to optimize existing capabilities—that we currently rely on in our daily quest to develop oil and gas—to make them more functional, easier and more accurate. SEG’s SEAM (SEG Advanced Modeling) program falls into the second category. A consortium of industry participants under the auspices of SEG, and with partial funding from RPSEA (Research Partnership to Secure Energy For America), SEAM began Phase I operations in 2007. Now, winding up Phase II, the SEAM program is poised to move into a third phase that, building on the first two phases, will address pressure prediction and hazard avoidance in deepwater operations through the use of advanced seismic imaging.
SEAM Phase I addressed the challenges of subsalt imaging in tertiary basins, with emphasis on the deepwater Gulf of Mexico. Primary goals and accomplishments of SEAM Phase I were:
SEAM chose land seismic challenges as the focus for Phase II after discussion with industry leaders on several potential projects. SEAM-facilitated industry discussions, during 2009 and 2010, identified three core challenge themes that Phase II should focus on.
High-density acquisition. Questions continue as to how to best deploy increasing channels and seismic sources. Such questions include: Is dense inline sampling with sparse cross-line spacing better than a grid of shots and receivers? Acquisition designs have progressed from orthogonal to brick to zig-zag to slash. Which is better, and when?
Simulated data sets acquired over high-resolution earth models offer a cost-effective approach to evaluate the technical benefits of high-density recording.
Near-surface complexities. Geological effects that generate unwanted noise and data processing hurdles include topography, sand dunes, dry river beds, steeply-dipping layers, outcropping refractors, lateral velocity variations, velocity reversals, layered basalts, carbonate karst and anisotropy. These result in a variety of surface waves, scattered noise, scattered signal and static/dynamic effects.
These near-surface effects on shear data are, in many ways, more challenging than for conventional p-wave recording. Shear- and converted-wave processing technology is not commonplace, with the result that delivery of final processed data is delayed. The benefits of simultaneous interpretation and/or inversion are rarely realized.
Fractured reservoirs. Advances in drilling and completion technology are driving an industry renaissance, with increasing use of seismic data for horizontal well trajectory planning and “sweet spot” identification. The economic objective of full azimuth P-wave and S-wave surveys is often to identify regions with lithology, structure and stress patterns (sweet spots) most conducive to hydraulic stimulation.
Imaging is complicated by vertical transverse isotropy (VTI), in both the overburden and the target interval. Horizontal transverse isotropy (HTI), in the target interval, provides the means to identify fracture density and differential horizontal stresses. What are the relative benefits of multi-component data as opposed to azimuthal anisotropy analysis of P-wave data only? How can the useable bandwidth be increased? Is surface seismic an occasional curiosity, or an essential component of a fractured reservoir exploration and development program?
SEAM’s latest project will focus on using data to solve the industry’s most pressing problems. SEAM Phase III (Pressure Prediction and Hazard Avoidance through Improved Seismic Imaging–funding pending) will evaluate and advance current methodologies for pre-drill pressure and hazard prediction.
The research consortium will provide a collaborative forum, where industry experts prioritize current challenges in the use of seismic velocity models to construct pre-drill pore pressure forecasts for well planning. These challenges will be used to design a comprehensive earth model and to “acquire,” through state-of-the-art computer simulation, benchmark data sets, to be used by industry for quantifying risk and uncertainty associated with velocity models derived from current and future state-of-the-art seismic acquisition, processing and imaging. Though the focus will be Gulf of Mexico deep water, the resultant advances in pressure prediction technology and methodology will be more broadly relevant. Phase III will commence in late 2014 and is expected to last two to three years.
For further information, see http://www.seg.org/resources/research/seam/.
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