What’s new in exploration

	Vol. 232 No. 3
NINA M. RACH, CONTRIBUTING EDITOR

Exploration technology benefits from collaboration

The future of the upstream business will be driven by our ability to manipulate the subsurface, says Shell’s Dirk Smit, and to improve this we need more data, of higher quality, at less expense: “We can model more than we can measure, and while we were previously constrained by compute power, exploration advances are now limited by measurement.”

To enhance exploration results, Smit says we need to collaborate more and form perhaps unusual alliances, in order to produce timely innovations. It is also critical to drill more efficiently, better delineating where and how we drill in deep water.

Smit was appointed chief scientist for geophysics at Royall Dutch Shell in October and continues to serve as vice president of exploration technology. His roles have included chief geophysicist for Shell UK and technology manager for global exploration.

There is an abundance of oil and gas, he argues—more than we can see or understand with current technology. The future of exploration requires new concepts in geoscience and new technologies exploiting this science.

Scale. There is a lot of geology hidden in data acquired at every scale, Smit says. He anticipates a shift toward continuous, integrated acquisition, computing and visualization. Satellite imagery, such as gravity measurements retrieved with the European Space Agency’s Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite, may be used for high-resolution gravity gradient maps (see sidebar, p. 70). Detailed structural interpretation can be greatly facilitated with satellite gravity and airborne data.

Curie depths can be used to assess temperature from magnetic data. High-resolution, airborne measurements of the magnetization of basement rocks provide a “depth thermometer” at basin scale.

Seismic. Seismic technologies will remain a major source of subsurface info, Smit says, although it can’t be relied upon to make robust predictions without tying in other types of data. The challenges are to bring down data acquisition and processing costs and to improve the quality of the data. We need wider bandwidths, including low frequencies for full waveform inversions, he says.

The size of seismic data volumes has increased significantly in the last several decades, but there is still a shortage of data redundancy, necessary to improve the signal-to-noise ratio. Velocity models are oversimplified to speed up data processing even though real velocity fields are almost certainly much more complex. Errors in velocity interpretation subsequently lead to inaccurate time-to-depth conversions. 

Quantitative 4D connected volume analyses have shown that seismically defined volumes match reasonably well to production data and can be used to ascertain the oil-water contact. But transient effects may not be captured and reflections may either “soften” or “harden” in response to a drawdown. How often do we need to sample to understand the subsurface process and seismic response? How can frequent acquisition of seismic data be made more cost-effective?

Smit notes that wide-azimuth seismic data sets are hardly used for exploration, and that often no more than 10% of seismic data acquired is used in actual decision processes. He anticipates that geoscientists will eventually use more of the data to derive useful information. WAZ data sets are a fertile area for research, and can be analyzed using unified five-dimensional geometric theory.

Sensors. Smit sees great promise in WAZ ocean-bottom seismic networks in combination with modern algorithms, such as anisotropic reverse time migration. RTM relies on a full, two-way solution to the wave equation and makes use of signal energy that is otherwise filtered out or discarded as noise.

UK-based GO Science Ltd. is focused on mobile sensor grid technologies that offer economies of scale in survey automation. GO Science developed self-propelled “flying” nodes that can position themselves at predetermined locations and is currently testing primary in-flight landing and corrective secondary positioning. Shell is interested in reducing the cost and improving the robustness of ocean-bottom receiver arrays, and Smit says this technology is cheaper and will cut deployment time in half compared to current systems.

Also, Shell is in a partnership with Hewlett Packard to develop microelectro-mechanical systems (MEMS) inertial sensing technology into an ultra-high-resolution wireless seismic sensor network, recently tested at a US Geological Survey site. HP MEMS sensors handle 200 samples a second, equivalent to USGS GS-13 sensors and surpassing the throughput of USGS STS-2 sensors, which handle 40 samples a second. Smit said the results so far indicate that it is reasonable to produce accelerometer networks at equal or better quality and lower cost.

Success. Smit is not surprised that we have discovered as much oil and gas as we have using rudimentary technologies, although “the tools that we bring to bear are almost unreasonably effective.” The landscape offers significantly richer opportunities than we can see with our current understanding, he said.

Shell’s alliance with HP began taking shape at a nanotechnology conference in late 2008 and was formalized in early 2010. Nanotechnology has two immediate applications: to create new materials that store acoustic or elastic energy, and to create new sensors—such as membrane films—that recognize turbulence and could be used to coat the interiors of pipelines. Another materials science advancement with oilfield applicability is the development of manufactured materials that perform with high surface (not bulk) dielectric constants.

These examples illustrate the need for the exploration industry to study and support research in materials science and chemistry. They also demonstrate how unusual alliances can be rich sources of innovation to develop breakthrough exploration technologies.