Immersive Visualization Provides An Insider's View Of Subsurface

Bob Tippee
Managing Editor-Economics and Exploration

ARCO Exploration & Production Technology is applying products of in-house visualization research to real-world seismic interpretation.

At the company's Immersive Visualization Environment (IVE) in Plano, Tex., earth scientists, engineers, and business planners take what literally can be an insider's view of the earth's subsurface.

From inside a projection cube with 10 ft sides, wearing stereoscopic eyeware, they view in three dimensions images of structures and horizons interpreted from 3D volumes of seismic and other types of geophysical data (see cover). With a capability called head-tracking they can study the images with the sensation of moving around within the subsurface features.

Perspectives like those are not available in the traditional media of geophysical work: computer workstations and paper records.

Geoffrey A. Dorn, research director at ARCO E&P Technology, says the new visualization technologies enable technicians to interpret 3D data more completely, handle more data at one time, and communicate results more accurately than they can with conventional media.

Because half of the human brain's neurons deal with vision, Dorn explains, visualization helps workers comprehend data that describe complex three dimensional shapes and processes.

Visualization techniques try to present data in an intuitive form in order to "free the mind of the interpreter to concentrate on the geology."

Some visualization techniques can be applied to flat screen displays: using perspective lines and rotating images, for example, to create 3D effects (Fig. 1 [106,348 bytes]and Fig. 2 [160,240 bytes]).

But flat screens crop the view and preclude the use of peripheral vision, creating what Dorn calls "perceptual dissonance."

The IVE brings peripheral vision into play along with other key visual cues to help users see structure, reducing the degree to which they must rely on imagination. They then can concentrate on more important aspects of the geology and petroleum systems, such as depositional history.

The benefits are the same for integrated data. Petrophysical attributes such as porosity can be color-coded and blended with a structural image interpreted from seismic data (Fig. 3 [126,888 bytes]). In the IVE, interpreters can see details and subtle changes in the data that they would miss in images presented on flat screens.

Current use

For now, ARCO divides the IVE's time between visualization research and use by asset teams for real geophysical interpretation.

Teams have used the facility to, among other things, study geophysical data from Pickerill field in the U.K. North Sea, a prospect off the Philippines, and Alaska's North Slope.

In the Pickerill case, the IVE was used to study the drilling plans for a multilateral hole complicated by pressure changes among different compartments of the reservoir and drilling hazards above the reservoir. This evaluation suggested some improvements, fine-tuning the drilling plan to avoid potential problems.

"If you don't use immersive visualization your interpretation is going to be incomplete," says Dorn. Geophysicists commonly identify two to three times as many faults using visualization than they could identify in the same data with conventional tools, he adds.

The IVE also enhances teamwork.

"I see a lot more animated interaction between people of different disciplines" in the IVE than in traditional work environments, Dorn says.

Mary J. Cole, senior exploration programmer who works with Dorn on the IVE and wrote the software that drives the system, offers an explanation: "If you're working on a flat workstation, everybody has his own viewpoint of what's going on in three dimensions." In the IVE, everyone sees the same structural interpretation in 3D.

Because of the teamwork benefit, Dorn plans to expand the IVE's visualization cube to have 12 ft sides so more users can work comfortably inside it at one time.

Dorn and Cole believe that the Plano IVE, in which ARCO has invested slightly less than $3 million, will retain a research role and that application of the technology will eventually shift to new IVE facilities in operating centers.

The IVE

The viewing area of the IVE has three walls of seamless screen and a floor painted grey to serve as a fourth screen. Images come from projectors and mirrors outside the cube.

An electromagnetic tracking system orients the viewer's perspective to the projected data. Stereoscopic viewers worn by users alternate left-eye and right-eye images with the help of infrared timing devices to create 3D visual effects.

The ARCO IVE at first used the Silicon Graphics Onyx Infinite Reality computer system, with two graphics pipelines and four processors with 5 gigabytes of random access memory (Gb of RAM).

The company recently upgraded the system to use the Onyx2 Reality Monster, with four graphics pipelines and eight processors with 4 Gb of RAM.

Dorn says he expects ARCO's operating companies to have workbench scale visualization equipment by 1999 and full-scale IVEs by 2000 but cautions, "All of my time estimates in the last few years have been on the conservative side."

He thinks ARCO will experience productivity gains from immersive visualization comparable to those it had when it began using interactive workstations.

"It's not just a toy," he stresses. "It really can have a major impact on the business."

Visualization keys

While immersive visualization enters the operating mainstream at ARCO, Dorn, Cole, and eight other visualization researchers continue to seek ways to help human technicians perceive complex 3D data.

Visualization technologies try to bring into play as many perceptual cues as is practicable in the study of 3D objects.

These cues include:

• Projection, the way in which the object and spatial relationships are portrayed graphically in a 2D plane.
• Lighting and shading, which tell much about shape and texture.
• Depth of field, the lack of focus of objects close to or far from a viewer when the viewer focuses on an object at an intermediate distance.
• Depth cueing, a lessening of intensity in the rendering of objects as distance from the viewer increases.
• Obscuration, in which nearer parts of an object block from view other parts of the object farther away from the viewer.
• Transparency, a way of overcoming obscuration by allowing the distant parts of an object to show wholly or partly through the closer parts.
• Stereopsis, the ability to compose a 3D image by viewing an object from two slightly different directions at the same time.
• Parallax, the apparent displacement of close objects in relation to farther away objects when viewed from two different positions.
• Motion, which takes advantage of human vision's great sensitivity to small relative changes in objects viewed and enhances effects of other 3D perception cues.

Human comprehension of a complex 3D object, Dorn says, improves "with each additional visual cue."

What's ahead?

Progress in visualization technology depends on computing power.

"We just flat need more powerful computers," Dorn says. Even the processors and graphics recently installed for the IVE upgrade are "not fast enough for the amount of data that we throw at them."

Also, the role of audio, both for controlling images in the IVE and for understanding complex data, will grow. At present, users manipulate images with a "space mouse," which positions a cursor on computer-like button panels that appear on the IVE screens.

Audio commands would eliminate the screen clutter. Workers would say out loud what they want to do, and the computers would recognize their commands and oblige.

Audio also will begin to play a role in the study of complex data. Humans are approaching their capacities to perceive things visually at one time. As Dorn puts it: "We exceed the bandwidth of visual input to the human brain."

The solution: Use other inputs, such as audio, which can communicate changes in data values with changes in pitch and volume the way visual images use color and shading.

Another area of potential advance is synchronization of immersive visualization so that technicians and managers in various locations can simultaneously study a common image.

How far away are such advances?

"We're working on these now," Dorn says.

Copyright 1998 Oil & Gas Journal. All Rights Reserved.