Q+A CENTER

The amount of data that must be mined during oil and gas exploration and production (E&P) is enormous.

"These guys are one of the biggest users of 3D in the world, but they're stealth users," says Michael M. Heck, Technical Director, Visualization and Sciences Group, Mercury Computer Services (Carlsbad, Calif.). "They have a huge and interesting challenge because their data sets are extremely large. My colleagues on the medical side talk about extremely large sets of 1 gigabyte. We're talking here about a terabyte (1,000 gigabytes) in a typical survey."

Why is there so much data? Think about what it takes to even find petroleum or natural gas. First, geologists find a "trap," a spot they believe may contain petroleum. There are five elements that all must be present for a prospect to contain the hydrocarbons that make up petroleum.

• A source rock—When organic-rich rock such as oil shale or coal is subjected to high pressure and temperature over an extended period of time, hydrocarbons form.
• Migration—The hydrocarbons are expelled from source rock by three density-related mechanisms: the newly-matured hydrocarbons are less dense than their precursors, which causes overpressure; the hydrocarbons migrate upwards due to buoyancy; and the fluids expand as further burial causes increased heating. Most hydrocarbons migrate to the surface as oil seeps, but some will get trapped.
• Trap—The hydrocarbons are buoyant and have to be trapped within a structural (for example Anticline or fault block) or stratigraphic (rock layers) trap.
• Seal or cap rock—The hydrocarbon trap has to be covered by an impermeable rock known as a seal or cap-rock to prevent hydrocarbons from escaping to the surface.
• Reservoir—The hydrocarbons are contained in a reservoir rock, usually porous sandstone or limestone. The oil collects in the pores within the rock. The reservoir must also be permeable so that the hydrocarbons will flow to surface during production.

Visible surface features such as oil seeps, natural gas seeps, pockmarks (underwater craters caused by escaping gas) provide basic evidence of hydrocarbon generation. However, most exploration depends on highly sophisticated technology to detect and determine the extent of these deposits. Areas thought to contain hydrocarbons are initially subjected to a gravity survey or magnetic survey to detect large scale features of the sub-surface geology. Features of interest are subjected to more detailed seismic surveys which work on the principle of the time it takes for reflected sound waves to travel through matter (rock) of varying densities and using the process of depth conversion to create a profile of the substructure.

3D visualization, Heck says has been the key to increased success and efficiency in many areas of E&P. In oil and gas, for example, visualization plays a critical role in gaining insight from data. The challenge is characterized by computationally expensive algorithms along with large and diverse data sets. "To meet this challenge, data management, computation and rendering have to be used together smoothly and efficiently," he adds.