Geosciences

Victor Schmidt - Houston

Faults

Engineers have their transients, geophysicist constantly attenuate, and geologists have their faults, which come in many different types and configurations. A special focus issue of the American Association of Petroleum Geologists Bulletin recently highlighted advances in our understanding of faults, or breaks in the earth. Our understanding of fault dynamics has made great progress.

A proper petroleum prospect needs three key elements: trap, seal, and petroleum charge. Faults are important because they can create trap and seal, localizing petroleum moving through the sediments. Trap is easily determined with good seismic data, but seal is often questionable and may not be fully determined until the first well is drilled and tested.

Faults are often thought to be continuous planes of discontinuity that break multiple-sediment horizons. They are presented as such on seismic sections and maps, but this is far from accurate. Many earth-breaks in softer, less consolidated rocks are a series of parallel planes or discontinuous planes offset like shingles from one another by a few inches or feet.

The zones of faulting "smear" the individual sediment units, in places sealing and in other places retaining some permeability. This creates a leaky fault.

The amount of offset on the fault plane is critical as well. If porous sediment is adjacent to other porous sediment across the fault plane, any petroleum charge in the pore space is free to move across the fault until an impermeable barrier traps it. If an up-dip porous section is juxtaposed to less permeable sediment, such as shale, a natural seal occurs, producing a barrier for petroleum movement.

The sediment relationships across any fault can be extremely complex where there are thin porous layers intercalated with impermeable layers. Depending on fault movement, a series of traps can occur based on the vertical permeability path available to the charge. Understanding these complex relationships is critical to an efficient development plan for the field. With the advent of higher density, smaller binned 3D surveys faults, and the special relationships they create, are easier to image and understand.

Linux virus

As the industry shifts more of its computing power onto the Linux operating system, it is important that virus control become a part of the shift. Most viruses are aimed at Microsoft operating systems, and the computer industry has responded by providing constantly updated virus traps. Now the same is needed for Linux computing to protect data.

As companies move to Linux desktops and servers, they create many new paths for viruses to move within a network across multiple operating system environments. Recent software bundles allow users to view documents that may contain viruses and resend them to associates unknowingly. This can quickly disable a network.

Vanishing data

How much data does your company have on old media? Chances are you have a lot of older flat magnetic sheets, tapes, and cartridges in storage. But can you read them? Media is generally device-specific, so having only the media is insufficient.

Since the introduction of digital technologies in the 1960s, the lifespan of device/media combinations has been dropping. In a recent newsletter, Ovation Data Services notes that the lifespan of technologies has dropped from 23 to four years for devices and from 30 to 6.5 years for media. This means you may not be able to read the older tapes in storage because the device required is no longer available. To compound the problem, new combinations are expanding rapidly. In the 1980s, there were two devices and 11 media to chose from. Today, there are 24 devices and 26 media available. The older data is still valuable but must to be transferred to a newer format for longer-term access.

EXPLORATION

Canadian clearance

Hunt Oil and Corridor Resources received clearance to gather seismic surveys off Cape Breton to evaluate their offshore licenses. Seismic activities can begin this coming fall/winter between Nov. 1, 2003, and Feb. 28, 2004.

Strict conditions apply, including shutdown of operations if whales come within 1 km of the vessel. Final mitigation plans are being drawn up in consultation with the Department of Fisheries and Oceans and the Canada-Nova Scotia Offshore Petroleum Board.

4D survey

Statoil awarded WesternGeco a contract for the world's first 4D Q-Reservoir survey. WesternGeco shot the baseline Q-Reservoir survey for the Norne field in 2001.