By using a new seismic survey technique ConocoPhillips has identified new untested potential oil traps on Alaska’s North Slope, Al Hirshberg, the company’s executive vice president for drilling and projects, commented during the company’s annual analyst and investor meeting on Nov. 8.
Matt Fox, ConocoPhillips executive vice president for exploration and technology, told the meeting that the company’s Willow discovery in the northeastern NPR-A had enabled the calibration of seismic techniques to specifically search for similar prospects.
“When we did that we could see a lot of follow up potential on the seismic structures and the sediments that look the same size as Willow, many of them right across that area,” Fox said.
ConocoPhillips has said that the Willow discovery, announced in January of this year, may hold 300 million barrels of recoverable oil. The discovery involves a subtle stratigraphic trap in the Nanushuk formation, a rock unit that has become associated with major new oil discoveries on the North Slope. A stratigraphic trap involves a situation where hydrocarbons become trapped underground because of rock strata geometry that results from the manner in which the strata were formed.
Fox cautioned that, with the involvement of stratigraphic traps, there is no guarantee that the new prospects actually hold oil.
“But every one of them we’ve drilled so far has had oil in it, so we’re hopeful that several of these Willow lookalikes will deliver additional production,” Fox said.
Compressive seismic imagingThe new seismic technique that ConocoPhillips is pioneering is called compressive seismic imaging, a technique which the company says it invented and which the company has patented. The company has been using the technique for about five years around the world, with demand for use of the method increasing as the company’s geoscientists have become aware of the technique’s capabilities, Hirshberg said.
In a conventional seismic survey, multiple seismic traces from multiple shots targeting the same subsurface region are stacked together, to amplify the sound echoes from subsurface rock structures while dampening out the background noise in the sound recordings. Apparently ConocoPhillips’ new technique involves the use of a sophisticated mathematical process to combine data from multiple seismic shots - similar mathematics are used in the medical field for the processing of magnetic resonance imaging, or MRI, a technique used to create images of the internal structures of people’s bodies.
The mathematical processing of the seismic data reveals detail finer than the resolution achievable from conventional seismic techniques. There is a 10-fold increase in the definition and resolution that can be obtained from the same raw seismic data, Hirshberg said.