'Faults and Fractures' Sharpens Seismic Imagery

As exploration and drilling activities come to a pause during this latest economic downturn, many operators are reprocessing their seismic data with the hope for a new discovery in that data.

Touted as a “revolutionary” fault-imaging attribute, Thinned Fault Likelihood (TFL) is proving to be a relatively new and successful tool for revealing sweet spots and fracture proximity in highly faulted formations, said AAPG member Hesham Refayee, a geoscientist at dGB Earth Sciences.

Refayee and other scientists at dGB have developed a commercial plugin around the TFL attribute that allows operators to quickly process seismic data and generate images that are much sharper and more accurate than semblance-based methods, which have been the preferred interpretation methods for visualizing faults.

“TFL is an ideal input attribute to compute fracture density and fracture proximity attributes,” he said. “Fracture density reveals sweet spots in fractured reservoirs, and fracture proximity shows where – in the data – clean, unfractured areas exist.”

The plugin, called “Faults and Fractures,” combines attributes, filters, fault plane extraction algorithms and various utilities all under one umbrella.

On the market since January, dGB is already selling licenses to the plugin, which is currently being used on seismic data from the Gulf of Mexico and the North Sea.

“This technology really sharpens faults and enhances seismic images,” Refayee said. “This is indeed a step forward in increased profit and reducing risk.”

Please log in to read the full article

As exploration and drilling activities come to a pause during this latest economic downturn, many operators are reprocessing their seismic data with the hope for a new discovery in that data.

Touted as a “revolutionary” fault-imaging attribute, Thinned Fault Likelihood (TFL) is proving to be a relatively new and successful tool for revealing sweet spots and fracture proximity in highly faulted formations, said AAPG member Hesham Refayee, a geoscientist at dGB Earth Sciences.

Refayee and other scientists at dGB have developed a commercial plugin around the TFL attribute that allows operators to quickly process seismic data and generate images that are much sharper and more accurate than semblance-based methods, which have been the preferred interpretation methods for visualizing faults.

“TFL is an ideal input attribute to compute fracture density and fracture proximity attributes,” he said. “Fracture density reveals sweet spots in fractured reservoirs, and fracture proximity shows where – in the data – clean, unfractured areas exist.”

The plugin, called “Faults and Fractures,” combines attributes, filters, fault plane extraction algorithms and various utilities all under one umbrella.

On the market since January, dGB is already selling licenses to the plugin, which is currently being used on seismic data from the Gulf of Mexico and the North Sea.

“This technology really sharpens faults and enhances seismic images,” Refayee said. “This is indeed a step forward in increased profit and reducing risk.”

Man Versus Computer

The idea behind the Faults and Fractures plugin comes from the Colorado School of Mines’ Center for Wave Phenomena. Recognizing a need for better processing for faults apparent in seismic images, geophysics professor Dave Hale and graduate student Xinming Wu developed an algorithm and software that was shared through the university’s open-source Mines Java Toolkit.

Hale recalled their efforts:

Reminding that well data provides accurate measurements of a formation’s density, porosity, permeability and other characteristics, Hale explained that the area between the wellbores is unknown. An important use of seismic data is to help correlate and predict rock properties between wells.

“Geologic faults get in the way of that,” Hale said, explaining that rocks can fracture and slip vertically and horizontally alongside those fractures – faults – between wellbores.

“If you know where the faults are and know how much slippage has occurred, you then know how to correlate rock properties from one side of a fault to the other. We can process 3-D seismic images to find faults, estimate fault slips and undo the faulting, automatically.”

While geologists and geophysicists have been combing though seismic data and picking faults for decades, Hale explained that it can be a tedious and error-prone process, especially for seismic images of formations that are highly faulted.

“Humans are good at seeing things in a photo, a 2-D image. It’s more difficult to see features of interest in a 3-D seismic image, because we can see only a few slices at a time,” Hale said.

“In contrast, computer programs see better in 3-D than in 2-D. In computing attributes like TFL, we process the entire 3-D seismic image simultaneously, not just the few slices visible to a human seismic interpreter.”

Hale added, “Software for automatically picking faults has been commercially available from others for many years. Our open-source programs are freely available, and include some computational tricks that make our algorithms accurate and fast; but you must be a programmer to use them.

Fortunately, others are making these same algorithms available in software that can be more widely used.”

Making It Commercial

With no doubt that Hale’s algorithm would benefit the industry, especially as the shale boom picked up momentum, Refayee and his colleagues worked for nearly a year to develop a plugin that would be compatible with OpendTect, dGB’s free, open-source Seismic Interpretation Software System.

A higher level of the software is available commercially as well. OpendTect Pro, the commercial version for professionals, was launched in January. It marks the transformation of a seismic interpretation platform mainly used by specialists into an easy-to-use platform for generalists as well as specialists.

“OpendTect Pro is a good source for a student researcher and the industry to use,” said AAPG member Nanne Hemstra, dGB’s executive vice president – Americas. “It is made for beginners, specialists and those who want to go into more high-level interpretation workflows.”

In essence, the plugin automatically extracts fault planes, un-faults seismic data and computes feature-specific attributes – namely fracture density and fracture proximity.

Refayee has demonstrated its ability using the Utica Shale formation, which is noted for its large reserve of oil and gas, thickness and fault density. “Utica is one of the most significant unconventional reservoirs in the United States,” Refayee said. “It’s very important in exploiting unconventional reservoirs to understand the tectonic history of the area you are studying.”

Furthermore, the Faults and Fractures plugin facilitates the smoothing of data, reducing the noise of seismic data while simultaneously enhancing features of interest, said Refayee, stressing that the exact position of faults and fractures must be known in order to maximize recovery of stimulation work.

“It’s crucial to know where the faults and fractures are and highlight this discontinuity without removing the characteristics of the seismic,” Hemstra said. “This is often a challenging job because any filtering you do also affects your seismic. This technology preserves the seismic characteristics and highlights the faults and fractures.”

TFL is important as it produces thin lines on 3-D section volumes to highlight faults and fractures, said Hemstra, explaining that thin lines give more detail.

“This helps us to determine which areas are more frac’able than others,” he added.

Convinced of the plugin’s value, several companies have already purchased licenses since its January launch, Refayee noted.

“People think it’s worth investing in. We have had positive feedback from clients,” he said. “We believe that this technology provides excellent return on investment. It is affordable and the outcome is really significant based on the results that we have seen so far.”

Refayee added: “Despite the current downturn, we believe this technology can give oil company operators or a consultant, the ability to enhance their benefits and reduce budget costs.”

uxduqasdxcevcwar

You may also be interested in ...