Tracking Fracture Corridors in Tight Gas Reservoirs: An Algerian Case Study
EAGE, ALL
 Summary
The interpretation of faulted systems is an essential step in E&P business, from a proper understanding of
prospects to optimal development well placements. The identification of fractured zones within a reservoir,
usually characterized by sub-seismic faults, is often neglected, while it can add significant value to the
development of a project. The present case study is focused on the very prolific Algerian Ordovician tight
reservoir target. It highlights a structure at the end of an appraisal well campaign, where an integrated fracture
reservoir study had been performed in order to track efficiently subtle fault corridors.
The utilization of advanced seismic attributes using the MultiFocusing technique has proven valuable when
determining the detection and extension of fracture corridors within the reservoir. At the well locations, results
matched reasonably well with the fracture orientation and density interpreted from cores, borehole images and
DST interpretations. This approach has a great value when planning well trajectories, for production predictions,
and eventually for locating any future development wells in the area.
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Multi-Focusing imaging and regularization of an irregular 3D dataset in an urban environment
First Break, 2014
Marianne Rauch-Davies
Summary
The generalized approach of the MF method of moveout correction allows processing of data acquired with irregular acquisition design and is very useful in cases where the subsurface is highly complicated.
The core of the Multi-Focusing stacking, based on paraxial approximation and dynamic ray tracing, is its Fresnel-zone basis for defining the large number of traces used in the stacking procedure. The resulting traces have a more densely sampled source-receiver distribution about each output location which allows the output dataset to be easily regularized.
The MF method not only provides coherent stacking of seismic data with arbitrary source-receiver distribution, creating high-quality time images, but also yields enhanced and regularized prestack gathers. In areas where acquiring aregular 3D dataset is impossible due to difficult terrain or high
population density, conventional gathering and stacking often results in shallow gaps in coverage. Stacking these regularized,enhanced gathers can often ‘heal’ these gaps in coverage.
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Diffraction imaging applied to pre-existing 3D seismic data to map fracture corridors in an unconventional play
First Break, 2014
Marianne Rauch-Davies, Kostya Deev, Danil Pelman, Maria Kachkachev-Shuifer
Summary
The MultiFocusing imaging technology is able to describe not only reflection but also diffraction events from conventionally acquired seismic data and is performed in the pre-stack domain. By optimally summing diffracted events and attenuating specular reflections, an image that contains mostly diffraction energy is being generated. Synthetic and seismic studies are indicating a direct relationship between fracture density and intensity of the diffractivity. This phenomenon is being exploited to use seismic to directly map zones within unconventional/tight reservoirs that are naturally fractured. The MultiFocusing diffraction imaging methodology makes it possible to extract the weak diffractive element from the overall wave field and suppresses the strong specular events.
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MultiFocusing 3D diffraction imaging for detection of fractured zones in mudstone reservoirs
ALL, 2014
Alana Schoepp (Shell Canada Ltd.), Evgeny Landa (Geomage), Stephane Labonte (Shell Canada Ltd.)
Summary
Unconventional reservoirs have a unique set of problems. Most production wells are drilled horizontally through the reservoir rock and hydraulic fracturing is applied to increase permeability in the reservoir. The pre-drilling knowledge of natural fracture corridors and small offset faults is very important in this case. Seismic resolution from conventional reflection imaging is generally not sufficient to resolve such small scale rock properties. Diffracted waves are events generated by small scale subsurface heterogeneities and discontinuities (including fractures). Detection and imaging the diffractive component of the total wavefield opens a new perspective to find and characterize fracture zones in carbonate environment.
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