Bulletin Article

 

Field analogs allow a better characterization of fracture networks to constrain naturally fractured reservoir models. In analogs, the origin, nature, geometry, and other attributes of fracture networks can be determined and can be related to the reservoir through the geodynamic history. In this article, we aim to determine the sedimentary and diagenetic controls on fracture patterns and the genetic correlation of fracture and diagenesis with tectonic and burial history. We targeted two outcrops of Barremian carbonates located on both limbs of the Nerthe anticline (southeastern France). We analyzed fracture patterns and rock facies as well as the tectonic, diagenetic, and burial history of both sites. Fracture patterns are determined from geometric, kinematic, and diagenetic criteria based on field and lab measurements. Fracture sequences are defined based on crosscutting and abutting relationships and compared with geodynamic history and subsidence curves. This analysis shows that fractures are organized in two close-to-perpendicular joint sets (i.e., mode I). Fracture average spacing is 50 cm (20 in.). Fracture size neither depends on fracture orientation nor is controlled by bed thickness. Neither mechanical stratigraphy nor fracture stratigraphy is observed at outcrop scale. Comparing fracture sequences and subsidence curves shows that fractures existed prior to folding and formed during early burial. Consequently, the Nerthe fold induced by the Pyrenean compression did not result in any new fracture initiation on the limbs of this fold. We assume that the studied Urgonian carbonates underwent early diagenesis, which conferred early brittle properties to the host rock.

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The fact that velocity models based on seismic reflection surveys commonly do not consider the near-surface geology necessitates filling the gap between the top of a velocity model and the surface of the Earth. In this study, we present a new workflow to build a shallow geologic model based exclusively on borehole data and corroborated by laboratory measurements. The study area is in Chemery (France), located at the southwestern border of the Paris Basin, where a large amount of borehole data is publicly available. The workflow starts with identifying lithologic interfaces in the boreholes and interpolating them between the boreholes. The three-dimensional (3-D) geometry of the lithologies then allows interpretation of the position, orientation, and offset of fault planes. Given the importance of the fault interpretation in the modeling process, a combination of different approaches is used to obtain the most reasonable structural framework. After creating a 3-D grid, the resulting 3-D structural model is populated with upscaled velocity logs from the boreholes, yielding the final near-surface P-wave velocity model. To better constrain the velocity model, we conducted laboratory measurements of P- and S-wave velocities in dry and water-saturated conditions on all lithologies in the model. The laboratory data were used to populate the 3-D near-surface model with VP/VS ratio values. The presented workflow accounts for one-dimensional borehole data and is much more iterative and time-consuming than workflows based on two-dimensional seismic sections. Nevertheless, the workflow results in a robust 3-D near-surface model allowing for structural interpretations and revealing the 3-D seismic velocity field.
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We describe the structure, microstructure, and petrophysical properties of fault rocks from two normal fault zones formed in low-porosity turbiditic arkosic sandstones, in deep diagenesis conditions similar to those of deeply buried reservoirs. These fault rocks are characterized by a foliated fabric and quartz-calcite sealed veins, which formation resulted from the combination of the (1) pressure solution of quartz, (2) intense fracturing sealed by quartz and calcite cements, and (3) neoformation of synkinematic white micas derived from the alteration of feldspars and chlorite. Fluid inclusion microthermometry in quartz and calcite cements demonstrates fault activity at temperatures of 195degC to 268degC. Permeability measurements on plugs oriented parallel with the principal axes of the finite strain ellipsoid show that the Y axis (parallel with the foliation and veins) is the direction of highest permeability in the foliated sandstone (10–2 md for Y against 10–3 md for X, Z, and the protolith, measured at a confining pressure of 20 bars). Microstructural observations document the localization of the preferential fluid path between the phyllosilicate particles forming the foliation. Hence, the direction of highest permeability in these fault rocks would be parallel with the fault and subhorizontal, that is, perpendicular to the slickenlines representing the local slip direction on the fault surface. We suggest that a similar relationship between kinematic markers and fault rock permeability anisotropy may be found in other fault zone types (reverse or strike-slip) affecting feldspar-rich lithologies in deep diagenesis conditions.
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Events Blog

 

Be a part of history by presenting at the premier integrated geosciences event in 2017 at ICE in London incorporating AAPG’s 100th Anniversary. Your expert contribution and practical guidance will help promote and advance the exploration and production of global energy resources.

American Association of Petroleum Geologists (AAPG)
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Explorer Article

 
Since the dramatic expansion of AAPG/ AAPG Foundation’s Visiting Geoscientist program in the fall of 2014, thousands of students around the globe have benefited from it.
American Association of Petroleum Geologists (AAPG)
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Team registrations are now being accepted for this year’s AAPG-AAPG Foundation’s Imperial Barrel Award program (IBA), an annual prospective basin evaluation competition for geoscience graduate students from universities around the world.

American Association of Petroleum Geologists (AAPG)
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Explorer Emphasis

 
While many are working to forecast when the price of oil might reach $80 a barrel again, renowned international strategist and geopolitical analyst Peter Zeihan, the author of “The Accidental Superpower,” predicts in stunning detail the rising and declining energy plays of 2025 and the countries that will ultimately triumph as the world’s leading producers.
American Association of Petroleum Geologists (AAPG)
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Seismic acquisition crews in southwest France attempt to gather data without disturbing the locals.

American Association of Petroleum Geologists (AAPG)
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Explorer Foundation Update

 
The AAPG Foundation’s L. Austin Weeks Undergraduate Grant program annually awards deserving geoscience students and geoscience student organizations across the world with $500 in grant funds.
American Association of Petroleum Geologists (AAPG)
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Explorer Regions and Sections

 
It has been an interesting and eventful year in Europe for AAPG. With all the less-than-good news around, we felt it was important to maintain a program of events and activities throughout the year. Although we are constrained by the events in the industry we have still tried to match the wishes of the members.
American Association of Petroleum Geologists (AAPG)
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Field Seminar

Houston Texas United States 06 April, 2017 06 April, 2017 36590
 
Houston, Texas, United States
6 April 2017

In Conjunction with AAPG 2017 Annual Convention & Exhibition (ACE)
The Spindletop trip takes participants to the site of the “Lucas Gusher,” where on January 10th, 1901 in Beaumont, Texas, 100,000 barrels per day gushed from a salt dome formation. This discovery changed the economy of Texas and helped to usher in the modern petroleum age. The first six gushers in the Spindletop field produced more oil per day than the combined production of all the other producing fields in the world. The Lucas geyser, found at a depth of 1,139 feet, blew a stream of oil over 100 feet high until it was capped nine days later. Lucas and the Hamills finally controlled the geyser on January 19, when a huge pool of oil surrounded it. By that time, throngs of oilmen, speculators, and onlookers had already transformed the city of Beaumont. A new age was born.

Houston Texas United States 05 April, 2017 10 April, 2017 36578
 
Houston, Texas, United States
5-10 April 2017

In Conjunction with AAPG 2017 Annual Convention & Exhibition (ACE)
This six day Pecos River Canyon trip uses the superb and remarkably laterally continuous outcrops of this upper Albian ramp-to-intrashelf basin profile to develop a process-based, sequence stratigraphic framework for analogous Cretaceous reservoir systems surrounding the Bab intrashelf basin in the Middle East.

Houston Texas United States 31 March, 2017 01 April, 2017 36560
 
Houston, Texas, United States
31 March - 1 April 2017

In Conjunction with AAPG 2017 Annual Convention & Exhibition (ACE)
This course combines detailed investigations of modern fluvial, estuarine, deltaic, shoreface, and tidal inlet depositional environments with subsurface examples in core to provide participants with a more holistic understanding of the physical, chemical, and biological characteristics of shallow marine and fluvial reservoirs.

Short Course

Houston Texas United States 06 April, 2017 07 April, 2017 35076
 
Houston, Texas, United States
6-7 April 2017

In Conjunction with AAPG 2017 Annual Convention & Exhibition (ACE)
This course is designed to provide the industry geologist and engineer with a working knowledge of fracture characteristics and variability as they affect production in hydrocarbon reservoirs. This is a hands-on, applied course in fracture interpretation, description, analysis, and effects.

Houston Texas United States 01 April, 2017 02 April, 2017 34815
 
Houston, Texas, United States
1-2 April 2017

In Conjunction with AAPG 2017 Annual Convention & Exhibition (ACE)
Through a combination of lecture and exercises, students will learn a systematic approach for quickly screening interpretations, maps, and prospects to ensure that the potential resources or reserves estimated from those maps are accurately assessed.

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