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Geomechanics and Fracture Analysis

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Bulletin Article

5770
 

We present a method of using fault displacement-distance profiles to distinguish fault-bend, shear fault-bend, and fault-propagation folds, and use these insights to guide balanced and retrodeformable interpretations of these structures. We first describe the displacement profiles associated with different end-member fault-related folding models, then provide examples of structures that are consistent with these model-based predictions. Natural examples are imaged in high-resolution two- and three dimensional seismic reflection data sets from the Niger Delta, Sichuan Basin, Sierras Pampeanas, and Cascadia to record variations in displacement with distance updip along faults (termed displacement-distance profiles). Fault-bend folds exhibit constant displacement along fault segments and changes in displacement associated with bends in faults, shear fault-bend folds demonstrate an increase in displacement through the shearing interval, and fault-propagation folds exhibit decreasing displacement toward the fault tip. More complex structures are then investigated using this method, demonstrating that displacement-distance profiles can be used to provide insight into structures that involve multiple fault-related folding processes or have changed kinematic behavior over time. These interpretations are supported by comparison with the kinematics inferred from the geometry of growth strata overlying these structures. Collectively, these analyses illustrate that the displacement-distance approach can provide valuable insights into the styles of fault-related folding.

5726
 

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.

DL Abstract

3103
 

Assets within the Appalachian Basin range from conventional clastic and carbonate reservoirs to source rocks of Devonian black shale and Pennsylvanian coal, all of which are fractured.

3105
 

Craquelure, the fine pattern of cracks found in old paintings, presents a rare opportunity to reach beyond the physical sciences for help in understanding a geological process as inscrutable as the development of joints in a fractured reservoir.

3099
 

Information on fractured reservoirs is often controversial. Engineers see lost circulation, negative skin and fracture well test signatures. Geologists see only matrix properties in their cores.

3091
 

Earth modeling, from the construction of subsurface structure and stratigraphy, to the accurate understanding of rock physics, through the simulation of seismic and nonseismic responses, is an enabling technology to guide decisions in acquisition, processing, imaging, inversion and reservoir property inference, for both static and time-lapse understanding. So it is crucial to capture those earth elements that most influence the geophysical phenomena we seek to study. This is notoriously difficult, probably because we regularly underestimate how clever the earth can be in producing various geophysical phenomena.

3082
 

Using examples from shale reservoirs worldwide, I demonstrate the diversity of shale-hosted fracture systems and present evidence for how and why various fractures systems form. Core and outcrop observations, strength tests on shale and on fractures in core, and geomechanical models allow prediction of fracture patterns and attributes that can be taken into account in well placement and hydraulic fracture treatment design. Both open and sealed fractures can interact with and modify hydraulic fracture size and shape. Open fractures can enhance reservoir permeability but may conduct treatment fluids great distances, in some instances possibly aseismically.

3083
 

Natural fractures are a prominent and dramatic feature of many outcrops and are commonly observed in core, where they govern subsurface fluid flow and rock strength. Examples from more than 20 fractured reservoirs show a wide range of fracture sizes and patterns of spatial organization. These patterns can be understood in terms of geochemical and mechanical processes across a range of scales. Fractures in core show pervasive evidence of geochemical reactions; more than is typical of fractures in many outcrops. Accounting for geochemistry and size and size-arrangement and their interactions leads to better predictions of fluid flow.

Explorer Article

8473
 

Shale formations can confound even the savviest geoscientist when it comes to determining the inner workings of the rock. After expert evaluation, even the most attractive prospecting deal can be a tough sell. And there’s almost always a new piece to each of these puzzles that requires some sophisticated high-tech explaining.

8060
 

Energized by the recent Statoil ASA-operated Bay du Nord light oil discovery in Newfoundland’s offshore Flemish Pass Basin, earth scientists are gearing up to host the fourth Atlantic Realm Conjugate Margins Conference in St. John’s, Newfoundland, Aug. 20-22.

Field Seminar

Great Falls Montana United States 08 September, 2014 13 September, 2014 150
 
Great Falls, Montana, United States
8-13 September 2014

The seminar will utilize traverses to examine multiple thrust sheets exposed in Sun River Canyon, the famous Teton Anticline, and an outstanding example of an exposed fractured reservoir along a fault‐propagated fold in Mississippian carbonates as Swift Reservoir. Participants will examine the mechanics of fracturing, folding, and faulting in thrust belt terrains, identify and discuss new ideas regarding the geometry and kinematics of the development of thrust belts, compare seismic interpretation with outcrop examples, and analyze stratigraphic concepts which are essential in the exploration of thrust belt targets.

Watkins Glen New York United States 23 June, 2014 27 June, 2014 147
 
Watkins Glen, New York, United States
23-27 June 2014

The attendee will gain a working knowledge concerning how faults and fractures develop and their terminology, methodologies utilized in collecting and analyzing fracture data, characteristics of faults and fractures that affect the sedimentary units (including black shales) in the northern Appalachian Basin of New York state, and tectonics that led to the formation of the structures in the northern Appalachian Basin and the adjacent Appalachian Orogen.

Short Course

Casper Wyoming United States 08 September, 2014 12 September, 2014 1513
 
Casper, Wyoming, United States
8-12 September 2014

Take advantage of this unique opportunity to learn all the aspects related to the understanding and modeling of fractured reservoirs. Attendees will take geologic concepts and use them in reservoir modeling through hands-on sessions devoted to the examination of outcrop, core and log data. They will use that information and a software to create 3D fractured reservoir models. Using actual Teapot Dome (Wyoming, USA) field data from the Tensleep and Niobrara Shale formations and a hands-on approach, the workshop allows the geoscientist to identify fractures and to construct predictive 3D fracture models that can be used to identify productive zones, plan wells and to create fracture porosity and permeability models for reservoir simulation.

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