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Sandstone pressures follow the hydrostatic gradient in Miocene strata of the Mad Dog field, deep-water Gulf of Mexico, whereas pore pressures in the adjacent mudstones track a trend from well to well that can be approximated by the total vertical stress gradient. The sandstone pressures within these strata are everywhere less than the bounding mudstone pore pressures, and the difference between them is proportional to the total vertical stress. The mudstone pressure is predicted from its porosity with an exponential porosity-versus-vertical effective stress relationship, where porosity is interpreted from wireline velocity. Sonic velocities in mudstones bounding the regional sandstones fall within a narrow range throughout the field from which we interpret their vertical effective stresses can be approximated as constant. We show how to predict sandstone and mudstone pore pressure in any offset well at Mad Dog given knowledge of the local total vertical stress. At Mad Dog, the approach is complicated by the extraordinary lateral changes in total vertical stress that are caused by changing bathymetry and the presence or absence of salt. A similar approach can be used in other subsalt fields. We suggest that pore pressures within mudstones can be systematically different from those of the nearby sandstones, and that this difference can be predicted. Well programs must ensure that the borehole pressure is not too low, which results in borehole closure in the mudstone intervals, and not too high, which can result in lost circulation to the reservoir intervals.


This article describes a 250-m (820-ft)-thick upper Eocene deep-water clastic succession. This succession is divided into two reservoir zones: the lower sandstone zone (LSZ) and the upper sandstone zone, separated by a package of pelitic rocks with variable thickness on the order of tens of meters. The application of sequence-stratigraphic methodology allowed the subdivision of this stratigraphic section into third-order systems tracts.

The LSZ is characterized by blocky and fining-upward beds on well logs, and includes interbedded shale layers of as much as 10 m (33 ft) thick. This zone reaches a maximum thickness of 150 m (492 ft) and fills a trough at least 4 km (2 mi) wide, underlain by an erosional surface. The lower part of this zone consists of coarse- to medium-grained sandstones with good vertical pressure communication. We interpret this unit as vertically and laterally amalgamated channel-fill deposits of high-density turbidity flows accumulated during late forced regression. The sandstones in the upper part of this trough are dominantly medium to fine grained and display an overall fining-upward trend. We interpret them as laterally amalgamated channel-fill deposits of lower density turbidity flows, relative to the ones in the lower part of the LSZ, accumulated during lowstand to early transgression.

The pelitic rocks that separate the two sandstone zones display variable thickness, from 35 to more than 100 m (115–>328 ft), indistinct seismic facies, and no internal markers on well logs, and consist of muddy diamictites with contorted shale rip-up clasts. This section is interpreted as cohesive debris flows and/or mass-transported slumps accumulated during late transgression.

The upper sandstone zone displays a weakly defined blocky well-log signature, where the proportion of sand is higher than 80%, and a jagged well-log signature, where the sand proportion is lower than 60%. The high proportions of sand are associated with a channelized geometry that is well delineated on seismic amplitude maps. Several depositional elements are identified within this zone, including leveed channels, crevasse channels, and splays associated with turbidity flows. This package is interpreted as the product of increased terrigenous sediment supply during highstand normal regression.


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.


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.

VG Abstract

The following short course option was developed for geology and geophysics students that have not had much exposure to how geoscience is applied in industry. It can be tailored for undergraduate juniors and seniors or graduate students. The agenda can be modified to meet specific needs and time constraints. Contact the presenter to discuss options.


In reservoir engineering, hydrodynamic properties can be estimated from downhole electrical data using heuristic models (e.g., Archie and Kozeny-Carman's equations) relating electrical conductivity to porosity and permeability. Although proven to be predictive for many sandstone reservoirs, the models mostly fail when applied to carbonate reservoirs that generally display extremely complex pore network structures.

In this article, we investigate the control of the three-dimensional (3-D) geometry and morphology of the pore network on the electrical and flow properties, comparing core-scale laboratory measurements and 3-D x-ray microtomography image analysis of samples from a Miocene reefal carbonate platform located in Mallorca (Spain).

The results show that micrometer- to centimeter-scale heterogeneities strongly influence the measured macroscopic physical parameters that are then used to evaluate the hydrodynamic properties of the rock, and therefore, existing models might not provide accurate descriptions because these heterogeneities occur at scales smaller than those of the integration volume of the borehole geophysical methods. However, associated with specific data processing, 3-D imagery techniques are a useful and probably unique mean to characterize the rock heterogeneity and, thus, the properties variability.


Criteria for recognizing stratigraphic sequences are well established on continental margins but more challenging to apply in basinal settings. We report an investigation of the Upper Devonian Woodford Shale, Permian Basin, west Texas based on a set of four long cores, identifying sea level cycles and stratigraphic sequences in an organic-rich shale.

The Woodford Shale is dominated by organic-rich mudstone, sharply overlain by a bioturbated organic-poor mudstone that is consistent with a second-order eustatic sea level fall. Interbedded with the organic-rich mudstone are carbonate beds, chert beds, and radiolarian laminae, all interpreted as sediment gravity-flow deposits. Bundles of interbedded mudstone and carbonate beds alternate with intervals of organic-rich mudstone and thin radiolaria-rich laminae, defining a 5–10 m (16–33 ft)-thick third-order cyclicity. The former are interpreted to represent highstand systems tracts, whereas the latter are interpreted as representing falling stage, lowstand, and transgressive systems tracts. Carbonate beds predominate in the lower Woodford section, associated with highstand shedding at a second-order scale; chert beds predominate in the upper Woodford section, responding to the second-order lowstand.

Additional variability is introduced by geographic position. Wells nearest the western margin of the basin have the greatest concentration of carbonate beds caused by proximity to a carbonate platform. A well near the southern margin has the greatest concentration of chert beds, resulting from shedding of biogenic silica from a southern source. A well in the basin center has little chert and carbonate; here, third-order sea level cycles were primarily reflected in the stratigraphic distribution of radiolarian-rich laminae.


Data derived from core and well-logs are essentially one-dimensional and determining eolian system type and likely dimensions and orientation of architectural elements present in subsurface eolian reservoir successions is typically not possible from direct observation alone. This is problematic because accurate predictions of the three-dimensional distribution of interdune and dune-plinth elements that commonly form relatively low-permeability baffles to flow, of net:gross, and of the likely distribution of elements with common porosity-permeability properties at a variety of scales in eolian reservoirs is crucial for effective reservoir characterization.

Direct measurement of a variety of parameters relating to aspects of the architecture of eolian elements preserved as ancient outcropping successions has enabled the establishment of a series of empirical relationships with which to make first-order predictions of a range of architectural parameters from subsurface successions that are not observable directly in core. In many preserved eolian dune successions, the distribution of primary lithofacies types tends to occur in a predictable manner for different types of dune sets, whereby the pattern of distribution of grain-flow, wind-ripple, and grain-fall strata can be related to set architecture, which itself can be related back to original bedform type.

Detailed characterization of individual eolian dune sets and relationships between neighboring dune and interdune elements has been undertaken through outcrop studies of the Permian Cedar Mesa Sandstone and the Jurassic Navajo Sandstone in southern Utah. The style of transition between lithofacies types seen vertically in preserved sets, and therefore measurable in analogous core intervals, enables predictions to be made regarding the relationship between preserved set thickness, individual grain-flow thickness, original bedform dimensional properties (e.g., wavelength and height), the likely proportion of the original bedform that is preserved to form a set, the angle of climb of the system, and the likely along-crest variability of facies distributions in sets generated by the migration of sinuous-crested bedforms. A series of graphical models depict common facies arrangements in bedsets for a suite of dune types and these demonstrate inherent facies variability.

VG Abstract

With technical advances in surface seismic and downhole electrical imaging techniques, it is now possible to not only map the distribution of reservoir sandstones in the subsurface, but to accurately define the orientation of productive fairways, or “sweet-spots”, within the sequence.

Channel sands frequently have favorable reservoir characteristics. Having often been laid down in higher energy settings, they commonly have coarser and better sorted grains, less clay and improved poroperm characteristics. However, they often have limited lateral extent and shoe-string geometries which make them more difficult to predict in the subsurface.

This paper will summarize the results of four case studies and some additional examples of how channel sands, laid down in different depositional settings, have been recognized with borehole imaging. From sedimentary features and palaeocurrent directions within the sands it has been possible to determine their orientation.

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In-Person Training
Houston Texas United States 10 November, 2014 10 November, 2014 10401
Houston, Texas, United States
10 November 2014

A one-day series of lectures covers the basic architecture of particulate sedimentary rocks, methods for petrologic characterization, grain assemblages, and diagenesis, including compaction, cementation, grain replacement, and fracturing. Examples of the nature and causes of reservoir quality variations in sandstones at low and high temperatures are provided with a focus on using the character of the primary grain assemblage as a predictive guide to what will happen in the subsurface.

Houston Texas United States 10 November, 2014 11 November, 2014 10487
Houston, Texas, United States
10-11 November 2014

This course summarizes the major advances and current controversies in dolomite research.

Houston Texas United States 11 November, 2014 11 November, 2014 10553
Houston, Texas, United States
11 November 2014

Through applied mineralogy, the student will learn what questions are relevant when formulating a work flow for a project, when evaluating real data, or when trying to figure out what might have “gone wrong” during a project.

Houston Texas United States 12 November, 2014 12 November, 2014 10568
Houston, Texas, United States
12 November 2014

This course provides a rigorous overview of how and where organic-rich rocks are deposited, how they evolve into oil- and gas-generating source rocks, how the porosity systems evolve with thermal maturation, and the petrophysical properties of shale-gas and shale-liquid fine-grained reservoirs.

Houston Texas United States 13 November, 2014 13 November, 2014 10572
Houston, Texas, United States
13 November 2014

The course begins with a short review of the basic principles of carbonate well logging and goes on to detail the different carbonate pore types and the logging methods used to differentiate the various pore types and to determine their hydrocarbon productive potential.

Houston Texas United States 13 November, 2014 13 November, 2014 10379
Houston, Texas, United States
13 November 2014

This course is an introduction to the Bakken/Three Forks resource play.

Golden Colorado United States 17 November, 2014 19 November, 2014 10243
Golden, Colorado, United States
17-19 November 2014

Participants will learn how to be successful in utilizing the Three Forks in a stacked-pay, pad-drilling strategy when producing various Bakken members.

Houston Texas United States 02 December, 2014 04 December, 2014 1516
Houston, Texas, United States
2-4 December 2014

Here is an introduction to the tools and techniques that geologists and geophysicists use to locate gas and oil, that drillers use to drill the wells and that petroleum engineers use to test and complete the wells and produce the gas and oil. Exercises throughout the course provide practical experience in well log correlation, contouring, interpretation of surface and subsurface, contoured maps, seismic interpretation, well log interpretation, and decline curve analysis.

Bogotá, D. C. Colombia 10 December, 2014 11 December, 2014 11015
Bogotá, D. C. , Colombia
10-11 December 2014
Join the GTW Colombia 2014 discussion with leading operators in Latin America, North America and across the globe to expand the science of unconventional resources in Colombia. Build on lessons learned since GTW Colombia 2011. Develop new knowledge from lively discussions with experienced practitioners and researchers. Gain greater understanding by sharing first-hand experiences and best practices in applying geology, geophysics and engineering to the challenges of exploration, appraisal, development drilling, reservoir characterization and simulation, and advances in recovery processes.
Abu Dhabi United Arab Emirates 05 October, 2015 07 October, 2015 13097
Abu Dhabi, United Arab Emirates
5-7 October 2015

This workshop is the outgrowth of continued cooperation between AAPG & EAGE to develop a series of multi-disciplined gatherings dedicated to understanding, completing & producing tight sandstone & carbonate reservoirs.

14 February, 3000 14 February, 3000 7813
14 February, 3000 14 February, 3000 7812
14 February, 3000 14 February, 3000 7815
14 February, 3000 14 February, 3000 7816
Online Training
02 October, 2014 02 October, 2014 10593
2 October 2014
This course is ideal for individuals involved in Midland Basin exploration and development. Successful development of Wolfcamp shale oil relies on complex inter-relationships (ultimately interdependencies) within and between a wide variety of scientific disciplines, financial entities, and company partnerships. 
09 September, 2014 09 September, 2014 10591
9 September 2014
Water cut is a big factor in gauging the success of horizontal drilling in the Mississippi Lime Play (MLP). The contributing factors are related in part to the spectrum of producing lithofacies and reservoir quality encountered that varies laterally and vertically, sometimes dramatically. 
24 October, 2013 24 October, 2013 1499
24 October 2013

This e-symposium will be introducing signal processing techniques as a means to maximize extracting geomechanical data from petrophysical logs.

13 December, 2012 13 December, 2012 1494
13 December 2012

The course will review core data, petrophysical comparisons, rock physics modeling (including pseudo logs and mechanical properties).

06 October, 2011 06 October, 2011 1479
6 October 2011

The e-symposium contains several case studies and log examples of bypassed pay and unconventional resources including Niobrara, Bakken, Marcellus, offshore GOM and others examples including processed log quality issues.

31 October, 2012 31 October, 2012 1492
31 October 2012

This e-symposium will focus on how surface geochemical surveys and Downhole Geochemical Imaging technologies can be utilized jointly to directly characterize the composition of hydrocarbons vertically through the prospect section.

29 September, 2011 29 September, 2011 1478
29 September 2011

This study will focus in the combination of λρ – μρ inversion with clustering analysis techniques in order to discriminate brittle zones in the Barnett Shale.

10 November, 2011 10 November, 2011 1481
10 November 2011

This work investigates how heterogeneity can be defined and how we can quantify this term by describing a range of statistical heterogeneity (e.g. coefficient of variation and the Lorenz coefficient).

21 February, 2013 21 February, 2013 1495
21 February 2013

The course will review core data, petrophysical comparisons, rock physics modeling (including pseudo logs and mechanical properties).

07 June, 2012 07 June, 2012 1488
7 June 2012

Unger Field, discovered in1955, has produced 8.6 million barrels of oil from a thinly (several ft) bedded, locally cherty dolomite containing vuggy and intercrystalline porosity.

30 August, 2012 30 August, 2012 1489
30 August 2012

The entire Middle Pennsylvanian–to–top Precambrian basement (500 m) interval was cored in early 2011 in the BEREXCO Wellington KGS #1-32 well in Wellington Field, Sumner County, KS.

16 February, 2012 16 February, 2012 1483
16 February 2012

This presentation describes a proven workflow that uses a standard narrow azimuth 3D seismic, conventional logs, image logs and core data to build five key reservoir properties required for an optimal development of shale plays.

15 March, 2012 15 March, 2012 1484
15 March 2012

This e-symposium presents techniques for predicting pore pressure in seals by examining case studies from the Gulf of Mexico and incorporating the relationship between rocks, fluids, stress, and pressure.

07 November, 2013 07 November, 2013 1500
7 November 2013

This e-symposium presentation places the interpretation of deep-water turbidites discernible in 3-D seismic inversion data within a geological context.

10 September, 2013 10 September, 2013 1498
10 September 2013

The goal of this e-symposium is to review an important dimension in the ways geologist can build and update geological models using information from performance data.

25 August, 2011 25 August, 2011 1475
25 August 2011

This e-symposium provides highlights of the hydraulic fracturing mechanics, analysis, and design, and is derived from a two and one-half (2-1/2) day course which is designed for drilling, completion, production engineers, engineering technicians, geologists, well-site and completion supervisors, and managers, who desire to possess a comprehensive and integral knowledge of Hydraulic Fracturing.

17 March, 2011 17 March, 2011 1470
17 March 2011

This e-symposium will provide information on which tools, processes, and procedures all geoscientists, engineers, and technical professionals working in shale plays need to understand and implement.

17 February, 2011 17 February, 2011 1469
17 February 2011

This presentation is designed for exploration/production geologists and geological managers or reservoir engineers.

25 March, 2010 25 March, 2010 1458
25 March 2010

The presentation describes a well established fracture modeling workflow that uses a standard 3D seismic, conventional logs, image logs and data from one core to build predictive 3D fracture models that are validated with blind wells.

25 January, 2011 25 January, 2011 1454
25 January 2011

This esymposium takes a close look at workflows associated with resource plays, and analyzes where integration must occur between disciplines, data, and workflows at all phases of the process.

22 October, 2009 22 October, 2009 1452
22 October 2009

This course can help you gain the ability to describe the complex and highly variable reservoirs, which are typified by complex internal heterogeneity.

11 February, 2010 11 February, 2010 1441
11 February 2010

Gas hydrates, ice-like substances composed of water and gas molecules (methane, ethane, propane, etc.), occur in permafrost areas and in deep water marine environments.

14 February, 3000 14 February, 3000 7817
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