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5686
 

Sequence stratigraphy and coal cycles based on accommodation trends were investigated in the coal-bearing Lower Cretaceous Mannville Group in the Lloydminster heavy oil field, eastern Alberta. The study area is in a low accommodation setting on the cratonic margin of the Western Canada sedimentary basin. Geophysical log correlation of coal seams, shoreface facies, and the identification of incised valleys has produced a sequence-stratigraphic framework for petrographic data from 3 cored and 115 geophysical-logged wells. Maceral analysis, telovitrinite reflectance, and fluorescence measurements were taken from a total of 206 samples. Three terrestrial depositional environments were interpreted from the petrographic data: ombrotrophic mire coal, limnotelmatic mire coal, and carbonaceous shale horizons. Accommodation-based coal (wetting- and drying-upward) cycles represent trends in depositional environment shifts, and these cycles were used to investigate the development and preservation of the coal seams across the study area.

The low-accommodation strata are characterized by a high-frequency occurrence of significant surfaces, coal seam splitting, paleosol, and incised-valley development. Three sequence boundary unconformities are identified in only 20 m (66 ft) of strata. Coal cycle correlations illustrate that each coal seam in this study area was not produced by a single peat-accumulation episode but as an amalgamation of a series of depositional events. Complex relations between the Cummings and Lloydminster coal seams are caused by the lateral fragmentation of strata resulting from the removal of sediment by subaerial erosion or periods of nondeposition. Syndepositional faulting of the underlying basement rock changed local accommodation space and increased the complexity of the coal cycle development.

This study represents a low-accommodation example from a spectrum of stratigraphic studies that have been used to establish a terrestrial sequence-stratigraphic model. The frequency of changes in coal seam quality is an important control on methane distribution within coalbed methane reservoirs and resource calculations in coal mining. A depositional model based on the coal cycle correlations, as shown by this study, can provide coal quality prediction for coalbed methane exploration, reservoir completions, and coal mining.

5684
 
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.
5683
 
Anomalously high porosities and permeabilities are commonly found in the fluvial channel sandstone facies of the Triassic Skagerrak Formation in the central North Sea at burial depths greater than 3200 m (10,499 ft), from which hydrocarbons are currently being produced. The aim of our study was to improve understanding of sandstone diagenesis in the Skagerrak Formation to help predict whether the facies with high porosity may be found at even greater depths. The Skagerrak sandstones comprise fine to medium-grained arkosic to lithic-arkosic arenites. We have used scanning electron microscopy, petrographic analysis, pressure history modeling, and core analysis to assess the timing of growth and origin of mineral cements, with generation, and the impact of high fluid pressure on reservoir quality. Our interpretation is that the anomalously high porosities in the Skagerrak sandstones were maintained by a history of overpressure generation and maintenance from the Late Triassic onward, in combination with early microquartz cementation and subsequent precipitation of robust chlorite grain coats. Increasing salinity of pore fluids during burial diagenesis led to pore-filling halite cements in sustained phreatic conditions. The halite pore-filling cements removed most of the remaining porosity and limited the precipitation of other diagenetic phases. Fluid flow associated with the migration of hydrocarbons during the Neogene is inferred to have dissolved the halite locally. Dissolution of halite cements in the channel sands has given rise to megapores and porosities of as much as 35% at current production depths.
5694
 
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.
3744
 

A three-dimensional seismic data set and published data from exploration wells were used to reconstruct the tectonostratigraphic evolution of the Mandal High area, southern North Sea, Norway. The Mandal High is an elongated southeast-northwest–trending horst. Three fault families in the Lower Permian sequence, inherited from the basement structural grain of Caledonian origin, are interpreted: (1) a north-northwest–south-southeast–striking fault family, (2) a northeast-southwest–striking fault family, and (3) a near east-west–striking fault family. In addition, an east-southeast–west-northwest–striking fault family (4) that formed during Late Jurassic rifting and was reverse reactivated in the Late Cretaceous is interpreted. We suggest that inversion occurred because of small dextral motion along fault family 1. A final fault family (5) displays various strike orientations and is associated with salt movements.

Seven chronostratigraphic sequences defined by well data and recognized on three-dimensional seismic data are interpreted and mapped: Early Permian rifting in a continental environment; Late Permian deposition of the Zechstein salt and flooding; Triassic continental rifting; uplift and erosion in the Middle Jurassic with deposition of shallow-marine and deltaic sediments; rifting and transgression in a deep-marine environment during the Late Jurassic; a post-rift phase in a marine environment during the Early Cretaceous; and flooding and deposition of the Chalk Group in the Late Cretaceous. An eighth sequence was interpreted—Paleogene–Neogene—but has not been studied in detail. This sequence is dominated by progradation from the east and basin subsidence. Well and seismic data over the Mandal High reveal that large parts of the high were subaerially exposed from Late Permian to Late Jurassic or Early Cretaceous, providing a local source of sediments for adjacent basins.

Similar to the Utsira High, where several large hydrocarbon discoveries have been recently seen, the Mandal High might consist of a set of petroleum plays, including fractured crystalline basement and shallow-marine systems along the flanks of the high, thereby opening up future exploration opportunities.

3722
 
The geometries of clay smears produced in a series of direct shear experiments on composite blocks containing a clay-rich seal layer sandwiched between sandstone reservoir layers have been analyzed in detail. The geometries of the evolving shear zones and volume clay distributions are related back to the monitored hydraulic response, the deformation conditions, and the clay content and strength of the seal rock. The laboratory experiments were conducted under 4 to 24 MPa (580–3481 psi) fault normal effective stress, equivalent to burial depths spanning from less than approximately 0.8 to 4.2 km (0.5 to 2.6 mi) in a sedimentary basin. The sheared blocks were imaged using medical-type x-ray computed tomography (CT) imaging validated with optical photography of sawn blocks. The interpretation of CT scans was used to construct digital geomodels of clay smears and surrounding volumes from which quantitative information was obtained. The distribution patterns and thickness variations of the clay smears were found to vary considerably according to the level of stress applied during shear and to the brittleness of the seal layer. The stiffest seal layers with the lowest clay percentage formed the most segmented clay smears. Segmentation does not necessarily indicate that the fault seal was breached because wear products may maintain the seal between the individual smear segments as they form. In experiments with the seal layer formed of softer clays, a more uniform smear thickness is observed, but the average thickness of the clay smear tends to be lower than in stiffer clays. Fault drag and tapering of the seal layer are limited to a region close to the fault cutoffs. Therefore, the comparative decrease of sealing potential away from the cutoff zones differs from predictions of clay smear potential type models. Instead of showing a power-law decrease away from the cutoffs toward the midpoint of the shear zone, the clay smear thickness is either uniform, segmented, or undulating, reflecting the accumulated effects of kinematic processes other than drag. Increased normal stress improved fault sealing in the experiments mainly by increasing fault zone thickness, which led to more clay involvement in the fault zone per unit of source layer thickness. The average clay fraction of the fault zone conforms to the prediction of the shale gouge ratio (SGR) model because clay volume is essentially preserved during the deformation process. However, the hydraulic seal performance does not correlate to the clay fraction or SGR but does increase as the net clay volume in the fault zone increases. We introduce a scaled form of SGR called SSGR to account for increased clay involvement in the fault zone caused by higher stress and variable obliquity of the seal layer to the fault zone. The scaled SGR gives an improved correlation to seal performance in our samples compared to the other algorithms.
3720
 
The continuity of clay smears evolving in sealed direct shear experiments of initially intact sandstone-mudrock sequences was quantified to large displacements up to more than ten times the thickness of the sealing layer. The sample blocks consisted of a preconsolidated clay-rich seal layer, which was embedded and synthetically cemented in quartz sand. The mineralogy and mechanical properties of the clay layer and the reservoir sandstones were varied systematically to mimic a range of natural clastic rock sequences. The fluid-flow response across the fault zone was monitored continuously during deformation using a new type of direct shear cell. The displacement at which seals break down is closely linked to the amount of phyllosilicates in the seal layer. Contrary to expectations, softer seal layers do not seal better than stiff seal layers for a given clay content. In the testing range of normal effective stresses between 4 to 24 MPa (580–3481 psi) covering maximum burial depth conditions of approximately 800 m (2625 ft) to approximately 4 km (2 mi) (assuming normal fault tectonics), a systematic trend is also observed, indicating better smear continuity by increasing the effective normal stress. Predominantly brittle processes such as slicing and wear, and not ductile drag or plastic flow, appear to be responsible for the generation of clay smears. The test results offer the prospect of incorporating critical shale smear factors (i.e., normalized displacement at which seal breakdown occurs) into probabilistic fault seal algorithms that consider important properties that can be measured or estimated, namely, clay content and fault-normal effective stress.
3717
 
Gas generation is a commonly hypothesized mechanism for the development of high-magnitude overpressure. However, overpressures developed by gas generation have been rarely measured in situ, with the main evidence for such overpressures coming from source rock microfractures, the physical necessity of overpressures for primary migration, laboratory experiments, and numerical modeling. Indeed, previous in-situ observations suggest that gas generation only creates highly localized overpressures within rich source rocks. Pore-fluid pressure data and sonic velocity–vertical effective stress plots from 30 wells reveal that overpressures in the northern Malay Basin are primarily generated by fluid expansion and are located basinwide within the Miocene 2A, 2B, and 2C source rock formations. The overpressures are predominantly associated with gas sampled in more than 83% of overpressure measurements and have a sonic-density response consistent with gas generation. The association of fluid expansion overpressures with gas, combined with the sonic-density response to overpressure and a regional geology that precludes other overpressuring mechanisms, provides convincing in-situ evidence for basinwide gas generation overpressuring. Overpressure magnitude analysis suggests that gas generation accounts for approximately one-half to two-thirds of the measured excess pore pressure in the region, with the remainder being generated by coincident disequilibrium compaction. Thus, the data herein suggest that gas generation, if acting in isolation, is producing a maximum pressure gradient of 15.3 MPa/km (0.676 psi/ft) and not lithostatic magnitudes as commonly hypothesized. The gas generation overpressures in this article are not associated with a significant porosity anomaly and represent a major drilling hazard, with traditional pore-pressure prediction techniques underestimating pressure gradients by 2.3 plusmn 1.5 MPa/km (0.1 plusmn 0.07 psi/ft).
3716
 
We use samples from undeformed and deformed sandstones (single deformation band, deformation band cluster, slip-surface cataclasite, and fault core slip zone) to characterize their petrophysical properties (porosity, permeability, and capillary pressure). Relationships between permeability and porosity are described by power-law regressions where the power-law exponent (D) decreases with the increasing degree of deformation (strain) experienced by the sample from host rock (D, sim9) to fault core (D, sim5). The approaches introduced in this work will allow geologists to use permeability and/or porosity measurements to estimate the capillary pressures and sealing capacity of different fault-related rocks without requiring direct laboratory measurements of capillary pressure. Results show that fault core slip zones have the highest theoretical sealing capacity (gt140-m [459-ft] oil column in extreme cases), although our calculations suggest that deformation bands can locally act as efficiently as fault core slip zones in sealing nonwetting fluids (in this study, oil and CO2). Higher interfacial tension between brine and CO2 (because of the sensitivity of CO2 to temperature and pressure) results in higher capillary pressure and sealing capacity in a brine and CO2 system than a brine and oil system for the same samples.
3713
 
Reservoir properties of Upper Triassic–Middle Jurassic sandstones, Spitsbergen, are studied as part of a CO2 storage pilot project in Longyearbyen. The reservoir formations show large contrasts in sandstone compositions, with unexpected low permeability despite moderate porosity values. Petrographic analyses were performed to investigate the influence and distribution of diagenesis. It is concluded that, because of various compaction, cementation, and dissolution processes, the sandstone porosity is mainly isolated molds and micropores and associated with fibrous illite and chamosite, explaining the low permeability. Diagenesis and the distribution of quartz cement is influenced by lithofacies and detrital compositions. Mineralogically immature sandstones (De Geerdalen Formation) show a homogeneous distribution of quartz cement overgrowths on quartz grains, distributed interstitial to labile grains and other cements (e.g., late calcite). The main silica source was from the dissolution of adjacent feldspar and labile grains as part of the chemical compaction. In contrast, quartz-dominated sandstones (Knorringfjellet Formation) show a heterogeneous patchy distribution of quartz cement influenced by the sedimentary bioturbation pattern, with silica sourced also from dissolution at clay-rich microstylolites. Phosphatic beds at the base and top of the formation are strongly influenced by marine eogenesis and reworking processes and associated with concentration of iron-rich authigenic minerals. The highest porosity appears in sand-supported conglomerate where moldic clay-mineral ooids contributed to reduce quartz cementation. The stratigraphic change from mineralogical immature (Triassic) to mature (uppermost Triassic–Jurassic) sandstone compositions is detected in wide areas of the Barents Shelf and has considerable implications for the distribution of sandstone reservoir properties.
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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.

14 February, 3000 14 February, 3000 7813
 
14 February, 3000 14 February, 3000 7812
 
14 February, 3000 14 February, 3000 7816
 
14 February, 3000 14 February, 3000 7815
 
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. 
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).

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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).

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.

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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