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Petrophysics and Well Logs

Explorer Emphasis Article

Deep water and tight rocks. These terms define most new discovery trends taking place across the globe today, according to Bob Fryklund, chief strategist for upstream at IHS Markit.

American Association of Petroleum Geologists (AAPG)
Explorer Article

Drones and other automata will be more commonplace in the oil field of tomorrow, but they have some obstacles to clear first.

American Association of Petroleum Geologists (AAPG)
Explorer Article

The oil and gas industry is facing a tidal wave of retirements as the Great Crew Change occurs, but the challenges of replacing technical professionals might not be as difficult as you think. On the other hand, they might be considerably worse.

American Association of Petroleum Geologists (AAPG)
Spheres of Influence Article

Reliable access to safe, clean drinking water is something most people in the United States take for granted. We turn on our tap and out comes clean water! We brush our teeth, wash our clothes, cook our meals and bathe our children. In the United States, it’s abundant, reliable and relatively cheap. Even kings of the past didn’t have such luxury.

American Association of Petroleum Geologists (AAPG)
Spheres of Influence Article

Environmental issues are a worldwide concern - the Division of Environmental Geosciences has an obligation to provide science-based opinions of these issues to educate the public, government officials and other petroleum industry professionals.

American Association of Petroleum Geologists (AAPG)
Search and Discovery Article

Relative permeability in shales is an important petrophysical parameter for purposes of accurate estimation of production rate and recovery factor, efficient secondary recovery, and effective water management. We present a method to estimate saturation-dependent relative permeability in shales based on the interpretation of the low-pressure nitrogen adsorption-desorption isotherm measurements. Relative permeability were determined for 30 samples from the gas — and oil — window of Eagle Ford and Wolfcamp shale formations. These sample have low-pressure helium porosity (LPHP) in the range of 0.04 to 0.09 and total organic content (TOC) in the range of 0.02 to 0.06. The samples were ashed to study the effects of removal of organic matter on the pore size distribution, pore connectivity, and relative permeability. The estimated irreducible water saturation and residual hydrocarbon saturation are directly proportional to the TOC and LPHP, and exhibit 15% variation over the entire range. Pore connectivity, in terms of average coordination number, decreases by 33% with the increase in TOC from 0.02 to 0.06. The estimated fractal dimension is close to 2.7 for all the samples. The estimated relative permeability of aqueous phase and that of hydrocarbon phase at a given saturation is inversely proportional to the TOC. Relative permeability curves of the hydrocarbon phase for geological samples from various depths in a 100-feet interval indicate that the hydrocarbon production rate will vary drastically over the entire interval and these variations will increase as the hydrocarbon saturations reduce in the formation. In contrast, relative permeability curves of the aqueous phase suggest limited variation in water production rate over the entire interval. Further, based on the relative permeability curves, the hydrocarbon production is predicted to be negligible for hydrocarbon saturations below 50% and the water production is expected to be negligible for water saturations below than 80%. Efforts are ongoing to use the laboratory-based estimates to predict field-scale production and recovery rates.

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American Association of Petroleum Geologists (AAPG)
Search and Discovery Article

Measurements of fluid wetting characteristic are made routinely on rock samples. However, there are no published petrophysical models to differentiate between oil-wet and water-wet fractions of a reservoir sequence using commonly available log suites. This presentation builds on our previous publication that describes the unconventional reservoir petrophysical model we have developed (Holmes, 2014). Essentially, we define four porosity components, namely total organic carbon, clay porosity, effective porosity, and “free shale porosity.” This last component is an indirect calculation if the first three components do not sum to total porosity.  Porosity/resistivity plots can be constructed for the total porosity and interpreted in a standard fashion. These will mostly indicate a water-wet system where the effective porosity fraction is examined. A second porosity/resistivity plot compares resistivity with “free shale porosity,” and is clearly interpreted to indicate Archie saturation exponents of much larger than 2 — frequently in excess of 3 — indicating the oil-wet fraction of the reservoir system. Additionally, the plots suggest low to very low values of cementation exponent, ranging from 1.0 to 1.5.   Examples from the Bakken of Montana and North Dakota, the Niobrara of Colorado, and the Wolfcamp and Spraberry of Texas are presented showing quantitative distinction of water-wet vs. oil-wet reservoir components.

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American Association of Petroleum Geologists (AAPG)
Search and Discovery Article

Interpretations of thermal maturation provide critical data needed for both conventional and unconventional resource assessments. The absence of true vitrinite in pre-Devonian sediments eliminates one of the most commonly measured geothermometers used for thermal maturity determination. Programmed pyrolysis parameters like Tmax can be of limited utility given the maturity regime. However, other organic macerals are potentially available to constrain thermal maturity. The current organic petrology study has been undertaken to provide a very detailed comparison of reflectance measurements on pyrobitumens, “vitrinite-like” material and graptolites.  In the Appalachian Basin of North America, Cambrian-aged source rocks were deposited in shallow water mixed carbonate-siliciclastic depositional environments. Solid pyrobitumen material is found to occur in both lenticular lens/layer morphology as well as distinct pore-filling angular varieties. Published formulas to calculate Equivalent Reflectance (Eq. Ro) from solid bitumens have been applied to these discrete morphological populations. In addition, a newly developed formula to calculate Eq. Ro from angular pyrobitumen (VRc=0.866*BRo ang + 0.0274) is introduced based upon statistical evaluation of reflectance readings from a global dataset. “Vitrinite-like” organic macerals were found in rare abundance within these potential source rocks, but their occurrence enables an independent comparison to pyrobitumen Eq. Ro values. Graptolites are another organic maceral that can be evaluated via organic petrology, but caution should be utilized since these tend to show a high degree of anisotropy. The results of this investigation provide additional geochemical guidance to assist geologists in more accurately interpreting thermal maturity in the Rome Trough region of the Appalachian Basin.

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American Association of Petroleum Geologists (AAPG)
Search and Discovery Article

Rock-Eval hydrogen index (HI) is often used to compare relative maturities of a source horizon across a basin. Usually, there are several measurements from the source horizon at a single well, and the mean hydrogen index is calculated, or the S2 is plotted against TOC. The slope of the best fit line through that data is used as the representative HI for that well (sometimes referred to as the ‘slope HI ’ methodology). There is a potential flaw in both these methodologies; however, that renders the calculated HI as misleading if the source horizon being examined is not relatively uniform in source quality, vertically in the stratigraphic column. From a geologic perspective, it would be unusual for the source rock quality not to vary vertically in the stratigraphic column. Organic matter input, preservation, dilution, and sediment accumulation rate typically vary in many depositional environments over the millions of years required to create a thick source rock package. Nevertheless, there are source rocks which do display remarkable source-quality uniformity from top to bottom of the stratigraphic package. We have examined source rocks from several basins where the source quality is relatively uniform over the stratigraphic column, and source rocks where the source quality varies greatly over the stratigraphic column. Methodologies to assess hydrogen index at specific wells for the se two scenarios differ. Most geoscientists may not be familiar with why a single technique is not suitable for both these scenarios, or how to correctly use hydrogen index as a relative maturation proxy in the case where source rock quality is not uniform. We will demonstrate how to determine if your source rock quality is uniform or varied relative to HI over the stratigraphic column, and how to assign a hydrogen index to the different source facies when that source rock quality is not uniform. Further we will illustrate how to estimate the original hydrogen index of the different source facies and assign each a transformation ratio. The transformation ratio is a better proxy for relative maturity, since different source facies may have different present-day hydrogen indices, but their present-day transformation ratio should be quite similar.

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American Association of Petroleum Geologists (AAPG)
Search and Discovery Article

The assessment of the natural temporal variability of source rock units is critical for the understanding of petroleum systems as changes in mineral matrix, organic matter (OM) concentration, and composition can significantly affect expulsion efficiency, primary and secondary migration processes, hydrocarbon quality as well as oil source rock correlation. Already small-scaled fluctuations within sediment successions can critically influence migration efficiency. High-resolution investigation of a well-preserved Lower Jurassic drill core (Toarcian Posidonia Shale) revealed seven discrete and systematic intervals of deviating source rock quality. These were composed of homogenized, non-laminated marls of light grey color, opposed to laminated dark grey background sedimentation. Both lithotypes differentiate not only in mineral composition, but particularly in OM content and quality. An average TOC content of app. 3.9 wt.% reached by the grey marl, is faced by an average TOC content of app. 7.8 wt.% measured for the laminated dark grey marls. Average hydrogen index for grey non-laminated marls was app. 550 mg HC/g TOC, whereas much higher source rock quality with 780 mg HC/g TOC was attained in the dark laminated marls. The marls lower OM concentration and inferior OM quality generates important domains for preferential migration of products, originated from the dark grey layers, or hydrocarbon cluster in case of limited migration into adjacent reservoirs. To assess the potential for preferential intake of hydrocarbons by the coarser-grained light marls and their qualification as migration avenues, artificial maturation experiments were performed with both lithotypes. Hydrocarbon generation was simulated by hydrous pyrolysis in two successive temperature steps 330 °C and 360 °C, covering an early maturity stage, as well as the end of the oil window. Both lithologies show striking differences, not only for the extract yield, but also for the timing of generation. OM quality differences were reflected by variable n-alkane distributions and molecular maturity parameters. High-resolution continuous data produced by non-destructive techniques allows to draw conclusions on i) source rock potential, ii) expulsion and migration processes , and iii) on prediction of petroleum accumulation within the sediment succession. High-resolution investigation in combination with artificial maturation experiments represent an easy-to-use tool in petroleum system analysis.

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American Association of Petroleum Geologists (AAPG)
Field Seminar
Palermo, Italy
Thursday, 25 April 2024, 8:00 a.m.–9:00 a.m.

This one-day field trip will provide an introduction to a Miocene-Pliocene succession of southern Sicily, which includes outcrops of the Messinian Salinity Crisis (MSC), as well as the Messinian-Zanclean GSSP (Global Boundary Stratotype Sections and Point) and Zanclean stratotype. The MSC sedimentary record consists of an evaporitic-carbonate unit at the base (the Basal Limestone), overlain the Lower Gypsum unit, in turn overlain by the Upper Gypsum unit, and sealed by transgressive chalk deposits of the Trubi Fm. The Lower Gypsum unit (massive gypsum with cm-sized selenite crystals) will be visited along the beach of Siculiana Marina (about 15 km NW of Agrigento). Next, we will visit near Capo Rossello (about 10 km NW of Agrigento) an outcrop of the Upper Gypsum unit consisting of clay-gypsum cycles and overlain by the Trubi Fm. The latter, at Scala dei Turchi beach, consists of chalk deposits arranged in a spectacular thick succession (~120 m thick) interpreted as astronomically-controlled depositional cycles. The uppermost interval of the MSC sedimentary record, including the Messinian-Zanclean GSSP, will be observed along the beach of Eraclea Minoa located about 20 km NW of Capo Rossello. Pricing Fee: €50 Attendee Limit: Min 15 - Max 50 People Registration Deadline: 11 April 2024 Field Trip Rendezvous Point Hotel nH Palermo Field Trip Leaders Antonio Caruso University of Palermo Attilio Sulli University of Palermo

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American Association of Petroleum Geologists (AAPG)
Field Seminar
Banff, Canada
Saturday, 11 May 2024, 8:00 a.m.–3:00 p.m.

Time: 8:00am - 5:00pm Fee: $300 AAPG members $350 Nonmembers $200 Academic/AAPG Emeritus Members $50 discount for workshop registrants Fee Includes: Transportation Insurance Field guide Entrance fee to Banff National Park Registration available during workshop registration This field trip will focus on the structural geology of the foothills and Front Ranges of Banff. Participants will be able to view excellent field examples of structures very similar to the producing oil and gas fields in the foothills to the west of Calgary and to learn about the complexities of sub-seismic-scale deformation. The field trip starts with an introduction to the interaction between thrust front with foreland basins and the interaction of basement trends with thrust belt geometries and (conventional) hydrocarbon fields. During the 1-day trip participants will follow a dip transect from the undeformed foreland basin, the eastern edge of the foothills marked by the triangle zone, the Front Ranges boundary and end at the Main Ranges west of Banff. Field Trip Itinerary Depart from Calgary – 8:00 a.m. Stop 1: Cochrane Retreat Road Overlook Trip overview and introduction; safety and logistics comments; interaction of thrust front with foreland basin; interaction of basement trends with thrust belt geometry and (conventional) hydrocarbon field distribution; appreciation of scale for subsurface play fairway. Stop 2: Scott Lake Stop 3: The Stony Nakoda Tim’s Classic stop, with historical importance for understanding the thrust belt and thrust geometry. Part 1 of displacement gradient on a large thrust. Most importantly, toilet stop after all the Tim’s coffee and driving. Review of Mt Yamnuska from a different perspective; preview of drive through McConnell damage zone and change in HW stratigraphy.. Stop 4: Lac des Arcs Imbricate thrust sheets in the Front Ranges and Banff Formation. Stop 5: Canmore T-junction Observe complexities of sub-seismic-scale deformation in mechanically layered rocks in the footwall of a large thrust Stop 6: Canmore strike view of the Rundle thrust Exposed strike view analogous to a cut-away of a giant conventional Foothills hydrocarbon field such as Turner Valley. Cross faults within the thrust sheet offset potential reservoir units at sub-seismic scale. Cross faults are arguably part of a regional trend associated with deeper, basement-rooted NE-SW structures. Stop 7: Mt Norquay Overlook Stop 8: Bow Falls Fracture systems in the Vega Siltstone Mbr of the Triassic Sulphur Mtn Fm. This outcrop of Vega Member siltstone of the Sulphur Mtn Fm is considered equivalent to upper Montney Fm. We will focus on the outcrop adjacent to the steps up to the Falls overlook.

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American Association of Petroleum Geologists (AAPG)
Workshop
Abu Dhabi, UAE
Monday, 27 May Wednesday, 29 May 2024, 8:00 a.m.–5:00 p.m.

In order to support the energy transition, optimizing exploration and production from complex stratigraphic-diagenetic conventional and unconventional plays remains highly important. At the same time, Carbon Capture and Storage (CCS) poses new technological challenges that will impact both the industry and academia for decades to come. This 2nd edition will present reviews and discuss technology developments in geological process-based forward modeling achieved during the last 2 years. New perspectives for future technology developments and implementation in industry workflows will be discussed and with the additional focus on CO₂ storage and other sustainability-related applications, the scope of the workshop will be considerably extended.

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American Association of Petroleum Geologists (AAPG)
VG Abstract

The Betic hinterland, in the westernmost Mediterranean, constitutes a unique example of a stack of metamorphic units. Using a three-dimensional model for the crustal structure of the Betics-Rif area this talk will address the role of crustal flow simultaneously to upper-crustal low-angle faulting in the origin and evolution of the topography.

Request a visit from Juan I. Soto!

American Association of Petroleum Geologists (AAPG)
DL Abstract

Physics is an essential component of geophysics but there is much that physics cannot know or address. 

Request a visit from John Castagna!

American Association of Petroleum Geologists (AAPG)
DL Abstract

As oil and gas exploration and production occur in deeper basins and more complex geologic settings, accurate characterization and modeling of reservoirs to improve estimated ultimate recovery (EUR) prediction, optimize well placement and maximize recovery become paramount. Existing technologies for reservoir characterization and modeling have proven inadequate for delivering detailed 3D predictions of reservoir architecture, connectivity and rock quality at scales that impact subsurface flow patterns and reservoir performance. Because of the gap between the geophysical and geologic data available (seismic, well logs, cores) and the data needed to model rock heterogeneities at the reservoir scale, constraints from external analog systems are needed. Existing stratigraphic concepts and deposition models are mostly empirical and seldom provide quantitative constraints on fine-scale reservoir heterogeneity. Current reservoir modeling tools are challenged to accurately replicate complex, nonstationary, rock heterogeneity patterns that control connectivity, such as shale layers that serve as flow baffles and barriers.

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Request a visit from Tao Sun!

American Association of Petroleum Geologists (AAPG)
VG Abstract

The carbonate sequences that were deposited in the now exhumed Tethyan Ocean influence many aspects of our lives today, either by supplying the energy that warms our homes and the fuel that powers our cars or providing the stunning landscapes for both winter and summer vacations. They also represent some of the most intensely studied rock formations in the world and have provided geoscientists with a fascinating insight into the turbulent nature of 250 Million years of Earth’s history. By combining studies from the full range of geoscience disciplines this presentation will trace the development of these carbonate sequences from their initial formation on the margins of large ancient continental masses to their present day locations in and around the Greater Mediterranean and Near East region. The first order control on growth patterns and carbonate platform development by the regional plate-tectonic setting, underlying basin architecture and fluctuations in sea level will be illustrated. The organisms that contribute to sequence development will be revealed to be treasure troves of forensic information. Finally, these rock sequences will be shown to contain all the ingredients necessary to form and retain hydrocarbons and the manner in which major post-depositional tectonic events led to the formation of some of the largest hydrocarbon accumulations in the world will be demonstrated.

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Request a visit from Keith Gerdes!

American Association of Petroleum Geologists (AAPG)
DL Abstract

Paleozoic North America has experienced multiple mountain building events, from Ordovician to Permian, on all margins of the continent. These have had a profound effect on the resulting complex basins and their associated petroleum systems. Subsequent uplift, erosion and overprinting of these ancient systems impedes the direct observation of their tectonic history. However, the basin sedimentary records are more complete, and provide additional insights into the timing and style of the mountain building events. In this study, we employ ~90 1D basin models, ~30 inverse flexural models, isopachs, and paleogeographic maps to better understand the Paleozoic history of North America.

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Request a visit from Kurt W. Rudolph!

American Association of Petroleum Geologists (AAPG)
DL Abstract

Local sea-level changes are not simply a function of global ocean volumes but also the interactions between the solid Earth, the Earth’s gravitational field and the loading and unloading of ice sheets. Contrasting behaviors between Antarctica and Scotland highlight how important the geologic structure beneath the former ice sheets is in determining the interactions between ice sheets and relative sea levels.

Request a visit from Alex Simms!

American Association of Petroleum Geologists (AAPG)
VG Abstract

In comparison with the known boundary conditions that promote salt deformation and flow in sedimentary basins, the processes involved with the mobilization of clay-rich detrital sediments are far less well established. This talk will use seismic examples in different tectonic settings to document the variety of shale geometries that can be formed under brittle and ductile deformations.

Request a visit from Juan I. Soto!

American Association of Petroleum Geologists (AAPG)
DL Abstract

President Biden has laid out a bold and ambitious goal of achieving net-zero carbon emissions in the United States by 2050.  The pathway to that target includes cutting total greenhouse gas emissions in half by 2030 and eliminating them entirely from the nation’s electricity sector by 2035. The Office of Fossil Energy and Carbon Management will play an important role in the transition to net-zero carbon emissions by reducing the environmental impacts of fossil energy production and use – and helping decarbonize other hard-to abate sectors.

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Request a visit from Jennifer Wilcox!

American Association of Petroleum Geologists (AAPG)
DL Abstract

For well over a century there have been conflicting indications of the strength of the crust and of faults and what controls them.  Much of our ignorance comes quite naturally from the general inaccessibility of the crust to measurement--in contrast with our understanding of the atmosphere, which is much more accessible to observation as well as more rapidly changing.  Crustal strength is best understood in deforming sedimentary basins where the petroleum industry has made great contributions, particularly in deforming petroleum basins because of the practical need to predict. In this talk we take a broad look at key issues in crustal strength and deformation and what we can learn from boreholes, earthquakes, active fault systems, and toy models.

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Request a visit from John Suppe!

American Association of Petroleum Geologists (AAPG)
DL Abstract

While there are many habitats that are associated with the deposition of organic-rich marine and lacustrine source rocks, one important pathway is linked to the onset of increased basin subsidence associated with major tectonic events. A key aspect is that this subsidence is spatially variable, with the uplift of basin flanks contemporaneous with the foundering of the basin center, resulting in a steeper basin profile.

Request a visit from Kurt W. Rudolph!

American Association of Petroleum Geologists (AAPG)

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