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Sedimentology and Stratigraphy

Search and Discovery Article

The driving forces for conventional accumulations (structural or stratigraphic traps) are Forces of Buoyancy which are due to differences in densities of hydrocarbons and water. In contrast, the driving forces for unconventional tight accumulations are Forces of Expulsion which are produced by high pressures. That is an enormous difference and creates unconventional petroleum systems that are characterized by very different and distinctive characteristics. The Force of Expulsion pressures are created by the significant increase in volume when any of the three main kerogen types are converted to hydrocarbons. At those conversion times in the burial history, the rocks are already sufficiently tight so the large volumes of generated hydrocarbons cannot efficiently escape through the existing tight pore system, thus creating a permeability bottleneck that produces an overpressured compartment over a large area corresponding to the proper thermal oil and gas maturities for that basin. The forces initially created in these source rocks can only go limited distances into adjacent tight reservoirs (clastics or carbonates) above or below the source. The exact distance will vary depending on the pressure increase, matrix permeability, and fractures of that specific tight reservoir system. In general, the distances are small, in the orders of 10s to 100s of feet for oil and larger for more mobile gas systems. Those exact distance numbers are subject to ongoing investigations.   A plot of the pressure data versus elevation for a given formation is critical in determining whether an accumulation is conventional or unconventional. Conventional accumulations will have hydrocarbon columns of 10s to 100s of feet with the pressure in the hydrocarbons and that in the water equal at the bottom of the accumulation (at the HC-water contact). In contrast, the unconventional accumulations will show HC column heights of 1000s of feet with the pressure in the hydrocarbon phase and the water phase being the same at the top of the accumulation (at the updip transition zone). Those significant differences are critical for understanding and differentiating these two play types. Because the system is a pore throat bottleneck with very little or minimum lateral migration, the type of hydrocarbon s are closely tied to the thermal maturity required to generate those hydrocarbons. Thus the play concept begins with two important geochemical considerations: (1) where are the source rocks and what are the kerogen types and organic richness (TOC), and (2 ) where are they mature in the basin for oil, condensate, and gas in the basin. These parameters will very quickly define the fairway for the play. Then one has to add the critical information on the reservoirs themselves: composition (brittleness), thickness, and reservoir quality (matrix porosity and permeability). In summary, these tight unconventional petroleum systems (1) are dynamic , and (2) create a regionally inverted petroleum system with water over oil over condensate over gas for source rocks wit h Type I or II kerogen types.

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American Association of Petroleum Geologists (AAPG)
Explorer Article

The AAPG Annual Convention and Exhibition will feature a variety of field trips that will bookend the meeting, spanning from March 26 to April 8.

American Association of Petroleum Geologists (AAPG)
Explorer Emphasis Article

The eastern Mediterranean Sea could become the hottest offshore play in the Middle East area, depending on the outcome of a key exploration attempt later this year.

American Association of Petroleum Geologists (AAPG)
Explorer Historical Highlights

Today, there are 31 sedimentary basins worldwide that produce or have economic discoveries in deepwater, in terms of both modern water depths and reservoir type.

American Association of Petroleum Geologists (AAPG)
Explorer Geophysical Corner

Interpretation of seismic amplitude anomalies could be a direct solution to finding hydrocarbons, or defining lithology, but is usually a tricky problem.

American Association of Petroleum Geologists (AAPG)
Explorer Article

The AAPG European Regional Conference, “Hydrocarbons in the Mediterranean: revisiting mature plays and understanding new and emerging ideas,” will be held Jan. 18-19 in Larnaca, Cyprus.

American Association of Petroleum Geologists (AAPG)
Learn! Blog

The dynamics of fluid behavior and structural movement on the nano-scale can be complicated and not always what was expected. New research that analyzes the well information and cores using new techniques and technologies is yielding important and useful results. Welcome to an interview with Wen Zhou, Chengdu University of Technology, who discusses recent research findings.

American Association of Petroleum Geologists (AAPG)
Learn! Blog

Primary research in hydrocarbon generation is yielding new insights into the natural gas geochemical characteristics of conventional and unconventional reservoirs, along with discoveries relating to the geomechanical processes. Welcome to an interview with Chenglin Liu, China University of Petroleum-Beijing, who discusses enlightening new findings regarding the relationship between salinity and hydrocarbon geochemical characteristics.

American Association of Petroleum Geologists (AAPG)
Learn! Blog

Eastern Mexico has been one of the most prolific and most complex regions of the world, and many believe there is still great potential for undiscovered giant and super-giant fields. Welcome to an interview with Stephen Cossey, whose work in eastern Mexico, both onshore and offshore, are pointing to exciting new potential.

American Association of Petroleum Geologists (AAPG)
Learn! Blog

Geoscientists have more opportunities than ever to make working with drones and drone data part of their skill set and services rendered. But, there are often a number of misconceptions, especially when getting started. Welcome to an interview with Michael Nash, who provides a reality check about drones and drone capabilities. Please note that the drones references are the small drones used by the general public, and are not the large UAVs used by the military and other entities.

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American Association of Petroleum Geologists (AAPG)
Short Course
Tunis, Tunisia
Monday, 12 September 2022, 8:00 a.m.–4:30 p.m.

This short course will comprise lectures, short exercises and discussion sessions. The course will focus on a number of case studies that link outcrop and subsurface geology and have relevance to petroleum exploration and production. Case studies range from Silurian to Miocene in age and come from North African and Mediterranean Basins. The course builds on basic knowledge of sedimentary geology but does not require specialist skills from participants.

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American Association of Petroleum Geologists (AAPG)
Workshop
Lisbon, Portugal
Thursday, 18 May Friday, 19 May 2023, 8:00 a.m.–5:00 p.m.

This 2-day conference brings together diverse experts working on modern and ancient turbidite, MTDs, contourite and hybrid/mixed systems in order to improve the present-day knowledge, models and predictive power.

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)
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.

Request a visit from Fred Schroeder!

American Association of Petroleum Geologists (AAPG)
VG Abstract

This lecture will discuss the differences between carbonates and siliciclastics from their chemical composition through their distributions in time and space. Building on these fundamental differences, we will explore the challenges carbonates pose to petroleum geologists in terms of seismic interpretation, reservoir quality prediction, field development, etc. Peppered with humorous personal stories, still raging academic debates, and the heartfelt frustrations of real industry professionals, the aim is to inspire students and young professionals to rise to the occasion and embrace the reservoir rocks that petroleum geologists love to hate.

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Request a visit from Noelle Joy Purcell!

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)

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