Bulletin Article


Diagenesis significantly impacts mudstone lithofacies. Processes operating to control diagenetic pathways in mudstones are poorly known compared to analogous processes occurring in other sedimentary rocks. Selected organic-carbon-rich mudstones, from the Kimmeridge Clay and Monterey Formations, have been investigated to determine how varying starting compositions influence diagenesis.

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Emission of carbon dioxide (CO2) from fossil-fueled power generation stations contributes to global climate change. Capture of CO2 from such stationary sources and storage within the pores of geologic strata (geologic carbon storage) is one approach to mitigating anthropogenic climate change. The large storage volume needed for this approach to be effective requires injection into pore space saturated with saline water in reservoir strata overlain by cap rocks. One of the main concerns regarding storage in such rocks is leakage via faults. Such leakage requires, first, that the CO2 plume encounter a fault and, second, that the properties of the fault allow CO2 to flow upward. Considering only the first step of encounter, fault population statistics suggest an approach to calculate the probability of a plume encountering a fault, particularly in the early site-selection stage when site-specific characterization data may be lacking. The resulting fault encounter probability approach is applied to a case study in the southern part of the San Joaquin Basin, California. The CO2 plume from a previously planned injection was calculated to have a 4.1% chance of encountering a fully seal offsetting fault and a 9% chance of encountering a fault with a throw half the seal thickness. Subsequently available information indicated the presence of a half-seal offsetting fault at a location 2.8 km (1.7 mi) northeast of the injection site. The encounter probability for a plume large enough to encounter a fault with this throw at this distance from the injection site is 25%, providing a single before and after test of the encounter probability estimation method.
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This study documents that Danian-aged sand remobilization of deep-water slope-channel complexes and intrusion of fluidized sand into hydraulically fractured slope mudstones of the Great Valley sequence, California, generated 400-m (1312 ft)–thick reservoir units: unit 1, parent unit channel complexes for shallower sandstone intrusions; unit 2, a moderate net-to-gross interval (0.19 sand) of sills with staggered, stepped, and multilayer geometries with well-developed lateral sandstone-body connectivity; unit 3, a low net-to-gross interval (0.08 sand) of exclusively high-angle dikes with good vertical connectivity; and unit 4, an interval of extrusive sandstone. Unit 2 was formed during a phase of fluidization that emplaced on an average 0.19 km3 (0.046 mi3) of sand per cubic kilometer of host sediment. Probe permeametry data reveal a positive relationship between sill thickness and permeability. Reservoir quality is reduced by the presence of fragments of host strata, such as the incorporation of large rafts of mudstone, which are formed by in-situ hydraulic fracturing during sand injection. Mudstone clasts and clay- and silt-size particles generated by intrusion-induced abrasion of the host strata reduce sandstone permeability in multilayer sills (70 md) when compared to that in staggered and stepped sills (586 and 1225 md, respectively). Post-injection cementation greatly reduces permeability in high-angle dikes (81 md). This architecturally based reservoir zonation and trends in reservoir characteristics in dikes and sills form a basis for quantitative reservoir modeling and can be used to support conceptual interpretations that infer injectite architecture in situations where sands in low net-to-gross intervals are anticipated to have well-developed lateral and vertical connectivity.
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Explorer Article


Robert Gray is a man on a mission. Gray, an AAPG Grover E. Murray Distinguished Geology Educator Award winner in 2014, said he is tired of lower-level geologic study at community and city college levels being treated like the Rodney Dangerfield of academia.

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Recent debates have flared in the western United States over federal versus state ownership of public lands. Bills concerning the transfer of some public lands to states have been introduced in the U.S. Congress and many western state legislatures, though none have become law.

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The Distinguished Lecture program, funded in part by the AAPG Foundation, is the Association’s flagship initiative for spreading the latest in science, technology and professional information.

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It don’t come easy: The oil rich Monterey Shale has proved to be the biggest conventional resource provider in California, and it promises even more – but the formation’s complex geology is just as intimidating as its potential is huge.

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Explorer Division Column EMD


In virtually all regions of sustained production, the industry is steadily improving in situ recovery methods and reducing environmental impacts of bitumen and heavy oil production, especially those associated with surface mining.

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Explorer Emphasis

Feisty. Funny. Determined. Competitive. Brilliant. Generous. The words used to describe Harris in advance of her posthumously receiving the AAPG Harrison Schmitt Award at the upcoming ACE in Denver.
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Explorer Foundation Update


It has a new name, a new energy and a new lineup of experts, all primed to spread geoscience knowledge around the world. “It” is AAPG’s newly named Global Distinguished Lecture Program – emphasis on the “global” – which dates back to 1941 but continues to be the Association’s flagship initiative for offering the latest in geologic science to AAPG affiliated geological societies and universities.

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Field Seminar

Palo Alto California United States 05 June, 2015 10 June, 2015 46
Palo Alto, California, United States
5-10 June 2015

This six-day field seminar is designed to provide participants with an appreciation of the broad range of deep-water reservoir facies, the mechanisms by which they were deposited, their predictive attributes, their reservoir heterogeneity and their stratigraphic architecture.

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Check back often. "Find an Expert" feature is coming online soon!