Geology topics

Mark Pawlewicz

Publications and source records attributed to Mark Pawlewicz.

6 recordsLinked to original sources

USGS2015

Standardization of reflectance measurements in dispersed organic matter: results of an exercise to improve interlaboratory agreement

Vitrinite reflectance generally is considered the most robust thermal maturity parameter available for application to hydrocarbon exploration and petroleum system evaluation. However, until 2011 there was no standardized methodology available to provide guidelines for vitrinite reflectance measurements in shale. Efforts to correct this deficiency resulted in publication of ASTM D7708: Standard test method for microscopical determination of the reflectance of vitrinite dispersed in sedimentary rocks . In 2012-2013, an interlaboratory exercise was conducted to establish precision limits for the D7708 measurement technique. Six samples, representing a wide variety of shale, were tested in duplicate by 28 analysts in 22 laboratories from 14 countries. Samples ranged from immature to overmature (0.31-1.53% R o ), from organic-lean to organic-rich (1-22 wt.% total organic carbon), and contained Type I (lacustrine), Type II (marine), and Type III (terrestrial) kerogens. Repeatability limits (maximum difference between valid repetitive results from same operator, same conditions) ranged from 0.03-0.11% absolute reflectance, whereas reproducibility limits (maximum difference between valid results obtained on same test material by different operators, different laboratories) ranged from 0.12-0.54% absolute reflectance. Repeatability and reproducibility limits degraded consistently with increasing maturity and decreasing organic content. However, samples with terrestrial kerogens (Type III) fell off this trend, showing improved levels of reproducibility due to higher vitrinite content and improved ease of identification. Operators did not consistently meet the reporting requirements of the test method, indicating that a common reporting template is required to improve data quality. The most difficult problem encountered was the petrographic distinction of solid bitumens and low-reflecting inert macerals from vitrinite when vitrinite occurred with reflectance ranges overlapping the other components. Discussion among participants suggested this problem could not be easily corrected via kerogen concentration or solvent extraction and is related to operator training and background. No statistical difference in mean reflectance was identified between participants reporting bitumen reflectance vs. vitrinite reflectance vs. a mixture of bitumen and vitrinite reflectance values, suggesting empirical conversion schemes should be treated with caution. Analysis of reproducibility limits obtained during this exercise in comparison to reproducibility limits from historical interlaboratory exercises suggests use of a common methodology (D7708) improves interlaboratory precision. Future work will investigate opportunities to improve reproducibility in high maturity, organic-lean shale varieties.

Marine and Petroleum Geology↗

USGS2007

Total Petroleum Systems of the Carpathian - Balkanian Basin Province of Romania and Bulgaria

The U.S. Geological Survey defined the Moesian Platform Composite Total Petroleum System and the Dysodile Schist-Tertiary Total Petroleum System, which contain three assessment units, in the Carpathian-Balkanian Basin Province of Romania and Bulgaria. The Moesian Platform Assessment Unit, contained within the Moesian Platform Composite Total Petroleum System, is composed of Mesozoic and Cenozoic rocks within the Moesian platform region of southern Romania and northern Bulgaria and also within the Birlad depression in the northeastern platform area. In Romania, hydrocarbon sources are identified as carbonate rocks and bituminous claystones within the Middle Devonian, Middle Jurassic, Lower Cretaceous, and Neogene stratigraphic sequences. In the Birlad depression, Neogene pelitic strata have the best potential for generating hydrocarbons. In Bulgaria, Middle and Upper Jurassic shales are the most probable hydrocarbon sources. The Romania Flysch Zone Assessment Unit in the Dysodile Schist-Tertiary Total Petroleum System encompasses three structural and paleogeographic subunits within the Pre-Carpathian Mountains region: (1) the Getic depression, a segment of the Carpathian foredeep; (2) the flysch zone of the eastern Carpathian Mountains (also called the Marginal Fold nappe); and (3) the Miocene zone (also called the Sub-Carpathian nappe). Source rocks are interpreted to be Oligocene dysodile schist and black claystone, along with Miocene black claystone and marls. Also part of the Dysodile Schist-Tertiary Total Petroleum System is the Romania Ploiesti Zone Assessment Unit, which includes a zone of diapir folds. This zone lies between the Rimnicu Sarat and Dinibovita valleys and between the folds of the inner Carpathian Mountains and the external flanks of the Carpathian foredeep. The Oligocene Dysodile Schist is considered the main hydrocarbon source rock and Neogene black marls and claystones are likely secondary sources; all are thought to be at their maximum thermal maturation. Undiscovered resources in the Carpathian-Balkanian Basin Province are estimated, at the mean, to be 2,076 billion cubic feet of gas, 1,013 million barrels of oil, and 116 million barrels of natural gas liquids.

Bulletin↗

USGS2006

Total Petroleum Systems of the North Carpathian Province of Poland, Ukraine, Czech Republic, and Austria

Three total petroleum systems were identified in the North Carpathian Province (4047) that includes parts of Poland, Ukraine, Austria, and the Czech Republic. They are the Isotopically Light Gas Total Petroleum System, the Mesozoic-Paleogene Composite Total Petroleum System, and the Paleozoic Composite Total Petroleum System. The Foreland Basin Assessment Unit of the Isotopically Light Gas Total Petroleum System is wholly contained within the shallow sedimentary rocks of Neogene molasse in the Carpathian foredeep. The biogenic gas is generated locally as the result of bacterial activity on dispersed organic matter. Migration is also believed to be local, and gas is believed to be trapped in shallow stratigraphic traps. The Mesozoic-Paleogene Composite Total Petroleum System, which includes the Deformed Belt Assessment Unit, is structurally complex, and source rocks, reservoirs, and seals are juxtaposed in such a way that a single stratigraphic section is insufficient to describe the geology. The Menilite Shale, an organic-rich rock widespread throughout the Carpathian region, is the main hydrocarbon source rock. Other Jurassic to Cretaceous formations also contribute to oil and gas in the overthrust zone in Poland and Ukraine but in smaller amounts, because those formations are more localized than the Menilite Shale. The Paleozoic Composite Total Petroleum System is defined on the basis of the suspected source rock for two oil or gas fields in western Poland. The Paleozoic Reservoirs Assessment Unit encompasses Devonian organic-rich shale believed to be a source of deep gas within the total petroleum system. East of this field is a Paleozoic oil accumulation whose source is uncertain; however, it possesses geochemical similarities to oil generated by Upper Carboniferous coals. The undiscovered resources in the North Carpathian Province are, at the mean, 4.61 trillion cubic feet of gas and 359 million barrels of oil. Many favorable parts of the province have been extensively explored for oil and gas. The lateral and vertical variability of the structure, the distribution and complex geologic nature of source rocks, and the depths of potential exploration targets, as well as the high degree of exploration, all indicate that future discoveries in this province are likely to be numerous but in small fields.

Bulletin↗

USGS2005

Transylvanian Composite Total Petroleum System of the Transylvanian Basin Province, Romania, Eastern Europe

The Transylvanian Composite Total Petroleum System and the Transylvanian Neogene Suprasalt Gas Assessment Unit were identified in the Transylvanian Basin Province (4057), which lies entirely within the country of Romania. The assessment unit is composed of middle Miocene (Badenian) to Pliocene strata. Gas from the assessment unit is biogenic and originated from bacterial activity on dispersed organic matter in shales and siltstones. Gas migration is believed to be minimal, both vertically and laterally, with gases trapped in local stratigraphic traps and in structural traps (most likely domes and anticlinal folds created by salt diapirism) in the central part of the basin. For this reason, the gas fields also are concentrated in the central part of the basin. Reservoirs are isolated and composed of vertically stacked sandstones and siltstones sealed by shales and possibly by evaporite layers. Traps result from stratigraphic and facies changes within the entire assessment unit stratigraphic section. Some gas fields contain as much or more than a trillion cubic feet, but in most, the estimated resources are between 6 billion and 96 billion cubic feet. Petroleum exploration in the province is in the mature stage, which, combined with the geologic complexity of the region, is considered to limit future discoveries to a relatively few small fields. The undiscovered resources for the Transylvanian Basin Neogene Suprasalt Composite AU in the Transylvanian Hybrid Total Petroleum System (4057) are, at the mean, 2.083 trillion cubic feet of gas. No oil is produced in the basin. Rocks underlying the salt layers were not assessed for hydrocarbon potential.

Bulletin↗

USGS2005

Vitrinite reflectance data for the Permian Basin, west Texas and southeast New Mexico

This report presents a compilation of vitrinite reflectance (Ro) data based on analyses of samples of drill cuttings collected from 74 boreholes spread throughout the Permian Basin of west Texas and southeast New Mexico (fig. 1). The resulting data consist of 3 to 24 individual Ro analyses representing progressively deeper stratigraphic units in each of the boreholes (table 1). The samples, Cambrian-Ordovician to Cretaceous in age, were collected at depths ranging from 200 ft to more than 22,100 ft. The R 0 data were plotted on maps that depict three different maturation levels for organic matter in the sedimentary rocks of the Permian Basin (figs. 2-4). These maps show depths at the various borehole locations where the R 0 values were calculated to be 0.6 (fig. 2), 1.3 (fig. 3), and 2.0 (fig. 4) percent, which correspond, generally, to the onset of oil generation, the onset of oil cracking, and the limit of oil preservation, respectively. The four major geologic structural features within the Permian Basin–Midland Basin, Delaware Basin, Central Basin Platform, and Northwest Shelf (fig. 1) differ in overall depth, thermal history and tectonic style. In the western Delaware Basin, for example, higher maturation is observed at relatively shallow depths, resulting from uplift and eastward basin tilting that began in the Mississippian and ultimately exposed older, thermally mature rocks. Maturity was further enhanced in this basin by the emplacement of early and mid-Tertiary intrusives. Volcanic activity also appears to have been a controlling factor for maturation of organic matter in the southern part of the otherwise tectonically stable Northwest Shelf (Barker and Pawlewicz, 1987). Depths to the three different Ro values are greatest in the eastern Delaware Basin and southern Midland Basin. This appears to be a function of tectonic activity related to the Marathon-Ouachita orogeny, during the Late-Middle Pennsylvanian, whose affects were widespread across the Permian Basin. The Central Basin Platform has been a positive feature since the mid to-late Paleozoic, during which time sedimentation occurred along its flanks. This nonsubsidence, along with the lack of supplemental heating (volcanism), implies lower maturation levels.

New Mexico, Texas↗

USGS2004

The Pre-Messinian Total Petroleum System of the Provence Basin, Western Mediterranean Sea

The Provence Basin is in that portion of the western Mediterranean Sea that is deeper than 2 kilometers. The basin lies essentially beyond the outer continental shelf, between the countries of France, Italy, and Algeria, the Balearic Islands, and the islands of Sardinia and Corsica. It encompasses nearly 300,000 square kilometers and includes the Rhone River submarine fan on the continental slope of southern France. It is province 4068 in the World Energy study. A single, hypothetical, total petroleum system (TPS), the Pre-Messinian TPS (406801), was described for the Provence Basin. The designation hypothetical is used because there is no hydrocarbon production from the basin. The Provence Basin is a deep-water Tertiary rift basin in which the geothermal gradients vary regionally. The Red Sea Basin shares a similar geologic and thermal history with the rifted western Mediterranean Sea and was used as an analog to better understand the genesis of the Provence Basin and as a guide to estimating possible undiscovered amounts of hydrocarbons. For this assessment the basin was given a potential, at the mean, for undiscovered resources of 51 trillion cubic feet (1.4 trillion cubic meters) gas, 0.42 billion barrels oil, and 2.23 million barrels natural gas liquids.

Bulletin↗