Christchurch, New Zealand
Christchurch, New Zealand

Time filter

Source Type

Hackley P.C.,U.S. Geological Survey | Araujo C.V.,Petrobras | Borrego A.G.,CSIC - National Coal Institute | Bouzinos A.,54 Energy | And 27 more authors.
Marine and Petroleum Geology | Year: 2015

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% Ro), from organic-lean to organic-rich (1-22wt.% 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 to 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 to 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. © 2014 Elsevier Ltd.

Araujo C.V.,Petrobras | Borrego A.G.,CSIC - National Coal Institute | Cardott B.,Oklahoma Geological Survey | das Chagas R.B.A.,Federal University of Rio de Janeiro | And 14 more authors.
International Journal of Coal Geology | Year: 2014

This paper presents results of an interlaboratory exercise on organic matter optical maturity parameters using a natural maturation series comprised by three Devonian shale samples (Huron Member, Ohio Shale) from the Appalachian Basin, USA. This work was conducted by the Thermal Indices Working Group of the International Committee for Coal and Organic Petrology (ICCP) Commission II (Geological Applications of Organic Petrology). This study aimed to compare: 1. maturation predicted by different types of petrographic parameters (vitrinite reflectance and spectral fluorescence of telalginite), 2. reproducibility of the results for these maturation parameters obtained by different laboratories, and 3. improvements in the spectral fluorescence measurement obtained using modern detection systems in comparison with the results from historical round robin exercises. Mean random vitrinite reflectance measurements presented the highest level of reproducibility (group standard deviation 0.05) for low maturity and reproducibility diminished with increasing maturation (group standard deviation 0.12).Corrected fluorescence spectra, provided by 14 participants, showed a fair to good correspondence. Standard deviation of the mean values for spectral parameters was lowest for the low maturity sample but was also fairly low for higher maturity samples.A significant improvement in the reproducibility of corrected spectral fluorescence curves was obtained in the current exercise compared to a previous investigation of Toarcian organic matter spectra in a maturation series from the Paris Basin. This improvement is demonstrated by lower values of standard deviation and is interpreted to reflect better performance of newer photo-optical measuring systems.Fluorescence parameters measured here are in good agreement with vitrinite reflectance values for the least mature shale but indicate higher maturity than shown by vitrinite reflectance for the two more mature shales. This red shift in λmax beyond 0.65% vitrinite reflectance was also observed in studies of Devonian shale in other basins, suggesting that the accepted correlation for these two petrographic thermal maturity parameters needs to be re-evaluated.A good linear correlation between λmax and Tmax for this maturation series was observed and λmax 600nm corresponds to Tmax of 440°C. Nevertheless if a larger set of Devonian samples is included, the correlation is polynomial with a jump in λmax ranging from 540 to 570nm. Up to 440°C of Tmax, the λmax, mostly, reaches up to 500nm; beyond a Tmax of 440°C, λmax is in the range of 580-600nm. This relationship places the "red shift" when the onset of the oil window is reached at Tmax of 440°C. Moreover, the correlation between HI and λmax (r2=0.70) shows a striking inflection and decrease in HI above a λmax of 600nm, coincident with the approximate onset of hydrocarbon generation in these rocks. © 2014.

Mendonca Filho J.G.,Federal University of Rio de Janeiro | Araujo C.V.,Petrobras | Borrego A.G.,CSIC - National Coal Institute | Cook A.,Keiraville Konsultants Pty. Ltd | And 14 more authors.
International Journal of Coal Geology | Year: 2011

This reply is motivated by Sahay's comments on the paper published by Mendonça Filho et al. (2010) dealing with the effect of concentration of an organic matter on optical maturity parameters. Four points were raised by Sahay: suggestion to use of chemical parameters to assess the effect of isolation, indication that suppression of vitrinite reflectance in liptinite-rich rocks was insufficiently addressed, discussion on the way to deal with the existence of multiple vitrinite populations in a dispersed organic matter, and contradictory explanation of results involving the influence of isolation procedure on fluorescence properties but no effect on vitrinite reflectance. The four points were separately addressed being the two first ones out of the scope of the paper. The existence of multiple vitrinite populations is a well-recognized problem whose importance in the results could be addressed because the participants provided individual records of vitrinite reflectance. These results indicated that election of different populations was not a major problem in the results. The influence of isolation procedure on the fluorescence spectra of alginite while the vitrinite reflectance remains unaltered is not considered contradictory because both parameters are measured on different components which may have a different response to the acid treatment. © 2011 Elsevier B.V.

Mendonca Filho J.G.,Federal University of Rio de Janeiro | Araujo C.V.,Petrobras | Borrego A.G.,CSIC - National Coal Institute | Cook A.,Keiraville Konsultants Pty. Ltd | And 14 more authors.
International Journal of Coal Geology | Year: 2010

The main objective of this work was to study the effect of the kerogen isolation procedures on maturity parameters of organic matter using optical microscopes. This work represents the results of the Organic Matter Concentration Working Group (OMCWG) of the International Committee for Coal and Organic Petrology (ICCP) during the years 2008 and 2009. Four samples have been analysed covering a range of maturity (low and moderate) and terrestrial and marine geological settings. The analyses comprise random vitrinite reflectance measured on both kerogen concentrate and whole rock mounts and fluorescence spectra taken on alginite. Eighteen participants from twelve laboratories from all over the world performed the analyses. Samples of continental settings contained enough vitrinite for participants to record around 50 measurements whereas fewer readings were taken on samples from marine setting. The scatter of results was also larger in the samples of marine origin. Similar vitrinite reflectance values were in general recorded in the whole rock and in the kerogen concentrate. The small deviations of the trend cannot be attributed to the acid treatment involved in kerogen isolation but to reasons related to components identification or to the difficulty to achieve a good polish of samples with high mineral matter content. In samples difficult to polish, vitrinite reflectance was measured on whole rock tended to be lower. The presence or absence of rock fabric affected the selection of the vitrinite population for measurement and this also had an influence in the average value reported and in the scatter of the results. Slightly lower standard deviations were reported for the analyses run on kerogen concentrates. Considering the spectral fluorescence results, it was observed that the λmax presents a shift to higher wavelengths in the kerogen concentrate sample in comparison to the whole-rock sample, thus revealing an influence of preparation methods (acid treatment) on fluorescence properties. © 2010 Elsevier B.V.

Edman J.,Edman Geochemical Consulting LLC | Sprunt E.,Newman Energy Research Ltd | Newman J.,Newman Energy Research Ltd | Ruder M.,Wintermoon Geotechnologies Inc. | Ellis J.,Ellis GeoSpatial
Society of Petroleum Engineers - SPE/AAPG/SEG Unconventional Resources Technology Conference | Year: 2016

With unconventional exploration expanding into basins with little seismic data and few wellbores, some lower cost technologies should be exploited up front to select areas of greater economic potential. Typically, 3D seismic is used for high grading, but it is expensive, ground access can be limited resulting in partial coverage, and, as with many technologies, interpretations can be ambiguous. However, there are less expensive alternatives such as remote sensing, gravity and magnetics, geochemistry, and petrography that can be used to initially identify areas with higher potential. After the initial screening evaluation, the high graded areas can subsequently be appraised using more expensive techniques. Using less expensive screening alternatives up front can improve results and project economics. As an example, in some unconventional plays, such as the Parshall Field in the Williston Basin, better production is related to areas of localized convective, high heat flow that is associated with recurrent movement of basement faults. Convective heat flow via hydrothermal fluids is much more efficient than the transfer of heat by conductive heat flow. In the greater Williston Basin, gravity and aeromagnetic data along with remote sensing data have been used in regional structural evaluation and statistical fracture analysis to identify different types of basement. Faults and lineaments that have been mapped in the area of the Parshall and Stanley fields may have served as conduits for acidic brines and hydrothermal fluids in the Parshall Field. Previously, Parshall Field was thought to be in an area that was thermally immature, but geochemical data indicate the Bakken at Parshall Field is actually at peak oil generation with significant amounts of oil having been generated in situ as a result of convective hydrothermal heat flow. The screening data support the hypothesis that recurrent movement on faults and lineaments provided conduits for hydrothermal fluids and igneous volatiles. This is interpreted to have had an important impact on in situ hydrocarbon generation, and petrography further suggests that precipitation of minerals from these hydrothermal fluids has affected porosity, permeability, rock fracturability and overpressuring. Parshall Field has produced more than 65 million barrels of oil and 30 billion cubic feet of natural gas. Copyright 2014, Unconventional Resources Technology Conference (URTeC).

Loading Newman Energy Research Ltd. collaborators
Loading Newman Energy Research Ltd. collaborators