Abstract Hyperspectral core imaging as a commercial technology is fairly new to the oil and gas industry, providing a rapid and non-destructive method for mapping mineralogy of drill core and cuttings. The technology makes use of infrared spectrometers that collect imagery across the visible, near infrared, short-wave infrared and thermal (long-wave) infrared range that contains information related to a variety of mineral species, and in some cases including mineral chemistry and texture. In this paper we illustrate how the mineralogical information can be used directly for a variety of applications relevant to reservoir quality, including mineral mapping, sedimentological mapping and upscaling of micro information to the well scale. Statistical analysis allows the data to be used to segment cores into different rock types, and via calibration to quantitative mineralogical techniques, the data can be used to construct continuous curves of quantitative mineralogy, total organic content and production parameters.

Abstract The U.S. Geological Survey (USGS) operates the Core Research Center (CRC) in Denver, Colorado, USA, a public access repository of rock cores from over 9800 wells and drill cuttings from over 53 000 wells, primarily from states in or adjacent to the Rocky Mountain Region. Annually, approximately 1400 visitors use the collection for traditional and innovative research. The CRC has an online, searchable database which includes downloadable core photos, analytical data, and thin-section images. When visitors sample for analyses, the results must be returned to the CRC for public dissemination providing immediate, free access to users while sparing the finite, irreplaceable collection from redundant testing. A representative quantity of every core depth is preserved in perpetuity. Studies on CRC materials, paired with new extraction methods, have unlocked new productive deposits. Materials drilled and curated decades ago remain in high demand while materials receiving little attention today may be crucial for future research. The collection provides immediate, inexpensive access to subsurface materials at a fraction of the cost of new drilling, sparing money, time and environmental impacts.

Abstract The most recent advance in infrared spectroscopy is in the use of real-time imaging reflectance spectrometers to study cores and cuttings. These are non-contact and non-destructive, and acquire continuous mineral and hydrocarbon data in a detailed sub-millimetre pixel image format. The main strength of this approach is the unique ability to accurately discriminate and quantify the clays, carbonates and sulfates, along with hydrocarbon information. Three hyperspectral core-scanning projects from the UK and Norwegian Continental Shelf highlight how these detailed, continuous mineral and hydrocarbon data can be used in geological and petrophysical evaluations. In the Dunbar Field of the Northern North Sea, UK, the spectral recognition of illite and kaolinite polytypes associated with faulted sandstone units contributed to a successful revision of lithostratigraphic correlation between wells with core material and those with only cuttings. These had been hitherto problematical. In Norway, hyperspectral mineral data from mixed carbonate–siliciclastic sequences across the Permo-Triassic boundary in the Alta Field, Barents Sea, helped in the delineation of a karstified dolomitic reservoir. A kaolinite cyclicity associated with an Upper Triassic stacked alluvial fan sequence was also identified in the Lorry Prospect, Norwegian Sea. Finally, it is demonstrated how hyperspectral data can be applied quantitatively to help to calibrate downhole petrophysical data, improve gamma log scaling for shale volume calculations and link mineralogy to permeability.

Abstract An automatic approach for analyses of Raman spectra of dispersed organic matter in diagenesis is proposed in this work. The need for a reproducible method of thermal maturity assessment by means of Raman spectroscopic analyses on the organic matter is essential for the development of this technique as a robust support in organic petrographical analyses. The new method was tested on concentrated kerogen derived from a set of 33 samples that originated from cuttings from a 5000 m-thick section drilled in offshore Angola. The proposed method can be applied separately in the D and G bands regions of the Raman spectra, and uses a fitting approach based on asymmetrical Gaussian deconvolution and on the measurement of the integrated area. Results from this work demonstrate that Raman parameters carried out by the new methods reflect the increase in aromaticity in kerogen in diagenesis. Finally, two parametric equations have been proposed to correlate Raman parameters and thermal maturity: the first is for the thermal maturity interval between 0.3 and 1.5% R o ; and the second has a higher precision of between 1.0 and 1.5% R o . The two equations are the result of a multi-linear regression based on robust correlations between Raman parameters and vitrinite reflectance (R o %).

ABSTRACT The Vaca Muerta Formation (Late Jurassic–Early Cretaceous) bears a high-quality, oil-prone kerogen deposited under mostly anoxic, marine conditions and constitutes a world-class source rock with outstanding geochemical characteristics for the generation of petroleum (oil and gas) throughout the Neuquén Basin. The formation has been identified as the main source for the majority of the hydrocarbon pools found in conventional reservoirs of the basin, but in the last ten years, it has also acquired significance as a self-sourced unconventional reservoir target for both oil and gas. An extended database that comprises several tens of thousands of samples, including cuttings, cores, sidewall cores, and outcrops of the Vaca Muerta Formation from wells and outcrop sections along the entire basin was evaluated. This allowed formulating patterns of organic richness, hydrocarbon source quality, and distribution of free hydrocarbons in six reference areas of the basin. These reference areas are defined based either on the impact of the sedimentary rock on generated hydrocarbons or on the significant thermal maturity differences. The areas are: Malargüe, Chihuido-Lomita, Northeast Platform, Embayment, Huincul Arch, and Picún Leufú. More than 300 oils and organic extracts from Vaca Muerta and nearly 500 mud and production gas samples completed the data set to understand the key features of the fluids occurring in the prospectable areas for unconventional resources (shale oil and shale gas). Collected and evaluated analytical data include total organic carbon (TOC), programmed pyrolysis, visual kerogen analyses, bulk chemical composition of fluids, gas chromatography (GC) and gas chromatography–mass spectrometry for biomarker fingerprints (GCMS), stable carbon isotopes, bulk and compositional kinetics, and x-ray fluorescence (XRF). Moreover, insights into the essential processes of the Vaca Muerta unconventional petroleum system including kerogen-related issues and basin-scale processes are discussed in terms of source rock kinetics, modeling of burial/exhumation histories, porosity development, and overpressure occurrence. The Embayment area stands out as the most attractive for unconventional development to produce middle-to-light oil with low sulfur content along with gas condensate westward. An analogous pattern is observed in the Chihuido-Lomita and Huincul Arch areas, with similar source rock characteristics but with overall lower thermal maturity compared with the Embayment area. However, in the transition to the Northeast Platform, the northeastern fringe of Chihuido-Lomita and Embayment areas present middle-to-heavy, mostly sulfur-rich oils, with limited gas potential, hence requiring higher permeability to yield commercial production. The Malargüe area is characterized by overall mid maturity and limited quality of oil (middle to heavy), predominantly sulfur-rich. Finally, the Picún Leufú area is conditioned by a source rock with low potential because of thinner organic-rich intervals and low-to-middle thermal maturity.

Abstract The Mansehra granite in the NW Himalaya is a typical Lesser Himalayan granite. We present here new whole-rock geochemistry, Rb–Sr and Sm–Nd isotope data, together with zircon U–Pb ages and Hf isotope data, for the Mansehra granite. Geochemical data for the granite show typical S-type characteristics. Zircon U–Pb dating yields 206 Pb/ 238 U crystallization ages of 483–476 Ma. The zircon grains contain abundant inherited cores and some of these show a clear detrital origin. The 206 Pb/ 238 U ages of the inherited cores in the granite cluster in the ranges 889–664, 1862–1595 and 2029 Ma. An age of 664 Ma is considered to be the maximum age of the sedimentary protoliths. Thus the Late Neoproterozoic to Cambrian sedimentary rocks must be the protolith of the Mansehra granitic magma. The initial Sr isotope ratios are high, ranging from 0.7324 to 0.7444, whereas the ε Nd(t) values range from −9.2 to −8.6, which strongly suggests a large contribution of old crustal material to the protoliths. The two-stage Nd model ages and zircon Hf model ages are Paleoproterozoic, indicating that the protolith sediments were derived from Paleoproterozoic crustal components.