A Summary of “Petrophysics and Geochemistry of Unconventional Reservoirs”

Unconventional reservoirs are discovered in all petroleum basins around the world [...

Integration of Thermal Core Profiling and Scratch Testing for the Study of Unconventional Reservoirs

Core analysis provides the essential information necessary for the characterization and development of hydrocarbon reservoirs. High core-scale heterogeneity and anisotropy, natural in unconventional reservoirs, complicate reservoir characterization and dictate the sampling methodology used. Continuous high-resolution thermal measurements with an optical scanner and scratcher along the core column can yield benefits in a sampling strategy. This article describes some features of the suggested integration of non-destructive thermal profiling with partially destructive scratch testing applied for the study of rocks from the Bazhenov Formation (West Siberia, Russia). The spatial variation in the unconfined compressive strength and thermal conductivity components parallel and perpendicular to bedding for more than 1000 samples are demonstrated and discussed on core and log scales. The relationships between these properties are established for different rock types composing the formation. The joint analysis allows specialists to correctly define multiscale heterogeneities and facies that would be difficult or impossible to observe with logging data analysis or geological description alone. The established relationships make it possible to partially replace the semi-destructive scratch test with non-destructive optical scanning, providing UCS estimation. One more important outcome of the present work is the lessons learned regarding how to organize future works. The integration of thermal core profiling and scratch testing data looks promising for unconventional reservoir characterization

Estimation of the Impact of Basement Heterogeneity on Thermal History Reconstruction: The Western Siberian Basin

Some of the simplifying assumptions frequently used in basin modelling may adversely impact the quality of the constructed models. One such common assumption consists of using a laterally homogeneous crustal basement, despite the fact that lateral variations in its properties may significantly affect the thermal evolution of the model. We propose a new method for the express evaluation of the impact of the basement’s heterogeneity on thermal history reconstruction and on the assessment of maturity of the source rock. The proposed method is based on reduced-rank inversion, aimed at a simultaneous reconstruction of the petrophysical properties of the heterogeneous basement and of its geometry. The method uses structural information taken from geological maps of the basement and gravity anomaly data. We applied our method to a data collection from Western Siberia and carried out a two-dimensional reconstruction of the evolution of the basin and of the lithosphere. We performed a sensitivity analysis of the reconstructed basin model to assess the effect of uncertainties in the basement’s density and its thermal conductivity for the model’s predictions. The proposed method can be used as an express evaluation tool to assess the necessity and relevance of laterally heterogeneous parametrisations prior to a costly three-dimensional full-rank basin modelling. The method is generally applicable to extensional basins except for salt tectonic provinces

Estimation of the Impact of Basement Heterogeneity on Thermal History Reconstruction: The Western Siberian Basin

Some of the simplifying assumptions frequently used in basin modelling may adversely impact the quality of the constructed models. One such common assumption consists of using a laterally homogeneous crustal basement, despite the fact that lateral variations in its properties may significantly affect the thermal evolution of the model. We propose a new method for the express evaluation of the impact of the basement’s heterogeneity on thermal history reconstruction and on the assessment of maturity of the source rock. The proposed method is based on reduced-rank inversion, aimed at a simultaneous reconstruction of the petrophysical properties of the heterogeneous basement and of its geometry. The method uses structural information taken from geological maps of the basement and gravity anomaly data. We applied our method to a data collection from Western Siberia and carried out a two-dimensional reconstruction of the evolution of the basin and of the lithosphere. We performed a sensitivity analysis of the reconstructed basin model to assess the effect of uncertainties in the basement’s density and its thermal conductivity for the model’s predictions. The proposed method can be used as an express evaluation tool to assess the necessity and relevance of laterally heterogeneous parametrisations prior to a costly three-dimensional full-rank basin modelling. The method is generally applicable to extensional basins except for salt tectonic provinces

Impact of differing heat flow solutions on hydrocarbon generation predictions: A case study from West Siberian Basin

Highlights • The workflow to minimise uncertainties in thermal modelling of the basin is presented. • Different methods of basin thermal history reconstruction are compared. • Accounting of the blanketing effect in West Siberian Basin is important. Abstract Knowledge of the thermal history of a sedimentary basin is necessary for the quantitative and qualitative estimation of hydrocarbons generated from buried organic matter. Usually, specialists use a combination of backstripping and forward temperature modelling techniques for a basin history reconstruction. However, this approach decouples the structural and thermal solutions and therefore results in the less consistent modelling. The reliability of a basin model can be increased by using coupled approaches that resolve the structural and thermal solutions simultaneously. In this work, we investigate how using a backstripping-based versus a coupled thermo-tectono-stratigraphic approach for computing basement heat flow influences the predicted total hydrocarbon generation using a 808 km transect across the West Siberian basin as an example. Both coupled and decoupled approaches are used to reconstruct a basal heat flow history for the transect. Corresponding models have identical geological parameters and are calibrated with a set of temperature and vitrinite reflectance data. Furthermore, reconstructed heat flow histories are used separately as a lower boundary condition in a petroleum system model to evaluate the consequences for hydrocarbon generation. We find that the backstripping-based approach significantly overestimates hydrocarbon generation mass with respect to the basement heat flow solution obtained from the more consistent thermo-tectono-stratigraphic model. Also, the onset and time evolution of hydrocarbon generation is substantially different. These findings, obtained for the West Siberian Basin, show that calibrating a thermal model to the wellbore temperature and vitrinite data can lead to the inaccurate interpretation of the thermal history. The study results suggest that the presented advanced basin modelling strategy can help in decreasing risks in petroleum system analysis by providing more reliable and consistent heat flow solutions

Advanced Determination of Heat Flow Density on an Example of a West Russian Oil Field

Reliable geothermal data are required for basin and petroleum system modeling. The essential shortcomings of the methods and results of previous geothermal investigations lead to a necessity to reappraise the data on the thermal properties and heat flow. A new, advanced experimental basis was used to provide reliable data on vertical variations in the thermal properties of formation and heat flow for the area surrounding a prospecting borehole drilled through an unconventional hydrocarbon reservoir of the Domanik Formation in the Orenburg region (Russia). Temperature logging was conducted 12.5 months after well drilling. The thermal properties of the rocks were measured with continuous thermal core profiling on all 1699 recovered core samples. Within non-cored intervals, the thermal conductivity of the rocks was determined from well-logging data. The influence of core aging, multiscale heterogeneity and anisotropy, in situ pressure and temperature on the thermal properties of rock was accounted for. The terrestrial heat flow was determined to be 72.6 ± 2.2 mW·m−2—~114% larger than the published average data for the studied area. The experiment presents the first experience of supporting basin modeling in unconventional plays with advanced experimental geothermal investigations