Estimating Oil Saturation Index OSI from NMR Logging and Comparison with Rock-Eval Pyrolysis Measurements in a Shale Oil Reservoir

Aiming to study the pore structure and its impact on shale oil enrichment, a total of nine lacustrine shales (including one immature shale and eight mature shales) from the Qingshankou Formation in the Songliao Basin were subjected to low-pressure gas sorption (LPGS) of CO2 and N2 and mercury intrusion capillary pressure (MICP) measurements. The combination of the LPGS and MICP methods demonstrates that the pore volumes of these shales are mainly associated with mesopores, whereas the micropores and macropores are relatively undeveloped. The correlation between the shale compositions and pore volumes of LPGS suggests that the micropores and mesopores are mainly contributed by illite/smectite mixed layer mineral. On the contrary, we have found that the oil/bitumen and carbonates could occupy the micropores and mesopores, respectively, and reduce these pore volumes significantly. The oil saturation index (OSI) was found to display a positive correlation with the maturity Ro value in the range of 0.37%–1.24%, and this may suggest that the shale-oil content is controlled by hydrocarbon generation. However, the pore structure also exerts a great influence on the shale oil enrichment. We suggested that the porosity of MICP could be considered as an index for appraising the shale-oil potential of a given shale player because there is a good positive correlation between the porosity of MICP and the OSI value. Furthermore, a negative correlation between the micropore volume and the OSI value may imply that the shale oil could be adsorbed in micropores, whereas a good positive correlation between the OSI value and the Hg-retained ratio suggests that shale oil is a kind of residual hydrocarbon, which is closely related with the mesopore volume of these shales.

Download Full-text

Geological and Geochemical Characteristics of the First Member of the Cretaceous Qingshankou Formation in the Qijia Sag, Northern Songliao Basin, Northeast China: Implication for Its Shale Oil Enrichment

Geofluids ◽

10.1155/2021/9989792 ◽

2021 ◽

Vol 2021 ◽

pp. 1-20

Author(s):

Fei Xiao ◽

Jianguo Yang ◽

Shichao Li ◽

Fanhao Gong ◽

Jian Zhang ◽

...

Keyword(s):

Organic Matter ◽

Saturated Hydrocarbon ◽

Saturation Index ◽

Effective Porosity ◽

Songliao Basin ◽

Geochemical Characteristics ◽

Type I ◽

Shale Oil ◽

Oil Saturation ◽

Extractable Organic Matter

The Qijia Sag, a secondary tectonic unit in the northern Songliao Basin, developed plentiful shale oil resources in the first member of the Cretaceous Qingshankou Formation (K2qn1) as its main target layer. However, the systematic study on the geological and geochemical characteristics of K2qn1 in the sag has not been carried out. Taking the core samples from the SYY1 well covering the whole K2qn1 as the main study object and concerning some relevant intervals from the SYY1HF well and other earlier wells, petrologic features, organic geochemical characteristics, oil-bearing property, and reservoir characteristics of K2qn1 were analyzed in detail. The results show that the lithology of K2qn1 is mainly dark mudstone genera accounting for more than 90% of the formation thickness with few macrostructural fractures, indicating that K2qn1 developing in deep to semideep lacustrine facies of the Qijia Sag belongs to the typical matrix reservoirs for shale oil. According to lithology features and logging curves, K2qn1 can be divided into three submembers consisting of K2qn11, K2qn12, and K2qn13 from above to below. Compared to the K2qn11 submember, the K2qn12 and K2qn13 submembers obviously are more enriched in shale oil, which is supported by the following three aspects: (i) the average TOC (total organic carbon) values of K2qn11, K2qn12, and K2qn13 are 1.96%, 2.42%, and 2.72%, respectively. The organic matter types of K2qn12 and K2qn13 are mainly type I and type II1, while those of K2qn11 are mainly type II1 and type II2. K2qn1 is at the end of the oil window with a R o (vitrinite reflectance) average of 1.26%, and the maturity of K2qn12 and K2qn13 is slightly higher than that of K2qn11. (ii) The average OSI (oil saturation index) values of K2qn11, K2qn12, and K2qn13 are 110.54 mg/g, 171.74 mg/g, and 150.87 mg/g, respectively, which all reach the zone of oil crossover. The saturated hydrocarbon of EOM (extractable organic matter) in K2qn12 and K2qn13 is of higher content than that in K2qn11, while it is the opposite for the aromatic hydrocarbon, nonhydrocarbon, and asphaltene, indicating better oil mobility for K2qn12 and K2qn13. The average oil saturation values of K2qn11, K2qn12, and K2qn13 are 24.77%, 32.86%, and 35.54%, respectively. (iii) The intragranular dissolution pores and organic pores in K2qn12 and K2qn13 are more developed than those in K2qn11. The average effective porosity values of K2qn11, K2qn12, and K2qn13 interpreted from NMR logging are 4.88%, 6.26%, and 5.86%, respectively. Based on the above-mentioned analyses, the lower K2qn12 and the upper K2qn13 are determined as the best intervals of shale oil enrichment for K2qn1 vertically in the Qijia Sag. There is a certain horizontal heterogeneity of TOC, S 1 , and effective porosity in the drilling horizontal section of K2qn1 of the SYY1HF well. Therefore, the lower K2qn12 and the upper K2qn13 in the area with relatively weak horizontal reservoir heterogeneity of the study area should be selected as the preferential targets for shale oil exploration.

Download Full-text

First evidence of the early cretaceous oceanic anoxic events (MBE and OAE1a) in the southern Tethyan margin (NE-Tunisia): biostratigraphy and shale resource system

Journal of Petroleum Exploration and Production Technology ◽

10.1007/s13202-021-01126-0 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1559-1575

Author(s):

Rachida Talbi ◽

Ahlem Amri ◽

Abdelhamid Boujemaa ◽

Hakim Gabtni ◽

Reginal Spiller ◽

...

Keyword(s):

Black Shale ◽

Saturation Index ◽

Black Shales ◽

Source Rocks ◽

Type I ◽

Hydrocarbon Generation ◽

Shale Oil ◽

Hydrocarbon Generation Potential ◽

Anoxic Events ◽

Rock Eval

AbstractThe Jebel Oust region (north-eastern Tunisia) recorded two levels of marine black shale in the Lower Cretaceous marly series. Geodynamic evolution, biostratigraphic and Rock–Eval analysies allow classifying those black shales as unconventional shale oil resource systems that were deposited during two oceanic anoxic events: the Middel Barremian Event "MBE" and the Early Aptian Event "OAE1a". Paleogeographic evolution highlights two transgressive–regressive cycles: the first one is Valanginian-Early Barremian, and the second is Late Barremian–Early Aptian. Each black shale deposit occurs at the end of the transgression that coincides with the highest sea level. During the Barreman–Aptian interval, sedimentation was controlled by extensional faults in a system of tilted fault blocks which were reactivated several times. Kerogen is of type I, II origin in black shales and of type III origin in marls. Tmax values indicate "oil window" stage. Average transformation ratio is around 67% and 82%, respectively, in the Lower Aptian and Middel Barremian source rock related to the relatively high thermal maturity degree due to the deep burial of the later. Estimated initial hydrocarbon generation potential is moderate to high. Oil saturation index records an "oil crossover" indicating expelled and migrated hydrocarbons from the organic-rich to the organic-poor facies. The petroleum system of the two mature source rocks with a high hydrocarbon generation potential enclose all elements characterizing a "shale oil hybrid system with a combination of juxtaposed organic-rich and organic-lean facies associated with open fractures".

Download Full-text

Bazhenov formation phosphate containing interlayers as potential collectors

Moscow University Bulletin. Series 4. Geology ◽

10.33623/0579-9406-2016-5-60-66 ◽

2016 ◽

pp. 60-66

Author(s):

A. G. Kalmykov ◽

E. A. Manuilova ◽

G. A. Kalmykov ◽

V. S. Belokhin ◽

N. I. Korobova ◽

...

Keyword(s):

Organic Matter ◽

Pore Space ◽

Saturation Index ◽

Geochemical Characteristics ◽

Productivity Index ◽

Oil Reservoir ◽

Oil Saturation ◽

Bazhenov Formation ◽

Reservoir Rocks ◽

Reservoir Type

Possible reservoir type of Bazhenov formation relative to the intervals with increased content of phosphate is described in the resent work. It is shown that phosphate formations have highly connected pore space, porosity may achieve values up to 14%. These rocks also have explicit geochemical characteristics of oil reservoir rocks in comparison with other rock samples in the well. For example, the productivity index and oil saturation index for phosphates is twice higher. The composition of such species may slightly vary, fluorine may present in phosphate minerals, meanwhile rocks are always maintain high content of organic matter (more than 8 wt%).

Download Full-text

Pore Structure Characterization and Reservoir Quality Evaluation of Analcite-Rich Shale Oil Reservoir from the Bohai Bay Basin

Energy & Fuels ◽

10.1021/acs.energyfuels.1c00811 ◽

2021 ◽

Author(s):

Rui Yang ◽

Aoqi Jia ◽

Sheng He ◽

Tao Wang ◽

Qinhong Hu

Keyword(s):

Pore Structure ◽

Quality Evaluation ◽

Structure Characterization ◽

Reservoir Quality ◽

Oil Reservoir ◽

Bohai Bay ◽

Shale Oil ◽

Bohai Bay Basin

Download Full-text

Effect of Nanopore Confinement on Fluid Phase Behavior and Production Performance in Shale Oil Reservoir

Industrial & Engineering Chemistry Research ◽

10.1021/acs.iecr.0c05814 ◽

2021 ◽

Vol 60 (3) ◽

pp. 1463-1472

Author(s):

Zhaojie Song ◽

Yilei Song ◽

Jia Guo ◽

Dong Feng ◽

Jiangbo Dong

Keyword(s):

Phase Behavior ◽

Fluid Phase ◽

Production Performance ◽

Oil Reservoir ◽

Shale Oil ◽

Nanopore Confinement

Download Full-text

Identification of Oil Reservoir Meeting Atypical Archie Phenomenon

The Open Petroleum Engineering Journal ◽

10.2174/1874834101508010354 ◽

2015 ◽

Vol 8 (1) ◽

pp. 354-357

Author(s):

Shixiong Yuan ◽

Haimin Guo ◽

Yu Ding ◽

Rui Deng

Keyword(s):

Pore Structure ◽

Water Saturation ◽

Saturation Index ◽

Oil Reservoir ◽

Formation Water ◽

Core Data ◽

Hydrocarbon Reservoir ◽

Pore Structures ◽

Structure Index ◽

Very High

According to core data, this paper studies variation of resistivity in different pore structures and wettability conditions. The results show that with the increase of pore structure index m, the resistivity will increase significantly when the saturation is constant. Similarly, with increasing saturation index n, the resistivity will also increase even with the same saturation. With fixed m and n, the calculated formation water saturation will be very high, resulting in hydrocarbon reservoir being ignored. This variation characteristic is significant for the identification of hidden reservoir with atypical Archie formula.

Download Full-text

THREE-DIMENSIONAL GEOLOGICAL MODELING OF OIL SATURATION OF PRODUCTIVE OIL RESERVOIR BASED ON LEVERETT J-FUNCTION

Oil and Gas Studies ◽

10.31660/0445-0108-2016-1-7-10 ◽

2016 ◽

pp. 7-10

Author(s):

Ya. O. Antipin

Keyword(s):

Porous Media ◽

Transition Zone ◽

Reliable Method ◽

Three Dimensional ◽

Hydrodynamic Modeling ◽

Oil Reservoirs ◽

Oil Reservoir ◽

Geological Modeling ◽

Oil Saturation ◽

The Impact

The author suggests and describes the most optimal, reliable method for modeling saturation of the productive oil reservoirs The method takes into account the impact of capillary forces in porous media, water-oil transition zone. This method most fully meets the modern requirements of threedimensional geological and hydrodynamic modeling.

Download Full-text