Lithofacies, Depositional Environment and Diagenetic Evolution of the Paleocene Patala Formation, Potwar Basin, Pakistan: Implication for Shale Gas Potential

2021 ◽  
Author(s):  
Nasar Khan ◽  
Rudy Swennen ◽  
Gert Jan Weltje ◽  
Irfan Ullah Jan
Keyword(s):  
Organic Matter ◽  
Shale Gas ◽  
Gas Reservoirs ◽  
Shallow Marine ◽  
Anoxic Conditions ◽  
Fine Grained ◽  
Potwar Basin ◽  
Diagenetic Evolution ◽  
Reservoir Assessment ◽  
Gas Potential

<p><span><strong>Abstract:</strong> Reservoir assessment of unconventional reservoirs poses numerous exploration challenges. These challenges relate to their fine-grained and heterogeneous nature, which are ultimately controlled by depositional and diagenetic processes. To illustrate such constraints on shale gas reservoirs, this study focuses on lithofacies analysis, paleo-depositional and diagenetic evolution of the Paleocene Patala Formation at Potwar Basin of Pakistan. Integrated sedimentologic, petrographic, X-ray diffraction and TOC (total organic carbon) analyses showed that the formation contained mostly fine-grained carbonaceous, siliceous, calcareous and argilaceous siliciclastic-lithofacies, whereas carbonate microfacies included mudstone, wackestone and packstone. The silicious and carbonaceous lithofacies are considered a potential shale-gas system. The clastic lithofacies are dominated by detrital and calcareous assemblage including quartz, feldspar, calcite, organic matter and clay minerals with auxiliary pyrites and siderites. Fluctuations in depositional and diagenetic conditions caused  lateral and vertical variability in lithofacies. Superimposed on the depositional heterogeneity are spatially variable diagenetic modifications such as dissolution, compaction, cementation and stylolitization. The δ</span><sup>13</sup><span>C and δ</span><sup>15</sup><span>N stable isotopes elucidated that the formation has been deposited under anoxic conditions, which relatively enhanced the preservation of mixed marine and terrigenous organic matter. Overall, the Patala Formation exemplifies deposition in a shallow marine (shelfal) environment with episodic anoxic conditions.</span></p><p><strong>Keywords</strong><strong>:</strong> Lithofacies, Organic Matter, Paleocene, Potwar Basin, Shale Gas, Shallow Marine.</p>

scholarly journals Adsorption Characteristics and Controlling Factors of CH4 on Coal-Measure Shale, Hedong Coalfield

Minerals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 63
Author(s):  
Weidong Xie ◽  
Meng Wang ◽  
Hongyue Duan
Keyword(s):  
Organic Matter ◽  
Adsorption Capacity ◽  
Mineral Composition ◽  
Shale Gas ◽  
Total Content ◽  
Coal Measure ◽  
Gas Reservoirs ◽  
Quartz Content ◽  
Adsorption Characteristics ◽  
Adsorbed Gas

Adsorbed gas is one of the crucial occurrences in shale gas reservoirs; thus, it is of great significance to ascertain the adsorption capacity of shale and the adsorption characteristics of CH4. In this investigation, the Taiyuan–Shanxi Formations’ coal-measure shale gas reservoir of the Carboniferous–Permian era in the Hedong Coalfield was treated as the research target. Our results exhibit that the shale samples were characterized by a high total organic carbon (TOC) and over to high-over maturity, with an average TOC of 2.45% and average Ro of 2.59%. The mineral composition was dominated by clay (62% on average) and quartz (22.45% on average), and clay was mainly composed of kaolinite and illite. The Langmuir model showed a perfect fitting degree to the experimental data: VL was in the range of 0.01 cm3/g to 0.77 cm3/g and PL was in the range of 0.23–8.58 MPa. In addition, the fitting degree depicted a linear negative correlation versus TOC, while mineral composition did not exhibit a significant effect on the fitting degree, which was caused by the complex pore structure of organic matter, and the applicability of the monolayer adsorption theory was lower than that of CH4 adsorption on the mineral’s pore surface. An apparent linear positive correlation of VL versus the TOC value was recorded; furthermore, the normalized VL increased with the growth of the total content of clay mineral (TCCM), decreased with the growth of the total content of brittle mineral (TCBM), while there was no obvious correlation of normalized VL versus kaolinite, illite and quartz content. The huge amount of micropores and complex internal structure led to organic matter possessing a strong adsorption capacity for CH4, and clay minerals also promoted adsorption due to the development of interlayer pores and intergranular pores.

The effects of clay minerals and organic matter on nanoscale pores in Lower Paleozoic shale gas reservoirs, Guizhou, China

2018 ◽  
Vol 37 (6) ◽  
pp. 791-804 ◽  
Author(s):  
Yuantao Gu ◽  
Quan Wan ◽  
Wenbin Yu ◽  
Xiaoxia Li ◽  
Zhongbin Yu
Keyword(s):  
Organic Matter ◽  
Clay Minerals ◽  
Shale Gas ◽  
Gas Reservoirs ◽  
Lower Paleozoic ◽  
Shale Gas Reservoirs

scholarly journals Water-Gas Two-Phase Flow Behavior of Multi-Fractured Horizontal Wells in Shale Gas Reservoirs

Processes ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 664 ◽  
Author(s):  
Lei Li ◽  
Guanglong Sheng ◽  
Yuliang Su
Keyword(s):  
Organic Matter ◽  
Shale Gas ◽  
Flow Behavior ◽  
Horizontal Wells ◽  
Gas Production ◽  
Phase Flow ◽  
Gas Reservoirs ◽  
Two Phase ◽  
Fractured Horizontal Wells ◽  
Water Gas

Hydraulic fracturing is a necessary method to develop shale gas reservoirs effectively and economically. However, the flow behavior in multi-porosity fractured reservoirs is difficult to characterize by conventional methods. In this paper, combined with apparent porosity/permeability model of organic matter, inorganic matter and induced fractures, considering the water film in unstimulated reservoir volume (USRV) region water and bulk water in effectively stimulated reservoir volume (ESRV) region, a multi-media water-gas two-phase flow model was established. The finite difference is used to solve the model and the water-gas two-phase flow behavior of multi-fractured horizontal wells is obtained. Mass transfer between different-scale media, the effects of pore pressure on reservoirs and fluid properties at different production stages were considered in this model. The influence of the dynamic reservoir physical parameters on flow behavior and gas production in multi-fractured horizontal wells is studied. The results show that the properties of the total organic content (TOC) and the inherent porosity of the organic matter affect gas production after 40 days. With the gradual increase of production time, the gas production rate decreases rapidly compared with the water production rate, and the gas saturation in the inorganic matter of the ESRV region gradually decreases. The ignorance of stress sensitivity would cause the gas production increase, and the ignorance of organic matter shrinkage decrease the gas production gradually. The water film mainly affects gas production after 100 days, while the bulk water has a greater impact on gas production throughout the whole period. The research provides a new method to accurately describe the two-phase fluid flow behavior in different scale media of fractured shale gas reservoirs.

scholarly journals Sedimentary Evolution Characteristics of Fine-Grained Lithofacies under the High-Resolution Isochronous Shelf System: Insights from the Wufeng-Longmaxi Shales in the Sichuan Basin

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 1) ◽  
Author(s):  
Guanping Wang ◽  
Zhijun Jin ◽  
Zongquan Hu ◽  
Guangxiang Liu ◽  
Tong Zhu ◽  
...  
Keyword(s):  
Organic Matter ◽  
High Resolution ◽  
Shale Gas ◽  
Transgressive System Tract ◽  
Fine Grained ◽  
Sedimentary Sequences ◽  
Evolution Characteristics ◽  
Sedimentary System ◽  
Siliceous Shale ◽  
System Tract

Abstract The deposition and evolution of fine-grained sediments is a hot topic in fine-grained sedimentary rock studies and is important for accurately evaluating shale gas sweet spots. In this paper, the fine-grained deposition and evolution characteristics of the Wufeng-Longmaxi shales, major targets for Chinese shale gas exploration, were studied by using core observations, thin section analyses, scanning electron microscopy, geochemical analysis, and fossil identification. This work accurately identified six typical lithofacies; among them, the organic matter-rich siliceous shale facies (OMRSSF), the high-organic matter siliceous argillaceous shale facies (HOMSASF), and the medium-high organic matter low calcareous siliceous shale facies (M-HOMLCSASF) are favorable facies for shale gas exploration. The high-resolution isochronous unit in the shelf fine-grained sedimentary system was established, and the differential evolution of lithofacies in the system tract was discussed. The lithofacies deposition and differentiation in the transgressive system tract were controlled by the transgressive scale and tectonics under increasingly shallow water conditions. The lithofacies deposition and differentiation in the regressive system tract were controlled by tectonics and the preexisting lithofacies. The lithofacies in the regressive system tract had more frequent facies transitions and greater differentiation than those in the transgressive system tract, and they exhibited significant spatiotemporal inheritance. Sequential differential sedimentary sequences and symmetric differential sedimentary sequences were distinguished in the continental shelf sedimentary system. The lithofacies depocenters and subsidence centers were consistent in the transgressive system tract, while the tectonically active paleocontinent was important in the regression system tract. This study is of great significance for further high-resolution exploration of marine shale and improvement of the theory of shelf fine-grained sedimentary systems.

Evaluation on Shale Gas Potential in the Sheling Group Yitong Basin

2014 ◽  
Vol 941-944 ◽  
pp. 2584-2587
Author(s):  
Han Yue Xu ◽  
Hai Tao Xue ◽  
Shuang Fang Lu ◽  
Wen Biao Huang ◽  
Lei Shi
Keyword(s):  
Organic Matter ◽  
Adsorption Isotherm ◽  
Chemical Kinetics ◽  
Shale Gas ◽  
Jilin Province ◽  
Resource Potential ◽  
Geochemical Parameters ◽  
High Maturity ◽  
Gas Potential

Yitong Basin is a Tertiary depression bas in Jilin Province , and from north to south were Chaluhe , Luxiang and Moliqing depression. As the depth is larger , high maturity of organic matter , more than 1% , mainly shale gas. Based on the geochemical parameters of sheling group , using chemical kinetics method study the birth hydrocarbon volume, using the sum of the largest shale gas tolerance capabilities , based on the adsorption isotherm experiments, combined hydrocarbon volume , calculated the shale gas resources in the region , the results showed that the total amount of resources sheling group Yitong Basin shale gas level was 238.215 billion square . Indicates that the area has huge shale gas resource potential

Upper Carboniferous Shale Gas Potential Analysis in Eastern Qaidam Basin, Northwestern China

2014 ◽  
Vol 1010-1012 ◽  
pp. 1425-1429
Author(s):  
Hai Yan Cheng ◽  
Yin Sheng Ma ◽  
Cheng Ming Yin ◽  
Yuan Yuan Yang
Keyword(s):  
Organic Matter ◽  
Shale Gas ◽  
Oil And Gas ◽  
Qaidam Basin ◽  
Source Rocks ◽  
Carbonaceous Shale ◽  
Silty Mudstone ◽  
Upper Carboniferous ◽  
Carboniferous Shale ◽  
Gas Potential

Shale of rich organic matter presents in Upper Carboniferous in Qaidam Basin, Northwest of China. Carboniferous shale thickness is between 100 ~ 300m in the Qaidam Basin, the shale includes silty mudstone shale, calcareous mudstone, shale and carbonaceous shale, and it is very favorable lithology type for shale gas. According to the shale organic geochemical analysis, the abundance of organic matter reaching the middle - good degree of hydrocarbon source rocks; the type of organic matter is mainly II2 and III type. The maturity of organic matter is mainly between 1 % -1.3 %. The Upper Carboniferous shale thermal evolution is in mature oil and gas stage. The Upper Carboniferous hydrocarbon-rich shale distribute stability, with great thickness. Shale gas potential in Upper Carboniferous is quite large.

scholarly journals Characteristics of Organic Matter Particles and Organic Pores of Shale Gas Reservoirs: A Case Study of Longmaxi-Wufeng Shale, Eastern Sichuan Basin

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 137
Author(s):  
Guochang Wang ◽  
Shengxiang Long ◽  
Yongmin Peng ◽  
Yiwen Ju
Keyword(s):  
Organic Matter ◽  
Shale Gas ◽  
Sichuan Basin ◽  
Pore System ◽  
Gas Reservoirs ◽  
Sem Images ◽  
Eastern Sichuan Basin ◽  
Eastern Sichuan ◽  
Organic Porosity ◽  
Organic Pores

Heterogeneity of organic matter (OM), including size, type, and organic pores within OM, is being recognized along with increasing study using SEM images. Especially, the contribution of organic pores to the entire pore system should be better understood to aid in the evaluation of shale reservoirs. This research observed and quantitatively analyzed over 500 SEM images of 19 core samples from Longmaxi-Wufeng Shale in the eastern Sichuan Basin to summarize the features of OM particles and OM-hosted pores and their evolution during burial. The features of organic pores as well as the embedded minerals within OM particles enables to recognize four different type of OM particles. The organic pore features of each type of OM particles were quantitatively described using parameters such as pore size distribution (PSD), pore geometry, and organic porosity. The PSD of weakly or undeformed porous pyrobitumen indicates that the large organic pores (usually 200 nm to 1 um) is less common than small pores but the major contributor to organic porosity. The organic porosity of OM particles covers a large range of 1–35%, indicating a high heterogeneity among OM particles. Based on analysis of 81 OM particles, the average of organic porosity of the five samples were calculated and ranges from 3% to 12%. In addition, samples from well JY1 have higher organic porosity than JY8. These results helped to reveal how significant the organic pores are for shale gas reservoirs. In addition to presenting many examples of OM particles, this research should significantly improve the understanding of type and evolution of OM particles and contribution of OM-hosted pores to the entire pore system of high to over mature shale.

scholarly journals Lithofacies and Sedimentation of Organic Matter in Fine Grained Rocks of Nanggulan Formation in Kulon Progo, Yogyakarta

2016 ◽  
Vol 1 (2) ◽  
pp. 82
Author(s):  
Donatus Hendra Amijaya ◽  
Najibatul Adibah ◽  
Ahmad Z.A. Ansory
Keyword(s):  
Organic Matter ◽  
Depositional Environment ◽  
Inorganic Material ◽  
Middle Eocene ◽  
Late Eocene ◽  
Geochemical Data ◽  
Environment Analysis ◽  
Shallow Marine ◽  
Fine Grained ◽  
Gas Source

Fine grained rocks especially shale play a significant role in shale hydrocarbon system. Research on Eocene Nanggulan shale becomes an interest lately since this shale is considered as prospective interval for shale gas source. It potentially contains significant organic matter because coaly sediment is found in this formation as well. Nanggulan Formation fine grained rocks was deposited in various depositional environment from estuary – shallow marine. This paper integrates the result of lithofacies and depositional environment analysis with organic geochemical data to understand the sedimentation process of organic matter. Samples were taken from cores. The result of 14 geochemically analysed samples shows Total Organic Carbon (TOC) content between 0.36–1.00 % for fin e grained rocks (shales) and 12.80 % for coaly shales. Nine samples are categorized as fair and 2 samples are categorized as good source rock. The depositional environment of Nanggulan Formation sediment, which was shallow marine at Late Eocene and estuary (salt marsh) at Early Eocene, produced sediment with higher TOC. Whereas the deposition of sediment in estuary (tidal flat) at Middle Eocene produced lower content of TOC. Vulcanic activity at Middle Eocene also caused less organic material preservation because it produced abundant inorganic material.

scholarly journals Application of Dipole Array Acoustic Logging in the Evaluation of Shale Gas Reservoirs

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3882
Author(s):  
Wenrui Shi ◽  
Xingzhi Wang ◽  
Yuanhui Shi ◽  
Aiguo Feng ◽  
Yu Zou ◽  
...  
Keyword(s):  
Shale Gas ◽  
Total Porosity ◽  
P Wave ◽  
S Wave ◽  
Gas Reservoirs ◽  
Acoustic Logging ◽  
Gas Saturation ◽  
Shale Gas Reservoirs ◽  
Gas Potential ◽  
The Relationship

In order to effectively evaluate shale gas reservoirs with low porosity, extra-low permeability, and no natural productivity, dipole array acoustic logging, which can provide various types of information including P-wave slowness (DTC) and S-wave slowness (DTS), is widely used. As the dipole array acoustic logging tool has a larger investigation depth and is suitable for complex borehole environments, such as those with a high wellbore temperature, high drilling fluid column pressure, or irregular borehole wall, it has been mainly applied to the evaluation of lithology, gas potential, fractures, and stimulation potential in shale gas reservoirs. The findings from a case study of the Sichuan Basin in China reveal that the acoustic slowness, S-P wave slowness ratio (RMSC), and S-wave anisotropy of the dipole array acoustic logging can be used to qualitatively identify reservoir lithology, gas potential, and fractures. Using the relationship between DTC and the total porosity of shale gas reservoirs, and combined with the compensated neutron (CNL) and shale content (Vsh) of the reservoir, a mathematical model for accurately calculating the total porosity of the shale gas reservoir can be established. By using the relationship between the RMSC and gas saturation in shale gas reservoirs and tied with density log (DEN), a mathematical model of gas saturation can be established, and the determination of gas saturation by the non-resistivity method can be achieved, delivering a solution to the issue that the electric model is not applicable under low resistivity conditions. The DTS, DTC, and DEN of shale can be used to calculate rock mechanic parameters such as the Poisson’s ratio (POIS) and Young’s modulus (YMOD), which can be used to evaluate the shale stimulation potential.

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