Comprehensive characterization and evaluation of deep shales from Wufeng-Longmaxi Formation by LF-NMR technology

Wang, Hongyan; Zhou, Shangwen; Li, Shuangshuang; Zhao, Meng; Zhu, Tao

doi:10.1016/j.uncres.2022.05.001

Cited by 18 publications

(8 citation statements)

References 20 publications

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“…The kerogen rich in organic sulfur can be broken at a relatively low temperature due to the low bond energy of the C-S bond. Pyrite Fe 2+ is a transition metal, it can significantly affect the electron cloud distribution of cracked organic matter, reduce the activation energy of cracking organic matter, and promote hydrocarbon generation (Loucks et al, 2012;Milliken et al, 2013;Sun et al, 2015;Zhang et al, 2020;Wang et al, 2022). As an inducer, pyrite can promote the formation of hydrocarbons by inducing the formation of free radicals in the process of organic hydrocarbon generation (Wyllie and Spangler, 1952;Tiab and Donaldson., 2004;Roy et al, 2014;Oluwadebi et al, 2019).…”

Section: Catalysis Of Pyritementioning

confidence: 99%

Hydrocarbon accumulation model influenced by “three elements (source-storage-preservation)” in lacustrine shale reservoir-A case study of Chang 7 shale in Yan’an area, Ordos Basin

et al. 2022

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The organic-rich shales of the Chang 7 Member in the Yan’an Formation of the Yan’an area, Ordos Basin is a hot spot for lacustrine shale gas exploration. In this paper, taking the Chang 7 Member shale in the Yan’an area as an example, the main controlling factors of lacustrine shale gas accumulation and the prediction of “sweet spots” are systematically carried out. The results show that the Yanchang Formation shale has the complete gas generating conditions. Shale gas accumulation requires three necessary accumulation elements, namely gas source, reservoir and good preservation conditions. The dynamic hydrocarbon generation process of the Chang 7 shale reservoirs is established according to the thermal simulation experiments of hydrocarbon generation, and the mechanism of catalytic degradation and gas generation in the Chang 7 Member under the background of low thermal evolution degree is revealed. The enriched authigenic pyrite can catalyze the hydrocarbon generation of organic matter with low activation energy, thereby increasing the hydrocarbon generation rates in the low-mature-mature stage. Different types of pores at different scales (2–100 nm) form a multi-scale complex pore network. Free gas and dissolved gas are enriched in laminar micro-scale pores, and adsorbed gas is enriched in nano-scale pores of thick shales, and silty laminates can improve the physical properties of the reservoir. This is because the laminar structure has better hydrocarbon generation conditions and is favorable for the migration of oil and gas molecules. The thickness of the lacustrine shale in the Chang 7 Member is between 40 and 120 m, which has exceeded the effective hydrocarbon expulsion thickness limit (8–12 m). At the end of the Early Cretaceous, the excess pressure of the Chang 7 shale was above 3 MPa. At present, horizontal wells with a daily gas production of more than 50,000 cubic meters are distributed in areas with high excess pressures during the maximum burial depth.

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Section: Catalysis Of Pyritementioning

confidence: 99%

Hydrocarbon accumulation model influenced by “three elements (source-storage-preservation)” in lacustrine shale reservoir-A case study of Chang 7 shale in Yan’an area, Ordos Basin

et al. 2022

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“…The increasing proportion of unconventional oil and gas resources in the global total makes the study of tight oil and gas reservoirs more pertinent (Fu, 2014;Shi et al, 2019;Zhang, 2016;Katz et al, 2021;Wang et al, 2022). The key to these reservoirs lies in the fine characterization of their properties.…”

Section: Introductionmentioning

confidence: 99%

Reservoir properties and genesis of tight sandstones—A case study from the Gaotaizi oil layer in the Qijia area, Songliao basin

Zhao²,

Er³

et al. 2023

Front. Earth Sci.

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The primary focus of oil and gas exploration for tight sandstone reservoirs is on a quantitative characterization of reservoir properties. This paper uses the tight sandstone reservoir developed in the Gaotaizi oil layer in the Qijia area of the Songliao Basin as an example. The petrology, physical properties, pore–throat characteristics, and the genesis of the densification of the oil-bearing sandstones are elucidated using casting thin-sections, scanning electron microscopy, 3D computerized tomography (CT), and petrophysical experimental techniques. The results show that the Gaotaizi oil layer is mainly composed of clastic rocks and contains small amounts of shell limestone. The clastic rocks are mainly lithic feldspar sandstone and feldspar lithic sandstone, while residual intergranular pores, intergranular dissolved pores, intragranular dissolved pores, intragranular pores and intercrystalline pores constitute the different pore types. Mercury intrusion and 3D computerized tomography analysis showed that micro-nano pores account for 53% of the total pores present. The pore–throat coordination number is distributed between 1 and 4, with an average of 1.8. The pores and throats in the Gaotaizi reservoir have poor connectivity. The porosity distribution of the Gaotaizi oil layer is 1.4%–22.5%, with an average of 9.5%, while the permeability distribution ranges from 0.01 to 27.10 mD, with an average of 0.41 mD. It is an ultra-low porosity and ultra-low permeability tight reservoir. The Gaotaizi oil layer is divided into three types of reservoirs through a systematic study of its pore developmental characteristics. Diagenetic processes like compaction and cementation result in a reduction in porosity and permeability. Compaction, calcite and siliceous cementation, and illite packing are primarily responsible for reservoir densification.

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“…As revealed by many cases, anomalously high porosity zones that deviate from normal compaction trend are frequently visible at one or more depth intervals from the profiles of depth vs porosity of many oilfields (Volkmar and Mc Donald, 1979;Su et al, 2018a;Vafaie et al, 2021). In addition to disequilibrium compaction, secondary dissolution can create a large amount of extra reservoir space, and the resultant high-quality reservoirs are of great practical significance for predicting favorable hydrocarbon accumulation areas (Katz et al, 2021;Jiang et al, 2022;Wang et al, 2022). Numerous previous studies indicated that a number of fluids in sedimentary basins, including organic carboxylic acid and CO 2 released from the thermal evolution of organic matter (Surdam et al, 1984), basinal hot fluids (Anna et al, 2009;Su et al, 2021a), meteoric freshwaters infiltrating downward (Ehrenberg, 1993), and deep mantle-derived CO 2 (Su et al, 2018b), can cause reservoir dissolution.…”

Section: Introductionmentioning

confidence: 99%

Alternating acid and alkaline diagenesis in the Shahejie Formation of E12 structure in the Laizhou Bay Sag, Bohai Bay Basin

Yang

Zhang²,

Su³

et al. 2023

Front. Earth Sci.

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The high-quality reservoirs in the Shahejie Formation of the Laizhou Bay Sag, Bohai Bay Basin, Eastern China formed in the Paleogene saline lacustrine environment and show complex diagenetic evolutionary processes caused by alternating acid and alkaline fluids. Through observations under an optical microscope and a scanning electron microscope, casting thin sections, and plane porosity measurements, this study investigated the diagenesis differences in the third member of the Shahejie Formation (Es3 Member) in the root and central portions of a fan delta in the E12 structure in the eastern Laizhou Bay Sag, respectively. The Es3 reservoirs in the well A-1 which have no any hydrocarbon shows, are relatively tight, and have high argillaceous content, poor particle sorting, strong mechanical compaction, and intense carbonate cementation due to long-term activities of alkaline fluids. Moreover, they were not altered by organic acid due to the far lateral distance from source rocks. By contrast, the Es3 reservoirs in the well A-2 with hydrocarbon accumulations, contain an anomalously high porosity zone due to the superimposition of five episodes of alternate acid-alkaline fluids. The diagenetic fluids controlling the formation of the high-quality Es3 reservoirs are sourced from connate saline pore waters, gypsum dehydration, salt diapir, and organic acid. Moreover, chlorite coats in the reservoirs in the well A-2 inhibit secondary overgrowth of quartz and, thus, protect primary pores. The chlorite coats and alkaline-acid dissolution alterations are critical to the formation of the high-quality reservoirs in well A-2.

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Comprehensive characterization and evaluation of deep shales from Wufeng-Longmaxi Formation by LF-NMR technology

Cited by 18 publications

References 20 publications

Hydrocarbon accumulation model influenced by “three elements (source-storage-preservation)” in lacustrine shale reservoir-A case study of Chang 7 shale in Yan’an area, Ordos Basin

Hydrocarbon accumulation model influenced by “three elements (source-storage-preservation)” in lacustrine shale reservoir-A case study of Chang 7 shale in Yan’an area, Ordos Basin

Reservoir properties and genesis of tight sandstones—A case study from the Gaotaizi oil layer in the Qijia area, Songliao basin

Alternating acid and alkaline diagenesis in the Shahejie Formation of E12 structure in the Laizhou Bay Sag, Bohai Bay Basin

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