Occurrence morphology of bitumen in Dengying Formation deep and ultra-deep carbonate reservoirs of the Sichuan Basin and its indicating significance to oil and gas reservoirs

Liu, Shugen; Li, Zeqi; Deng, Bin; Sun, Wei; Ding, Yi; Song, Jinming; Wu, Juan

doi:10.1016/j.ngib.2022.01.001

Cited by 19 publications

(17 citation statements)

References 11 publications

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“…The homogenization temperature of the oil and gas inclusions in the Dengying Formation of the Well GS1 ranges from 90–240 °C. As the homogeneous temperature of inclusions increases, these inclusions gradually change from oil inclusions to gas inclusions . This is consistent with the thermal evolution of the organic-rich shale of the Qiongzhusi Formation, implying that the Qiongzhusi Formation continuously expelled hydrocarbons during the burial process.…”

Section: Discussionmentioning

confidence: 99%

“…Additionally, Well B is located in the Sichuan Basin, where the intensity of tectonic movements is generally lower than in the outer basin . The burial history curve of Well GS1, which is close to that of Well B, reveals that the Qiongzhusi Formation began to be buried rapidly from the Triassic and changed to rapid uplift in the Late Cretaceous . Hence, different member shales in the Qiongzhusi Formation for Well B underwent similar thermal and structural evolution processes.…”

Section: Discussionmentioning

confidence: 99%

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Impact of Minerals and Sealing Systems on the Pore Characteristics of the Qiongzhusi Formation Shale in the Southern Sichuan Basin

Liu

Zhou

et al. 2022

ACS Omega

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The characteristics, distribution, and preservation of pores are vital in controlling the storage and distribution of shale gas. The Qiongzhusi Formation shales taken from different members with similar tectonic and thermal evolutions were used to evaluate the response of pore characteristics to minerals and sealing systems using field-emission scanning electron microscopy and gas adsorption. Because of differences in mineral structure and arrangement, feldspar, organic matter (OM)–clay, OM–rutile, and OM–apatite aggregates facilitate multiple types of pores in the shale and influence the relative proportions of surface porosity for different types of pores owing to differences in mineral structure and arrangement. Rigid frameworks and pressure shadows formed by rigid minerals and OM–mineral aggregates preserved OM and pores to some extent. The sealing capacity of the floor controls the sealing system and hydrocarbon expulsion efficiency of the Qiongzhusi Formation in different members. During thermal evolution, the amount of hydrocarbons generated and expelled affected the stress equilibrium state between the pore pressure and external stress, influencing the compaction intensity of shales. The OM pore development characteristics were evolved with variation in the stress equilibrium state in different sealing systems. Once the stress equilibrium state was disrupted, the OM pores deformed, narrowed, or even closed under the influence of compaction owing to the loss of overpressure support. The pore characteristics of the Qiongzhusi Formation shales responded significantly to different sealing systems. A few OM pores are flat and slitlike in the open system, whereas numerous OM pores are round and elliptical in the semiopen system. Meanwhile, the average diameter of the OM pores in the open system was reduced by approximately 40.2% compared with that of the semiopen system. Furthermore, the pore volume and specific surface area of the mesopores for open system shales were reduced by 38.4% and 37.7%, respectively, compared to the semiopen system. These findings will improve the understanding of the distribution and preservation of pore in shale and help assess the sweet-spot members for the Qiongzhusi Formation shale gas.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Impact of Minerals and Sealing Systems on the Pore Characteristics of the Qiongzhusi Formation Shale in the Southern Sichuan Basin

Liu

Zhou

et al. 2022

ACS Omega

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“…The trends in the formation pressure of the Є 1 q showed that the overpressure started with hydrocarbon expulsion in the late Permian and culminated in the middle Jurassic with a maximum pressure coefficient of 2.4, before eventually stabilizing with a pressure coefficient of 2.2 (Liu et al, 2018). The pressure coefficients of the Є 1 q after hydrocarbon generation clearly exceeded those (1.11-1.59) of the Z 2 dn 4 (Liu et al, 2022). This may be evidence supporting a downward charging pattern; however, the capillary pressure and hydrocarbon buoyancy are not quantitively constrained, and further investigation is required concerning the superimposed effect of the hydrocarbon expelling zone, source rock overpressure area, and hydrocarbon conducting faults in the GMA.…”

Section: Hydrocarbon Chargingmentioning

confidence: 91%

“…Solid bitumen exists prevailingly in reservoir spaces in the Z 2 dn in the GMA (Gao et al, 2018). Its occurrence in the matrix porosities demonstrates direct evidence for the existence of paleo-reservoirs (Wang Z. Y. et al, 2020;Liu et al, 2022), while its content and distribution can indicate the dominant migration path of hydrocarbons (Mastalerz et al, 2018). The contents of solid bitumen in single boreholes of Z 2 dn 4 in the GMA were evaluated quantitatively by Song et al (2021) via a multi-mineral volumetric inversion pattern established by five conventional logging curves (viz.…”

Section: Hydrocarbon Chargingmentioning

confidence: 99%

Multi-Factor Evaluation of Deep Karst Dolomite Reservoir Based on Paleogeomorphological Reconstruction, a Case Study From the 4th Member of the Dengying Formation in the Central Sichuan Basin, China

Zhou

Wang²,

Yang³

et al. 2022

Front. Earth Sci.

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The evaluation of reservoirs is of great importance in exploration practices, and reservoir distribution is dependent on multiple geological factors. The carbonate platform of the fourth member (Z2dn4) of the Dengying Formation (Z2dn) in the Gaoshiti-Moxi area (GMA) was uplifted above sea level during episode II of the Tongwan movement and underwent prolonged karstification by meteoric freshwater in the terminal Sinian, leading to a strong heterogeneity in reservoirs. Paleogeomorphology reflects hydraulic gradients that can affect the intensities of surface karstification and may be approximated by terrain slope gradients. Karst products (especially solution vugs and caverns) exist prevailingly in the Z2dn4; their development mirrors the extents of internal dissolution. Based on paleogeomorphological reconstruction using the elevation method, the slope angles of single boreholes were calculated through the digital elevation model (DEM). In accordance with single-borewell Fullbore Formation MicroImager (FMI) logging data, four electrofacies (host rock, vug, fracture, and cave) were identified in boreholes possessing FMI data. The identified electrofacies were matched with corresponding conventional logging curves to obtain the training data. A model generalized for other boreholes without FMI data was established with the random forest algorithm and the thicknesses of the four electrofacies in each borehole were determined to characterize the extent of karstification. Slope gradients and electrofacies thicknesses, together with multiple physical parameters of reservoirs in boreholes, were utilized for factor analysis. Four factors were obtained and fused into one comprehensive score based on their ratios of variance proportions. The favorability of reservoirs was described by the comprehensive scores of each borehole. These analyses showed that the most advantageous reservoirs are distributed in the vicinity of the platform margin in the west of the GMA, where they enjoy several benefits. Deposition of porous mound-shoal complexes occurs predominantly in the platform margin where large-scale caves are more developed in the mixing karst zone of seawater and freshwater. Meanwhile, the transmeridional lateral migration of hydrocarbons from the regional hydrocarbon-generating center abutting the west of the GMA contributes to earlier entrapment and accumulation in the mound-shoal complexes in the platform margin.

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“…As a result, the paleo-oil-reservoirs of the Dengying Formation on the North Slope and in the Gaoshiti-Moxi area entirely cracked, and paleo-gas-reservoirs widely distributed in these two regions. Also, abundant reservoir solid bitumen was retained as another typical product of oil-cracking (Gao et al, 2018;Liu et al, 2021). 4) During the Himalayan Movement, since the vertical tectonic movement dominated the central Sichuan Basin, the North Slope, and Gaoshiti-Moxi area were relatively structurally stable.…”

Section: Research Areamentioning

confidence: 99%

Dynamic reconstruction of the hydrocarbon generation, accumulation, and evolution history in ultra-deeply-buried strata

Song

Ding

Zhang³

et al. 2022

Front. Earth Sci.

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The evolution mechanism of hydrocarbons in ultra-deeply-buried and ultra-old strata is the core issue of petroleum geology moving towards Deep Earth. Reconstructing the evolutionary history of ultra-deeply-buried hydrocarbons is the key to shedding light on deep hydrocarbon accumulation and evolution mechanisms. Furthermore, it can help point out directions for oil and gas exploration in Deep Earth. Anyue gas field in the central Sichuan Basin is the Frontier of deep natural gas exploration in China. This study selected the natural gas reservoirs of the Upper Sinian Dengying Formation in the central Sichuan Basin as the research object. By integrating analysis of natural gas geochemical characteristics, source rock evaluation, reservoir bitumen-source correlation, inclusion analysis, one-dimensional and two-dimensional hydrocarbon accumulation simulations, the generation and evolution of hydrocarbons in different structural regions, namely the inherited paleo-uplift and slope area in central Sichuan Basin, have been dynamically restored and compared. The results show that: 1) The natural gas of the ultra-deeply-buried Sinian Dengying formation in central Sichuan is typical oil-cracking gas from the paleo-oil reservoir. The Sinian gas is mainly sourced from the Qiongzhusi/Maidiping Formation. 2) The formation of Sinian gas reservoirs includes three stages: the formation of paleo-oil-reservoirs; the cracking of paleo-oil-reservoirs into paleo-gas-reservoirs; the adjustment of the paleo-gas-reservoirs. 3) Source rock and reservoir evaluation, quantitative solid bitumen analysis, and hydrocarbon accumulation simulation show that the natural gas accumulation conditions in the slope area are better than in the inherited uplift area. The scale of the paleo-oil-reservoirs in the slope area may be greater than that in the inherited uplift area.

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Occurrence morphology of bitumen in Dengying Formation deep and ultra-deep carbonate reservoirs of the Sichuan Basin and its indicating significance to oil and gas reservoirs

Cited by 19 publications

References 11 publications

Impact of Minerals and Sealing Systems on the Pore Characteristics of the Qiongzhusi Formation Shale in the Southern Sichuan Basin

Impact of Minerals and Sealing Systems on the Pore Characteristics of the Qiongzhusi Formation Shale in the Southern Sichuan Basin

Multi-Factor Evaluation of Deep Karst Dolomite Reservoir Based on Paleogeomorphological Reconstruction, a Case Study From the 4th Member of the Dengying Formation in the Central Sichuan Basin, China

Dynamic reconstruction of the hydrocarbon generation, accumulation, and evolution history in ultra-deeply-buried strata

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