An inland facies-controlled eogenetic karst of the carbonate reservoir in the Middle Permian Maokou Formation, southern Sichuan Basin, SW China

Xiao, Di; Tan, Xiucheng; Xi, Aihua; Hong, Liu; Shan, Shujiao; Xia, Ji-Wen; Cheng, Yao; Lian, Chengbo

doi:10.1016/j.marpetgeo.2016.02.001

Cited by 69 publications

(29 citation statements)

References 17 publications

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“…Dissolution and filling are typical phenomena associated with karstification (James & Choquette, ). The three dissolution‐filling zones from the matrix to the conduit in the grainstone of the Bancun section (Figure 9a and b), closely resemble the eogenetic karst features of the Maokou Formation of the Middle Permian in the southern Sichuan Basin (Xiao et al, ). The half‐dissociated zone is stacked with dark carbonaceous mud between grey‐white disscociated granular fabrics, closely resembling the “Feiable Halo” rim along the conduit in modern eogenetic karsts in central and northern Florida (Moore, Martin, Screaton, & Neuhoff, ).…”

Section: Resultsmentioning

confidence: 63%

“…In terms of the pore type, the moldic pore and interparticle pore resutling from the selective dissolution of grains, gypsum, breccia, and early‐stage cement mainly exist in the palaeokarst zone of the Longwangmiao Formation. Previous palaeokarst features are similar to the eogenetic karst in the Halfaya Oilfield in Upper Cretaceous (Zhong et al, ), Maokou Formation of the middle Permian of the Sichuan Basin (Tan et al, ; Xiao et al, ), and Mississippian in New Mexico (Meyers, ). Besides that, the dissolution of the early‐stage fibrous cement and the selective‐dissolution in oolite indicate that the dissolution occurred in the penecontemporaneous or the early diagenetic stage (Longman, ).…”

Section: Discussionmentioning

confidence: 82%

“…Over time, dissolution accelerates with increasing water flow, so that the conduit formed by dissociation and dissolution gradually increases in size, and the flow pattern evolves to conduit flow. The difference between the hydraulic head inside and outside the conduit is the main cause of conduit development (Xiao et al, ). The microspar and micritization of the grains in the grainstone are similar to the microscopic features of a Mississippian eogenetic karst in New Mexico (Meyers, ).…”

Section: Resultsmentioning

confidence: 99%

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The eogenetic karst of the Cambrian Longwangmiao Formation in the Yangtze Platform: Implications for the eustatic and stratigraphic correlations of Toyonian (Cambrian)

Jia

Hai-qin

et al. 2018

Geological Journal

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To make a better understanding of the stratigraphic correlation and ocean processes during the transition from Series 2 to Series 3 in the Cambrian, this study investigated the characteristics and origin of the palaeokarst in the uppermost part of the Longwangmiao Formation (Toyonian) and established the carbon isotopic curves of the shallow‐water succession. Macroscopically, the palaeokarst features have been identified, including the exposed surface, karstic trough, discolouration, and breccia in the upper part of the Longwangmiao Formation. The exposed surface is divided into the bedrock, weakly weathering zone, intensely weathering zone, dissolved‐collapsed zone, and weathering clay layer at the Dingzhai section. The reddish aluminous oxide and the stratiform‐dissolved pore are recognized in the Gaodongmiao section. The clast‐support breccia and matrix‐support breccia develop in the palaeokarst zone. Microscopically, three dissolution‐filling zones in grainstone (the matrix zone, half‐dissociated zone, and mixed‐filling zone) dissolved fibrous cement in the early diagenetic stage, microspar cement in a bright homogeneous luminescence, and medium‐crystal calcite showing a zonation luminescence are identified indicating the facies‐controlled attributes. The δ13C values are characterized by a lower range (4.4‰ to −2.1‰) in the karst zone. The REE pattern shows enriched middle REE, negative Eu anomalies, and low Y/Ho ratio, which is different from the nature of seawater. It is proposed that the palaeokarst in the upper part of the Longwangmiao Formation is the eogenetic karst controlled by high‐frequency sea‐level fluctuations. Two negative δ13C excursions (values −4.4‰ in D2 and −3.6‰ in D1) are respectively recognized, the top boundary and middle part of the Longwangmiao Formation. Based on the regional and global correlations, the excursion of D2 is the diagenetic signal in the shallow‐water setting, which correlated to ROECE event (Redlichiid‐Olenellid Extinction Carbon isotope Excursion) that occurred around the boundary between Series 2 and Series 3 in the Cambrian. The local signal of D2 is attributed to the sea‐level falling.

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Section: Resultsmentioning

confidence: 63%

Section: Discussionmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

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The eogenetic karst of the Cambrian Longwangmiao Formation in the Yangtze Platform: Implications for the eustatic and stratigraphic correlations of Toyonian (Cambrian)

Jia

Hai-qin

et al. 2018

Geological Journal

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“…The Yucatan Peninsula study of Lace and Mylroie [39] provided a reference model for studying karst cave genesis formed during short-term exposure. Some scholars have used this pore development model of karst formation for reference when studying the formation of paleokarst pores-caves using outcrop investigation, core, seismic attribute, and other methods [16,47,48]. Karsts in the Tazhong area display different characteristics from karsts in modern island settings.…”

Section: Comparison Between the Yingshan Formation Karst Characteristmentioning

confidence: 99%

“…This model has successfully guided the exploration of carbonate karst fracture-cavern reservoirs in the Lunnan and Tahe oil fields [14,15]. However, it is extremely rare to find diagenetic carbonate rocks that underwent long-term exposure and karstification, and continental freshwater cannot explain how karstification occurred immediately after the deposition of carbonate rocks [16]. It is theorized that the exposure time may be limited to 10 Ma (1 Ma = 1 million anniversaries) or less [17].…”

Section: Introductionmentioning

confidence: 99%

Eogenetic Karst Control of Carbonate Reservoirs during a Transient Exposure: A Case Study of the Ordovician Yingshan Formation in the Northern Slope of the Tazhong Uplift, Tarim Basin, China

et al. 2018

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Abstract:The Tazhong area of the Tarim Basin contains abundant oil and gas resources in Ordovician carbonate rocks, especially in the karst pores and caves of the Yingshan Formation. Research has indicated that the Yingshan Formation underwent a 7-11 Ma exposure during the middle Caledonian Period, resulting in large-scale karst pores and caves. However, the continental freshwater karst model cannot adequately explain the origin and distribution of karst pores and caves. In order to develop a more accurate karst model to guide petroleum exploration in the region, we analyzed the karst morphology, cave development statistics, and paleokarst environments. Karst reservoir characteristics were analyzed on the basis of the following analysis: (1) Karst morphological analyses based on core description and formation micro-imager (FMI) log analyses. The results showed that alveolar-like and Swiss cheese-like solution pores, spongy dissolution zones, pit cenotes, and small continuous karst caves developed in the Yingshan Formation. (2) The statistical analysis of pore and cave characteristics indicated that most of the karst pores and caves developed within 50 m below the unconformity where the average height of these features ranged from 0.1 to 3.0 m and their widths ranged up to 100 m. These pores and caves were commonly filled with gravel, clay, and calcite. Horizontal well and seismic attribute analysis indicated that these pores and caves were distributed over a large area. In plain view, the karst pore-cave system is comprised of cross-linked anastomosing networks of horizontal cave passages. And (3) Cathode luminescence and electron microprobe analyses suggested that clay filling within karst caves was freshwater related, while calcite filling was of seawater origin. Cements within solution pores showed three phases of luminescence, suggesting an alternating freshwater and seawater environment. Based on these characteristics, the karsts of the Yingshan Formation in the Tazhong area are interpreted to be similar to the eogenetic karsts in the Yucatan Peninsula of modern Mexico. Accordingly, this study indicates that the pore-caves of the Yingshan Formation can be subdivided into three sections. Further, the development and filling of these pore-cave sections are interpreted to have formed by eogenetic mixed-water karstification during three phases of relatively stable sea level in a coastal margin environment.

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Reconstructing large‐scale karst paleogeomorphology at the top of the Ordovician in the Ordos Basin, China: Control on natural gas accumulation and paleogeographic implications

Xiao

Tan

Fan

et al. 2019

Energy Science & Engineering

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Karstification in carbonate successions has an important influence on hydrocarbon accumulation. Taking the Ordos Basin, currently the largest petroliferous basin in China, as an example, this study examines the large‐scale, long‐term (~120 Myr) paleokarst at the top of the Ordovician. The objectives of the study are to characterize the karst paleogeomorphology of this area, to explain the inconsistency between existing understandings of karst paleogeomorphology and exploration in the eastern Ordos Basin, and to reveal the control of paleokarst on natural gas accumulation and its paleogeographic significance. A total of 860 exploration wells were used for detailed stratigraphic correlation and analysis, along with core observations, well‐logging analyses, physical property characterization, and isotope analyses. Results of residual thickness and moldic thickness reconstruction reveal variation in karst paleogeomorphology between north and south in the eastern Ordos Basin, differing from the traditionally recognized E‐W variation. Two geomorphic units are classified as follows: the karst highland and the karst slope from north to south, with the karst slope being subdivided into northern and southern slope areas. The karst highland area has negligible reservoir capacity and hydrocarbon accumulation owing to the enhanced denudation that occurred there. In contrast, the northern karst slope shows favorable reservoir properties and has abundant gas wells according to well‐logging interpretations, whereas the southern karst slope is of poor reservoir quality and hosts mainly water wells. Differences in dissolution‐filling effects controlled by the surface paleodrainage system are suggested to be the main contributor to differential reservoir space preservation, which, together with the variable width and depth of source rocks in the grooves (thereby variably exposing source rock), further promoted differential gas accumulation. The Ordos Basin and its periphery in the southwestern North China Craton (NCC) show inheritance of sedimentary‐tectonic patterns from the Middle Ordovician to the Late Carboniferous. These results should provide a reference for hydrocarbon exploration in the Ordovician of other basins in the NCC in which karst occurs and karst basins worldwide, and deepens understanding of the paleogeographic framework in the context of regional uplift of the North China Platform.

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An inland facies-controlled eogenetic karst of the carbonate reservoir in the Middle Permian Maokou Formation, southern Sichuan Basin, SW China

Cited by 69 publications

References 17 publications

The eogenetic karst of the Cambrian Longwangmiao Formation in the Yangtze Platform: Implications for the eustatic and stratigraphic correlations of Toyonian (Cambrian)

The eogenetic karst of the Cambrian Longwangmiao Formation in the Yangtze Platform: Implications for the eustatic and stratigraphic correlations of Toyonian (Cambrian)

Eogenetic Karst Control of Carbonate Reservoirs during a Transient Exposure: A Case Study of the Ordovician Yingshan Formation in the Northern Slope of the Tazhong Uplift, Tarim Basin, China

Reconstructing large‐scale karst paleogeomorphology at the top of the Ordovician in the Ordos Basin, China: Control on natural gas accumulation and paleogeographic implications

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