Geological modeling of excellent fracture-vug carbonate reservoirs: A case study of the Ordovician in the northern slope of Tazhong palaeouplift and the southern area of Tabei slope, Tarim Basin, NW China

Ni, Xinfeng; Shen, Anjiang; Pan, Wenqing; Zhang, Ronghu; Yu, Hao‐Cheng; Dong, Y. R.; Zhu, Yongfa; Wang, Chaofeng

doi:10.1016/s1876-3804(13)60056-7

Cited by 29 publications

(10 citation statements)

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“…The microstructures present show more than 90% porosity is of dissolution porosity ( Figures 5-8). This is consistent with the fact that the Ordovician carbonate reservoirs are mainly characterized by dissolution vugs and caves [28,33,34], and almost all occur along the fault damage zones [30,31]. Regardless of the intense cementation, there is much stronger dissolution in the fault damage zones (Figure 8) than the country rocks (Figures 4a and 6a).…”

Section: Fault Controls On the Structural Diagenesissupporting

confidence: 81%

“…The major production in this area is from dissolution vugs (diameter between 2-100 mm) and caves (diameter >100 mm) found in the tight matrix carbonate reservoirs [28,33]. The "sweet spots" of fracture-cave reservoirs (assemblages of caves, vugs and fractures) showing "bead-shape" strong reflection in the seismic profile [28]) are main targets for the production in the carbonate reservoirs [29,33,34]. The fracture-cave reservoirs are quite different from the high matrix reservoirs and meteoric karst reservoirs [35,36], but are strongly heterogeneous reservoirs that are close to hypogene or hydrothermal karstification along fault zones [37][38][39].…”

Section: Geological Settingmentioning

confidence: 99%

“…The primary porosity of the Ordovician carbonate rocks from the Halahatang area has been almost totally occluded during burial diagenesis [28,40]. Reservoir porosity is primarily the result of dissolution [28,30,33,34]. Multiple dissolution events have affected the carbonate rocks in the fault damage zones whereby the dissolution porosity occurs along the fractures (Figure 8a), along rectangular stylolites (Figure 8b), and within the cataclasites (Figure 8c).…”

Section: Dissolutionmentioning

confidence: 99%

“…Regardless of the intense cementation, there is much stronger dissolution in the fault damage zones (Figure 8) than the country rocks (Figures 4a and 6a). This suggests the dissolution porosity mainly occurred within the fault damage zones, although it is still ambiguous for the process of the large caves [34]. There is generally a complicated interplay between cementation and dissolution as a consequence of mechanical deformation in the Ordovician carbonates [7,13,14,53].…”

Section: Fault Controls On the Structural Diagenesismentioning

confidence: 99%

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Structural Diagenesis in Carbonate Rocks as Identified in Fault Damage Zones in the Northern Tarim Basin, NW China

Xie

Zhang

et al. 2019

Minerals

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The identification of structural diagenesis and the reconstruction of diagenetic paragenesis in fault damage zones is important for understanding fault mechanisms and fluid flow in the subsurface. Based on the examination of core and sample thin section data, we deciphered the diagenetic parasequence and their fault controls for Ordovician carbonates in the northern Tarim intracratonic basin in NW China (Halahatang area). In contrast to the uniform nature of diagenesis observed in country rocks, there is a relatively complicated style of compaction and pressure solution, multiple fracturing, and cementation and dissolution history along the carbonate fault damage zones. The relative paragenetic sequence of the structure related diagenesis suggests three cycles of fracture activities, following varied fracture enlargement and dissolution, and progressively weaker calcite cementation. These processes of structure related diagenesis are constrained to the fault damage zones, and their variation is affected by the fault activities. The results of this study suggest that the carbonate reservoir and productivity could be impacted by the structure related diagenesis locally along the fault damage zones.

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Section: Fault Controls On the Structural Diagenesissupporting

confidence: 81%

Section: Geological Settingmentioning

confidence: 99%

Section: Dissolutionmentioning

confidence: 99%

Section: Fault Controls On the Structural Diagenesismentioning

confidence: 99%

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Structural Diagenesis in Carbonate Rocks as Identified in Fault Damage Zones in the Northern Tarim Basin, NW China

Xie

Zhang

et al. 2019

Minerals

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“…Over the past ten years, karst pores of the Yingshan Formation in the Tazhong area have generally been classified as continental freshwater karsts [19][20][21][22][23]. However, some special dissolution phenomena (e.g., the large-area distribution of karst caves) have recently been encountered in some drilling wells.…”

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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Carbonate reservoir fracture‐cavity system identification based on the improved YOLOv5s deep learning algorithm

Feng,

Zhao,

Zhang

et al. 2024

Energy Science & Engineering

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In carbonate reservoirs characterized by the fracture‐cavity system as storage spaces, the drilling process is highly prone to the loss of drilling fluid. This not only affects drilling efficiency but can also lead to severe accidents, such as blowouts. Therefore, it is crucial to understand the distribution pattern of these fractures. However, the formation of carbonate rock fracture‐cavity system systems, being controlled by various factors, is difficult to precisely identify. This limitation hampers the efficient development of such types of oil and gas fields. This paper presents a case study of the M55 sub‐section carbonate gas reservoir in the Sulige gasfield, proposing an improved You Only Look Once v5s (YOLOv5s) deep learning algorithm. It utilizes enhanced training with conventional logging data to identify response characteristics of fractures in the carbonate reservoirs. And its identification results have been confirmed to be accurate by various fracture data obtained through different means, such as the core samples, cast thin section photographs, imaging logging data, and seismic attributes. This method incorporates the Ghost convolution module to replace the Conv module in the backbone network of the YOLOv5s model, and modifies the C3 module into a Ghost Bottleneck module, effectively making the model more lightweight. Additionally, a Convolutional Block Attention Module is integrated into the Neck network, enhancing the model's feature extraction capabilities. Finally, the method employs the Efficient Intersection over Union Loss function instead of the Complete Intersection over Union Loss, reducing the network's regression loss. The validation results using actual data demonstrate that this method achieves an average recognition accuracy of 87.3% for the fracture‐cavity system, which is a 3% improvement over the baseline model (YOLOv5s). This enhancement is beneficial for precisely locating the drilling fluid loss positions in carbonate reservoirs.

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Geological modeling of excellent fracture-vug carbonate reservoirs: A case study of the Ordovician in the northern slope of Tazhong palaeouplift and the southern area of Tabei slope, Tarim Basin, NW China

Cited by 29 publications

References 2 publications

Structural Diagenesis in Carbonate Rocks as Identified in Fault Damage Zones in the Northern Tarim Basin, NW China

Structural Diagenesis in Carbonate Rocks as Identified in Fault Damage Zones in the Northern Tarim Basin, NW China

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

Carbonate reservoir fracture‐cavity system identification based on the improved YOLOv5s deep learning algorithm

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