Characterization and discrimination of paleokarst breccias and pseudobreccias in carbonate rocks: Insight from Ordovician strata in the northern Tarim Basin, China

2019 ◽  
Vol 382 ◽  
pp. 61-74 ◽  
Author(s):  
Qilong Fu
Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-19 ◽  
Author(s):  
Wenwen Wei ◽  
Daizhao Chen ◽  
Hairuo Qing ◽  
Yixiong Qian

The burial dissolution of carbonate rocks has long been an interesting topic of reservoir geologists. Integrated with geological studies and reactive transport modeling, this study investigated the Cambrian dolomites that were buried at depths up to 8408 m and still preserved a large amount of unfilled dissolution vugs from the borehole TS1 in the northern Tarim Basin. Studies indicate that these vugs were formed in association with fault-channeled hydrothermal fluids from greater depth through “retrograde dissolution” as the fluid temperature dropped during upward migration. The reactive transport modeling results suggest an important control of the vertical permeability of wall-rock on fluid and temperature patterns which, in turn, would control the spatial distribution of dissolving-originated porosity. The hydrothermal dissolution mainly occurred in dolomite wall-rocks with higher vertical permeability (extensive development of tensional fractures and connected pore spaces), producing additional dissolved porosity there during deep burial. This study implicates the importance of multidisciplinary approaches for understanding the burial/hydrothermal dissolution of dolomite rocks and predicting favourable deep/ultradeep carbonate reservoirs.


2020 ◽  
Vol 57 (12) ◽  
pp. 1463-1477
Author(s):  
Tianyu Ji ◽  
Wei Yang ◽  
Renhai Pu ◽  
Xueqiong Wu

Based on the study of cores, thin sections, and outcrops, the sedimentary facies of the lower Cambrian carbonate rocks in the northern Tarim Basin can be divided into four types: restricted platform, open platform, ramp, and basin. Based on the lithologic analysis of thin sections, two-dimensional seismic data interpretation, and an isopach map of the lower Cambrian Xiaoerbulake Formation in the study area, seven sedimentary facies of carbonate rocks were identified, including inner platform depression, shoal, intershoal sea, platform margin, gypsum salt lake, ramp, and basin. The depositional model of the lower Cambrian Xiaoerbulake Formation in the northern Tarim Basin is constructed based on this integrated research. The topset, foreset, and bottomset of oblique progradational reflections are interpreted as the platform margin beach, ramp, and basin environments, respectively. The thicker area with micritic dolomite as the dominant lithology is interpreted as a platform depression. The low-amplitude hummocky reflections are interpreted as shoals that consist of a variety of granular dolomite and algal dolomite. The thinner uplifted area with gypsum and dolomite present in cores is interpreted as a restricted platform with a gypsiferous dolomite tidal flat or lake environment. Well LT1, which was drilled recently in the platform margin and ramp region, as indicated by seismic progradational clinoform reflections, has produced high yields of oil and gas. Supported by the above research results, the map of the lithofacies and paleogeography of the Xiaoerbulake Formation in the northern Tarim Basin was recompiled.


Minerals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 360 ◽  
Author(s):  
Guanghui Wu ◽  
En Xie ◽  
Yunfeng Zhang ◽  
Hairuo Qing ◽  
Xinsheng Luo ◽  
...  

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.


2021 ◽  
Author(s):  
Jiaxu Chen ◽  
Xiaowen Guo

<p>Determining the timings of oil charge in sedimentary basins are essential to understand the evolutionary histories of petroleum systems, especially in sedimentary basins with complicated tectonic evolution and thermal histories. The Ordovician carbonate reservoir in the Tahe Oilfield, which is located in the northern Tarim Basin, comprises the largest marine reservoirs in China with reserves up to 3.2×10<sup>8</sup> t. This study aims to determine the timings of oil charge in the Ordovician carbonate reservoir in the Tahe Oilfield, Tarim Basin, which basin is subjected to multiple phases of tectonic deformations and oil charge. The phases of calcite veins that contain oil inclusions were systematically investigated by cathodoluminescence observation, in situ rare earth element, C, O, and Sr isotope analyses. The homogenization temperatures of aqueous inclusions that are coeval with oil inclusions were measured to determine the timings of oil charge by combining the burial and geothermal histories. Two phases of calcite veins were judged by the differences in cathodoluminescence color, Ce anomaly, δ<sup>18</sup>O, and <sup>87</sup>Sr/<sup>86</sup>Sr values, which might be caused by variations in the water-rock interaction processes during different calcite phases. Primary oil inclusions with yellow fluorescence were observed in the two phases of calcite veins, suggesting two phases of oil charge. By combining the homogenization temperatures of aqueous inclusions with the burial and geothermal histories, the timing of phase I oil charge was inferred to be 336–312 Ma, and the timing of phase II oil charge was inferred to be 237–217 Ma.</p>


2018 ◽  
Vol 53 (6) ◽  
pp. 2896-2907 ◽  
Author(s):  
Xiao-Lin Chang ◽  
Ming-Cai Hou ◽  
Xin-Chun Liu ◽  
Elizabeth Orr ◽  
Min Deng ◽  
...  

Author(s):  
Michael R. Drompp

The Uyghurs (Chinese Huihe迴 紇, Huihu回鶻) were a pastoral nomadic people living in the region of the Selenga and Orkhon river valleys in modern Mongolia; they spoke a Turkic language. The empire that they created on the steppe lasted for nearly a century (744–840) and played an important role, both politically and culturally, in East Asia. Centered on the Mongolian Plateau, the Uyghur Empire at its height controlled numerous other peoples within a territory that included lands to the north in the modern regions of Tuva and Buryatia, as well as some parts of the northern Tarim Basin and eastern Inner Mongolia.1 During its eventful history, the Uyghur Empire sent cavalry to help the Tang Dynasty put down the An Lushan rebellion, maintained strong political and economic ties with China, fought with the Tibetan Empire for control of important international trade routes, built cities on the steppe, celebrated its rulers’ achievements in stone stelae, and—uniquely in the world—adopted Manichaeism as its state religion. After their empire collapsed, the Uyghurs developed new polities in Gansu and the Tarim Basin that continued to exercise influence in Inner Asia.


2004 ◽  
Vol 27 (1) ◽  
pp. 67-84
Author(s):  
Jiangyu Zhou ◽  
Zhongmin Lin ◽  
Chuangrong Luo ◽  
Xiepei Wang

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