scholarly journals Forced Fold Amplitude and Sill Thickness Constrained by Wireline and 3-D Seismic Data Suggest an Elastic Magma-Induced Deformation in Tarim Basin, NW China

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 293
Author(s):  
Wei Tian ◽  
Xiaomin Li ◽  
Lei Wang
Keyword(s):  
Tarim Basin ◽  
Seismic Data ◽  
Inelastic Deformation ◽  
Northwest China ◽  
Well Log ◽  
Total Thickness ◽  
Nw China ◽  
Seismic Method ◽  
Two Parameters ◽  
Outer Area

Disparities between fold amplitude (A) and intrusion thickness (Hsill) are critical in identifying elastic or inelastic deformation in a forced fold. However, accurate measurements of these two parameters are challenging because of the limit in separability and detectability of the seismic data. We combined wireline data and 3-D seismic data from the TZ-47 exploring area in the Tarim Basin, Northwest China, to accurately constrain the fold amplitude and total thickness of sills that induced roof uplift in the terrain. Results from the measurement show that the forced fold amplitude is 155.0 m. After decompaction, the original forced fold amplitude in the area penetrated by the well T47 ranged from 159.9 to 225.8 m, which overlaps the total thickness of the stack of sills recovered by seismic method (171.4 m) and well log method (181.0 m). Therefore, the fold amplitude at T47 area is likely to be elastic. In contrast, the outer area of the TZ-47 forced fold is characterized by shear-style deformation, indicating inelastic deformation at the marginal area. It is suggested that interbedded limestone layers would play an important role in strengthening the roof layers, preventing inelastic deformation during the emplacement of intrusive magma.

scholarly journals Forced Fold Amplitude and Sill Thickness Constrained by Wireline and 3-D Seismic Data Suggest an Elastic Magma-Induced Deformation in Tarim Basin, NW China

2020 ◽  
Author(s):  
Wei Tian ◽  
Xiaomin Li ◽  
Lei Wang
Keyword(s):  
Tarim Basin ◽  
Seismic Data ◽  
Inelastic Deformation ◽  
Solid Rock ◽  
Northwest China ◽  
Total Thickness ◽  
Nw China ◽  
Rock Density ◽  
Measurement Results ◽  
Two Parameters

Disparities between fold amplitude (A) and intrusion thickness (Hsill) are critical in identifying elastic or inelastic deformation in a forced fold. However, accurate measurement of these two parameters is challenging because of the limit in separability and detectability for the seismic data. In the TZ-47 exploring area from the Tarim Basin, Northwest China, we combined wireline data and 3-D seismic data, to accurately constrain the fold amplitude and total thickness of sills that inducing the roof uplift. The measurement results show that the forced fold amplitude is 155 m and the total sill thickness is 148.4 m. When using a magma density of 2.7 g/cm3, and solid rock density of 3 g/cm3, the molten magma thickness at the time of intrusion would be 153.8 m, which is almost no difference from the forced fold amplitude. Therefore, the TZ-47 fold is a pure elastic forced fold induced by emplacement of multiple sills. Measurement solely based on seismic data may not be able to detect some thin interlayers and may result in large errors.

Characteristics and evolution process of strike-slip fault in Halahatang area, North Tarim Basin, NW China

2020 ◽  
Author(s):  
Debo Ma
Keyword(s):  
Tarim Basin ◽  
Seismic Data ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
Evolution Process ◽  
3D Seismic ◽  
Flower Structure ◽  
Nw China ◽  
Area North ◽  
3D Seismic Data

<p>Characteristics and evolution process of strike-slip fault is a key issue restricting further exploration in Halahatang area, North Tarim Basin, NW China. This paper uses the new-acquired 3D seismic data and applies fault structural analysis method to study the characteristics of Halahatang area, and discusses evolution process of the faults.<br>The data used in this paper include 1960 km<sup>2</sup> 3D seismic data in prestack time migration in Halahatang area, and 4 wells logging data used to calibrate seismic horizon. The bin size of 3D seismic is 25 m×25 m with sampling rate of 4ms, and data length of 7000 ms. Firstly, the Eigen-structure coherency and SO semblance are used to identify the distribution of the strike-slip fault. Secondly, the segmentation of Ordovician strike-slip fault in the study area is studied and the control effect of segmentation on reservoir development and oil and gas enrichment is discussed.<br>The slip distance of strike-slip fault is very small, the maximum is no more than 2 km. They are typical cratonic strike-slip faults which are developed inside the craton. There are four kinds of structural styles on the profile, which are vertical and steep, positive flower structure, negative flower structure and semi-flower structure. Five structural styles of linear extension, X type, braided structure, horsetail structure, and en-echelon structure are developed on the plane. There are obvious segmentation along the fault trend.<br>According to the strata subjected to strike-slip deformation and the structural styles in different strata, it is determined that the strike-slip faults have three stages of activity in Halahatang area. <br>In the Late Ordovician, NNE, NNW, NE, and NEE strike-slip faults are mainly developed in the study area. The faults on the seismic profile are steep and upright, with small displacements. Faults generally only break into the Ordovician, and later activities will cause faults to go up to the Silurian and even the upper Palaeozoic, which have different tectonic styles with that of the Ordovician faults. The NNE and NNW strike-slip faults form an “X”-type conjugate strike-slip fault, reflecting the conjugate strike-slip fault is generated by near north-south compression.<br>In the Late Permian, 4 NNW transtensional strike-slip faults are generated by the activation of some Ordovician strike-slip faults. In the Late Cretaceous-Palaeocene, the study area mainly develop several groups of NNE, near SN transtensional strike-slip faults. These transtensional strike-slip faults appear as graben and horst or stepped faults on the section. These transtensional strike-slip faults are R-shear faults in the Mesozoic and Cenozoic strata formed by the Ordovician NNE faults slip dextrally under the tectonic stress.</p>

scholarly journals Large-Scale Precipitation Variability over Northwest China Inferred from Tree Rings

2011 ◽  
Vol 24 (13) ◽  
pp. 3457-3468 ◽  
Author(s):  
Keyan Fang ◽  
Xiaohua Gou ◽  
Fahu Chen ◽  
Edward Cook ◽  
Jinbao Li ◽  
...  
Keyword(s):  
Tree Ring ◽  
Large Scale ◽  
Principal Component ◽  
Northwest China ◽  
Poor Quality ◽  
Contour Method ◽  
Precipitation Reconstruction ◽  
Nw China ◽  
Climate Station ◽  
Instrumental Records

Abstract A preliminary study of a point-by-point spatial precipitation reconstruction for northwestern (NW) China is explored, based on a tree-ring network of 132 chronologies. Precipitation variations during the past ~200–400 yr (the common reconstruction period is from 1802 to 1990) are reconstructed for 26 stations in NW China from a nationwide 160-station dataset. The authors introduce a “search spatial correlation contour” method to locate candidate tree-ring predictors for the reconstruction data of a given climate station. Calibration and verification results indicate that most precipitation reconstruction models are acceptable, except for a few reconstructions (stations Hetian, Hami, Jiuquan, and Wuwei) with degraded quality. Additionally, the authors compare four spatial precipitation factors in the instrumental records and reconstructions derived from a rotated principal component analysis (RPCA). The northern and southern Xinjiang factors from the instrumental and reconstructed data agree well with each other. However, differences in spatial patterns between the instrumentation and reconstruction data are also found for the other two factors, which probably result from the relatively poor quality of a few stations. Major drought events documented in previous studies—for example, from the 1920s through the 1930s for the eastern part of NW China—are reconstructed in this study.

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