Anticlines

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Shu Jiang - One of the best experts on this subject based on the ideXlab platform.

  • accumulation mechanism of marine shale gas reservoir in Anticlines a case study of the southern sichuan basin and xiuwu basin in the yangtze region
    Geofluids, 2019
    Co-Authors: Kun Zhang, Yan Song, Shu Jiang, Zhenxue Jiang, Yizhou Huang, Pengfei Wang, Xin Li, Changan Shan
    Abstract:

    The study of tectonics is one of the important aspects of shale gas preservation. It is vital for understanding how to determine the enrichment regularity of marine shale gas in Anticlines. This paper focuses on typical shale blocks in the southern Sichuan Basin and shale in the Upper Ordovician and the Lower Silurian. In this study, triaxial unloading tests, permeability tests perpendicular and parallel to the stratification plane, FIB-HIM tests, and inclusion analyses are carried out with real drilling data. The enrichment regularity of marine shale gas in Anticlines is studied by considering 2 aspects: the angle of the limbs and the burial depth. For Anticlines with adjacent synclines, the migration regularity of shale gas is considered by 3 aspects: the dynamics, channels, and processes of migration. This study reveals that a limb angle greater than 120° reflects relatively good conditions for shale gas preservation, while limb angles lesser than 70° indicate relatively poor conditions. This study also suggests that during the process of uplift, large-scale concentrated fractures will form at a certain depth range and horizontal stress field, resulting in the large loss of shale gas. The regression equation of the fractured depth ( ) and the horizontal stress ( ) is presented as (with a correlation coefficient ). The stratification plane and the organic pores form the migration channel of natural gas that is horizontal to the stratification plane in shale. Under the condition of both Anticlines and contiguous synclines, shale gas escapes through fractures resulting from extrusion along the anticline and the uplift effect. In addition, driven by differences in the formation pressure coefficients, shale gas is capable of migrating in a short-distance stair-type style from synclines to the adjacent Anticlines. Thus, if the drilling costs allow, the well locations should be placed in the more deeply buried synclines.

Mohammad Yazdani - One of the best experts on this subject based on the ideXlab platform.

  • Accommodation of the different structural styles in the foreland fold-and-thrust belts: northern Dezful Embayment in the Zagros belt, Iran
    International Journal of Earth Sciences, 2020
    Co-Authors: Raana Razavi Pash, Khalil Sarkarinejad, Hesam Zarehparvar Ghoochaninejad, Hossein Motamedi, Mohammad Yazdani
    Abstract:

    Structural styles in the Zagros foreland fold-and-thrust belt vary spatially. Differential lateral propagation of folds causes to create tear faults in this belt. In this research, tear faults are studied in northern Dezful Embayment. Tear faults have been accommodated the different structural styles in sedimentary cover during the compressional regime in the Zagros fold-and-thrust belt. Different structural styles indicate a difference in intensity deformation. These faults originated as the pre-existing inverted reactive deep-seated faults or which activate in the sedimentary strata during the compressional regime. Investigation of the structural style of folds in the sedimentary cover is a key point to recognize tear faults. In this research, the structural style of the Kabood, Qale Nar, Bala Rud and Lab-e-Safid subsurface Anticlines in the northern Dezful Embayment has been studied. The interpretation of seismic profiles, balanced cross sections, restoration, and 3D structural modeling is investigated to study the structural style of mentioned Anticlines. The area of the studied region is 92 × 20 km^2. Two tear faults with NNE trending have been separated Qale Nar and Bala Rud Anticlines (in the central part) from Lab-e-Safid and Kabood Anticlines in eastern and western parts, respectively. The intensity of deformation in the Lab-e-Safid anticline is less than the Qale Nar and Bala Rud Anticlines on its western side. Displacement and deformation of the Kabood anticline are more than the Qale Nar anticline in its eastern side. Kabood anticline is multi-bend fault bend fold, Qale Nar and Bala Rud are fault bend folds and Lab-e-Safid is detachment fold. Tear faults have been accommodated by these different structural styles in this region.

  • Deformation and kinematic evolution of the subsurface structures: Zagros foreland fold-and-thrust belt, northern Dezful Embayment, Iran
    International Journal of Earth Sciences, 2018
    Co-Authors: Khalil Sarkarinejad, Raana Razavi Pash, Hossein Motamedi, Mohammad Yazdani
    Abstract:

    The Dezful Embayment is located in the foreland part of the Zagros fold-and-thrust belt. Structural style of folding and thrusting vary in the Dezful Embayment. In this study, balanced cross sections and subsurface data including 2D seismic profiles and wells data decoded structural style of the subsurface structures in the northern Dezful Embayment. Presence of the multiple décollement horizons is the main controlling factor of the structural style in this area. The subsurface Anticlines have been formed between two main décollement horizons, which include the Miocene Gachsaran Formation as upper decollement and Permian Dashtak evaporites and Lower Cretaceous Garau shales as the middle décollement horizons. Geometry of the subsurface Anticlines differs much vertically and horizontally. Growth strata indicate folding is started in Middle Miocene time in this region. Anticlines formed as open, wide and disharmonic structures. Active processes in the evolution of Anticlines are limb rotation and hinge migration, which was resulted in increase of inhomogeneous shortening rate. More shortening rate indicates more structural relief in Anticlines. These Anticlines are formed as a detachment folds in initiation and then during their evolution converted to fault propagation fold and fault-bend fold. Final geometric shape of these Anticlines depends on the geometry of thrusts propagation that formed in the forelimb.

Xi Yuan Zhou - One of the best experts on this subject based on the ideXlab platform.

  • Seismic interpretation of the Kelasu triangle zone in the southern Tian Shan foothills, northwestern China
    AAPG Bulletin, 2007
    Co-Authors: Chunming Xu, Xi Yuan Zhou
    Abstract:

    Seismic reflection data show that the Kelasu structure, a frontal structure of the south Tian Shan foothills thrust belt, is a triangle zone with the upper detachment following an overpressured lower Tertiary anhydrite zone and the lower detachment zone probably in the lowerMesozoic seismic reflectors. The south-verging thrusts emerging at the surface are the small roof structures rooted in the upper detachment.Although the upper detachment was a relatively lubricated surface, the passively folded formations show strong resistance to the blind wedging underneath, particularly in the Anticlines, during the triangle zone development. As a result of the massive shear forces created by the opposing movement of the two tectonostratigraphic units, the top part of the thrust sheets immediately under the crest of the frontal anticline was ripped off in the form of backthrusting and brecciation. The large backthrust fault blocks and breccias were retained in the Anticlines, whereas the underlying duplex continued wedging toward the foreland. In the early formed duplex structures in the hinterland, the tips of the thrust sheets were completely shredded, leaving sharp angular contacts between the thrust sheets and the upper detachment surface. Different types of fractures and present-day geostress (stress of the earth measured along the wellbore) interpreted fromthe borehole image logs suggest a complex deformation history and reversal of geostress. The Kelar gas reservoirs are located within the backthrust fault blocks under the frontal anticline. The current model reduces the previous concerns about potential damage to the anhydrite seal by the surface thrusts because the thrusts occurred entirely above the seal. More importantly, because the reservoir rocks are repeated many times in the duplex thrust sheets below the continuous anhydrite seal, any anticlinal structure of the upper detachment surface is a potential prospect.

Changan Shan - One of the best experts on this subject based on the ideXlab platform.

  • accumulation mechanism of marine shale gas reservoir in Anticlines a case study of the southern sichuan basin and xiuwu basin in the yangtze region
    Geofluids, 2019
    Co-Authors: Kun Zhang, Yan Song, Shu Jiang, Zhenxue Jiang, Yizhou Huang, Pengfei Wang, Xin Li, Changan Shan
    Abstract:

    The study of tectonics is one of the important aspects of shale gas preservation. It is vital for understanding how to determine the enrichment regularity of marine shale gas in Anticlines. This paper focuses on typical shale blocks in the southern Sichuan Basin and shale in the Upper Ordovician and the Lower Silurian. In this study, triaxial unloading tests, permeability tests perpendicular and parallel to the stratification plane, FIB-HIM tests, and inclusion analyses are carried out with real drilling data. The enrichment regularity of marine shale gas in Anticlines is studied by considering 2 aspects: the angle of the limbs and the burial depth. For Anticlines with adjacent synclines, the migration regularity of shale gas is considered by 3 aspects: the dynamics, channels, and processes of migration. This study reveals that a limb angle greater than 120° reflects relatively good conditions for shale gas preservation, while limb angles lesser than 70° indicate relatively poor conditions. This study also suggests that during the process of uplift, large-scale concentrated fractures will form at a certain depth range and horizontal stress field, resulting in the large loss of shale gas. The regression equation of the fractured depth ( ) and the horizontal stress ( ) is presented as (with a correlation coefficient ). The stratification plane and the organic pores form the migration channel of natural gas that is horizontal to the stratification plane in shale. Under the condition of both Anticlines and contiguous synclines, shale gas escapes through fractures resulting from extrusion along the anticline and the uplift effect. In addition, driven by differences in the formation pressure coefficients, shale gas is capable of migrating in a short-distance stair-type style from synclines to the adjacent Anticlines. Thus, if the drilling costs allow, the well locations should be placed in the more deeply buried synclines.

Earl R Verbeek - One of the best experts on this subject based on the ideXlab platform.

  • fracture history of the divide creek and wolf creek Anticlines and its relation to laramide basin margin tectonism southern piceance basin northwestern colorado
    Bulletin, 1992
    Co-Authors: Marilyn A Grout, Earl R Verbeek
    Abstract:

    The Divide Creek and Wolf Creek Anticlines are two north-northwest-trending, gas-producing intrabasin folds near the eastern margin of the Piceance basin of northwestern Colorado. Natural gas is produced principally from fractured sandstone reservoirs and coals of the Upper Cretaceous Mesaverde Group, the uppermost part of which is exposed sparingly on both folds. The southern part of the Piceance basin was selected for study because it contains obvious intrabasin folds, the Divide Creek and Wolf Creek Anticlines, of previously unknown origin adjacent to the tectonically thrusted and folded eastern basin margin. The origin and tectonics of the Anticlines are explored in this paper. New seismic and gravity data show that the Anticlines are products of late Laramide thrusting. The distribution of several fracture sets discussed in this report are related to this deformation.

  • late laramide thrust related and evaporite domed Anticlines in the southern piceance basin northeastern colorado plateau
    AAPG Bulletin, 1991
    Co-Authors: Marilyn A Grout, G A Abrams, Rex L Tang, Timothy J Hainsworth, Earl R Verbeek
    Abstract:

    New seismic and gravity data across the hydrocarbon-producing Divide Creek and Wolf Creek Anticlines in the southern Piceance basin reveal contrasting styles of deformation within two widely separated time frames. Seismic data indicate that prebasin Paleozoic deformation resulted in block faulting of the Precambrian crystalline basement rocks and overlying Cambrian through Middle Pennsylvanian strata. Movement along these block faults throughout much of Pennsylvanian time, during northeast-southwest crustal extension, likely influenced distribution of the Middle Pennsylvanian (Desmoinesian) evaporite-rich facies. Younger rocks, including the thick succession of Cenozoic basin strata, then buried the Paleozoic structures. Tectonic reconfiguration of the basin's eastern margin occurred during late Laramide northeast-southwest compression, when a basement-involved thrust block, whose surface expression is the Grand Hogback monocline, moved into the Piceance basin. A decollement developed in front of the thrust block within the mechanically weak Desmoinesian evaporites and splayed out basinward as small-scale imbricate thrusts in the Upper Cretaceous Mancos Shale. The Divide Creek anticline formed above these splays as thrusting locally overthickened the shale and repeated the sandstone units between it and the evaporites. The Wolf Creek anticline to the east, however, is due to both depositional and tectonic thickening of the evaporite section along the decollement. Gravity data confirm that excess mater al of relatively low density exists beneath the Wolf Creek structure, whereas material of relatively higher density (overthickened shale) is found beneath the Divide Creek anticline. Thrust-related basin margins and intrabasin folds structurally analogous to the Divide Creek and Wolf Creek Anticlines may be more common than presently recognized in the Rocky Mountain foreland. One well-documented example is the Pinedale anticline in the northern Green River basin, Wyoming, which, like the Divide Creek anticline, developed above a zone of splay faults from a decollement in front of a large thrust block.