The Xujiaweizi fault depression is located in the northern part of the Songliao Basin, China. The Yingcheng Formation of the Xujiaweizi fault depression is a fractured tight volcanic reservoir. Many primary pores exist in the tight volcanic reservoirs of the Yingcheng Formation, but their connectivity is very poor. The degree of development of tectonic fractures determines the reservoir quality and the probability of hydrocarbon accumulation. To elucidate the fracture characteristics and their effects on hydrocarbon migration and accumulation, we analyze the fracture genetic types, characteristics, and controlling factors using data from cores, image logs, and thin sections. Then, we evaluate the matching relationship between tectonic fractures and hydrocarbon migration and accumulation by combining the evolution of the source rocks, analysis of the gas-source fault activity period and evolution of the cap rock sealing ability. We find two types of fractures developed in tight volcanic rocks: primary fractures and secondary fractures. Primary fractures mainly include cooling contraction fractures and cryptoexplosive fractures. Secondary fractures could be further divided into tectonic fractures, dissolution fractures, and weathering fractures. Among them, tectonic fractures are dominant. The distribution of tectonic fractures is controlled by lithology, lithofacies, faults, rock anisotropy, and an unconformity. Tectonic fractures are mainly formed in three phases. The time when the second phase of tectonic fractures formed (the Late Quantou-Qingshankou period) coincided with the peak hydrocarbon generation of the source rocks of the Shahezi Formation. Also at that time, the gas-source faults were active and the cap rock had a good top-seal capacity. Thus, the Late Quantou-Qingshankou period was the main period of natural gas accumulation.
This work focuses on quantitative discrimination of fault segment growth and its effect on sedimentation and stratigraphic evolution in the Tanan Depression, the Tamtsag Basin, Mongolia. Integrated seismic data sets and stratigraphic data suggest that normal faults evolve as fault segments grow, link and amalgamate to form a larger fault. Three main stages in the evolution of fault zone are recorded in the syn-rift stratigraphy. This paper applies a method to effectively discriminate the locus of fault segments by 'three diagrams' and quantitatively reconstruct process of fault growth by the maximum throw subtraction method. Backstripped to T23 SB event, the F1 fault comprises four hard-linked segments, and the F2 fault is divided into four soft-linked segments (F2-4 and F2-5 segments are shown by hard linkage) at the T23 structural level. The F1 and F2 fault comprise hard-linked segments at the T23-1 structural level when the F1 and the F2 are backstripped to the T22 (133.9 Ma) SB event. The F1 fault is divided into three soft-linked segments (F1-2 and F1-3 segments are shown by hard linkage), and the F2 fault is divided into four isolated fault segments at the T23-1 structural level when the F1 and the F2 is backstripped to the T23 SB event. Incorporation of paleo-fault geometry, isochron thickness map and sedimentary facies suggest that the transfer zone provided accommodation space for sediment discharge and deposition, and the depocentres were formed at the locus of maximum throw along a fault segment during its overall deposition.
Mesoporous ceramic functional nanomaterials (MCFN) is a self-assembled environmental adsorbent with a monolayer molecular which is widely used in the treatment of industrial wastewater and contaminated soil. This work aimed to study the relationship between the adsorption behaviour of Cd(II) by MCFN and contact time, initial concentration, MCFN dosage, pH, oscillation rate and temperature through a batch adsorption method. The adsorption kinetic and isotherm behaviours were well described by the pseudo-second-order and Langmuir models. The batch characterization technique revealed that MCFN had several oxygen-containing functional groups. Using Langmuir model, the maximum adsorption capacity of MCFN for Cd(II) was 97.09 mg g −1 at pH 6, 25°C, dosage of 0.2 g and contact time of 180 min. Thermodynamic study indicated that the present adsorption process was feasible, spontaneous and exothermic at the temperature range of 25–55°C. The results of this study provide an important enlightenment for Cd removal or preconcentration of porous ceramic nanomaterial adsorbents for environmental applications.
As an unconventional resource, shale reservoirs recently have attracted considerable attention in the petroleum industry. Shale plays are highly heterogenous vertically and laterally and are characterized by rapid changes in mineral composition. Thus, identification of dominant lithofacies is a key issue in the development of shale oil and gas reservoirs. In this study, various existing lithofacies in a shale section as a target unit in the Qingshankou Formation are divided based on organic matter content, sedimentary structure, and mineral composition. To delineate the electrofacies from the log, the multiresolution graph-based clustering (MRGC) is used to optimize the conventional logs that are sensitive to the electrofacies clustering analyses. Based on the principle of lithofacies identification, the electrofacies are artificially related to the lithofacies as well. This was done by analyzing the petrophysical characteristics of various shale lithofacies, to enable obtaining the main log parameters for the facies of the lacustrine shale section understudy. The results showed that by considering the underlying geologic criterion of each lithofacies, the MRGC method is able to correlate geophysical characteristics of each identified electrofacies for an optimal selection of six lithofacies.
Natural fractures provide the main path for fluid flow in tight oil reservoirs and can control the flow direction in the subsurface. Tight sandstones commonly have intense mechanical anisotropy, which means that fracture development in such tight formations may vary widely with respect to fracture orientations. However, the prediction of the degree of fracture development for each orientation is challenging. Focusing on the tight sandstones of the Chang 4 and 5 Member in the Jiyuan oil field, Ordos Basin, China, a new approach was presented for better prediction of the tectonic fracture occurrence in different directions based on fracture characterization, controlling factor, and formation mechanism analysis. First, fracture types, characteristics, formation time, and controlling factors were determined using data from outcrops, cores, and image logs. Then, triaxial tests were conducted to measure the mechanical parameters of rock samples in different directions that assessed the mechanical anisotropy of the formation and its impact on the development of fracture networks in the basin. Next, finite element numerical simulations of the paleotectonic stress field during fracturing were performed based on the fracture formation mechanism and controlling factors (lithology, bed thickness, sedimentary microfacies, and rock anisotropy). Finally, according to the failure criteria established using the measured mechanical parameters, the failure ratio and strain energy were calculated. These criteria could be employed to predict the fracture occurrence and the degree of development of each fracture network. The simulation predictions in this work are in good agreement with observed data from outcrops, cores, and image logs.
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