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Evaluation of stress and rock mechanics parameters in the carbonate rock based on cross-dipole acoustic logging——A case study of the Shunbei 4 zone
, Available online  , doi: 10.12090/j.issn.1006-6616.2023110
Abstract (6) PDF (1361KB)(1)
Rock mechanics parameters and single well in-situ stress are the basic parameters for basin tectonic stress field simulation, oil and gas field drilling and completion and reservoir fracturing stimulation design. Based on the experiment of rock mechanics and array acoustic waves, the rock mechanics parameters and in-situ stress of the carbonate reservoirs of the Lower Paleozoic Ordovician Yingshan Formation and Yijianfang Formation in the Shunbei 4 zone were analyzed. The results show that the Young's modulus of the Yijianfang Formation and the Yingshan Formation in the Shunbei 4 zone is 50-89 GPa, the compressive strength is 99-136 MPa, and the Poisson's ratio is 0.25-0.32. Combined with logging interpretation of reservoir classification, the differences in rock mechanics parameters of different reservoir types were compared and analyzed. From type I, type II, type III to non-reservoir, the Young's modulus and compressive strength of carbonate rock increased significantly, while Poisson's ratio is not much different. The maximum horizontal stress of the Yijianfang Formation and the Yingshan Formation in the Shunbei 4 zone is 200-225 MPa, and the minimum horizontal stress is 125-160 MPa; from type I, type II, type III to non-reservoir, the maximum horizontal principal stress of carbonate rocks The maximum horizontal maximum horizontal stress increases significantly, while the minimum horizontal stress has little difference. There are early cracks and caves in carbonate rocks, which significantly weaken the rock's ability to resist external forces and reduce the rock's compressive strength and Young's modulus.
Fission track ages and Mesozoic tectonic uplift in the Niushoushan-Luoshan area on the western edge of Ordos
, Available online  , doi: 10.12090/j.issn.1006-6616.2023030
Abstract (59) PDF (4836KB)(14)
The western edge of the Ordos Basin and its adjacent areas have undergone a complex tectonic evolution process from the Mesozoic to the Cenozoic. There is still controversy about the uplift in the region since the Mesozoic. The thermal evolution process in the western regions of the Ordos Basin still needs more chronological data. The Niushoushan-Luoshan area is situated at the northeastern margin of the Qinghai-Tibet Plateau, close to the western thrust belt of the Ordos Basin. The uplift process of the Mesozoic in this region is of great significance for recording Mesozoic tectonic events on the western edge of the basin. The article select nine sandstone samples from the Ordovician sandstone in Niushoushan-Luoshan area were selected for apatite fission track (AFT) analysis and thermal history simulation. The test results show that the Mesozoic uplift in this area mainly occurred in the Middle Jurassic (170 Ma) to the end of the Early Cretaceous (110 Ma), and the uplift in the Luoshan area (170 Ma) was slightly earlier than that in Niushoushan area (160 Ma). The uplift is mainly related to the extrusion of the Qilian orogenic belt towards the northeast. According to the results of previous studies, the Mesozoic uplift in the western margin of the Ordos and its adjacent areas can be divided into two stages: the early uplift occurred in the late Triassic (220 Ma) to the end of the early Jurassic (185 Ma); The late uplift occurred from the Middle Jurassic (175 Ma) to the end of the Early Cretaceous (110 Ma). The two stages of tectonic uplift also showed the characteristics of transmission from south to north and southwest to northeast, presumably related to the collision of the North China and South China plates and the convergence of the Lhasa block to the northeast.
Accumulation conditions and exploration potential of deep natural gas in Qaidam Basin
, Available online  , doi: 10.12090/j.issn.1006-6616.2022084
Abstract (35) PDF (2223KB)(3)
In order to clarify the exploration potential of deep natural gas in Qaidam Basin, based on seismic, geological and drilling data, the enrichment conditions of deep natural gas reservoir in Qaidam Basin are comprehensively analyzed from the aspects of source rock, reservoir, structure and reservoir formation, and the favorable exploration direction of deep natural gas is defined. The results show that two sets of high-quality gas sources of Jurassic and Paleogene are developed in the deep layer of Qaidam Basin, with high degree of evolution and strong gas generation capacity; Three types of reservoirs including bedrock, clastic rock and lacustrine carbonate are developed in the deep layer, and many types of pores such as primary pores, dissolution pores and fractures are developed, which provides a broad storage space for the enrichment of deep gas reservoirs; The multi-stage tectonic activities developed the faults in the basin, formed a variety of dredging systems dominated by faults, and provided a high-quality channel for gas migration. Qaidam source rock has the characteristics of early and multi-stage filling, and the structural formation period matches the natural gas generation period. In particular, the crude oil generated in the early stage is conducive to deep buried cracking and gas generation in the later stage, with strong gas generation capacity and great resource potential. The widely developed salt rock, argillaceous rock and abnormally high pressure layer in the deep layer of the basin are conducive to the preservation of deep natural gas. The traps around the hydrocarbon generating sag developed by deep and large faults are favorable areas for deep natural gas accumulation. The deep layers of Piedmont paleouplift, abdominal structural belt in the north margin of Qaidam and Yxiongling structural belt in West Ring of Qaidam are favorable exploration directions for deep natural gas.
Paleoenvironment and organic matter enrichment of the Lucaogou Formation in the Jimsar Sag
, Available online  , doi: 10.12090/j.issn.1006-6616.2022127
Abstract (51) PDF (2357KB)(2)
The Lucaogou Formation in the Jimsar Sag is the main target layer of shale oil exploration and development in continental basins, but its paleoenvironmental information and organic matter enrichment mechanism are still unclear . In order to investigate the paleoenvironment of the Permian Lucaogou Formation, on the basis of core and thin section observation, we carried out major and trace element analyses on 26 source rocks from Well J10025 by using X-ray fluorescence spectroscopy(XRF) and inductively coupled plasma mass spectrometry(ICP-MS). Combined with the data of biomarker compounds measured by GC-MS and typical sedimentary structures, the paleoenvironmental  characteristics of the Lucaogou Formation was reflected. Geochemical proxies such as C-value, Sr/Ba, V/Cr, Pr/Ph, P and Co show that the Lucaogou Formation was generally developed in a saline lake environment under arid to semi-arid climate. The deep water body was suboxic to anoxic in the sedimentary period. The upper member was deposited in a semi-arid, brackish lake with weak reducibility, deep water body and high productivity. In contrast, the lower member was deposited in a extremely dry, highly saline and strongly reductive shallow lake with low productivity. The paleoenvironment of the upper member fluctuated greatly while that of the lower member was relatively stable. The correlation analyses between paleoenvironmental indicators and TOC show that the preservation conditions and dilution rate of organic matter have limited influence on organic matter enrichment of the Lucaogou Formation, while the primary productivity is the main controlling factor.
Palynological records and paleoclimatic significance during middle and late Late Pleistocene in Qingshuihe Basin, Ningxia
, Available online  , doi: 10.12090/j.issn.1006-6616.2023015
Abstract (45) PDF (1501KB)(8)
The extraction of paleovegetation and paleoclimate information from loess-paleosol strata is the most direct evidences of the history of inner Asia desertification and aridification. In this paper, the palynological records during the middle and late Late Pleistocene in Qingshuihe Basin of southern Ningxia are analyzed. The results show that four pollen assemblage zones were identified from bottom to top, clarifying the paleovegetation and paleoclimate change during the middle and late Late Pleistocene in this region. It is speculated that the middle Late Pleistocene (75-50ka B.P.) was a period of an Artemisia–dominated steppe landscape and the climate was cooling and relatively drying. During the period of late Late Pleistocene (25-15 Ka B.P.), the vegetation appeared alternately from desert-steppe or steppe and forest-steppe and gradually transited to desert-steppe. During this period, the summer monsoon gradually increased, resulting in the climate becoming cold and dry gradually, and the climate transiting from warm, cool and wet to cold and dry. The further study of palynological records during the middle and late Late Pleistocene in the Qingshuihe Basin of southern Ningxia is of great significance not only for the correct understanding of the evolution of the natural environment history of the Loess Plateau, but also for the decision-making of the governance of the Loess Plateau.
Regional geological characteristics and evolution history of the Gagarin region on the far side of the moon
, Available online  , doi: 10.12090/j.issn.1006-6616.2023035
Abstract (49) PDF (3231KB)(15)
This paper takes the Gagarin region on the far side of the moon as the research object, interprets multi-source remote sensing data, and reveals the geological characteristics of the typical region on the far side of the moon through quantitative statistics of geological elements, distribution characteristics and genetic analysis, and then discusses the regional geological evolution history of the Gagarin region. The relationship between the geological characteristics of this area and the evolution of the moon has been preliminarily established. The results show that: (1) The longest deep fault in the whole moon developed in the region is the result of the combined action of the South Pole Aiken impact event and the lunar thermal expansion and other internal and external stresses. (2) The linear anomalies of the thickness of the lunar crust extending outward from the South Pole-Aiken Basin extend to the major basins on the frontal side of the moon, indicating that the influence range of the South Pole-Aiken basin on the far side of the moon can radiate to the frontal side of the moon at the depth of the moon. (3) The variation of the number and area of impact craters in the Gagarin region on the far side of the moon is related to the evolution of the Earth-Moon system and the Solar System. (4) According to the quantitative statistical results of the impact crater and the dating results of the basalt units, the regional geological evolution history was clarified, and the active periods of geological processes in Gagarin region are divided.
Metamorphism of Neoarchean mafic granulites in the Qingyuan terrane, North Liaoning, North China Craton
, Available online  , doi: 10.12090/j.issn.1006-6616.2023049
Abstract (80) PDF (5970KB)(13)
  The tectonic evolution of the Neoarchean North China Craton has been diversely debated, and it is necessary to conduct metamorphic studies. Mafic granulites from the Qingyuan terrane in North Liaoning were selected for systematic studies of petrography, mineral chemistry, phase equilibria modeling, and zircon dating to document their metamorphic evolution and tectonic significance. The selected mafic granulite sample is divided into garnet-bearing domains (19DJ07-GD) and garnet-free domains (19DJ07-NGD). The garnet-bearing domains are banded and inhomogeneous distributed. Both domains develop two phases of granulite facies assemblages. The first phase assemblages are dominated by orthopyroxene, clinopyroxene, amphibole, biotite, plagioclase, and quartz with garnet in the garnet-bearing domains. The first phase plagioclase (Pl1) has complex compositional zoning with XAn (anorthite content) increasing from core to mantle and decreasing towards rim. The first phase amphibole (Amp1) shows increasing Ti from core to mantle and decreasing Ti to rim. These mineral zoning and inferred mineral assemblages suggest that the first phase granulite facies metamorphism shows anticlockwise P–T paths characterized by pre-peak compression with heating and post-peak cooling with decompression. The peak PT conditions are constrained to be 0.8~0.9 GPa/900~950 ℃ according to pseudosection modeling, reaching HT–UHT (high–ultrahigh temperature) conditions. Zircon dating yielded a metamorphic age of 2498 ± 6.9 Ma (MSWD = 0.39), representing the time of the post-peak cooling process. Combined with the “dome-and-keel” structure, the anticlockwise P–T paths, and the metamorphic time of mafic granulite which is consistent with the late pulse of the TTG magmatic activity, the UHT granulite facies metamorphism is considered to be controlled by the Archean unique vertical tectonics/sagduction. The second phase assemblages are characterized by the locally grown symplectites or coronae of garnet + quartz ± clinopyroxene, representing HP granulite facies related to a Paleoproterozoic orogeny.
Study on deformation mechanism and large deformation control method of a strongly weathered carbonaceous slate tunnel in western China
, Available online  , doi: 10.12090/j.issn.1006-6616.2023020
Abstract (79) PDF (1536KB)(9)
Based on the engineering research background of Minxian tunnel in Dingxi section of national G75 Weiwu expressway, the surrounding rock type belongs to jointed-high stress-expansive ( JHS ) composite soft rock. In the process of tunnel construction, the original support design scheme has serious soft rock large deformation disaster. After analyzing its deformation mechanism, the mechanical transformation countermeasures for different mechanical mechanisms are proposed. The high pre-tightening force constant resistance large deformation anchor cable widely used in rock fields such as mines and edge breaking is introduced, and a new high pre-stress active and passive combined support technology of ' advance support + NPR anchor cable support technology + permanent lining ' is proposed. The numerical simulation method is used to simulate and compare the control effects of different support technologies. The results show that different support technologies all control the surrounding rock. By monitoring the deformation of surrounding rock and the stress of constant resistance large deformation anchor cable in the field test section, the control effect of large deformation support is remarkable. The maximum deformation of surrounding rock is only 73 mm, and the preload of constant resistance large deformation anchor cable is in the range of 280 ~ 300 kN, which effectively plays the role of constant resistance yield support.