Meandering river reservoirs are essential targets for hydrocarbon exploration, although their characterization can be complex due to their multiscale heterogeneity. Multipoint geostatistics (MPS) has advantages in establishing reservoir architectural models. Training image (TI) stationarity is the main factor limiting the uptake of MPS modeling algorithms in subsurface modeling. A modeling workflow was designed to reproduce the distribution of heterogeneities at different scales in the Miocene Minghuazhen Formation of the Yangerzhuang Oilfield in the Bohai Bay Basin. Two TIs are established for different scales of architecture. An initial unconditional model generated with a process-based simulation method is used as the megascale TI. The mesoscale TI of the lateral accretion layers is characterized by an uneven spatial distribution of mudstone in length, thickness, frequency, and spacing. Models of different scales are combined by the probability cube obtained by lateral accretion azimuthal data as an auxiliary variable. Moreover, the permeability function sets are more suitable than the porosity model for collaboratively simulating the permeability model. Model verification suggests this workflow can accurately realize the multiscale stochastic simulation of channels, point bars, and lateral accretion layers of meandering fluvial reservoirs. The produced model conforms geologically realistically and enables the prediction of interwell permeability variation to enhance oil recovery.
Ordovician carbonate rock formation is an important target for oil and gas exploration. In this paper, on the basis of regional structure backgrounds , Ordovician lithologic intervals are divided in Tazhong area and, structural-depositional model is built up. With the help of three dimension finite element simulation method, the favorable areas of carbonate fracture reservoirs are predicted. The purpose of this paper is to give a direction for carbonate oil and gas exploration in Tazhong area. Conclusions could be summed up as follows:(1) The lithologic characters of middle- upper Ordovician in the major part of Ordovician uplift in Tazhong are dramatically different from that of adjacent slope, especially from that of slope of south Manjiaer depression in the north of Tazhong number one fault. The lithology of Ordovician in the major part of Tazhong uplift is dominated by carbonate rocks, and the lithology of middle-upper Ordovician is mainly sandy mudstone in the slope of south Manjiaer in the north of Tazhong number one fault.(2) Sedimentation during Ordovician in Tazhong area is controlled by intracratonic depression and Cratonic margin aulacogen, which are with different properties of prototype basin. The uplift and sag in intracratonic depression have prominent control to the sedimentation of Ordovician. Middle-upper Ordovician deposition in the major part of Tazhong uplift is controlled by the large scale anticline in the intracratonic depression formedn early Caledonian (the end of early Ordovician). The restrained platform facies are developed in shallow water in such places where platform clinoform, platform margin, semi-restrained platform (include platform flat, lagoon) and Carbonate morphologic units are found. The northeast boundary of Tazhong area is sharp margin controlled by the early movement of normal fault of Tazhong number one fault. The sedimentation of south Manjiaer depression in north Tazhong is controlled by Kuluketage-Manjiaer aulacogen, the sediments are clastic rocks with slope and deep water basin facies. Middle-upper Ordovician deposition of Tanguzibasi area in south Tazhong is controlled by the syncline of intracratonic depression, the sediments consist of clastic and carbonate rocks with deeper open platform facies. Lower Ordovician in Tazhong area is platform facies controlled by the intracratonic depression, and the structure-sedimentation is no apparent difference between the major part of uplift and adjacent areas.(3) The first favorable fracture zones of Ordovician carbonate reservoirs being predicted in the major part of Tazhong uplift include the following areas:Tz161-Tz44 area, Tz24-Tz26-Tz27 area, Tz45 area, Tz3 area, Tz52 area, Tz403 area, Tz2 area, Tz22 area, the east part of Tz35 area, the west part of number one fault and so on. Correlation the results predicted with the observations of core fractures and well logging evaluating, the fitness is about over sixty-six percent. So it is proposed that three dimension finite element simulation method is very efficient in predicting carbonate fracture zone.
To orient at special environment (such as weak satellite signals or no signals areas of high-rise apartment buildings in the city areas tunnels underground space indoor and under canopy, and the disaster environment and the region that satellite navigation cannot reach) precision navigation, positioning and monitoring, to aim at breaking through technical problems of high-precision angular measurement and rapid long-range precision measurement, and developing the high-end Smart Station positioning system products of physical structure and data-processing integration, to realize high-precision, low-cost and real time localization and precise monitoring with engineering deformation in special environment. This paper adds the location baseline position monitoring and three-dimensional location and other special functions based on the increase of accuracy of photoelectric angle measuring distance; solution positioning in the special environment; to solve bottleneck technology issue of low efficiency low accuracy poor reliability and multi-factor interference in the special environment and realize high-precision, low-cost and real-time location and precise monitoring.
Chrome chlorites are usually found as secondary phases formed by hydrothermal alteration of chromite deposits and associated mafic/ultramafic rocks. Here, we report the 40Ar/39Ar age of chrome chlorites separated from the Luobusa massive chromitites which have undergone secondary alteration by CO2-rich hydrothermal fluids. The dating results reveal that the intermediate heating steps (from 4 to 10) of sample L7 generate an age plateau of 29.88 ± 0.42 Ma (MSWD = 0.12, plateau 39Ar = 74.6%), and the plateau data points define a concordant inverse isochron age of 30.15 ± 1.05 Ma (MSWD = 0.08, initial 40Ar/36Ar = 295.8 ± 9.7). The Ar release pattern shows no evidence of later degassing or inherited radiogenic component indicated by an atmospheric intercept, thus representing the age of the hydrothermal activity. Based on the agreement of this hydrothermal age with the ~30 Ma adakitic plutons exposed in nearby regions (the Zedong area, tens of kilometers west Luobusa) and the extensive late Oligocene plutonism distributed along the southeastern Gangdese magmatic belt, it is suggested that the hydrothermal fluids are likely related to the ~30 Ma magmatism. The hydrothermal fluid circulation could be launched either by remote plutons (such as the Sangri granodiorite, the nearest ~30 Ma pluton west Luobusa) or by a similar coeval pluton in the local Luobusa area (inferred, not found or reported so far). Our results provide important clues for when the listwanites in Luobusa were formed.
Ground Penetrating Radar (GPR) is a geophysical method that uses antennas to transmit and receive high-frequency electromagnetic waves to detect the properties and distribution of materials in media. In this paper, geological observation, UAV detection and GPR technology are combined to study the recent sediments of the Yungang braided river study area in Datong. The application of the GPR technique to the description of fluvial facies and reservoir architecture and the development of geological models are discussed. The process of GPR detection technology and application includes three parts: GPR data acquisition, data processing and integrated interpretation of GPR data. The geological surface at different depths and scales can be identified by using different combinations of frequencies and antenna configurations during acquisition. Based on outcrop observation and lithofacies analysis, the Yandong Member of the Middle Jurassic Yungang Formation in the Datong Basin has been identified as a typical sandy braided river sedimentary system. The sandy braided river sandbody changes rapidly laterally, and the spatial distribution and internal structure of the reservoir are very complex, which has a very important impact on the migration and distribution of oil and gas as a reservoir. It is very important to make clear the characteristics of each architectural unit of the fluvial sand body and quantitatively characterize them. The architectural elements of the braided river sedimentary reservoir in the Datong-Yungang area can be divided into three types: Channel unit, bar unit and overbank assemblages. The geological radar response characteristics of different types of sedimentary units are summarized and their interfaces are identified. The channel sediments form a lens-shaped wave reflection with a flat at the top and convex-down at the bottom in the radar profile, and the angles of the radar reflection directional axes are different on both sides of the sedimentary interface. In the radar profile, the deposit of the unit bar is an upward convex reflection structure. The overbank siltation shows a weak amplitude parallel reflection structure. The flood plain sediments are distributed continuously and stably in the radar profile, showing weak reflection characteristics. Different sedimentary units are identified by GPR data and combined with Unmanned Aerial Vehicle (UAV) detection data, and the establishment of the field outcrop geological model is completed. The development pattern of the diara is clarified, and the swing and migration of the channel in different stages are identified.
Digital rock physics (DRP) has become an important tool to analyze the characteristics of pore structures and minerals and reveal the relationships between microscopic structures and the physical properties of reservoirs. However, it is greatly difficult to upscale the rock physical parameters, such as P-wave velocity, S-wave velocity, and elastic moduli, from DRP to large-scale boreholes and reservoirs. On the other hand, theoretical rock physical modeling can establish the internal relationship between the elastic properties and physical parameters of tight sandstones, which provides a theoretical basis for seismic inversion and seismic forward modeling. Therefore, the combination of digital rock physics and rock physical modeling can guide the identification and evaluation of the gas reservoir’s “sweet spot.” In this study, the CT images are used to analyze the mineral and pore characteristics. After that, the V-R-H model is used to calculate the equivalent elastic moduli of rocks containing only the mineral matrix, and then, the differential equivalent medium (DEM) model is used to obtain the elastic moduli of dry rocks containing minerals and pores. Subsequently, the homogeneous saturation model is used to fill the fluids in the pores and the Gassmann equation is used to calculate the equivalent elastic moduli of the saturated rock of tight sandstones. Rock physical modeling is calibrated, and the reliability of the rock physical model is verified by comparing those with the logging data. Afterward, the empirical relationship of rock porosity established from CT images and rock elastic moduli is obtained, and then, the elastic parameters obtained by seismic data inversion are converted into porosity parameters by using this empirical relationship. Finally, the porosity prediction of large-scale reservoirs in the study area is realized to figure out the distribution of gas reservoirs with high porosity. The results show that the H3b and H3c sections of the study area exhibit higher porosity than H3a. For the H3b reservoir, the northeast and middle areas of the gas field are potential targets since their porosity is larger than that of others, from 10% to 20%. Because of the effects of the provenance from the east direction, the southeast region of the H3c reservoir exhibits higher porosity than others.
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