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Geoscience Frontiers 2019年第3期10卷 1113-1124页

作者： Triveni Gogoi Rima Chatterjee department of applied geophysics Indian Institute of Technology (Indian School of Mines)

Estimation of petrophysical parameters is an important issue of any reservoirs. Porosity, volume of shale and water saturation has been evaluated for reservoirs of Upper Assam basin, located in northeastern India from well log and seismic data. Absolute acoustic impedance(AAI) and relative acoustic impedance(RAI) are generated from model based inversion of 2-D post-stack seismic data. The top of geological formation, sand reservoirs, shale layers and discontinuities at faults are detected in RAI section under the study area. Tipam Sandstone(TS) and Barail Arenaceous Sandstone(BAS) are the main reservoirs,delineated from the logs of available wells and RAI section. Porosity section is obtained using porosity wavelet and porosity reflectivity from post-stack seismic data. Two multilayered feed forward neural network(MLFN) models are created with inputs: AAI, porosity, density and shear impedance and outputs: volume of shale and water saturation with single hidden layer. The estimated average porosity in TS and BAS reservoir varies from 30% to 36% and 18% to 30% respectively. The volume of shale and water saturation ranges from 10% to 30% and 20% to 60% in TS reservoir and 28% to 30% and 23% to 55% in BAS reservoir respectively.

关键词： Upper Assam basin Relative acoustic impedance Porosity Volume of shale Water saturation Neural network model

Prediction of abnormal pressure from AVO velocities over“Safety”field,onshore Niger delta,Nigeria

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Petroleum Research 2021年第1期6卷 26-41页

作者： O.Abiola T.G.Ayenuro department of applied geophysics Federal University of TechnologyAkureNigeria

Abnormal pressure prediction was undertaken in“Safety”field,onshore Niger Delta,Nigeria using amplitude variation with offset(AVO)velocities *** of the methods used form an integral part of a process that produces AVO Analysis,AVO velocity inversion,extraction of seismic velocity from AVO velocities inversion results and pore pressure *** pressure predicted from the seismic velocity has a better resolution than the pressure predicted from the interval transit *** pore pressure within the field ranges from 14.7psi to *** and underpressured zones were delineated on the field from the pressure predicted from the seismic *** the field,the overpressured zones were delineated at depth 6855 fte7802 *** pressure top was delineated at a depth of 6855 ft with a pore pressure of 3053psi and a corresponding hydrostatic pressure of *** under-pressured zones were also delineated at depth 7883 fte9288 *** under pressure top was delineated at a depth of 7883 ft with a pressure of 1093psi and a corresponding hydrostatic pressure of *** values within the over pressure zone ranges from 23%to 53%which could be considered as relatively *** could be as a result of the fact that the pore fluid cannot be expelled rapidly thereby causing the pore fluid to increase rapidly since they are no longer compacted;thus leading to *** a result of overpressure top which is directly above the reservoir top within the shale zone,drilling this reservoir vertically could not be suggested so as to avoid possible blow *** was also observed that the primary cause or mechanism of overpressure within this field could be disequilibrium compaction.

关键词： Abnormal pressure Amplitude variation with offset Velocities information Pore pressure Disequilibrium compaction

An improved reverse time migration for subsurface imaging over complex geological structures:A numerical study

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Energy Geoscience

Energy Geoscience 2024年第2期5卷 290-297页

作者： Alok Kumar Routa Priya Ranjan Monahty department of applied geophysics IIT(ISM)DhanbadJharkhandIndia

In seismic exploration,it is a critical task to image and interpret different seismic signatures over complex geology due to strong lateral velocity contrast,steep reflectors,overburden strata and dipping *** understand the behavior of these seismic signatures,nowadays Reverse Time Migration(RTM)technique is used extensively by the oil&gas *** the extrapolation phase of RTM,the source wavefield needs to be saved,which needs high storage memory and large computing *** two are the main obstacles of RTM for production *** order to overcome these disadvantages,in this study,a second-generation improved RTM technique is *** this improved form,a shift operator is introduced at the time of imaging condition of RTM algorithm which is performed automatically both in space and time *** effort is made to produce a better-quality image by minimizing the computational time as well as numerical *** proposed method is applied over various benchmark models and validated by implementing over one field data set from the Jaisalmer Basin,*** the analysis,it is observed that the method consumes a minimum of 45%less storage space and reduce the execution time by 20%,as compared to conventional *** proposed RTM is found to work efficiently in comparison to the conventional RTM both in terms of imaging quality and minimization of numerical artefacts for all the benchmark models as well as field data.

关键词： Imaging condition Reverse time migration(RTM) Seismic imaging Velocity-depth model Wave propagation

Determination of gas reservoir(s) using AVO inversion within “XY” field offshore Niger Delta

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Petroleum Research 2019年第1期4卷 52-58页

作者： B.S.Ajanaku O.J.Akintorinwa department of applied geophysics Federal University of TechnologyAkureNigeria

The AVO inversion analysis of pre-stack seismic data of“XY”field located within the offshore,Niger Delta Basin has been considered in this research work with the aim of using AVO inversion to delineate gas reservoirs within the *** different inversion techniques are carried out in order to obtain accurate reservoir *** conventional AVO inversion analysis of the field do not identify the gas reservoirs clearly as there are other zones without gas with similar signatures,however,the cross-plots analysis of elastic parameters and the inverted volumes are used to delineate two gas reservoirs at 2000 and 2100 ***,the inversion techniques help to map the reservoir zone in a better way by increasing the vertical *** inversion analysis as used in this research help for better understanding of the physical properties of the delineated reservoirs.

关键词： Pre-stack seismic Reservoir AVO inversion Cross-plots Compressional Shear wave

Sequence stratigraphy and depositional sequence interpretation:A case study of“George”Field,offshore Niger Delta,Nigeria

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Petroleum Research 2018年第1期3卷 25-32页

作者： O.Abiola M.T.Olowokere J.S.Ojo department of applied geophysics Federal University of TechnologyAkureNigeria

The seismic sequence stratigraphic analysis revealed four depositional sequences(DS-1,DS-2,DS-3 and DS-4).The accompanying systems tracts were interpreted and mapped in the study area based on the log motifs of the reference well and the spatial distribution of the recognized constrained surfaces:maximum flooding surfaces(MFSs),sequence boundaries(SBs)and transgressive surfaces(TSs)on the seismic *** systems in the study area comprise lowstand systems tracts(LSTs),transgressive systems tracts(TSTs)and highstand systems tracts(HSTs).The LSTs are represented by coeval facies dominated by deposition basinward of the shelf-edge during maximum regression and are characterized by shallow-water deposition from gravity flows and/or traction processes within the shelf-edge or canyon-head *** sediments associated with lowstand systems tracts recognized in the study area are the fluvial channel sands and slope fans(SF).The transgressive sand units were interpreted as shoreface sands deposited in the shelf region during rising sea *** systems tracts are characterized by intervals of coarsening and shallowing upwards,with both fluvial and deltaic sands prograding laterally into neritic *** the study area,the units are very *** highstand and lowstand system tracts exhibit blocky log patterns and are associated with the reservoirs while the transgressive system tracts serve as seals to the *** environment of sediments deposition in this area is delta plain,shelf,slope to toe of slope.

关键词： Sequence stratigraphic analysis Depositional systems Log motifs Systems tracts Environment of sediments deposition

Myanmar-Andaman-Sumatra Subduction Margin Revisited:Insights of Arc-Specific Deformations

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Journal of Earth Science 2017年第4期28卷 683-694页

作者： Prosanta Kumar Khan Sk Shamim Manoranjan Mohanty Prabhat Kumar Jayashree Banerjee department of applied geophysics Indian Institute of Technology(ISM)Dhanbad 826 004India

We address the role of the concave and convex arcs （as observed from the subducting plate） on the deformation occurring along the Myanmar-Andaman-Sumatra margin. We categorize the pre- and post-seismic deformations of the lithosphere using earthquake database occurring either prior to 26th December 2004 Mw 9.3 off-Sumatra mega-event or after the incidence. Analysis under pre-seismic domain shows that area near Sumatra records highest seismicity, which largely drops in the area past the North Andaman, and further increases towards north. Shallowest depth and mini- mum dip of the subducting lithosphere is recorded at the central segment where the arc transformed into concave shape. The annual moment energy release during earthquake decreases to more than two orders of magnitude past the North Andaman towards north under post-seismic deformation phase. Higher depths of continuity of events are presumably associated with more dipping Benioff zones in both the Indo-Myanmar and Andaman-Nicobar convex arcs. These observations obviously account for tectonic subdivision of the margin near concave shape arc around the central part. Absence of vol- canism, presence of splay faults in the back-arc, sharp reduction in seismicity near central segment are interpreted to be caused by major tectonic impact of the NNE-ward converging buoyant Ninety-east Ridge against the Asian Plate. Shallowest dip, small elastic thickness, weak converging Indian litho- sphere, and evidences of series of en-echelon blocks off the eastern side of the broken northern Ninety- east Ridge might be incapable of generating great earthquake in this area.

关键词： Myanmar-Andaman-Sumatra margin double arc Ninety-east Ridge buoyancy.

Geometries, stabilities, and electronic properties analysis in In_nNi^((0,±1)) clusters: Molecular modeling and DFT calculations

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Chinese Physics B 2017年第8期26卷 130-139页

作者：史顺平张传瑜赵晓凤李侠闫珉蒋刚 department of applied Physics College of Geophysics Chengdu University of Technology Institute of Atomic and Molecular Physics Sichuan University

Density functional theory（DFT） with the B3 LYP method and the SDD basis set is selected to investigate In_nNi,In_nNi^-, and In_nNi~＋（n = 1–14） clusters. For neutral and charged systems, several isomers and different multiplicities are studied with the aim to confirm the most stable structures. The structural evolution of neutral, cationic, and anionic In_nNi clusters, which favors the three-dimensional structures for n = 3–14. The main configurations of the In_nNi isomers are not affected by adding or removing an electron, the order of their stabilities is also nearly not affected. The obtained binding energy exhibits that the Ni-doped In_（13） cluster is the most stable species of all different sized clusters. The calculated fragmentation energy and the second-order energy difference as a function of the cluster size exhibit a pronounced even–odd alternation phenomenon. The electronic properties including energy gap（E_g）, adiabatic electron affinity（AEA）, vertical electron detachment energy（VDE）, adiabatic ionization potential energy（AIP）, and vertical ionization potential energy（VIP） are studied. The total magnetic moments show that the different magnetic moments depend on the number of the In atoms for charged In_nNi. Additionally, the natural population analysis of In_nNi^（（0,±1）clusters is also discussed.

关键词： InnNi(0,±1) clusters stability electronic property density functional theory

P-wave velocity prediction in porous medium with liquid-pocket patchy saturation

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applied Mathematics and Mechanics(English Edition) 2015年第11期36卷 1427-1440页

作者： Jiawei LIU Weitao SUN Jing BA Zhou Pei-Yuan Center for applied Mathematics Tsinghua University department of Computational geophysics Xi'an Jiaotong University

It becomes increasingly clear that non-uniform distribution of immiscible fluids in porous rock is particularly relevant to seismic wave dispersion. White proposed a patchy saturation model in 1975, in which spherical gas pockets were located at the center of a liquid saturated cube. For an extremely light and compressible inner gas, the physical properties can be approximated by a vacuum with White＇s model. The model successfully analyzes the dispersion phenomena of a P-wave velocity in gas-water- saturated rocks. In the case of liquid pocket saturation, e.g., an oil-pocket surrounded by a water saturated host matrix, the light fluid-pocket assumption is doubtful, and few works have been reported in White＇s framework. In this work, Poisson＇s ratio, the bulk modulus, and the effective density of a dual-liquid saturated medium are formulated for the heterogeneous porous rocks containing liquid-pockets. The analysis of the difference between the newly derived bulk modulus and that of White＇s model shows that the effects of liquid-pocket saturation do not disappear unless the porosity approaches zero. The inner pocket fluid can no longer be ignored. The improvements of the P-wave velocity predictions are illustrated with two examples taken from experiments, i.e., the P-wave velocity in the sandstone saturated by oil and brine and the P-wave velocity for heavy oils and stones at different temperatures.

关键词： White's model porous medium P-wave dispersion liquid pocket

Structure of the mantle transition zone in the central and western parts of the North China Craton using the receiver function 3D Kirchhoff migration method

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Science China Earth Sciences 2024年第9期67卷 2783-2795页

作者： Min ZHU Qingju WU Jieyuan NING Ruiqing ZHANG Institute of geophysics China Earthquake AdministrationBeijing 100081China Institute of Theoretical and applied geophysics Peking UniversityBeijing 100871China

Using data from the regional broadband dense temporary array deployed by the ChinArray project,we applied the three-dimensional(3D)Kirchhoff migration method of the teleseismic P-wave receiver function to investigate discontinuity structures of the mantle transition zone(MTZ)in the central and western parts of the North China Craton(NCC)using a highresolution 3D velocity model of the East Asian *** results show that the 410-km discontinuity beneath the Datong Volcano is depressed by~10 km,indicating the presence of a high-temperature anomaly near the depth of 410 km,which is likely related to small-scale mantle upwelling caused by the dehydration of the stagnant Pacific Plate in the *** upwelling of hot material provides a heat source for surface magmatic *** the Bohai Bay Basin,significant subsidence of the 660-km discontinuity is observed,and the transition zone here is extensively ***’s suggested that the anomalies in this region are related to the stagnation of the Pacific slab in the *** the thickness of the transition zone west of the North-South Gravity Lineament appears normal,we propose that the subducting front of the Pacific slab did not cross the gravity lineament in the *** comparison,the small-scale subsidence of the 660-km discontinuity and the thickening of the MTZ observed north of the Hannuoba Volcano likely indicate that the slab crossed the gravity lineament at its turning point and remained in the ***,a local thickening of the MTZ is observed in the Dabie orogenic belt of the Qinling *** is believed to be a combined effect of lithospheric delamination into the transition zone in the lower Yangtze region and the stagnation of the Pacific Plate.

关键词： North China Craton Mantle transition zone Receiver function migration Datong Volcano

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Hour-to-hour variability of the ionosphere: An application of the classical multidimensional scaling method

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Science China Earth Sciences 2015年第7期58卷 1243-1250页

作者： SHI Hao ZHANG DongHe HAO YongQiang XIAO Zuo department of geophysics Peking University

The classical multidimensional scaling(MDS) method is introduced and applied in the study of the hour-to-hour ionospheric variability based on the ionospheric fo F2 observed at three ionosonde stations in East-Asia in 2002 and 2007. Results from the matrix eigen decompositions indicate that the annual part of the ionospheric variation is large in middle latitude and solar maximum period(2002) while low in the low latitude and solar minimum period(2007). The connectivity maps of the hour-to-hour ionospheric variability based on MDS method show some common diurnal features. The ionospheric connectivity between adjacent hours near noon hours and near midnight hours is high. The ionospheric connectivity between adjacent hours near sunrise hours and near sunset hours is poor, especially for the sunrise hours. Also there are latitudinal and solar activity dependences in this kind of connectivity. These results revealed from the ionospheric connectivity maps are useful physically and in practice for the ionospheric forecasting on the hour-to-hour scale.

关键词： ionospheric variability classical multidimensional scaling connectivity map