The Triassic fluvial sandstones of the Skagerrak Formation were deposited in a series of salt-walled mini-basins and act as important hydrocarbon reservoirs for several high-pressure, high-temperature（HPHT） fields i...The Triassic fluvial sandstones of the Skagerrak Formation were deposited in a series of salt-walled mini-basins and act as important hydrocarbon reservoirs for several high-pressure, high-temperature（HPHT） fields in the Central Graben, North Sea. The HPHT reservoirs exhibit excellent reservoir quality considering their depth of burial and hence have been of high interest for hydrocarbon exploration. This research uses a multidisciplinary approach to assess the Skagerrak Formation fluvial reservoir quality from the Seagull field incorporating core analysis, petrography, electron microscopy, XRD analysis, fluid inclusion appraisal and burial history modelling. Halokinesis and salt withdrawal at the margin of the saltwalled mini-basin induced early disaggregation bands and fractures at shallow burial and led to increased influx of meteoric water and clay mineral infiltration from overlying sedimentation. The density of disaggregation bands correlates with the occurrence and magnitude of pore-filling authigenic clay minerals, concentrated along the margin of the saltwalled mini-basin. The fluvial channel sandstones of the Skagerrak Formation are subject to strong intra-basinal spatial reservoir quality variations despite diagenesis and low vertical effective stress having played a favourable role in arresting porosity loss.展开更多
The Ma5_(1-4)submembers of Jingbian gas field in Ordos basin of China belongs to epeiric sea evaporative carbonate tidal flat facies.Supratidal zone of gypsum nodule dolostone and upper part of intertidal zone of gyps...The Ma5_(1-4)submembers of Jingbian gas field in Ordos basin of China belongs to epeiric sea evaporative carbonate tidal flat facies.Supratidal zone of gypsum nodule dolostone and upper part of intertidal zone of gypsum crystal dolostone are most favorable reservoir.The carbonate rocks of Ma5_(1-4)had undergone complex diagenesis.Penecontem-poraneous dolomitization and gypsification provided the material foundation of the reservoir.Epidiagenesis selective dissolution of gypseous dolostone constructs the origin shape of pore structure.The dissolution and filling of various minerals in the burial period determine whether the early dissolution pores can be preserved,and the final state of the reservoir.Burial dissolution and filling of various minerals determined the preservation of early dissolved pores and the final condition of the reservoir.The concept of“minus cement porosity”directly reflects that sedimentary facies have great influence on the growth of reservoir in Ma5_(1-4).Combined with sedimentary microfacies and diagenetic facies,a concise numerical symbol is used to express semiquantitatively sed-imentary microfacies and diagenesis facies.This descriptive method has great benefit in reservoir evaluation and prediction.展开更多
基金sponsored by BG, BP, Chevron, Conoco Phillips, DONG Energy, E. ON, ENI, Petrobras, Petronas, Statoil and Tullow Oil at Durham University is thanked for funding this research
文摘The Triassic fluvial sandstones of the Skagerrak Formation were deposited in a series of salt-walled mini-basins and act as important hydrocarbon reservoirs for several high-pressure, high-temperature（HPHT） fields in the Central Graben, North Sea. The HPHT reservoirs exhibit excellent reservoir quality considering their depth of burial and hence have been of high interest for hydrocarbon exploration. This research uses a multidisciplinary approach to assess the Skagerrak Formation fluvial reservoir quality from the Seagull field incorporating core analysis, petrography, electron microscopy, XRD analysis, fluid inclusion appraisal and burial history modelling. Halokinesis and salt withdrawal at the margin of the saltwalled mini-basin induced early disaggregation bands and fractures at shallow burial and led to increased influx of meteoric water and clay mineral infiltration from overlying sedimentation. The density of disaggregation bands correlates with the occurrence and magnitude of pore-filling authigenic clay minerals, concentrated along the margin of the saltwalled mini-basin. The fluvial channel sandstones of the Skagerrak Formation are subject to strong intra-basinal spatial reservoir quality variations despite diagenesis and low vertical effective stress having played a favourable role in arresting porosity loss.
基金This workwas financially supported by the National Natural Science Foundation of China(41772150,41972120).
文摘The Ma5_(1-4)submembers of Jingbian gas field in Ordos basin of China belongs to epeiric sea evaporative carbonate tidal flat facies.Supratidal zone of gypsum nodule dolostone and upper part of intertidal zone of gypsum crystal dolostone are most favorable reservoir.The carbonate rocks of Ma5_(1-4)had undergone complex diagenesis.Penecontem-poraneous dolomitization and gypsification provided the material foundation of the reservoir.Epidiagenesis selective dissolution of gypseous dolostone constructs the origin shape of pore structure.The dissolution and filling of various minerals in the burial period determine whether the early dissolution pores can be preserved,and the final state of the reservoir.Burial dissolution and filling of various minerals determined the preservation of early dissolved pores and the final condition of the reservoir.The concept of“minus cement porosity”directly reflects that sedimentary facies have great influence on the growth of reservoir in Ma5_(1-4).Combined with sedimentary microfacies and diagenetic facies,a concise numerical symbol is used to express semiquantitatively sed-imentary microfacies and diagenesis facies.This descriptive method has great benefit in reservoir evaluation and prediction.
