Drill cuttings,though rarely used,are crucial subsurface samples to understand petrographic properties affecting reservoir quality.Unlike core material,cuttings are continuously available along the wellbore and can be...Drill cuttings,though rarely used,are crucial subsurface samples to understand petrographic properties affecting reservoir quality.Unlike core material,cuttings are continuously available along the wellbore and can be used during drilling to monitor progress.Therefore,cuttings may allow a semi-quantitative,statistical calibration of rock properties from the subsurface,but they are often underutilized.Although fracture and vein orientations cannot be reconstructed from drill cuttings,the presence of veins and their internal textures(open,partially sealed or sealed) in specific formation sections and depths can be identified and analyzed using e.g.,transmitted light microscopy and cathodoluminescence to supplement characterization at the well site and subsequently assess production behavior.Borehole gamma ray logs in combination with handheld portable X-ray fluorescence(pXRF) analyses on cleaned and dried drill cuttings can be used to further improve the depth accuracy of the cutting samples and to geochemically fingerprint the samples,based on the Si/Al ratio,as a proxy for sandstone-rich and mudrock-rich sections of the well.In this study,eighty-three sandstone cutting samples from two wells,covering~400 m of stratigraphy targeting the Paleocene-Eocene Greifenstein Fm.equivalent(Glauconite Sandstone,GLS) in the Vienna Basin(Austria),were studied.They also cover parts of three different reservoir sections(1.to 3.GLS).The Flysch play in the Vienna Basin hosts several sand stone-mud rock interbeds and is composed of several nappes,forming complex reservoir compartments.The glauconite contents vary between different sections of the GLS,where the highest is observed in the 3.GLS.The sandstones are predominantly cemented by ferroan calcite,resulting in low optical porosity(<5 %)in both wells,with only individually elevated porosity,related to partially dissolved K-feldspar grains.A paragenetic sequence solely based on cuttings further highlights that reservoir quality in the studied section is independent of sandstone compaction,but is related to lower optical porosity in finer-grained sa ndstones and higher carbonate vein cement conte nts.Furthermo re,productive intervals are related to lower Fe+Mg contents.The understanding of reservoir properties,diagenesis,and their influence on fluid flow is crucial for successful exploration and reduction of uncertainty in reservoir production and development.The diagenetic variations from cuttings and the geochemical fingerprint by pXRF are linked to reservoir quality and production performance of individual well perforations.This approach can provide additional information on reservoir quality where core material is unavailable.展开更多
砂岩的石英胶结作用与颗粒包膜相(grain coating phases)及成岩蚀变密切相关。由被氧化铁和氢氧化铁浸染的伊利石-蒙脱石组成的颗粒包膜能够抑制石英共轴加大胶结物的生长,因而有助于大量孔隙的保存。选取Penrith组砂岩作为赤底统(Rotli...砂岩的石英胶结作用与颗粒包膜相(grain coating phases)及成岩蚀变密切相关。由被氧化铁和氢氧化铁浸染的伊利石-蒙脱石组成的颗粒包膜能够抑制石英共轴加大胶结物的生长,因而有助于大量孔隙的保存。选取Penrith组砂岩作为赤底统(Rotliegend)储层的类比对象,研究颗粒包膜对石英胶结作用的影响。这有助于丰富现有的胶结作用模型。颗粒包膜覆盖率的差异可能与粒度有关。在部分样品的较细粒纹层内可见大量的颗粒包膜,而较粗纹层内包膜的数量较少。基于标准岩相学分析的颗粒包膜研究与高分辨率QEMSCANR分析结合在了一起。构造特征包括不同年龄的变形带。根据颗粒包膜所记录的断层周围的成岩蚀变,可以确定其形成时间的相对关系,揭示与正断层作用相关的至少两期变形带的形成。在伊登谷(Vale of Eden)层序中,一次正断层作用事件晚于埋藏成岩石英胶结作用,流体集中沿断层流动和相关的铁漂白作用(bleaching of iron)以及缺乏石英加大的现象都说明了这一点。展开更多
文摘Drill cuttings,though rarely used,are crucial subsurface samples to understand petrographic properties affecting reservoir quality.Unlike core material,cuttings are continuously available along the wellbore and can be used during drilling to monitor progress.Therefore,cuttings may allow a semi-quantitative,statistical calibration of rock properties from the subsurface,but they are often underutilized.Although fracture and vein orientations cannot be reconstructed from drill cuttings,the presence of veins and their internal textures(open,partially sealed or sealed) in specific formation sections and depths can be identified and analyzed using e.g.,transmitted light microscopy and cathodoluminescence to supplement characterization at the well site and subsequently assess production behavior.Borehole gamma ray logs in combination with handheld portable X-ray fluorescence(pXRF) analyses on cleaned and dried drill cuttings can be used to further improve the depth accuracy of the cutting samples and to geochemically fingerprint the samples,based on the Si/Al ratio,as a proxy for sandstone-rich and mudrock-rich sections of the well.In this study,eighty-three sandstone cutting samples from two wells,covering~400 m of stratigraphy targeting the Paleocene-Eocene Greifenstein Fm.equivalent(Glauconite Sandstone,GLS) in the Vienna Basin(Austria),were studied.They also cover parts of three different reservoir sections(1.to 3.GLS).The Flysch play in the Vienna Basin hosts several sand stone-mud rock interbeds and is composed of several nappes,forming complex reservoir compartments.The glauconite contents vary between different sections of the GLS,where the highest is observed in the 3.GLS.The sandstones are predominantly cemented by ferroan calcite,resulting in low optical porosity(<5 %)in both wells,with only individually elevated porosity,related to partially dissolved K-feldspar grains.A paragenetic sequence solely based on cuttings further highlights that reservoir quality in the studied section is independent of sandstone compaction,but is related to lower optical porosity in finer-grained sa ndstones and higher carbonate vein cement conte nts.Furthermo re,productive intervals are related to lower Fe+Mg contents.The understanding of reservoir properties,diagenesis,and their influence on fluid flow is crucial for successful exploration and reduction of uncertainty in reservoir production and development.The diagenetic variations from cuttings and the geochemical fingerprint by pXRF are linked to reservoir quality and production performance of individual well perforations.This approach can provide additional information on reservoir quality where core material is unavailable.
文摘砂岩的石英胶结作用与颗粒包膜相(grain coating phases)及成岩蚀变密切相关。由被氧化铁和氢氧化铁浸染的伊利石-蒙脱石组成的颗粒包膜能够抑制石英共轴加大胶结物的生长,因而有助于大量孔隙的保存。选取Penrith组砂岩作为赤底统(Rotliegend)储层的类比对象,研究颗粒包膜对石英胶结作用的影响。这有助于丰富现有的胶结作用模型。颗粒包膜覆盖率的差异可能与粒度有关。在部分样品的较细粒纹层内可见大量的颗粒包膜,而较粗纹层内包膜的数量较少。基于标准岩相学分析的颗粒包膜研究与高分辨率QEMSCANR分析结合在了一起。构造特征包括不同年龄的变形带。根据颗粒包膜所记录的断层周围的成岩蚀变,可以确定其形成时间的相对关系,揭示与正断层作用相关的至少两期变形带的形成。在伊登谷(Vale of Eden)层序中,一次正断层作用事件晚于埋藏成岩石英胶结作用,流体集中沿断层流动和相关的铁漂白作用(bleaching of iron)以及缺乏石英加大的现象都说明了这一点。
