Bo Liu - Academia.edu (original) (raw)
Uploads
Papers by Bo Liu
OTC 2022, 2022
Shale gas reservoirs in the LongMaxi Formation, Sichuan Basin, are the biggest proven shale gas r... more Shale gas reservoirs in the LongMaxi Formation, Sichuan Basin, are the biggest proven shale gas reservoirs in China. The natural fracture system plays an important role in the shale gas exploration and development. Both high-angle calcite-cemented fractures and low-angle bedding fractures were observed in the core and resistivity image logs but the relationships between these two kinds of fractures is still not clear. Identifying and characterizing the natural fracture system in the shale gas reservoir were the objective of this case study. The borehole resistivity image logs were acquired in several shale gas wells in southeast Sichuan Basin. We observed a spiky resistivity log response in some intervals of Longmaxi Formation. Image logs reveal that all these intervals have low-angle conductive features. Based on the crosscutting relationship of bedding and fractures, these features are conductive bedding fractures, which cut the high-angle resistive fractures in the formation. Both conductive and resistive bedding fractures are identified in the image logs and core data. The geochemical spectroscopy logs in this interval show low pyrite volume, which indicates the conductive bedding fractures are not filled by conductive minerals. It could be an effective pathway of fluid flow. The natural fractures can be divided into three types: low-angle conductive bedding fracture, low-angle resistive bedding fracture, and high-angle resistive fracture. The bedding fractures and high-angle resistive fractures are mainly in the brittle zone of the LongMaxi Formation. We observed that the high density of the conductive bedding fractures will appear spiky on the resistivity logs, which will cause high horizontal permeability. Multiwell correlation shows that there will be more conductive bedding fractures in areas where the shale gas reservoir was undergoing tectonic stresses, which could have a negative impact on the shale gas enrichment. The bedding fractures were formed after the high-angle resistive fractures. Some bedding fractures were cemented by calcite, while some are still open. The identification of bedding fractures will help to understand the complex natural fracture system in the tight shale gas reservoir. The conductive bedding fractures will greatly enhance the horizontal permeability and will influence the fluid flow dramatically.
SPE Conference, 2023
The Lower Silurian Longmaxi Shale Formation of Sichuan Basin is the largest shale gas reservoir i... more The Lower Silurian Longmaxi Shale Formation of Sichuan Basin is the largest shale gas reservoir in China. It was formed mainly in a deepwater shelf depositional environment with a relatively stable tectonic background. More and more cores and borehole images data from the Longmaxi Shale revealed that the sedimentary features show considerable changes in mineralogy or texture in different regions. Mass-transport complexes (MTC) were identified for the first time in the Longmaxi Shale based on the integration of logs, borehole images, and seismic data. The MTC have led to a clearly abnormal formation thickening in both well and seismic data. Identifying and characterizing the MTC in the Longmaxi Shale is the objective of this case study. The integration of the logs, borehole images, and seismic data brings more insights into different aspects of MTC. The repeat section that results from the MTC can be identified based on the well logs directly. Detailed analysis of the borehole images yields additional evidence such as lithofacies and textures in the MTC. The faults and fractures in the MTC can also reveal the controlling factors on the shale gas enrichment. The analogs between the concept model and seismic reflections have improved our understanding of when and how the MTC are likely to form in the Longmaxi Shale. The MTC in the Longmaxi Shale are developed above the detachment surface between the calcitecemented sandstone body and the high-clay-volume shale. It brings more than 20 m of repeat section inside the Longmaxi Formation. The boundary between the original and repeat sections is a low-angle thrust fault. The repeat sections can be divided into four zones based on their log responses. The gamma ray (GR) response and the borehole image features have validated the presence of the repeat section. The minerology differences between the original and repeat sections have highlighted the facies variations in the Longmaxi Shale. This is also the reason why the MTC could occur in this area. Based on the calibrations of well data, the geometry and architecture of the MTC are readily observed in 3D
ADIPEC, 2021
Carbonate reservoir is one of the most complex and important reservoirs in the world. It was conf... more Carbonate reservoir is one of the most complex and important reservoirs in the world. It was confirmed that the slip-strike fault played a crucial role in the fault-dominated carbonate reservoir in Tarim basin. It is challenging to evaluate this kind of reservoir using the open-hole log or seismic data. Identifying and characterizing the fault-dominated carbonate reservoir were the objectives of this case study. High-definition borehole resistivity image and dipole sonic logs were run in several wells in the research area. It was revealed the detail features of the fault-dominated carbonate reservoir, such as natural fractures, faults or breccias. Compared with the typical geological model of strike-slip faults and outcrop features, the characteristics of the breccia zone and the fracture zone in the strike-slip fault system were summarized from the borehole image interpretation. A unique workflow was innovated with the integration of image and sonic data. Breccias and fractures were observed in the borehole image; and reflections or attenuations in Stoneley waveforms can provide indicating flag for permeable zones. Integrated with the other related geological data like mud logging or cores, the best pay zones in the fault-dominated carbonate reservoir were located. The characteristics of the strike-slip fault was revealed with the integration of the full-bore formation microimager and dipole shear sonic imager data. The fault core was a typical breccia zone with strong dissolution, which showed good potential in permeability, but it was found that some fault cores were filled with siliceous rock or intrusive rock. The features of the fillings in the fault zone were described based on the image and sonic data. The side cores or geochemical spectroscopy logs data helped to determine the mineralogy of the fillings. The fracture zones had clear responses in the image and sonic data too. The un-filled or half-filled breccia zone were the best zones in the fault-dominated carbonated reservoir. The details of the fault-dominated carbonate reservoir could be used in the future three-dimensional geological modelling.
OTC 2022, 2022
Shale gas reservoirs in the LongMaxi Formation, Sichuan Basin, are the biggest proven shale gas r... more Shale gas reservoirs in the LongMaxi Formation, Sichuan Basin, are the biggest proven shale gas reservoirs in China. The natural fracture system plays an important role in the shale gas exploration and development. Both high-angle calcite-cemented fractures and low-angle bedding fractures were observed in the core and resistivity image logs but the relationships between these two kinds of fractures is still not clear. Identifying and characterizing the natural fracture system in the shale gas reservoir were the objective of this case study. The borehole resistivity image logs were acquired in several shale gas wells in southeast Sichuan Basin. We observed a spiky resistivity log response in some intervals of Longmaxi Formation. Image logs reveal that all these intervals have low-angle conductive features. Based on the crosscutting relationship of bedding and fractures, these features are conductive bedding fractures, which cut the high-angle resistive fractures in the formation. Both conductive and resistive bedding fractures are identified in the image logs and core data. The geochemical spectroscopy logs in this interval show low pyrite volume, which indicates the conductive bedding fractures are not filled by conductive minerals. It could be an effective pathway of fluid flow. The natural fractures can be divided into three types: low-angle conductive bedding fracture, low-angle resistive bedding fracture, and high-angle resistive fracture. The bedding fractures and high-angle resistive fractures are mainly in the brittle zone of the LongMaxi Formation. We observed that the high density of the conductive bedding fractures will appear spiky on the resistivity logs, which will cause high horizontal permeability. Multiwell correlation shows that there will be more conductive bedding fractures in areas where the shale gas reservoir was undergoing tectonic stresses, which could have a negative impact on the shale gas enrichment. The bedding fractures were formed after the high-angle resistive fractures. Some bedding fractures were cemented by calcite, while some are still open. The identification of bedding fractures will help to understand the complex natural fracture system in the tight shale gas reservoir. The conductive bedding fractures will greatly enhance the horizontal permeability and will influence the fluid flow dramatically.
SPE Conference, 2023
The Lower Silurian Longmaxi Shale Formation of Sichuan Basin is the largest shale gas reservoir i... more The Lower Silurian Longmaxi Shale Formation of Sichuan Basin is the largest shale gas reservoir in China. It was formed mainly in a deepwater shelf depositional environment with a relatively stable tectonic background. More and more cores and borehole images data from the Longmaxi Shale revealed that the sedimentary features show considerable changes in mineralogy or texture in different regions. Mass-transport complexes (MTC) were identified for the first time in the Longmaxi Shale based on the integration of logs, borehole images, and seismic data. The MTC have led to a clearly abnormal formation thickening in both well and seismic data. Identifying and characterizing the MTC in the Longmaxi Shale is the objective of this case study. The integration of the logs, borehole images, and seismic data brings more insights into different aspects of MTC. The repeat section that results from the MTC can be identified based on the well logs directly. Detailed analysis of the borehole images yields additional evidence such as lithofacies and textures in the MTC. The faults and fractures in the MTC can also reveal the controlling factors on the shale gas enrichment. The analogs between the concept model and seismic reflections have improved our understanding of when and how the MTC are likely to form in the Longmaxi Shale. The MTC in the Longmaxi Shale are developed above the detachment surface between the calcitecemented sandstone body and the high-clay-volume shale. It brings more than 20 m of repeat section inside the Longmaxi Formation. The boundary between the original and repeat sections is a low-angle thrust fault. The repeat sections can be divided into four zones based on their log responses. The gamma ray (GR) response and the borehole image features have validated the presence of the repeat section. The minerology differences between the original and repeat sections have highlighted the facies variations in the Longmaxi Shale. This is also the reason why the MTC could occur in this area. Based on the calibrations of well data, the geometry and architecture of the MTC are readily observed in 3D
ADIPEC, 2021
Carbonate reservoir is one of the most complex and important reservoirs in the world. It was conf... more Carbonate reservoir is one of the most complex and important reservoirs in the world. It was confirmed that the slip-strike fault played a crucial role in the fault-dominated carbonate reservoir in Tarim basin. It is challenging to evaluate this kind of reservoir using the open-hole log or seismic data. Identifying and characterizing the fault-dominated carbonate reservoir were the objectives of this case study. High-definition borehole resistivity image and dipole sonic logs were run in several wells in the research area. It was revealed the detail features of the fault-dominated carbonate reservoir, such as natural fractures, faults or breccias. Compared with the typical geological model of strike-slip faults and outcrop features, the characteristics of the breccia zone and the fracture zone in the strike-slip fault system were summarized from the borehole image interpretation. A unique workflow was innovated with the integration of image and sonic data. Breccias and fractures were observed in the borehole image; and reflections or attenuations in Stoneley waveforms can provide indicating flag for permeable zones. Integrated with the other related geological data like mud logging or cores, the best pay zones in the fault-dominated carbonate reservoir were located. The characteristics of the strike-slip fault was revealed with the integration of the full-bore formation microimager and dipole shear sonic imager data. The fault core was a typical breccia zone with strong dissolution, which showed good potential in permeability, but it was found that some fault cores were filled with siliceous rock or intrusive rock. The features of the fillings in the fault zone were described based on the image and sonic data. The side cores or geochemical spectroscopy logs data helped to determine the mineralogy of the fillings. The fracture zones had clear responses in the image and sonic data too. The un-filled or half-filled breccia zone were the best zones in the fault-dominated carbonated reservoir. The details of the fault-dominated carbonate reservoir could be used in the future three-dimensional geological modelling.