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Since its successful debut in the United States, the popularity of shale gas around the globe has... more Since its successful debut in the United States, the popularity of shale gas around the globe has been rising considerably. The International Energy Agency predicted that in a period of less than four decades, around 30% of global gas demand will be sustained by shale gas. While this giant energy source sheds lights to a promising future, however, our current understanding about the optimization and risks management of shale gas potentials is still far from sophisticated. Uncertainty in resource estimation, fracability assessment of shale reservoirs, and fluid flow models are currently the most prevalent technical challenges that need to be tackled. This paper discusses briefly about how shale gas becomes a critical component that serves as a transition from high carbon-emitting fuel to clean-renewable energy in the near-future, and also provides in-depth discussions regarding the aforementioned technical issues from geological, geophysical and petroleum engineering perspectives. In summary, calculation of shale gas in-place volume is based primarily on cores and well analysis (i.e., one dimensional data), while an accurate resource estimation should consider the 2D or 3D heterogeneity of gas content throughout the shale reservoirs. Furthermore, a parameter that truly reflects fracability is in controversy. In the past, brittleness index (BI) was thought to be correlated with, to a certain degree, the propensity of shale reservoirs to break under artificial stimulations. However, this parameter is ambiguous and recent studies indicate that BI may be unreliable. Moreover, in shale gas reservoir simulations, simple Darcy Equation can only provide an accurate prediction for short-term reservoir performance, whereas in the long run, this method exhibits a considerable amount of error. These three technical challenges pose serious obstructions to shale gas development and will potentially render shale gas development unviable in the future.

ABSTRACT In well correlation, biostratigraphy typically serves as a tool to underpin the chronos... more ABSTRACT

In well correlation, biostratigraphy typically serves as a tool to underpin the chronostratigraphic framework. However, biostratigraphic analysis is commonly performed using cuttings data, where caving, mixing during transport and improper sampling are commonplace. These inherent shortcomings can lead to erroneous age interpretation, which can render well correlation inaccurate. In order to improve the chronostratigraphic correlation in the West Natuna Basin, an integrated approach using the seismic as a complementary for the biostratigraphy has been utilized.

The first step of this approach was to characterize the key seismic markers, i.e. continuous and consistent reflectors across the study area. These markers potentially represent flooding surfaces, regionally extensive coal layers or other major events. These were then tied to each well and used as age-equivalent horizons. The seismic markers were then compared and combined—when possible—to the biostratigraphic age markers to form an integrated interpretation. Finally, incised valleys identified on seismic were incorporated with the environment signals from the biostratigraphy to interpret sequence stratigraphic surfaces. The combination of these datasets revealed that the seismic markers rarely matched with the biostratigraphic age markers, thus causing a dilemma. Based on the relative quality of each data, the seismic markers were interpreted to be more reliable and, therefore, were used as the primary source for the chronostratigraphic framework. Nonetheless, a combination of seismic and biostratigraphy were still useful for identifications of major events, such as sequence boundaries (SB) and maximum flooding surfaces (MFS). Using these methods, five seismic markers, seven possible sequence boundaries (SB) and two maximum flooding surfaces (MFS) were identified.
In summary, this study illustrates that biostratigraphy alone may not be sufficient to identify and correlate key events. An integrated approach using both seismic and biostratigraphy is the best method to determine chronostratigraphic correlation. For the West Natuna Basin, this methodology has provided new insights in correlation of the Miocene Arang Formation across the basin.

Keywords: Chronostratigraphy, Biostratigraphy, Seismic Marker, West Natuna Basin, Arang Formation

In well correlation, biostratigraphy typically underpins the chronostratigraphic framework. Unfor... more In well correlation, biostratigraphy typically underpins the chronostratigraphic framework. Unfortunately, biostratigraphy has some shortcomings. These issues arise because biostratigraphic analysis is commonly performed using cuttings data which is prone to caving, mixing during transport and improper sampling. These issues can lead to erroneous age interpretation which can make well correlation sometimes inaccurate. In order to improve the chronostratigraphic correlation in the West Natuna Basin, an integrated approach using both the biostratigraphic data and the seismic has been utilized.

The first step of this method was to characterize the key seismic markers (i.e. reflectors) which are continuous and consistent across the study area. These markers potentially represent flooding surfaces, regionally extensive coal or other major events. These markers were then tied to each well and used as age-equivalent horizons. The seismic markers were then compared and combined when possible to the biostratigraphic age to form an integrated interpretation. Finally, incised valleys identified on seismic were incorporated with the environment signal from the biostratigraphic analysis to interpret sequence stratigraphic surfaces. After combining this data, it was observed that the seismic markers rarely matched the biostratigraphic age. Based on the relative quality of the data, the seismic markers were interpreted to be more reliable and therefore were used as the primary source for the chronostratigraphic framework. For major events such as sequence boundaries (SB) and maximum flooding surfaces (MFS), a combination of seismic and biostratigraphy were used. Using these methods, five seismic markers, seven possible sequence boundaries (SB) and two maximum flooding surfaces (MFS) were identified.

In conclusion, this study illustrates that biostratigraphy alone may not be sufficient to identify and correlate key events. An integrated approach using both seismic and biostratigraphy is the best method to determine chronostratigraphic correlation. For the West Natuna Basin, this methodology has provided new insights in correlation of the Miocene Arang Formation across the basin.

Since its successful debut in the United States, the popularity of shale gas around the globe has... more Since its successful debut in the United States, the popularity of shale gas around the globe has been rising considerably. The International Energy Agency predicted that in a period of less than four decades, around 30% of global gas demand will be sustained by shale gas. While this giant energy source sheds lights to a promising future, however, our current understanding about the optimization and risks management of shale gas potentials is still far from sophisticated. Uncertainty in resource estimation, fracability assessment of shale reservoirs, and fluid flow models are currently the most prevalent technical challenges that need to be tackled. This paper discusses briefly about how shale gas becomes a critical component that serves as a transition from high carbon-emitting fuel to clean-renewable energy in the near-future, and also provides in-depth discussions regarding the aforementioned technical issues from geological, geophysical and petroleum engineering perspectives. In summary, calculation of shale gas in-place volume is based primarily on cores and well analysis (i.e., one dimensional data), while an accurate resource estimation should consider the 2D or 3D heterogeneity of gas content throughout the shale reservoirs. Furthermore, a parameter that truly reflects fracability is in controversy. In the past, brittleness index (BI) was thought to be correlated with, to a certain degree, the propensity of shale reservoirs to break under artificial stimulations. However, this parameter is ambiguous and recent studies indicate that BI may be unreliable. Moreover, in shale gas reservoir simulations, simple Darcy Equation can only provide an accurate prediction for short-term reservoir performance, whereas in the long run, this method exhibits a considerable amount of error. These three technical challenges pose serious obstructions to shale gas development and will potentially render shale gas development unviable in the future.

ABSTRACT In well correlation, biostratigraphy typically serves as a tool to underpin the chronos... more ABSTRACT

In well correlation, biostratigraphy typically serves as a tool to underpin the chronostratigraphic framework. However, biostratigraphic analysis is commonly performed using cuttings data, where caving, mixing during transport and improper sampling are commonplace. These inherent shortcomings can lead to erroneous age interpretation, which can render well correlation inaccurate. In order to improve the chronostratigraphic correlation in the West Natuna Basin, an integrated approach using the seismic as a complementary for the biostratigraphy has been utilized.

The first step of this approach was to characterize the key seismic markers, i.e. continuous and consistent reflectors across the study area. These markers potentially represent flooding surfaces, regionally extensive coal layers or other major events. These were then tied to each well and used as age-equivalent horizons. The seismic markers were then compared and combined—when possible—to the biostratigraphic age markers to form an integrated interpretation. Finally, incised valleys identified on seismic were incorporated with the environment signals from the biostratigraphy to interpret sequence stratigraphic surfaces. The combination of these datasets revealed that the seismic markers rarely matched with the biostratigraphic age markers, thus causing a dilemma. Based on the relative quality of each data, the seismic markers were interpreted to be more reliable and, therefore, were used as the primary source for the chronostratigraphic framework. Nonetheless, a combination of seismic and biostratigraphy were still useful for identifications of major events, such as sequence boundaries (SB) and maximum flooding surfaces (MFS). Using these methods, five seismic markers, seven possible sequence boundaries (SB) and two maximum flooding surfaces (MFS) were identified.
In summary, this study illustrates that biostratigraphy alone may not be sufficient to identify and correlate key events. An integrated approach using both seismic and biostratigraphy is the best method to determine chronostratigraphic correlation. For the West Natuna Basin, this methodology has provided new insights in correlation of the Miocene Arang Formation across the basin.

Keywords: Chronostratigraphy, Biostratigraphy, Seismic Marker, West Natuna Basin, Arang Formation

In well correlation, biostratigraphy typically underpins the chronostratigraphic framework. Unfor... more In well correlation, biostratigraphy typically underpins the chronostratigraphic framework. Unfortunately, biostratigraphy has some shortcomings. These issues arise because biostratigraphic analysis is commonly performed using cuttings data which is prone to caving, mixing during transport and improper sampling. These issues can lead to erroneous age interpretation which can make well correlation sometimes inaccurate. In order to improve the chronostratigraphic correlation in the West Natuna Basin, an integrated approach using both the biostratigraphic data and the seismic has been utilized.

The first step of this method was to characterize the key seismic markers (i.e. reflectors) which are continuous and consistent across the study area. These markers potentially represent flooding surfaces, regionally extensive coal or other major events. These markers were then tied to each well and used as age-equivalent horizons. The seismic markers were then compared and combined when possible to the biostratigraphic age to form an integrated interpretation. Finally, incised valleys identified on seismic were incorporated with the environment signal from the biostratigraphic analysis to interpret sequence stratigraphic surfaces. After combining this data, it was observed that the seismic markers rarely matched the biostratigraphic age. Based on the relative quality of the data, the seismic markers were interpreted to be more reliable and therefore were used as the primary source for the chronostratigraphic framework. For major events such as sequence boundaries (SB) and maximum flooding surfaces (MFS), a combination of seismic and biostratigraphy were used. Using these methods, five seismic markers, seven possible sequence boundaries (SB) and two maximum flooding surfaces (MFS) were identified.

In conclusion, this study illustrates that biostratigraphy alone may not be sufficient to identify and correlate key events. An integrated approach using both seismic and biostratigraphy is the best method to determine chronostratigraphic correlation. For the West Natuna Basin, this methodology has provided new insights in correlation of the Miocene Arang Formation across the basin.