The Upper Tukau Formation is exposed along the Sungai Rait Road and can be described as follows: ... more The Upper Tukau Formation is exposed along the Sungai Rait Road and can be described as follows: the lowermost member is formed by soft clay and silt, the “Brick Shale”, and contains meandering sandy channels. The clay is thoroughly excavated in the area and used as raw material for bricks. The second and hilltop-forming layer is built by relatively hard amalgamated, and partly channelized sandstone layers, often lined with diagenetically precipitated iron minerals (i.e., pyrite and siderite concretions). The youngest member is characterized by intertidal channels and mud flats. Geochemical studies point to a polymictic source of already recycled sediments, deposited in predominantly oxic, partly suboxic environments, with rapid transitions observed from one milieu to the other. In broad terms, the entire sequence appears to be a shallowing-upwards cycle, leading from subtidal to intertidal realms. The surprising sharp boundaries between clay and sand packages are discussed and may ...
Bulletin Of The Geological Society Of Malaysia, 2021
The onshore Baram Delta, located in NW Sarawak is the birthplace of petroleum production in Malay... more The onshore Baram Delta, located in NW Sarawak is the birthplace of petroleum production in Malaysia. The Miri oilfield was first discovered in 1910 and subsequently abandoned in 1972 with intermittent exploration activities in the late 1980’s to early 1990’s. To rejuvenate exploration interest and to identify remaining hydrocarbon potential of the study area, in 2009-2010 JX Nippon acquired gravity, then regional 2D seismic data, followed-by exploration well drilling from 2011-2014. This paper discusses the social-environmental impacts and concerns associated with these petroleum exploration activities, from acquisition of seismic where explosives and vibroseis were used as a source of propagating signals, to exploration drilling with petroleum chemicals such as water-based muds used to facilitate the drilling operations. Overall, the inquiry addresses operational challenges, security of explosive storage and concern for handling explosives in the field, the social-environmental im...
Bulletin Of The Geological Society Of Malaysia, 2021
Suppression of vitrinite reflectance is a well-known phenomenon and, if not recognised and correc... more Suppression of vitrinite reflectance is a well-known phenomenon and, if not recognised and corrected for, could potentially have a big impact on the results of thermal history and basin modelling, and seriously affect exploration decisions. The Malay Basin is known to have shown evidence of vitrinite reflectance (Ro) suppression in a selection of wells that were also analysed using the FAMM (Fluorescence Alteration of Multiple Macerals) technique. Analysis of available data suggests that potential vitrinite reflectance suppression may be identified using an empirical regression line which separates “suppressed” from “normal” Ro values based on the FAMM data. The “FAMM minimum regression line” was used to screen through Ro data from 142 wells (drilled between 1969 and 2005) in the Malay Basin and it is estimated that a quarter of those wells might be affected by suppression. Possible suppression was also noted in the Penyu Basin, where bottom-hole temperatures in some wells are consi...
Bulletin Of The Geological Society Of Malaysia, 2020
Following the successful production from fractured basement in similar Tertiary basins, the basem... more Following the successful production from fractured basement in similar Tertiary basins, the basement play was pursued in the Malay Basin, particularly during the 2000-2010 period but, unfortunately, that effort fell short of expectations. The only oil discovery in fractured basement reservoir was Anding in the southwestern part of the basin. Despite its development being delayed due to economic reasons, the Anding discovery had been the basis for the basement play concept: namely, a fractured reservoir formed of pre-Tertiary metamorphic rock, charged from overlying Tertiary lacustrine source rocks in an adjacent half-graben and sealed by a transgressive shale unit. This paper examines seismic, gravity and well evidences on the pre-Tertiary basement geology, with the aim of assessing further the hydrocarbon potential of pre-Tertiary basement. The pre-Tertiary basement subcrops beneath the Malay and Penyu basins represent a continuation of the onshore geology of Sundaland Mesozoic ter...
The new coastal Miri-Bintulu road intersects, near the Tusan junction some 40 km South of Miri, a... more The new coastal Miri-Bintulu road intersects, near the Tusan junction some 40 km South of Miri, a series of normal faults, vested in a 80 deg dipping clastic sequence located near to the core of the complex Lambir Anticline are observed. The outcrop shows beautiful examples of clay gouging, fault drag and concussion. Faults have been measured and correlated (Figs. 1, 2). Clay gouging indicate a correlation between gouging thickness and fault throw (Fig. 3). Development of fault rock (Fig. 4) is noted within competent (hence brittle) sandstone units, regardless of hanging wall or footwall position, whereas clay bodies react ductile and show fault drag. The authors intend to further investigate the clay gouge sealing capacity, calibrate the outcrop data with modeling packages such as FaultRiskTM, and approach industry players for sponsorship.
In an effort to reconcile different data sources (seafloor spreading, seismic and gravity images,... more In an effort to reconcile different data sources (seafloor spreading, seismic and gravity images, well calibrations, outcrop studies) in the South China Sea (SCS), we reviewed the unconformity records, in particular in the context with the shut-off of seafloor spreading in the SCS. With respect to the start of spreading, there is a consensus: ca. 34-41 Ma. Recent data infer an end of spreading, near to the magnetic Anomaly 5 = ca. 15.5 Ma (Langhian age). In Northwest Borneo, it is suggested that this event is coeval with the Deep Regional Unconformity (DRU) in Sabah and Brunei, and the Mid-Miocene Unconformity (MMU) in Sarawak. The MMU is also recognized in offshore Vietnam and Palawan, on the Western and Southeastern margins of the SCS, respectively. The MMU/DRU may constitute the border between active margin and passive margin deposits within the marine SCS sub-basins. The progradation of clastic shelves post-MMU/DRU may have hampered growth of bioherms whilst creating prolific s...
This paper reviews the complex interaction of basin subsidence, erosion and uplift of mountain ra... more This paper reviews the complex interaction of basin subsidence, erosion and uplift of mountain ranges that enclose the South China Sea (SCS). We found that recent uplift is a feature occurring dominantly at the fringes of the Sundaland Plate, around Sumatra/Java, Borneo, the Philippines and Taiwan. More significantly, there is a positive age correlation between regional unconformities, formation of oceanic crust and uplift of the peripheral mountain ranges. However, the magnitude of erosion related to each major unconformity can vary regionally, and could partly be subjected to climatic influence. The oldest truly regional unconformity recognizable is of very Late Oligocene age, and acts as an angular unconformity in Sabah, Sarawak, and the Malay/Penyu Basins (at Base ‘K’ level), at or very close to the base of the Miocene sedimentary package. We call this unconformity the Base Miocene Unconformity (BMU). Other than the BMU, the widely-known seismic event called the Mid-Miocene Unconformity (MMU) could be correlated with the end of proto-SCS spreading, and uplift may have occurred only in segments of the SCS, in particular at the southern fringe. The Late Miocene Shallow Regional Unconformity (SRU) points to a short compressive pulse that affected mainly areas of Sabah and Sarawak. The more recent Intra-Pliocene unconformity (IPU), commonly forming the base of some uplifted coastal terraces can be seen in particular in the south and eastern parts of the SCS, and correlates with uplift of areas such as NW Borneo and Taiwan. The event is a likely consequence of the Taiwan collision interplayed with the docking of the Philippines Plate in the Early Pliocene with NW Borneo at the Palawan/Philippines Margin. The Malay, Penyu, Natuna Basins and Vietnam Margin are predominantly Oligocene to Lower Miocene fills, whereas the NW Borneo Foredeep/Palawan Trough, deepwater Nam Con Son Basin and the Bunguran Trough have predominantly a Neogene fill. This observation points to a reduced extensional regime if compared with the south-eastern margin, where fault activity continued to the Mid/Late Miocene. The compiled uplift data in the surroundings of the SCS, as well as the presence of seismically mapped regional unconformities suggest that the greater Sundaland Plate has seen a number of extensions and compression/inversion/rotation phases; however there appears to be no positive evidence for the presence of microplates and/or subduction during the Oligocene/Miocene. In summary, crustal stretching, uplift and the resulting unconformities can be compared to different instruments of an orchestra playing individually; no harmonic tune can be achieved and there is little merit in looking at each contributing factor in isolation. Keywords: Eocene, erosion, sea-level changes, sediments, South China Sea, subsidence, unconformity, uplift, Tertiary.
The Eocene to Lower Oligocene deposits of the Penyu and Malay basins are formed by fluvial-lacust... more The Eocene to Lower Oligocene deposits of the Penyu and Malay basins are formed by fluvial-lacustrine deposits with marine influence in the latter. The sequence consists mainly of siltstone, with several intercalations of fine-grained sand and volcanic tuff. Based on well data, Mid-Upper Eocene sediments exist in Penyu Basin in the deeper parts of the half grabens and sub-basins. Hence, this implies the age of basin initiation at Mid-Eocene, rather than Oligocene as traditionally and commonly stated in the literature. By correlation, and as seismic evidences show, Eocene sediments also appear to exist in the deeper, undrilled parts of the Malay Basin, again implying that at the latest, a Mid-Eocene age of basin initiation.In the Penyu Basin, aprominent near-Base Oligocene Unconformity can potentially be correlated to the Base-Tertiary Unconformity in the adjacent Malay Basin, however the latter term implies all Tertiary sequences, including potential Paleogene deposits above the unc...
The greater Miri area in NW Sarawak can be seen as a basin extension of the NW Borneo Foredeep to... more The greater Miri area in NW Sarawak can be seen as a basin extension of the NW Borneo Foredeep to the onshore with uplifted and exposed outcrops of Neogene sediments suitable for both lithological and chrono-stratigratigraphic investigations. The Neogene sequence contains also up to four prominent unconformities that can be studied in a number of outcrops including the well-established Mid-Miocene Unconformity and the less well-defined Shallow Regional Unconformity, Intra-Pliocene Unconformity and the Lower Pleistocene Unconformity. However, it is noted that the geological timings of the unconformities observed are yet-to-be fully established due to a lack of detailed chrono-biostratigraphic investigations for age assignment of the exposed outcrops. Nonetheless, the stratigraphic importance and the presence of the mentioned unconformities may be related to other established regional tectonic events mapped in offshore Sarawak and Sabah with better seismic coverage. Their significance cannot be underestimated and may provide a better insight on the regional uplift history and the tectonic evolution of the structurally complex NW Borneo margin.
The greater Miri area offers particularly well-exposed examples of fault geometry and clay gougin... more The greater Miri area offers particularly well-exposed examples of fault geometry and clay gouging. Such data are important analogues for predicting, or to simulating pressure and retention of hydrocarbon columns in fields in Brunei, Sabah and Sarawak. This short paper focuses on two excellent outcrop areas, where measurements were dominantly carried out on normal faults. Our fieldwork suggests a good correlation between normal fault throw, and gouge thickness. The studied outcrops offer further research potential in the areas of gouge mineralogy, gouge stratification and pressure retention.
The Upper Tukau Formation is exposed along the Sungai Rait Road and can be described as follows: ... more The Upper Tukau Formation is exposed along the Sungai Rait Road and can be described as follows: the lowermost member is formed by soft clay and silt, the “Brick Shale”, and contains meandering sandy channels. The clay is thoroughly excavated in the area and used as raw material for bricks. The second and hilltop-forming layer is built by relatively hard amalgamated, and partly channelized sandstone layers, often lined with diagenetically precipitated iron minerals (i.e., pyrite and siderite concretions). The youngest member is characterized by intertidal channels and mud flats. Geochemical studies point to a polymictic source of already recycled sediments, deposited in predominantly oxic, partly suboxic environments, with rapid transitions observed from one milieu to the other. In broad terms, the entire sequence appears to be a shallowing-upwards cycle, leading from subtidal to intertidal realms. The surprising sharp boundaries between clay and sand packages are discussed and may ...
Bulletin Of The Geological Society Of Malaysia, 2021
The onshore Baram Delta, located in NW Sarawak is the birthplace of petroleum production in Malay... more The onshore Baram Delta, located in NW Sarawak is the birthplace of petroleum production in Malaysia. The Miri oilfield was first discovered in 1910 and subsequently abandoned in 1972 with intermittent exploration activities in the late 1980’s to early 1990’s. To rejuvenate exploration interest and to identify remaining hydrocarbon potential of the study area, in 2009-2010 JX Nippon acquired gravity, then regional 2D seismic data, followed-by exploration well drilling from 2011-2014. This paper discusses the social-environmental impacts and concerns associated with these petroleum exploration activities, from acquisition of seismic where explosives and vibroseis were used as a source of propagating signals, to exploration drilling with petroleum chemicals such as water-based muds used to facilitate the drilling operations. Overall, the inquiry addresses operational challenges, security of explosive storage and concern for handling explosives in the field, the social-environmental im...
Bulletin Of The Geological Society Of Malaysia, 2021
Suppression of vitrinite reflectance is a well-known phenomenon and, if not recognised and correc... more Suppression of vitrinite reflectance is a well-known phenomenon and, if not recognised and corrected for, could potentially have a big impact on the results of thermal history and basin modelling, and seriously affect exploration decisions. The Malay Basin is known to have shown evidence of vitrinite reflectance (Ro) suppression in a selection of wells that were also analysed using the FAMM (Fluorescence Alteration of Multiple Macerals) technique. Analysis of available data suggests that potential vitrinite reflectance suppression may be identified using an empirical regression line which separates “suppressed” from “normal” Ro values based on the FAMM data. The “FAMM minimum regression line” was used to screen through Ro data from 142 wells (drilled between 1969 and 2005) in the Malay Basin and it is estimated that a quarter of those wells might be affected by suppression. Possible suppression was also noted in the Penyu Basin, where bottom-hole temperatures in some wells are consi...
Bulletin Of The Geological Society Of Malaysia, 2020
Following the successful production from fractured basement in similar Tertiary basins, the basem... more Following the successful production from fractured basement in similar Tertiary basins, the basement play was pursued in the Malay Basin, particularly during the 2000-2010 period but, unfortunately, that effort fell short of expectations. The only oil discovery in fractured basement reservoir was Anding in the southwestern part of the basin. Despite its development being delayed due to economic reasons, the Anding discovery had been the basis for the basement play concept: namely, a fractured reservoir formed of pre-Tertiary metamorphic rock, charged from overlying Tertiary lacustrine source rocks in an adjacent half-graben and sealed by a transgressive shale unit. This paper examines seismic, gravity and well evidences on the pre-Tertiary basement geology, with the aim of assessing further the hydrocarbon potential of pre-Tertiary basement. The pre-Tertiary basement subcrops beneath the Malay and Penyu basins represent a continuation of the onshore geology of Sundaland Mesozoic ter...
The new coastal Miri-Bintulu road intersects, near the Tusan junction some 40 km South of Miri, a... more The new coastal Miri-Bintulu road intersects, near the Tusan junction some 40 km South of Miri, a series of normal faults, vested in a 80 deg dipping clastic sequence located near to the core of the complex Lambir Anticline are observed. The outcrop shows beautiful examples of clay gouging, fault drag and concussion. Faults have been measured and correlated (Figs. 1, 2). Clay gouging indicate a correlation between gouging thickness and fault throw (Fig. 3). Development of fault rock (Fig. 4) is noted within competent (hence brittle) sandstone units, regardless of hanging wall or footwall position, whereas clay bodies react ductile and show fault drag. The authors intend to further investigate the clay gouge sealing capacity, calibrate the outcrop data with modeling packages such as FaultRiskTM, and approach industry players for sponsorship.
In an effort to reconcile different data sources (seafloor spreading, seismic and gravity images,... more In an effort to reconcile different data sources (seafloor spreading, seismic and gravity images, well calibrations, outcrop studies) in the South China Sea (SCS), we reviewed the unconformity records, in particular in the context with the shut-off of seafloor spreading in the SCS. With respect to the start of spreading, there is a consensus: ca. 34-41 Ma. Recent data infer an end of spreading, near to the magnetic Anomaly 5 = ca. 15.5 Ma (Langhian age). In Northwest Borneo, it is suggested that this event is coeval with the Deep Regional Unconformity (DRU) in Sabah and Brunei, and the Mid-Miocene Unconformity (MMU) in Sarawak. The MMU is also recognized in offshore Vietnam and Palawan, on the Western and Southeastern margins of the SCS, respectively. The MMU/DRU may constitute the border between active margin and passive margin deposits within the marine SCS sub-basins. The progradation of clastic shelves post-MMU/DRU may have hampered growth of bioherms whilst creating prolific s...
This paper reviews the complex interaction of basin subsidence, erosion and uplift of mountain ra... more This paper reviews the complex interaction of basin subsidence, erosion and uplift of mountain ranges that enclose the South China Sea (SCS). We found that recent uplift is a feature occurring dominantly at the fringes of the Sundaland Plate, around Sumatra/Java, Borneo, the Philippines and Taiwan. More significantly, there is a positive age correlation between regional unconformities, formation of oceanic crust and uplift of the peripheral mountain ranges. However, the magnitude of erosion related to each major unconformity can vary regionally, and could partly be subjected to climatic influence. The oldest truly regional unconformity recognizable is of very Late Oligocene age, and acts as an angular unconformity in Sabah, Sarawak, and the Malay/Penyu Basins (at Base ‘K’ level), at or very close to the base of the Miocene sedimentary package. We call this unconformity the Base Miocene Unconformity (BMU). Other than the BMU, the widely-known seismic event called the Mid-Miocene Unconformity (MMU) could be correlated with the end of proto-SCS spreading, and uplift may have occurred only in segments of the SCS, in particular at the southern fringe. The Late Miocene Shallow Regional Unconformity (SRU) points to a short compressive pulse that affected mainly areas of Sabah and Sarawak. The more recent Intra-Pliocene unconformity (IPU), commonly forming the base of some uplifted coastal terraces can be seen in particular in the south and eastern parts of the SCS, and correlates with uplift of areas such as NW Borneo and Taiwan. The event is a likely consequence of the Taiwan collision interplayed with the docking of the Philippines Plate in the Early Pliocene with NW Borneo at the Palawan/Philippines Margin. The Malay, Penyu, Natuna Basins and Vietnam Margin are predominantly Oligocene to Lower Miocene fills, whereas the NW Borneo Foredeep/Palawan Trough, deepwater Nam Con Son Basin and the Bunguran Trough have predominantly a Neogene fill. This observation points to a reduced extensional regime if compared with the south-eastern margin, where fault activity continued to the Mid/Late Miocene. The compiled uplift data in the surroundings of the SCS, as well as the presence of seismically mapped regional unconformities suggest that the greater Sundaland Plate has seen a number of extensions and compression/inversion/rotation phases; however there appears to be no positive evidence for the presence of microplates and/or subduction during the Oligocene/Miocene. In summary, crustal stretching, uplift and the resulting unconformities can be compared to different instruments of an orchestra playing individually; no harmonic tune can be achieved and there is little merit in looking at each contributing factor in isolation. Keywords: Eocene, erosion, sea-level changes, sediments, South China Sea, subsidence, unconformity, uplift, Tertiary.
The Eocene to Lower Oligocene deposits of the Penyu and Malay basins are formed by fluvial-lacust... more The Eocene to Lower Oligocene deposits of the Penyu and Malay basins are formed by fluvial-lacustrine deposits with marine influence in the latter. The sequence consists mainly of siltstone, with several intercalations of fine-grained sand and volcanic tuff. Based on well data, Mid-Upper Eocene sediments exist in Penyu Basin in the deeper parts of the half grabens and sub-basins. Hence, this implies the age of basin initiation at Mid-Eocene, rather than Oligocene as traditionally and commonly stated in the literature. By correlation, and as seismic evidences show, Eocene sediments also appear to exist in the deeper, undrilled parts of the Malay Basin, again implying that at the latest, a Mid-Eocene age of basin initiation.In the Penyu Basin, aprominent near-Base Oligocene Unconformity can potentially be correlated to the Base-Tertiary Unconformity in the adjacent Malay Basin, however the latter term implies all Tertiary sequences, including potential Paleogene deposits above the unc...
The greater Miri area in NW Sarawak can be seen as a basin extension of the NW Borneo Foredeep to... more The greater Miri area in NW Sarawak can be seen as a basin extension of the NW Borneo Foredeep to the onshore with uplifted and exposed outcrops of Neogene sediments suitable for both lithological and chrono-stratigratigraphic investigations. The Neogene sequence contains also up to four prominent unconformities that can be studied in a number of outcrops including the well-established Mid-Miocene Unconformity and the less well-defined Shallow Regional Unconformity, Intra-Pliocene Unconformity and the Lower Pleistocene Unconformity. However, it is noted that the geological timings of the unconformities observed are yet-to-be fully established due to a lack of detailed chrono-biostratigraphic investigations for age assignment of the exposed outcrops. Nonetheless, the stratigraphic importance and the presence of the mentioned unconformities may be related to other established regional tectonic events mapped in offshore Sarawak and Sabah with better seismic coverage. Their significance cannot be underestimated and may provide a better insight on the regional uplift history and the tectonic evolution of the structurally complex NW Borneo margin.
The greater Miri area offers particularly well-exposed examples of fault geometry and clay gougin... more The greater Miri area offers particularly well-exposed examples of fault geometry and clay gouging. Such data are important analogues for predicting, or to simulating pressure and retention of hydrocarbon columns in fields in Brunei, Sabah and Sarawak. This short paper focuses on two excellent outcrop areas, where measurements were dominantly carried out on normal faults. Our fieldwork suggests a good correlation between normal fault throw, and gouge thickness. The studied outcrops offer further research potential in the areas of gouge mineralogy, gouge stratification and pressure retention.
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