CBTH Researchers at AAPG ICE 2013

• TITLE: Subsurface Structure, Stratigraphy and Hydrocarbons of the Falcon Basin: An Inverted, Hydrocarbonbearing Rift Basin in Western Venezuela
  AUTHORS: Joan M. Blanco (1), Paul Mann (1), Peter Bartok (2)
  INSTITUTIONS: 1. Earth and Atmospheric Sciences, University of Houston, Houston, TX, United States. 2. Bartok, Inc., Houston, TX, United States.
  ABSTRACT: The surface geology of the Falcon basin (FB) of western Venezuela has been intensively studied since the early studies of Senn, Kugler and Renz in the 1930s and 40s. In this presentation we use 2000 km of 2D seismic data, 1130 km2 of 3D seismic data, and 65 correlated wells within the basin and on its northern flank to define its regional stratigraphic and structural history. This history provides many useful insights and analogs for ongoing exploration to the northwest in the Gulf of Venezuela and to the east in the deepwater Bonaire basin. The main structures of the FB consist of: 1) a well imaged, northern border thrust dipping NE; 2) an anticlinorium of basin fill with ENE-WSW vergence and ranging in age from middle to late Miocene with fold axes trending east - northeast and wavelengths of 5 to 12 km; 3) northeastern border thrusts in the eastern offshore basin in the transition area to the Bonaire basin; and 4) a southern boundary thrust that is not covered by the seismic data used in this study. Wedging along subsurface stratigraphic units seen on seismic and in wells show that the main phase of NS extension occurred along EW-striking normal faults from Eocene to Oligocene and NS shortening and normal fault inversion began in the Late Miocene and extends up to the present day. The timing of extension (Late Oligocene – Early Miocene) is younger than observed in the offshore Bonaire basin (Paleogene) and may be related to a slab rollback effect following the emplacement of the Lara nappes to the south. Marine source rocks of Oligocene-Miocene age are present across the basin and appear to have matured during deep burial in early Miocene time; reservoirs are mainly well sorted, coastal sands now deformed into tilted antinclines formed during Late Miocene to recent fault inversion. For 2000, the official production of the basin was 375 MMBO of mainly light oil. While the earlier extensional history of the FB is shared with the Gulf of Venezuela and Bonaire basin, the late inversion history of the FB appears localized as a result of NS shortening of the basin between the northwardmoving Maracaibo block and the Paraguaná basement block of NW Venezuela.



• TITLE: Cenozoic Source Rocks of the Southwestern Nicaraguan Rise, Caribbean Sea: Distribution, Burial History, and Maturation
  AUTHORS: Luis Carlos Carvajal Arenas (1), Paul Mann (1), K.K. (Adry) Bissada (1), Mike Saunders (2)
  INSTITUTIONS: 1. Earth and Atmospheric Sciences, University of Houston, Houston, TX, United States. 2. Spectrum Geo Inc., Houston, TX, United States.
  ABSTRACT: Understanding the burial and thermal maturation histories of the main source rocks in the Southwestern Nicaraguan rise (SWNR) is critical for defining and characterizing the petroleum systems in this frontier region characterized by localized, fault-bounded depocenters. This study utilized data from five exploratory wells with TOC%, four ODP-DSDP wells, more than 5500 Km of 2D seismic, and surficial - bottom hole heat flow measurements. Exploration wells have previously documented oil and gas shows in the stratigraphic interval from Lower-Middle Eocene through Miocene in SWNR. Lower-Middle Eocene source rocks encountered in these wells correlate with the Yellow Limestone and Chapelton Formations of Jamaica; Jamaican samples show Total Organic Matter (TOC %) of 15.32%; with an average of 3.83%. Miocene source rocks present in Perlas-3 well (Nicaragua) share same age range and similar TOC% as Monterey interval in California (maximum 6.23%, average 2.76%) indicating the possibility of the same Monterey paleoceanographic event affecting large areas of the Caribbean Sea. The purpose of this work is to establish the lateral continuity of the Eocene-Miocene source rocks into the SWNR, to define zones that have reached the oil window, and to examine potential migration pathways. Source rocks found in the SWNR corresponds to 1) Lower Eocene, dark greenish-gray , calcareous clay with total thickness of 56 m; 2) Middle Eocene calcareous limestone-claystone with thickness average of 132.3 m; 3) Middle Miocene greenish-gray, foram-rich chalk with 139 m of total thickness. In order to determine the Source Potential Index (SPI) (Tissot et al., 1980), adjacent wells were used to extrapolate known TOC % values across the 225,000 Km2 study area. TOC% values range from 2.76 to 3.83%, and heat flow values vary between 2.5°C to 3.5°C per 100m. Considering all the limitations present in SWNR, we conclude that i) an expulsion of 10.5 MMBO of oil per km2, ii) main depocenters were recognized ranging between 3 to 8 km depth; in which, according to subsidence plots, source rocks reached the oil window between the intervals 3 to 3.5 km, and iii) the migration is most likely vertical than laterally drained due to the high angle faulting (polygonal faults) present between the Eocene-Miocene intervals; iv) therefore, we consider that the main possibility to find hydrocarbon accumulations is close to the depocenters of the source rocks. Possible reservoirs and seals are illustrated.



• TITLE: Early History of the Orinoco Delta on the Northeastern Margin of South America
  AUTHORS: Karilys Castillo (1), Paul Mann (1)
  INSTITUTIONS: 1. Earth and Atmospheric Sciences, University of Houston, Houston, TX, United States.
  ABSTRACT: The 12-km-thick Orinoco delta in the Atlantic Ocean of northeastern South America is formed by the Orinoco River which is the seventh largest river in the world and drains an 880,000 km2 area that extends across the continent to the northwestern Andes. This study uses 620 km2 of 3D seismic, 650 km of 2D seismic, and 14 wells with well logs from the Punta Pescador area of northeastern Venezuela near the Columbus Channel and border with Trinidad combined with maps from previous subsurface studies to the west (8500 km2) and east (10000 km2) in Venezuela and to the southeast in Guyana (3000 km2) to reconstruct the margin geometry and paleogeography prior to the arrival of the Orinoco delta in its present location. The main seismic sequences in the northern area in Venezuela consist of: 1) transgressional, 1.2 to 3-km-thick Lower Miocene marine sandstone and shale deposited in a foreland basin setting and with a basal foredeep unconformity dated approximately 25.5 Ma and a top defined by the Middle Miocene unconformity dated at 16.5 Ma; 2) regressional late Miocene shallower water marine sandstone and shale overlying a major erosional unconformity marked by deepwater channels on the slope filled by shale; previous workers have correlated this unconformity with the latest Miocene (Messinian) eustatic low stand event. In the southern area, the margin of Guyana exhibits a similar late Miocene erosional event that we correlated with this latest Miocene event. Based on correlations of these major units and unconformities along the margin, we propose the following sequence of events affecting the development of the Orinoco delta: 1) ponding of fluvial-deltaic sediments of the Orinoco fluvial system in the restricted marine embayment of the Eastern Venezuelan foreland basin during the Oligocene and Miocene; the onset of major input of the Orinoco in this area is thought by most workers to be Late Miocene in age; 2) the late Miocene event lowered sea level and produced a major erosional event that breached a continental high that allowed the Orinoco delta to suddenly prograde into the deeper water Atlantic area in the earliest Pliocene; and 3) early Pliocene to recent progradation of the Orinoco delta is well documented into the deeper water areas of Trinidad and offshore Venezuela.



• TITLE: Application of Seismic Attributes and Fluvial Channel Morphology in the Carbonera Formation in the Llanos Foreland Basin of Colombia
  AUTHORS: Lucia Torrado (1), Paul Mann (1), Janok Bhattacharya (1)
  INSTITUTIONS: 1. Earth and Atmospheric Sciences, University of Houston, Houston, TX, United States.
  ABSTRACT: Hydrocarbon exploration in the Llanos foreland basin of Colombia has been focused on the basis of structural entrapment. However, in the last decade the country´s oil demand has generated an increased interest in exploration of stratigraphic traps. The study integrated 700 km2 of 3D seismic data volumes with 9 wells in the eastern Casanare Province. The objective of the study is to assess the reservoir potential of the fluvial channel deposits of Late Eocene-Oligocene Carbonera Formation in the Casanare Province, where distinguishing non-productive, mud-filled channels from productive sand-filled channels becomes important, since both channel types can appear similar on seismic character. Interpretation of the reservoir distribution includes 3D seismic attributes such as coherence, curvature, and spectral decomposition, as well a complimentary fluvial geomorphology, and well data analysis. Flattened time slices through coherence, iso-frequency cubes, and curvature cubes respectively show: 1) a meandering fluvial system with changes in the rivers’ paleoflow directions from southwest to northeast, and development of tributaries systems with a northwest to southeast orientation, 2) development of prospective sandy point bars, scrolls and sand bars deposits, not shown initially by coherence, and 3) most positive and most negative curvature shows ridges and channel base based on differential compaction dependant of the channel´s filling material, where some fluvial channels fills has been reinterpreted as non prospective mud plugs with good sealing attitude. Finally, variations in accommodation and sediment supply conditioned the morphology of these fluvial deposits, where the channels exhibit: i) moderate width to depth (W/D) ratio, moderate sinuosity with high avulsion frequency for the main drainage; ii) low W/D ratio, low sinuosity with high lateral accretion for the tributary channels in member Carbonera 1; iii) higher mud content in the Carbonera members 3 to 5; iv) wider channels with thicker floodplain deposits, localized sandstone bodies, higher avulsion rates in Carbonera member 5 to 3; v) fewer intra-formational seal development in the Eastern Llanos area, and vi) sand-prone channels deposits in the Carbonera member 7 with high lateral migration.