Miocene Sands Research Articles

Petrophysical and seismo-stratigraphic analysis of the tertiary formations of the South onshore of the Rio Del Rey Basin (Cameroon margin, Gulf of Guinea) from well logs and seismic data

The present study used well log and seismic data to determine the main lithology types, characterize and evaluate the reservoirs properties and discuss about the hydrocarbon quality and productivity in the onshore south of the Rio Del Rey Basin (RDRB). The main results show seven lithologies inside the Isongo, Diongo and Nguti including clays, sandstones and clayey sandstones, the most dominant, and limestones, dolomites, sandstone limestones and clayey limestones, the less dominant. Seventeen reservoir zones with fifteen gas-bearing and two oil-bearing were identified in the Miocene sands of the Isongo, Diongo and Nguti Formations and very few in the Upper Oligocene sands of Akata Formation. The average values of petrophysical parameters obtained are Vshale (13.26–31.3%), NTG (64.48–87.07%), ∅eff (18.54–26.60%), ∅avg (23.27–33.59%), Sw (4.84–11.10%), Shc (88.90–95.16%), and K (1258.96–2187.26 mD). It shows that the identified reservoirs are of the good quality and can be commercially viable for the gas. Knowing that the RDRB and the neighbouring ones (Niger Delta, Rio Muni and Gabon basins which are OPEC members) have good petrophysical parameters, findings from this investigation show that the key difference between RDRB and others lay on the low continuity and vertical extension of these reservoirs, as well as the lower sedimentary thickness (6–7 km), the tectono-stratigraphic architecture and the production essentially focused on the Miocene horizons.

Rejuvenating exploration opportunities in Egypt's Mediterranean region using basin-scale 3D seismic reprocessing and subsurface evaluations

The Eastern Mediterranean region has proven to be a key province for natural gas resources over the last two decades. Gas discoveries in the Nile Delta Basin, Levantine Basin, and over the Eratosthenes platform have proven that an efficient working petroleum system extends to the deepwater areas and into the distal parts of the Nile Delta and Levantine basins. While the suprasalt biogenic post-Messinian play is adequately imaged in various areas in the Eastern Mediterranean region, seismic imaging of the deeper subsalt pre-Messinian plays is challenged by legacy seismic acquisition and processing techniques. Moreover, the complexity of the Messinian salt structures and the heterogeneity of the lithology of the Messinian layer across the Mediterranean basins represent a key subsurface challenge. In phase 1 of the study presented in this paper, we reprocessed 12 legacy 3D seismic data sets over 12,000 km2 and constructed a consistent basin-scale earth model from the shelf areas offshore Sinai to the deepwater areas around the Zohr carbonate platform. The data processing and imaging sequences incorporate full-waveform inversion and tomography in the earth model building process followed by a basin-to-lead evaluation to delineate exploration opportunities in phase 1. The evaluations resulted in delineating Cretaceous and Oligo-Miocene untested structures. Furthermore, potential deepwater Lower Miocene sand fairways were outlined, supported by improved regional seismic imaging and consistent seismic attributes over multiple legacy surveys. The authors of this paper expect to update the results of their work after completing the earth model building and the prestack depth migration workflows of an additional 13 legacy surveys over 35,000 km2 in phase 2 of the study.

Early Miocene sand wedge deposits in Southwestern Tarim Basin and Implications for the Uplift of the Northern Tibetan Plateau

The uplift of the Tibet Plateau and its climatic effects have long been a hot topic in academic research. However, there is still significant controversy regarding the uplift history and related climate changes along the northern margin of the plateau. In this paper, we present sand wedge deposits from the base of the Wuqia Group (∼20 Ma) on the southwestern Tarim Basin, representing the oldest reported sand wedges in the Tibetan Plateau. A comprehensive study was conducted on lithostratigraphy, sedimentary environment, and macroscopic–microscopic features of the sand wedge deposits. The results indicate that the lithostratigraphic succession preserving the sand wedge deposits consists mainly of lenticular conglomerates and cross-bedded gravelly sandstone interbedded with medium–thin-bedded mudstone, consistent with the braided fluvial environment. The sand wedge deposits commonly exhibit a V-shape geometry and are filled with gravelly sandstone, with the gravels arranged parallel to the walls of the wedge. The clasts of the wedge-filled sandstone are well-rounded and show a unimodal grain size distribution. The quartz surfaces commonly display dish-shaped and crescent-shaped impact features, indicating an eolian origin and an arid climate. Based on the relationship between the formation temperature of modern sand wedges, the atmospheric temperature gradient, and altitude, the reconstructed paleo-elevation of the sand wedge deposits at the base of the Wuqia Group in the southwestern Tarim Basin is approximately ∼ 1000 m. These results indicate that the northern margin of the Tibet Plateau had already reached an elevation of ∼ 1000 m during the Early Miocene, forming a seasonal arid and cold climate.

Palaeontological and taphonomical investigations of the exceptionally rich concentration of Miocene vertebrate coprolites from Pécs-Danitzpuszta (Hungary, Mecsek Mts.)

ABSTRACT Thousands of coprolites have been collected from the Upper Miocene (Tortonian/Pannonian) sands of the Pécs-Danitzpuszta sand pit, one of the most important mixed Neogene vertebrate localities in Hungary. Although, the locality has been known for centuries, the coprolites have not been investigated in detail. We describe these fossils and explore their palaeoecological significance. Coprolites were examined with thin sections, X-ray powder diffraction and computed tomography. Their surface is mostly smooth, desiccation cracks were not observed. All coprolites mainly consist of apatite, indicating most probably a carnivorous diet. No evidence of herbivory has been found so far. The coprolites contain remains belonging to several groups: ostracod carapaces, bivalve shells, vertebrae from bony fishes, fish scales, as well as teeth. The CT scans show inhomogeneities in the matrix; however, in most cases they do not reliably indicate inclusions. The taphonomical features suggest rapid burial and most likely an aquatic origin. The spiral morphotype could be attributed to fishes with spiral intestinal valves. Teeth of reef-associated fish taxa indicate Badenian age for some specimens, though the coprolite assemblage might include older and younger specimens as well.

Fossils from the Upper Miocene (Pannonian) sands of the Pécsvárad sand pit (Eastern Mecsek Mts., SW Hungary)

The Mecsek Mountains in SW Hungary represent an uplifted basement block of the Pannonian Basin. Their Neogene cover includes deposits both from the Middle Miocene Central Paratethys and from its Late Miocene (Pannonian) brackish?water descendant, Lake Pannon. Along the mountain front, the Pannonian sands of the P?csv?rad sand pit contain a mixed vertebrate fossil assemblage, which gives insight into terrestrial and aquatic biota during various time intervals of the Miocene. The fossil?bearing sands accumulated between 7.6?6.8 Ma, in a high?energy littoral setting of Lake Pannon, as indicated by the mollusc remains. The verte brate fossil assemblage is relatively diverse compared to the number of finds. The most abundant group, aquatic mammals, encompasses a minimum of four odontocete species and a few mysticete taxa, which originally lived in the Para tethys during the Badenian and the Sarmatian. Rhinocerotid remains are reworked from sediments aged somewhere between the Karpatian and earliest Pannonian. The single shark tooth must be Badenian, and the scombrid fishes probably also date back to that age. Fossils of other fishes (sparids, latids and acipenserids), giant salamanders, turtles, crocodilians and cervids might originate from older Miocene deposits but can be coeval with the host sands as well. Tapirs and giraffids must have lived on the lakeshores of Lake Pannon, probably contemporaneously with sand deposition or not much earlier. The erosion, enrichment and mixing of the fauna is a result of the uplift and denudation of the Mecsek Mountains during Lake Pannon sedimentation, caused by neotectonic basin inversion. This example shows that in spite of the uncertainties in the dating of some fossils, mixed faunas can provide important data on the evolution history of an area.

Elastic full-waveform inversion on Caesar-Tonga — Case study

Full-waveform inversion (FWI) has been widely used on 3D data sets to build detailed velocity models over the past 10 years. Most of these projects used pressure data and an acoustic approximation, with the assumption that the field data were dominated with P-waves. This approach of FWI can determine parameters related to the acoustic wave equation. It focuses on updating velocities by minimizing the misfit between observed and model data. Acoustic FWI, using the pressure component of collected data, has shown tremendous potential in simple geologic settings. Successful FWI projects, using wide-azimuth streamer, ocean bottom, and land survey geometries, have convinced the oil industry to pursue the next step by involving more physical properties. However, questions remain on how far we can properly describe field data with the acoustic approximation and at what point we need to switch to a much more expensive elastic wave equation implementation. In a complicated geologic region such as the Gulf of Mexico (GoM), the seismic wavefield can be complex and elastic FWI is needed to achieve a better velocity model, even when using mostly pressure data alone. We demonstrate the application of elastic FWI on sparse-node ocean-bottom-node data from the GoM and show comparisons to the acoustic solution. The comparisons demonstrate the benefits of the elastic FWI implementation when applied to image steeply dipping Miocene sands beneath a complex salt canopy, despite the increased computational expense. Furthermore, we demonstrate that when elastic FWI is applied to sufficiently high frequencies, the FWI-derived reflectivity product and velocity model are reliable interpretation products.

Unstructured-grid approach to develop high-fidelity groundwater model to understand groundwater flow and storage responses to excessive groundwater withdrawals in the Southern Hills aquifer system in southeastern Louisiana (USA)

Study regionThe Southern Hills aquifer system (SHAS) in the Louisiana Capital Area Groundwater Conservation District (CAGCD), USA. Study focusThe SHAS provides abundant groundwater for public and industrial supplies in the CAGCD. Groundwater depletion, saltwater intrusion, and land subsidence are potential concerns due to prolonged excessive groundwater withdrawals. This study develops a high-fidelity groundwater flow model utilizing a complex unstructured grid to investigate groundwater flow and storage responses to excessive groundwater withdrawals for the SHAS in the CAGCD. The groundwater model incorporates the Mississippi River alluvial aquifer down to the Miocene sands extending to depths around 1 km. New hydrological insightsGroundwater modeling results indicate large cones of depression in the Evangeline and Jasper formations in the Baton Rouge area due to prolonged groundwater withdrawals. Low-permeability faults are inferred by significant groundwater level difference across the faults. While local groundwater storage depletion in deeper aquifers is evident, overall estimated groundwater storage changes of the SHAS in the CAGCD are close to zero in the past two decades, indicating insignificant groundwater storage changes. This is attributed to dominant interactions between the major rivers and the shallower alluvial aquifer. In addition, the simulated groundwater storage changes exhibit patterns similar to those derived by the Gravity Recovery and Climate Experiment (GRACE) model that has been used in evaluation of groundwater depletion in many regional studies.

E&P Notes (August 2022)

E&P Notes (August 2022)

The Great Preglacial “Bell River” of North America: Detrital Zircon Evidence for Oligocene–Miocene Fluvial Connections Between the Colorado Plateau and Labrador Sea

The idea of a great pre-glacial river that drained much of North America into the Arctic waters of modern Canada was first suggested in 1895 by Robert A. Bell. In the 1970s, petroleum exploration in Hudson Strait and the Labrador Sea located the massive, submerged delta of what is now known as the Bell River. Reconstructions suggest that three main branches of the Bell River joined up near modern Hudson Bay. The eastern branch largely drained the Canadian Shield, but the central and western branches had headwaters in the Cordilleran orogenic belt and its foreland in the present-day U.S. and northwestern Canada, respectively. We present new detrital zircon U–Pb data from Lower Oligocene and Lower Miocene sand from an exploration well in the Saglek delta of the northern Labrador Sea. In conjunction with other detrital zircon results from the Labrador Sea (and elsewhere) these data record the configuration and history of this continental-scale drainage basin in more detail. Mesozoic and younger detrital zircon grains (< 250 Ma) are subordinate to Precambrian age groupings, but Cenozoic populations become more abundant during the Oligocene, suggesting that the basin had expanded into areas now occupied by the Colorado Plateau and the Basin-and-Range Province. Proterozoic and Phanerozoic detrital zircon grain populations in Saglek delta sediments are similar to those of the Pliocene Colorado River. The results support an earlier idea that initial incision of the Grand Canyon and denudation of the Colorado Plateau were associated with a north-flowing paleo-river that fed into the Bell River basin. This contribution continued until the Pliocene capture of this ancestral river by the Gulf of California basin, after which the excavation of the modern Grand Canyon was completed. The Bell River drainage basin was later blocked by the expansion of Pleistocene ice sheets.

Triassic evaporites and the structural architecture of the External Hellenides and Albanides (SE Europe): controls on the petroleum and geoenergy systems of Greece and Albania

A combination of well data, seismic information on thrusting and tectonic shortening, plus analyses of the nature and depth of the Mesozoic units related to main detachment horizons (Triassic evaporites, flysch), are used to review, and further update the complex structural styles of the External Hellenides and Albanides Orogenic Belts, SE Europe. In the study area, the late Alpine orogenic evolution resulted in a structural architecture characterised by the successive westward thrusting of tectonic nappes (Gavrovo/Kruja, Ionian), with an imbricate tectonic style prevailing in all external zones. In the internal and central Ionian zone, imbricate thrusts and duplex structures are recorded, especially where about 24 km of stacked Mesozoic–Tertiary successions have been formed in Albania. Triassic evaporites, up to 3.5 km thick, acted as a detachment horizon for the internal deformation of the Ionian and Pre-Apulia zones (1.7–1.8 km thick in Greece), whereas the flysch unit of Upper Eocene–Oligocene (External Hellenides) and Oligocene–Aquitanian (Albanides) contributed to the deformation of the Ionian zone. In the Ionian zone, Triassic evaporites are laterally continuous and act as an effective seal unit when thrusted above Mesozoic carbonate/Tertiary units. Most of the oil and gas fields, oil shows and surface seeps have been developed in association with the relative more complex structure styles in the internal and the central Ionian zone of Albania and Greece. The Triassic evaporite detachment is detected at depths of 8–22 km in Albania, and about 5 km to 12–13 km in Greece. Thin and probably combination of thin- and thick-skinned deformation (SW Greece) of the Meso-Cenozoic succession above the Triassic evaporite and Permian sequences better depicts the complex structural architecture of the External Hellenides and Albanides, later affected by strike-slip tectonics and extensional deformation active since the Early Pliocene times. The main source rock levels, Lower Cretaceous shale/carbonate, Toarcian Posidonia and Triassic shales, are common in the Albanides and the Hellenides forelands. The thickness and Total Organic Carbon of these levels significantly increase in Albania, whereas trapping mechanism is almost the same and the Triassic evaporites play a significant role in both forelands. The hydrocarbon migration primarily followed developed thrust faults and important halokinesis, to charge fractured Cretaceous–Eocene carbonate reservoirs in the overthrust unit (Ionian zone), likely beneath the thrusted anticlinal belts. These sub-thrust structural models are related to the evaporites. Sub-thrust plays, referred to the autochthonous units (Apulia, Pre-Apulia/Paxos, Sazani zones), may also present reservoir potential in Albania and Western Greece. Upper Miocene and Pliocene deposits (sands) record reservoir potential in stratigraphic traps and good caprock characteristics in the Peri-Adriatic depression (Albania), whereas Messinian evaporites and clays may document seal potential for Upper Miocene sands in the southern areas of the Ionian Sea (Kyparissiakos Gulf, SW Kythira).

Middle Miocene (Badenian) macroinvertebrates from Pécs-Danitzpuszta (Mecsek Mts, SW Hungary)

This paper examines Badenian (middle Miocene) macroinvertebrates – corals and molluscs – from the Pécs-Danitzpuszta sand pit (Mecsek Mts, SW Hungary) in order to extend our knowledge on Miocene normal marine deposits of the Mecsek region. Corals occur reworked in the upper Miocene sand that was deposited in the brackish Lake Pannon, and presumably originate either from the middle Badenian Pécsszabolcs or the upper Badenian Rákos Member of the Lajta Formation. A total of seven taxa were identified. These taxa suggest subtropical conditions and a lack of coral reefs in the Badenian. Molluscs were found in situ in the upper Badenian Szilágy Clay Marl Member of the Baden Formation and the Rákos Member of the Lajta Formation. They dominantly consist of bivalves and represent benthic assemblages typical of the middle Miocene Central Paratethys.

Variation of sediment provenance at the 09 - 1 Block, Cuu Long Basin: their significance in assessing the Oligocene - Miocene reservoir quality

The Cuu Long Basin is one of the Tertiary sedimentary basins situated on the continental shelf of Vietnam, which demonstrates the high potential of oil and gas. Apart from fractured granite reservoirs, the Oligocene - Miocene sand bodies are thought to have significant potential for forming non - structural traps. The results of the study on the composition and physical properties of the sediments derived from wells "X" and "Y", block 09 - 1, Cuu Long Basin show that there is a clear difference between the Late Oligocene and Early Miocene sandstone in the well "X", namely the Miocene sandstone shows larger particle size, higher roundness and sortness (TB: 434.2; Ro: 0.69; So: 2.22) than those of the Late Oligocene sandstone (TB: 104.28; Ro: 0.64; So: 1.46). This difference is likely attributed to the fact that the Miocene sandstone was influenced by the marine environment, which intensified the roundness and sortness. Meanwhile, the well "Y" did not show much difference in the physical parameters of the sediments between the Late Oligocene and Early Miocene age ranges. However, the grain size was slightly increased and the roundness was less during the Early Miocene. It is possible that the “Y” well is located closer to the local source. The variation in the physical parameters of the sediments, proportion of sand grains and clay minerals shows that the quality of late Oligocene reservoir is better than that of Early Miocene reservoir, and the Late Oligocene reservoir quality in the "X" well is better than that in the borehole "Y".

Geogenic organic carbon in terrestrial sediments and its contribution to total soil carbon

Abstract. Geogenic organic carbon (GOC) from sedimentary rocks is an overlooked fraction in soils that has not yet been quantified but influences the composition, age, and stability of total organic carbon (OC) in soils. In this context, GOC is the OC in bedrock deposited during sedimentation. The contribution of GOC to total soil OC may vary, depending on the type of bedrock. However, no studies have been carried out to investigate the contribution of GOC derived from different terrestrial sedimentary rocks to soil OC contents. In order to fill this knowledge gap, 10 m long sediment cores from three sites recovered from Pleistocene loess, Miocene sand, and Triassic Red Sandstone were analysed at 1 m depth intervals, and the amount of GOC was calculated based on 14C measurements. The 14C ages of bulk sedimentary OC revealed that OC is comprised of both biogenic and geogenic components. The biogenic component relates to OC that entered the sediments from plant sources since soil development started. Assuming an average age for this biogenic component ranging from 1000–4000 years BP (before present), we calculated average amounts of GOC in the sediments starting at 1.5 m depth, based on measured 14C ages. The median amount of GOC in the sediments was then taken, and its proportion of soil mass (g GOC per kg−1 fine soil) was calculated in the soil profile. All the sediments contained considerable amounts of GOC (median amounts of 0.10 g kg−1 in Miocene sand, 0.27 g kg−1 in Pleistocene loess, and 0.17 g kg−1 in Red Sandstone) compared with subsoil OC contents (between 0.53 and 15.21 g kg−1). Long-term incubation experiments revealed that the GOC appeared comparatively stable against biodegradation. Its possible contribution to subsoil OC stocks (0.3–1.5 m depth) ranged from 1 % to 26 % in soil developed in the Miocene sand, from 16 % to 21 % in the loess soil, and from 6 % to 36 % at the Red Sandstone site. Thus, GOC with no detectable 14C content influenced the 14C ages of subsoil OC and may partly explain the strong increase in 14C ages observed in many subsoils. This could be particularly important in young soils on terrestrial sediments with comparatively low amounts of OC, where GOC can make a large contribution to total OC stocks.

Construction and application of an adapted rock physics template (ARPT) for characterizing a deep and strongly cemented gas sand in the Nam Con Son Basin, Vietnam

The Hai Thach field is one of the biggest gas and condensate producing fields in Vietnam. Located in the Nam Con Son Basin, offshore southern Vietnam, the field consists of multiple, stacked reservoir units, for which petrophysical characterization is challenging and a site-adapted rock physics template (ARPT) was proposed to solve this task. As reported in many publications, rock physics templates (RPTs) have been successfully applied for the characterization of shallow unconsolidated and weakly cemented reservoirs with cementation of less than 5% like in the North Sea or some other sites. However, the construction of RPT is very site-dependent. In this study, an approach of rock physical modelling, named the adapted stiff sand model (ASSM), was proposed to construct a site-adapted RPT of Vp/Vs versus acoustic impedance (AIP) for characterizing the upper part of Middle Miocene Sand in the Nam Con Son Basin, which is a 3.5-km deep and strongly cemented gas sand with 10% up quartz-overgrowth and clayey cementation. A key point in this approach was the use of a modified Biot-Gassmann's equation and in situ well log data to calculate the dry moduli of reservoir rock frame. As a result, the elastic and petrophysical parameters of this upper MMS sand, named as MMF30, are well evaluated, i.e., AIp from 9000 to 11,000 m/s*g/cc, Vp/Vs from 1.65 to 1.8, porosity from 12 to 16%, and gas saturation from 50% up, which match well with the core data and were used further in a prestack elastic inversion of a seismic inline that could map well the multiple stacked gas zones of the study reservoir. The rock physical modelling approach in this study could help characterize successfully deep and highly-cemented clayey gas sands in the Nam Con Son Basin.

Numerical Simulation of Low Salinity Water Flooding on Core Samples for an Oil Reservoir in the Nam Con Son Basin, Vietnam

Low-salinity water flooding (LSWF) is environment-friendly and operates similarly to conventional waterflooding without the need for synthetic chemical materials. The application of LSWF makes sense in Vietnam as HC production has steadily declined since 2002, and the majority of main oil fields have become near mature and mature fields. In the next years, Enhanced Oil Recovery (EOR) should be a top priority for Petro Vietnam to boost its oil production, for which the key issue is how to select a suitable EOR technology. In this study, LSWF of the Lower Miocene sand using low salinity water from Lower Oligocene sand was investigated. Previously at the Ruby field in the Cuu Long Basin, an LSWF feasibility study was carried out based on a conventional core flooding experiment, which is time-consuming and costly. This study targets the Chim Sao field in the Nam Con Son Basin, for which a cheaper and faster assessing method is required. As a result, a numerical code written in Matlab was developed and successfully validated with the core flooding experiment results obtained at the Ruby field. The LSWF simulation was conducted using the multiple ion-exchange mechanisms (MIE), and the results obtained showed an increase in the oil recovery factor by 2.19% for the Lower Miocene Sand. Another important outcome of this study is the innovative proposal and successful simulation to use the abundant low salinity water from the underlying Lower Oligocene sand as a natural LSW source to inject into the Lower Miocene oil reservoir that can be a decisive factor to help apply LSWF in practice on a wide scale not only for Chim Sao but also other similar oil fields in southern offshore Vietnam.

Diversity and biostratigraphy of the late Oligocene-late Miocene sand dollars (Echinoidea: Scutelliformes) of Argentina and Uruguay

Introduction: Scutelliforms were diverse and widespread in shallow marine environments during Neogene times in South America. Nevertheless, they have almost never been used as biostratigraphic tools. Objective: To provide a refined stratigraphic frame useful for calibrating temporal dimensions of scutelliform diversity from Argentina and Uruguay and its correlation with the molluscan assemblages previously proposed. Methods: A detailed survey of their geographic and stratigraphic provenance was carried out. We revised both the bibliography and collections (institutional and from our own field work). Results: The group is represented by 14 species belonging to six genera, and four assemblages were identified. Numerical dates of the Neogene marine rocks obtained recently allowed their placement in a chronological scheme: “Iheringiella” sp. A is restricted to the late Oligocene, the genera Camachoaster and “Eoscutella” and the species Monophoraster telfordi to the early Miocene, Abertella gualichensis and Abertella miskellyi to the middle Miocene, and Monophoraster duboisi, Amplaster coloniensis and Amplaster ellipticus to the late Miocene. Non-lunulate scutelliforms are not restricted to the late Oligocene as previously supposed. The oldest occurrence of the genus Monophoraster corresponds to the early Miocene, and along with Iheringiella are long-living taxa that embrace the 25.3 Ma-18.1 Ma (Iheringiella patagonensis) and approximately 15 Ma-6.48 Ma (Monophoraster darwini) intervals. The presence of Iheringiella in the early Miocene of northeastern Patagonia is corroborated, reaching there its northernmost distribution. Monophoraster darwini has a temporal range from the late Miocene (where it was previously thought to be restricted) back to the middle Miocene, since this is the species yielded in the well-known and discussed “Monophoraster and Venericor Beds”. Conclusions: The Paleogene-Neogene scutelliforms of Argentina and Uruguay range from the late Oligocene to the late Miocene. There is a good correspondence among the numerical ages, molluscan biozones and scutelliform assemblages.

The effects of lithology and facies types on the anisotropy parameters and upscaling factor of the sand reservoirs in the deep-water Sadewa field, Kutei Basin, East Kalimantan, Indonesia

Abstract The anisotropy and upscaling factors adjustment are very important in the proper integration of the core ultrasonic and log sonic data for hydrocarbon reservoir characterization. Related to this issue, this paper evaluates the effects of the lithology and facies types on the anisotropy parameters and upscaling factor. The data are taken from the deep-water oil-gas Sadewa field located in the Kutei Basin, East Kalimantan, Indonesia at water depths of 500–750 m. The main reservoirs in this field are the Upper Miocene sand reservoirs deposited in the upper slope fan and channel facies. Fifty core plugs sampled at depths around 3000–4000 m were collected for thin-section petrography analysis and ultrasonic measurements. The thin-section petrography analysis shows that both facies areas are dominated by greywackes with parallel lamination structure and/or intergranular porosity. The 1 MHz ultrasonic velocities were measured in the 50 core plugs. Meanwhile, 10–40 KHz dipole sonic log data sampled at the same plug’s depth positions were used to calculate the elastic (Vp, Vs, Poisson ratio, etc) and Thomsen’s e, γ and δ anisotropy parameters. The results show that for the parallel lamination and intergranular porosity greywacke samples, e parameter is the best for compensating the anisotropy effect in the integrated core and log data reservoir quality determination (sand shale ratio, percentage of quartz contents, the effective and the total porosities). However, when the samples are non-intergranular porosity greywacke, the anisotropy effect in the core-log data correlation, is too irregular to be compensated by any elastic and anisotropy parameter. The core-log data upscaling factor in the channel facies is much smaller than the upper slope fan facies, and it is in line with the gamma-ray log data which indicates that the sandy channel facies is more homogeneous than the intercalated shale-sand upper slope fan facies. The overall results suggest that the lithology and facies types significantly affect the anisotropy parameters and upscaling factor. In addition, the best elastic or anisotropic parameters) should be determined to minimize the effects in the core and log data integration for hydrocarbon reservoir characterization.

Detrital zircon and rutile U–Pb, Hf isotopes and heavy mineral assemblages of Israeli Miocene sands: Fingerprinting the Arabian provenance of the Levant

AbstractIsolated, Miocene continental basins scattered over Israel and Jordan represent the remnants of a continental‐wide fluvial system, which originated in Arabia and transported siliciclastic sediments westward to the deep Levant Basin. These basins define two geographically separated sedimentary provinces. The detrital zircon age spectra in both provinces are dominated by Neoproterozoic U‐Pb ages (550–1,000 Ma), resembling those of Paleozoic‐Mesozoic sandstones exposed along the uplifted Red Sea Rift flank. However, while the southern province exhibits two prominent peaks at ~600 and ~1,000 Ma, similar to those seen in Cambrian‐Ordovician sandstones in southern Israel and Jordan, the northern province shows an additional significant age peak at ~800 Ma and its overall spectrum resembles that of Devonian sandstones in northern Saudi Arabia. These variations distinguish the two Miocene clastic outliers as pertaining to two separate, NW‐directed transport systems delivering siliciclastic sediments from Arabia towards the deep Levant Basin. The detrital zircon U‐Pb‐Hf signal of the Israeli Miocene clastic units differs from that of the River Nile, particularly in the lack of Cenozoic‐Mesozoic‐aged zircons in the former. This allows us to distinguish the properties of the fluvial system that existed in Arabia, on the eastern side of the Red Sea, from that of the River Nile that drained its western flanks. While it is commonly accepted that the (proto‐)Nile River played a key role in the Levant Basin fill, the eastern fluvial system that prevailed on the Arabian side may have been also important.

The architecture of the Kattendijk Formation and the implications on the early Pliocene depositional evolution of the southern margin of the North Sea Basin

An east-west correlation profile through the upper Neogene succession north of Antwerp, based on cone penetration tests, reveals the architecture of the lower Pliocene Kattendijk Formation. It shows a basal incision of the Kattendijk Formation down to 20 m in Miocene sands and locally even Lower Oligocene clays. The incision is part of a much larger gully system in the region at the base of the Kattendijk Formation. The strongest gully incision is observed along the western profile, and coincides with increases in the thickness of the Kattendijk Formation from its typical four to six meters thickness in the east towards a maximum of 15 m in the west. Correlations show that this additional thickness represents a separate sequence of the Kattendijk Formation that first filled the deepest part of the gully prior to being transgressed and covered by the second sequence deposited in a larger gully system. Both sequences of the Kattendijk Formation have basal transgressive layers, and are lithologically identical. Initial, deep incision at the base of the Kattendijk Formation might have been the result of the constriction of early Pliocene tidal currents that invaded and expanded fluvial or estuarine gullies that had developed during the latest Miocene sea-level low. A similar mechanism had been proposed for the development of late Miocene gully system at the base of the Diest Formation further southeast in northern Belgium. As the wider area was transgressed and covered by the second sequence of the Kattendijk Formation, flow constriction ended, currents weakened and gully incisions were reduced in size.

Giant salamander from the Miocene of the Mecsek mountains (P\xe9cs-Danitzpuszta, southwestern Hungary)

The Late Miocene fossil locality Pécs-Danitzpuszta (Mecsek Mts., Hungary) has yielded cranial and postcranial bones of giant salamanders. Based on taxonomical studies, these relatively well-preserved, isolated bones belong to the cryptobranchid species Andrias scheuchzeri. Whereas the species is well documented from Neogene of Central Europe, this is the first record of the genus Andrias from Hungary, representing the sole record of giant salamanders from the country. The fossils were found in Upper Miocene sands deposited in the brackish Lake Pannon, but their late Miocene age is uncertain, because they occur together with vertebrate remains reworked from older sediments. The mild and humid climate and the presence of freshwater wetlands on the mainland indicated by the fossil flora, the syn-depositional uplift of the mountains providing for a rugged topography, and the intense clastic sediment input into Lake Pannon indicative of a fluvial network on the Mecsek Island and of sufficient precipitation support that conditions were convenient for the giant salamanders in the early late Miocene. Together with three other late Miocene localities in Austria, the Pécs-Danitzpuszta site is the fourth Miocene occurrence of Andrias in the Pannonian Basin System. It resembles the first three localities in lying at the foot of elevated terrain and in having freshwater input, conditions thought to be necessary for giant salamander habitats.