Recent Exploration Activities Research Articles

Basin modelling and source rock characteristics of the Late Palaeoproterozoic Cuizhuang Formation in the Yuncheng sub‐basin, North China: Implications for hydrocarbon generation and expulsion history

The present investigation is the first to provide information on the formation, process and influence factors for hydrocarbon generation and expulsion potential of the Cuizhuang Formation source rock in the Yuncheng sub‐basin to decipher the reason why no commercial petroleum resources have been found so far. In this study, data from the Jitan‐1 well in the Yuncheng sub‐basin were applied for the Cuizhuang Formation source rock basin modelling and organic geochemical analyses to reconstruct the burial and thermal evolution history and reveal the timing and process of hydrocarbon generation and expulsion. The modelling results indicate that the peak palaeotemperature of the Cuizhuang Formation source rock reached ~205°C in the Middle Carboniferous (~327 Ma) at a maximum burial depth of ~4000 m, when rapid burial subsidence and thermal events played a significant role in increasing thermal maturity. The Cuizhuang Formation generated and expelled small amounts of hydrocarbons from the Early Ordovician until the Middle Carboniferous, starting with the primary kerogen cracking and conversion to oil from the Early to Middle Ordovician (~476–461 Ma), corresponding to the thermal maturity values of 0.55–0.70 %VRo and transformation ratio (TR) <10%. The expulsion of most generated oil (0.70–1.30 %VRo, TR of 10%–90%) started from the Middle Ordovician to the Early Carboniferous (~461–351 Ma), before reaching the secondary cracking of the retained oil into gas (>1.30 %VRo and TR of 90%–100%) from the Early to Middle Carboniferous (~351–327 Ma). Destruction of the initial formation of hydrocarbon reservoirs in the Yuncheng sub‐basin was primarily controlled by the Middle Carboniferous tectonic event with its major uplift‐erosion, resulting in the absence of potential hydrocarbon reservoirs in recent exploration activities in some parts of the Yuncheng sub‐basin.

Play Fairway analysis of geothermal resources across the State of Hawai‘i: 4. Updates with new groundwater chemistry, subsurface stress analysis, and focused geophysical surveys

This paper is the fourth in a series on a play fairway analysis of geothermal resources across the State of Hawai‘i. Here we describe recent exploration activities that include groundwater sampling in ten locations statewide, as well as geophysical surveys on Lāna‘i, across the SW rift of Haleakalā Volcano (Maui), and surrounding Mauna Kea Volcano (Hawai‘i Island). We derive a first-order method for computing topographic stress using Green’s functions, finding that topography can induce appreciable crustal stress. We develop a new method for incorporating depth information about resistivity, density, and topographic stresses into our previously published equations to calculate resource probability and confidence. We incorporate newly collected and modeled data into our calculations to update statewide maps of probability and confidence. Lāna‘i Island and southeast Mauna Kea are identified as the top targets for exploratory drilling. The east rift of Haleakalā Volcano, the southern-most region of Mauna Loa’s SW rift (Hawai‘i Island), and central Kauai are identified as targets for geophysical surveying.

Biostratigraphy and sequence stratigraphy of the Oligocene succession, offshore Nile Delta, southeastern Mediterranean, Egypt, and its paleoenvironmental implications

Following recent hydrocarbon exploration activity, a new study has been carried out with the goal of defining the high-resolution biochronologic sequence stratigraphy of the Oligocene section in the offshore Nile Delta. A total of 98 samples were selected from 2 wells: Burullus 1 Memphis and Petrobel 1 Habbar. The study is based on a high-resolution microfossil biochronology including benthic and planktonic foraminifera and nannofossils as well as facies analysis and wire-line log calibration to investigate the evolution of Oligocene gas-bearing sequences in the southeastern Mediterranean region. The planktonic–benthic ratio, foraminiferal diversity, and upper depth limit of benthic foraminiferal taxa as well as the abundance of calcareous nannoplankton help in interpreting the depositional paleoenvironments of the Oligocene succession as fluvial, shallow-marine, middle- to outer-shelf, and bathyal domains. Six sequences were identified, three of which are lower Oligocene (Rupelian) (RuSeq1, RuSeq2, and RuSeq3), and the others are upper Oligocene (Chattian) (ChSeq4, ChSeq5, and ChSeq6). The sequence boundaries and flooding surfaces were correlated with the global eustatic sea-level models. Three major breaks—Eocene–Oligocene, lower–upper Oligocene, and upper Oligocene–lower Miocene boundaries—with intraformational breaks were well defined.

The socio-economic and environmental implications of oil and gas exploration: Perspectives at the micro level in the Albertine region of Uganda

The recent oil and gas exploration activities in the Albertine region of western Uganda has raised a debate on the plight of the local people at various scales. We used local perspectives on the socio-economic and environmental impacts of oil and gas exploration activities as a lens to examine the extent to which the “resource curse” and “resource blessing” theories are applicable in the oil and gas exploration sites in Uganda. Data was collected from Kyeihoro and Kaiso villages in Hoima district, western Uganda. Exploratory research design in which a total of 285 households randomly selected participated in a survey. The most mentioned positive socio-economic impacts were not directly linked to oil and gas exploration and these included: construction of roads and increased business opportunities. Direct positive impacts such as employment and increased wage rates were the least mentioned. The views of proponents of the “resource curse” theory were also reflected in the perspectives and these included: price inflation, increase in social ills and environmental degradation especially noise pollution, soil erosion and wildlife disturbance. The perceptions of local people indicate that oil and gas exploration activities can be both a “blessing” or “curse”.

Oligocene stratigraphic traps at the SouthEastern, Cuu Long basin

Up to recent years, major targets of oil and gas exploration in Cuu Long basin have been carried ort at structural traps in anticlines or basement highs in PreTertiary basement, Oligocene / Miocene clastics. As petroleum resources from reservoirs of traditional types become exhausted after many years of production (the remaining unexplored potential targets do not have sufficient reserves for development and production), exploration activities in Cuu Long basin have being focused in Oligocene stratigraphic/combination traps that have been discovered in recent years. Since the 1980s, petroleum explorers have identified oil in pinchouts trap in the Southeastern Cuu Long basin. However, these prospects have been evaluated to be of low potential due to be concerned of poor reservoir quality or incomplete petroleum system (lacking of source rocks or seals). Recent exploration activities in the region have identified several stratigraphic/ combination traps not only as pinch-outs but also as traps formed by appropriate facies changes. This article discusses types of stratigraphic traps that have been recently discovered in the studied area as well as exploration methods for predicting the distribution of these traps.

Optimizing a Knowledge-driven Prospectivity Model for Gold Deposits Within Peräpohja Belt, Northern Finland

This paper combines knowledge- and data-driven prospectivity mapping approaches by using the receiver operating characteristics (ROC) spatial statistical technique to optimize the process of rescaling input datasets and the process of data integration when using a fuzzy logic prospectivity mapping method. The methodology is tested in an active mineral exploration terrain within the Paleoproterozoic Perapohja Belt (PB) in the Northern Fennoscandian Shield, Finland. The PB comprises a greenschist to amphibolite facies, complexly deformed supracrustal sequence of variable quartzites, mafic volcanic rocks and volcaniclastic rocks, carbonate rocks, black shales, mica schists and graywackes. These formations were deposited on Archean basement and 2.44 Ga layered intrusions, during the multiple rifting of the Archean basement (2.44–1.92 Ga). Younger intrusive units in the PB comprise 2.20–2.13 Ga gabbroic sills or dikes and 1.98 Ga A-type granites. Metamorphism and complex deformation of the PB took place during the Svecofennian orogeny (1.9–1.8 Ga) and were followed by intrusions of post-orogenic granitoids (1.81–1.77 Ga). The recent mineral exploration activities have indicated several gold-bearing mineral occurrences within the PB. The Rompas Au-U mineralization is hosted within deformed and metamorphosed calc-silicate veins enclosed within mafic volcanic rocks and contains uranium-bearing zones without gold and very high-grade (>10,000 g/t Au) gold pockets with uraninite and uraninite-pyrobitumen nodules. In the vicinity of the Rompas, a magnesium skarn hosted disseminated-stockwork gold mineralization was also recognized at the Palokas-Rajapalot prospect. The exploration criteria translated into a fuzzy logic prospectivity model included data derived from regional till geochemistry (Fe, Cu, Co, Ni, Au, Te, K), high-resolution airborne geophysics (magnetic field total intensity, electromagnetic, gamma radiation), ground gravity and regional bedrock map (structures). The current exploration licenses and exploration drilling sites for gold were used to validate the knowledge-driven mineral prospectivity model.

Uranium in South Africa: Exploration and Supply Capacity

The major uranium deposits types are quartz-pebble conglomerate of the Central Rand Group (Witwatersrand Supergroup) and the Dominion Group, sandstone of the Karoo Uranium Province, surficial deposits of the Namaqualand region, as well as coal of the Springbok Flats Basin. Recent exploration activities (both greenfields and near-mine) have increased the resource potentials of these deposits. South Africa's Council for Geoscience has conducted high resolution magnetic and radiometric surveys in the Namaqualand region. Witwatersrand Basin is the only deposit where uranium mining is active at present in South Africa. Total uranium production in 2015 was 448 t. However, with production expected to increase in the Witwatersrand Basin, production is expected to reach 700 t U by the end of 2018. Furthermore, with uranium production envisaged to begin in the Karoo Uranium Province, uranium production may exceed 1000 t U by the year 2020.

南米での近年の石油探鉱の動向について

South America is one of the most promising exploration area, including exploration frontiers. As a result of recent exploration activities, remarkable discoveries were made especially in deep-water area including the presalt carbonate sections in the Santos Basin, offshore Brazil and the Upper Cretaceous turbidite sandstones offshore French Guiana.

The hydrocarbon potential of the 2015 Offshore Acreage Release Areas for petroleum exploration

The Australian Government formally releases new offshore exploration areas at the annual APPEA conference. These areas are located across various offshore hydrocarbon provinces ranging from mature basins with ongoing oil and gas production to exploration frontiers. A total of 23 areas are released for work-program bidding and six areas for cash bidding (Fig. 1). The two work-program bidding rounds will remain open until 29 October 2015 and 21 April 2016, respectively, while cash bid submissions will close on 4 February 2016. The 2015 Release Areas are located in 13 distinct geological provinces across eight basins and all were supported by industry nominations. Six areas are located in the Bonaparte Basin, two of which are cash bid areas over the Turtle/Barnett oil accumulations. In the Browse Basin, three areas in the Caswell Sub-basin and one area on the Yampi Shelf are released. In support of recent exploration activities and success, one large area has been gazetted in the central Roebuck Basin. The Northern Carnarvon Basin offering comprises 11 areas on the Exmouth Plateau and in the Dampier Sub-basin, including four for cash bidding. This year, the usual predominance of North West Shelf Release Areas is counterbalanced by seven large areas in the Bight, Otway, Sorell and Gippsland basins. This includes one area in the Ceduna Sub-basin, three areas in the deepwater Otway Basin, one area in the northern Sorell Basin and two areas in the southeastern Gippsland Basin. The nominations received for these areas highlights the industry’s interest in evaluating the hydrocarbon potential of Australia’s underexplored southern margin. Geoscience Australia continues to support industry activities by acquiring, interpreting and integrating pre-competitive datasets that are made freely available as part of the agency’s regional petroleum geological studies.

NEW STAGE OF HYDROCARBON EXPLORATION IN THE BLACK SEA BASIN: UPDATING OF ITS GEOLOGICAL STRUCTURE AND PROSPECTS DEVELOPMENT

The Black Sea basin is one of the last immature but closest to the European market hydrocarbon exploration frontier with rather high petroleum potential assessment. Several factors, including the understanding of its tectonic and sedimentary evolution, postpone a full-scale development of oil and gas prospects including deepwater sub-hydrate gas accumulations and shale gas resources in the circum-Black Sea region. The geological risks of its development based on recent exploration activity results are analyzed.

Gold Exploration and Potential of the Appalachian Piedmont of Eastern Alabama

ABSTRACT: The discovery and production of gold from epithermal and volcanogenic massive sulfide deposits in the Carolina slate belt of the southern Appalachians perhaps have overshadowed the gold potential of orogenic gold deposits in relatively higher grade metamorphic terranes of the southern Appalachian Piedmont. There has been a limited amount of exploration in the non-Carolina slate belt southern Appalachians since the early 1980s. Here we describe some of the recent exploration activity and geology of gold occurrences in the most productive part of the Alabama Piedmont, including the Goldville and Devil’s Backbone districts. In this area, there is a strong geochemical association of gold and arsenic in bedrock, saprolite, and soils, which reflects the mineralogical association of gold with arsenian pyrite and arsenopyrite in mineralized zones.

Middle East/North Africa Region Focuses on Tight Gas

Conference review As the era of the easy extraction of conventional hydrocarbon is over, energy companies across the world are tapping into difficult resources and developing unconventional reserves, such as shale gas and tight gas. In the Middle East and North Africa region, results from recent gas exploration and appraisal activities indicate that the region holds substantial resources of unconventional gas, especially tight gas. Regardless of the existence of highly productive conventional gas fields in this region, tight gas-related exploration and appraisal activities in several countries in the region have increased and are expected to pick up pace going forward. With this background, the SPE Middle East Unconventional Gas Conference and Exhibition (UGAS) was held in Oman to address the best practices and techniques used for the development of unconventional resources in the region. Under the theme “Unconventional and Tight Gas: Bridging the Gap for Sustainable Economic Development,” the conference highlighted the latest developments related to tight gas and shared success stories about the development of tight wells from regions all over the world. The 3-day conference highlighted the criteria, challenges, and environment required for successful unconventional gas production and how it implicates the long-term global supply of natural gas. Thirteen technical sessions along with poster and e-poster stations offered 90 presentations from more than 35 companies and 18 countries. Delivering the keynote speech, Zaid bin Khamis al Siyabi, director general of oil and gas exploration and production at the Ministry of Oil and Gas in the Sultanate of Oman, said the Sultanate recently began searching for and exploring unconventional gas resources, and needs to make more natural gas available to local industries. “The importance of unconventional resources for the sultanate is really huge,” al Siyabi said. Al Siyabi revealed that oil companies operating in Oman—such as Petroleum Development Oman, Shell, and BP—have drilled approximately 50 wells to explore unconventional gas resources using the latest technologies. Darryl Willis, vice president resources, North American Gas, BP, said in his presentation titled “Development of Unconventional Resources: Past, Present and Future” that unconventional gas continues to be a journey of discovery and challenge. “The future of our industry is increasingly unconventional. In the US, about 40% of the gas comes mainly from shale gas,” Willis said. The industry is now capable of producing gas from difficult geological structures at reasonable cost, making such resources economically viable, Willis said. “Among the success factors is the application of conventional techniques to unconventional, including the sweet-spot identification, integrated reservoir description, as well as the long-term development,” he said.

On the results of recent exploration activities at the Pallca mine, the Republic of Peru

On the results of recent exploration activities at the Pallca mine, the Republic of Peru

"On the results of recent exploration activities at the Huanzala ore deposits, Peru"

"On the results of recent exploration activities at the Huanzala ore deposits, Peru"

Are Carboniferous coals from the Danish North Sea oil-prone?

The Central Graben in the North Sea is a mature petroleum province with Upper Jurassic – lowermost Cretaceous marine shale of the Kimmeridge Clay Formation and equivalents as the principal source rock, and Upper Cretaceous chalk as the main reservoirs. However, increasing oil prices and developments in drilling technologies have made deeper plays depending on older source rocks increasingly attractive. In recent years exploration activities have therefore also been directed towards deeper clastic plays where Palaeozoic deposits may act as petroleum source rocks. Carboniferous coaly sections are the most obvious source rock candidates. The gas fields of the major gas province in the southern North Sea and North-West Europe are sourced from the thick Upper Carboniferous Coal Measures, which contain hundreds of coal seams (Drozdzewski 1993; Lokhorst 1998; Gautier 2003). North of the gas province Upper Carboni-ferous coal-bearing strata occur onshore in northern England and in Scotland, but offshore in the North Sea area they have been removed by erosion. However, Lower Carboniferous strata are present offshore and have been drilled in the Witch Ground Graben and in the north-eastern part of the Forth Approaches Basin (Fig. 1A), where most of the Lower Carboniferous sediments are assigned to the sandstone/shale-dominated Tayport Formation and to the coal-bearing Firth Coal Formation (Bruce & Stemmerik 2003). Highly oil-prone Lower Carboniferous lacustrine oil shales occur onshore in the Midland Valley, Scotland, but they have only been drilled by a single well off shore and seem not to be regionally distributed (Parnell 1988). In the southern part of the Norwegian and UK Central Graben and in the Danish Central Graben a total of only nine wells have encountered Lower Carboniferous strata, and while they may have a widespread occurrence (Fig. 1B; Bruce & Stemmerik 2003) their distribution is poorly constrained in this area. The nearly 6000 m deep Svane-1/1A well (Fig. 1B) in the Tail End Graben encountered gas and condensate at depths of 5400–5900 m, which based on carbon isotope values may have a Carboniferous source (Ohm et al. 2006). In the light of this the source rock potential of the Lower Carboniferous coals in the Gert-2 well (Fig. 1C) has recently been assessed (Petersen & Nytoft 2007).

The application of an integrated approach in exploration of lacustrine turbidites in Jiyang Sub-basin, Bohai Bay Basin, China

This study presents an integrated approach that has been successfully used in delineation of turbidite reservoirs in the Jiyang Sub-basin, Bohai Bay Basin, China. The techniques involve an integration of multi-disciplinary investigations, which comprise firstly the determination of depositional areas of turbidites using a sequence stratigraphic approach, then mapping the spatial distribution of turbidites using seismic velocity data, and finally, the selection of drilling prospects by an optimization process using available well logs and core data. Interpreted turbidites with a moderate burial depth and thickness of at least 10 m were targeted for drilling. The integrated approach has been proved to be quite successful in recent exploration activities with approximately 60 million tonnes (438 million bbls) of proven in place oil reserves had been discovered for the 6-year period of 1996 to 2001 in turbidite reservoirs, highlighting the importance of turbidite plays in current and future exploration.

Reservoir Compaction

Reservoir Compaction

Controls on the structural architecture and sedimentary character of syn-rift sequences, North Falkland Basin, South Atlantic

The Falkland Islands lie in a critical location for our understanding of Gondwana supercontinent break-up. Subsurface data obtained during recent exploration activity provide important new insights into the structure and stratigraphy of the North Falkland Basin's Late Jurassic syn-rift fill history. Results of seismic interpretation indicate that deposition was largely controlled by prominent planar normal faults, which divide the basin into a series of north-south trending half-grabens and minor grabens. Well data (in the form of exploration wireline logs, cores, petrographic thin sections, major and trace element analyses) indicate that their syn-rift fill was dominated by abundant volcaniclastic sediment supplied through debris flows, hyperconcentrated flows and pyroclastic ash-fall. The geochemical affinity of the volcanic sedimentary components shows a direct link to the widespread, Middle Jurassic to Early Cretaceous, silicic Chon Aike Large Igneous Province, in southern South America and Antarctica. Diagenesis has obscured provenance information and severely reduced porosity within the syn-rift sediments, causing them to have poor reservoir potential. The results enable a radically new interpretation of this key period in the North Falkland Basin's evolution, which helps modify and unify previously disparate views. It is now suggested that basin development was the direct result of the Chon Aike back-arc stretching, influenced in part by the underlying Palaeozoic basement trends. This was followed by Cretaceous-Recent post-rift thermal subsidence of the basin, which was only arrested by local structural inversion related to Atlantic opening. Consequently, it is thought that the extension that created the North Falkland Basin was independent of both Early–Middle Jurassic rotation of the Falkland Islands microplate and the evolution of the South Atlantic Ocean in the Cretaceous and Cenozoic.

Deep structure of the Campanian–Lucanian Arc (Southern Apennine, Italy)

Recent exploration activities and successful discovery of large oil fields in the upper Val d'Agri area (Southern Apennine, Italy) have encouraged the collection of large quantities of geological and geophysical data, and their integration into comprehensive geological models. Here we present a series of structural profiles based on several hundred kilometres of seismic lines (two- and three-dimensional) and the results of many deep wells. The best seismic lines have been extensively reprocessed, and also tied to magnetotelluric data. Geological interpretations of those lines have been interactively tested, and verified by gravity and magnetic modelling and structural balancing. The wells and seismic data demonstrate that the fundamental tracts of the deep architecture of the orogen, as it appears today, were developed only at the end of the Late Pliocene. The final closure of the ensialic shear-zone responsible for the subduction of at least 150 km of continental lithosphere originally underlying the Lagonegro Basin can be dated as Early Pliocene. The involvement of the Inner Apulian Platform in the core of the belt and the activation of a new and more external (left-lateral) oblique ensialic shear-zone can be constrained to the Late Pliocene–Pleistocene. The seismic profiles clearly show the underthrusting of the Outer Apulian Platform unit beneath the Inner Apulian Platform unit. The thick-skinned character of the Plio-Pleistocene contractional structures is evident from the structural profiles. This geometry is constrained by gravity–magnetic data and structural considerations, according to the relatively steep angle of dip (about 10°) of the Apulian foreland beneath the chain. The structural profiles depict the general architecture of the Campanian–Lucanian Arc: the Apennine Platform and Lagonegro Unit are largely allochthonous and a part of the Lagonegro basement could be buried below the Apennine Platform sole-thrust. The Neogene plastic successions of the Apennine Platform and Lagonegro Basin were detached and now outcrop in the Bradanic Foredeep. The Inner Apulian Platform constitutes a huge thrust-sheet, structured as a wide antiform in the core of the belt; its regional culmination roughly corresponds to the Val d'Agri area. Extensional and transtensional structures cross cut the pre-existing compressional structures as shown by the Quaternary valleys of Vallo di Diano and Val d'Agri. The profiles shown also highlight the existing contrast between the deep structures in the core of the belt and the tectonic style of the Lagonegro, Liguride and Sicilide Units. These units were in fact subjected to brittle–ductile deformation under metamorphic (part of Liguridi Units) and deep diagenetic to anchizonal conditions (Lagonegro Units) and were affected by a general overthrust-shear directed towards the NE. The Inner Apulian Platform was, on the contrary, involved in the thrust-belt together with its basement, whereas the Outer Apulian Platform, affected by A-subduction, underwent a regional bending with associated normal faulting.

The Turonian play in the Faeroe–Shetland Basin

Recent exploration in the Faeroe–Shetland Basin has concentrated on the Paleocene, following the successes of the Foinaven and Schiehallion fields. However, a number of deeper Mesozoic plays may still exist in the basin. This paper describes results of recent exploration activity targeted at a Turonian play in the Faeroe–Shetland Basin, west of the Rona Ridge, and discusses implications for future prospectivity in the area. The play tested is a slope fan pinchout against the Rona Ridge, comprising Cenomanian–Turonian high density turbidite sandstones. These were shed into a deep-water basin in the hanging wall of the Rona Fault during a base-level change in the adjacent West Shetland Basin. Two wells have proven considerable thicknesses of interbedded sandstones and shales in the Cenomanian–Turonian interval. Reservoir quality is locally excellent with porosities exceeding 20% and permeabilities up to 1 D. While hydrocarbon shows have been encountered, targeted prospects appear to have failed because of a lack of up-dip seal, emphasizing that the key risk for down-thrown plays against the Rona Fault remains trap integrity. The presence of both oil and gas shows though, confirms that the Turonian sandstone package has acted as a migration focus and may represent the main conduit from the deeper Jurassic source kitchen into the Clair Field. A sedimentological and diagenetic model for the sandstones based on recently acquired core data implies that clean, high quality deposits may also exist in a more basinward setting, possibly as detached fan complexes. This stratigraphic interval remains a potential play for future exploration, but with the depth of burial increasing rapidly westwards, overpressuring may be required to preserve porosity and permeability.