Set Of Normal Faults Research Articles

Subsurface basement structures of the Usangu basin, East African rift system, with implications for basin structural configuration and hydrocarbon potential

The Usangu basin is a rift basin developed along the Eastern arm of the East African rift system trending in the NE-SW direction. Although the general structures of the basin have been well studied, the structural configuration of the basin and the spatial and depth variations of sediment thickness are still not well known. This study investigates the structures related basement configuration and the variation of sediment thickness within the basin using the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM), aeromagnetic and gravity data. Results from DEM data indicate a few lineaments on the basin flanks representing the Usangu and Chimala border faults with no structures in the central part of the basin. The aeromagnetic and gravity data highlight three sets of normal and strike-slip faults, most of which trend NE-SW and others NNE-SSW, while a few trends WNW-ESE or NW-SE. Structures on the southwest of the basin reveal complex patterns attributed to the concentration of important tectonic and seismic activities in the study area. The Euler deconvolution and gravity models used to calculate the depth to the basement show that the basement is shallow in the north and south to southwest, and the basin deepens in the northeastern, northwestern and western parts. The findings also reveal that the basin has two grabens, troughs, depression and intrabasinal basement trending in the same direction as the basin configuration. The general thickness of sediments filling the basin ranges from 3 to 4.5 km, with the maximum accumulation of sediments reaching up to 4.8 km in the two depocenters at the south and southwest of the basin. The depth range of the sediments obtained implies that the basin has potential for hydrocarbon exploration with the possibility of natural gas occurrence.

Integrated seismic, petrophysical, and geochemical studies for evaluating the petroleum system of the Upper Bahariya-Abu Roash G sequence in the Karama Field, Abu Gharadig Basin, North Western Desert, Egypt

The main aim of this study is to delineate the hydrocarbon potential and evaluate the petroleum system elements of the Cenomanian Abu Roash G (AR/G) and the Upper Bahariya Members in the Karama Field. It lies at the southeast borders of the Abu Gharadig Basin, a well-known basin in the W.D. to the NE of Africa. We accomplish this study by analyzing a total of thirty 2D seismic profiles, a complete data set of well logs for five wells, and their geochemical data. The workflow starts with illustrating the dominant subsurface structural features, defining the main potential reservoirs and their parameters, and checking the maturity of the probable source rocks. The seismic interpretation indicated that the research area had been influenced by a NE-SW anticlinal structure accompanied by a set of WNW-ESE and NW-SE normal faults that are controlled by the positive compression inversion process that dominated during the Late Cretaceous. Analyzing and processing the well log data sets suggest that the reservoirs of the Abu Roash G (AR/G) and the Upper Bahariya Members are characterized by poor to good reservoir settings with net-pay thickness reaching up to 13–50 feet in the different wells (av. Effective porosity (∅eff) = 17.7 % and 15.6% for the AR/G and the Upper Bahariya Members, av. Shale volume (Vsh) = 17.4 % and 13.6 %, av. Water saturation (Sw) = 38.9 % and 39.8 %, while av. Hydrocarbon saturation values (So) = 60.2 % and 61.1%, respectively). The geochemical and maturity analyses assisted in determining the potential mature source rocks of the Jurassic Khatatba Shale (TOC = 0.70–5.67%; S1+S2 = 0.43–5.97 mg/g, Ro = 0.54–1.06 %) with some contribution from the Cretaceous sources (Alam El-Bueib and Bahariya Formations). Studying elements of the petroleum regime of the Karama Field indicates that the trapped hydrocarbons are structurally controlled by three-way dip closures, horst blocks, sealing faults, and vertical sealing by impervious shale and limestone beds. This case study could be applied to similar analogs in other oil fields in the Egyptian Western Desert to delineate their hydrocarbon potential and structural setting.

Assessment of the hydrocarbon potential in the black shales of the Jurassic Khatatba Formation and generated hydrocarbons, North Western Desert, Egypt: Depositional mechanism of organic rich rocks related to syn-rift differential subsidence

Jurassic rocks comprise the main source rocks in the Western Desert of Egypt. In this study, a rare case of Jurassic oil shale occurrence is recorded and studied as an extension of the Khatatba Formation. The study is based on an integrated model for oil shale deposition using seismic data, organic geochemical analyses, and palynomorph thermal alteration assessment to determine the hydrocarbon generation potential of these rocks. The seismic data were used to construct structure and lithofacies models and to relate the facies distribution with the geochemical parameters of the different rock units in addition to examining the lithofacies changes between the study wells adding value to the understanding of the environment of deposition and the structure of the study area. The Zahra, U. Safa, and L. Safa members are affected by two sets of normal faults, the first of which has a downthrown side to the east while the second set has downthrown westward sides. The 3D facies models show that the Zahra Member is composed mainly of limestone encountered in the central parts of the basin, while shale is mostly found in the north. The U. Safa consists mainly of sandstone and the L. Safa consists of sandstone and siltstone. The geochemical evaluation shows organic richness ranging from poor to good for the Zahra, while the Safa shows poor to excellent richness. Kerogen is Type III and IV in most samples. The Zahra samples are immature in the TUT-21X well and mature in only one sample from the AMOUN NE-2X well. The U. Safa samples are immature to marginally mature while the L. Safa samples are marginally mature to mature in the TUT-21X well and immature in the SHAMS-15X well. Palynomorph thermal alteration data confirm the above maturation levels. The bulk and biomarker composition of two oils samples from U. and L. Safa, AMOUN NE-1X well, are similar and indicate a terrigenous source of the kerogen. The oils are not biodegraded but are normal mature oils generated by kerogen that was deposited under oxic conditions. Data integration from this study can be used to show the variation in organic richness (TOC) and thermal maturity (Tmax) in the area between the four wells, which will help define the exploration risk and provide for a new vision for more exploration activity.

Use of remote sensing, spatial and geophysical modeling, and real recharging capabilities to identify suitable areas for groundwater exploitation in dry coastal areas

Accurate identification of groundwater potential areas in arid regions is an important task for groundwater management and sustainability. As a result, this study used the innovative integration of remote sensing (RS), geographic information system (GIS), watershed modeling system (WMS), geophysical survey, and water mass balance equation to identify potential groundwater areas in the W. Dara, Eastern Desert, Egypt. A weighted spatial probability model (WSPM) of groundwater potential based on eight regulatory factors was implemented within ArcGIS software. Drainage density (DD), precipitation (P), net groundwater recharge (NGR), terrain slope (TS), lineament density (LD), lithologic group (LG), water quality (TDS), and depth to groundwater level (DGW) are the aspects considered. The Analytical hierarchy process (AHP) method was used to assign weights to these parameters, and their accuracy was estimated using the consistency ratio (CR). The resulting groundwater potential map classified W. Dara study area into five categories, ranging from very low to very high potential. A geophysical survey, in the form of Vertical Electrical Sounding (VES) and Transient Electromagnetic (TEM), was conducted along W. Dara to validate the results of the WSPM, which identified areas of high groundwater potential. The 1D inversion of VES/TEM shows that the central and western parts of W. Dara are considered the most promising areas for groundwater occurrence, and are located in areas of high and very high potential classes derived from WSPM. Moreover, the results of VES and TEM surveys showed that the proposed aquifers (Nubian Sandstone, Miocene, and Quaternary) in the study area are horizontally and vertically connected through a set of normal faults traversing NW-SE. Ten sites have been proposed for drilling additional exploitative wells in W. Dara area based on the WSPM and geophysical survey with the aim of sustainable development. Thus, the integrated techniques applied in this study proved effective in accurately determining the development strategy for arid and semi-arid coastal areas, especially those that suffer from scarcity of rainfall and increased agricultural reclamation requirements in remote areas.

Fault Networks in Triaxial Tectonic Settings: Analog Modeling of Distributed Continental Extension With Lateral Shortening

AbstractTriaxial deformation is a general feature of continental tectonics, but its controls and the systematics of associated fault networks remain poorly understood. We present triaxial analog experiments mimicking crustal thinning resulting from distributed longitudinal extension and lateral shortening. Contemporary longitudinal extension and lateral shortening are related by the principal horizontal strain ratio (PHSR). We investigate the effect of crustal geometry, rheology and strain rate on deformation localization, faulting regime and pattern, and PHSR in brittle and brittle‐viscous crustal‐scale models. We find that in brittle models the fault networks reflect the basal boundary condition and fault‐density scales inversely with brittle layer thickness. In brittle‐viscous models, as strain rate (ė) decreases, (a) Three fault patterns emerge: conjugate sets of strike‐slip faults (ė > 3 × 10−4 s−1, PHSR > 0.31), sets of parallel oblique normal faults (ė = 0.3–3 × 10−4 s−1, PHSR = 0.15–0.25), horst‐and‐graben system (ė < 0.3 × 10−4 s−1, PHSR < 0.1). (b) The strain localization increases systematically and gradually. We interpret the strain rate dependent of faulting regimes to be controlled by vertical coupling between the model upper mantle and model upper crust resulting in spontaneous permutation of principal stress axes. Rate‐dependency of strain localization can be related to mechanical coupling between the upper and lower crust. We identify the following parameters controlling triaxial tectonic deformation: upper crustal thickness and friction coefficient, lower crustal thickness and viscosity, as well as strain rate. We test our models and predictions against natural prototypes (Tibet, Anatolia, Apennines, and Basin and Range Province) thus providing new perspectives on triaxial deformation.

Continental subduction of Adria in the Apennines and relation with seismicity and hazard

The subduction of continental lithosphere is a complex process because the buoyancy of the crust is higher than the oceanic and should resist sinking into the mantle. Anyway, studies on the Alpine-Himalayan collision system indicate that a large portion of the continental crust is subducted, while some material is accreted in the orogens. The Apennine is a perfect case for studying how such processes evolve, thanks to high quality seismic images that illuminate a critical depth range not commonly resolved in many collisional settings. In this paper, we show the structure of the Apennines orogen, as jointly revealed by seismicity and deep structure from regional and teleseismic tomography and receiver function profiles. The westward subducting Adria lithosphere is well defined along the orogen showing a mid-crustal delamination. Seismicity within the underthrusting lower crust and velocity anomalies in the mantle wedge highlight how the subduction evolution is entangled with the liberation of fluids. The eclogitization of subducted material enhances the fluid release into the wedge, the delamination and retreat of the Adria plate. This delamination/subduction generates a coupled compression and extension system that migrates eastward following the retreat of the lithosphere, with broad sets of normal faults that invert or interfere with pre-existing compressional structures all over the roof plate. The sparseness and non-ubiquity of intermediate depth earthquakes along the subduction panel suggest that the brittle response of the subducting crust is governed by its different composition and fluid content. Therefore, the lower crust composition appears essential in conditioning the evolution of continental subduction.

Integrated geophysical, petrophysical and petrographical characterization of the carbonate and clastic reservoirs of the Waihapa Field, Taranaki Basin, New Zealand

Despite the economic importance of the Waihapa Field in Taranaki Basin in New Zealand, the structural setting, petrographic and petrophysical properties of its Cenozoic reservoirs are still poorly understood. This research integrates a 3D seismic survey with core and well logs data, as well as petrographic description in order to discuss the structural setting and the reservoir characterization of the Cenozoic reservoirs along the Waihapa Field, Taranaki Basin, New Zealand. A major thrust fault was interpreted dissecting both the Kapuni (Paleocene- Eocene) and Ngatoro (Oligocene- Early Miocene) groups and another opposite thrust fault affecting the Ngatoro Group and the Waihapa anticline. These compressional structures were resulted from the regional compression which affected the Taranaki Basin during the Miocene. Wai-iti Group (Miocene) is dissected by a set of NE-SW normal faults. These normal faults remark the end of the compressional phase and the beginning of a new extensional phase along the Taranaki Basin.The petrographic data of the studied reservoirs indicate that the Late Miocene Mount Messenger Formation is composed of feldspathic wacke, micaceous feldspathic quartz arenite and mudstone microfacies, whereas the Oligocene Tikorangi Formation is composed of five microfacies (bioclastic grainstone, bioclastic packstone, sandy wackestone, highly fractured silty mudstone and sandy glauconitic packstone microfacies). Downward, the Upper Eocene Mangahewa Formation is composed of ferruginated quartz arenite, micaceous quartz arenite, and ferruginated calcareous quartz arenite microfacies. Cementation and compaction are mostly affected the Mangahewa Formation while fracturing and dissolution are primarily affected the Tikorangi and the Mount Messenger formations respectively. The studied core data was discriminated into four petrophysical static rock types (PSRTs). The PSRT1, representing the Mount Messenger reservoir, has the best reservoir quality (av. porosity = 23.3%, av. permeability = 45.0 md, and meso pores, 2.60 μm) while the PSRT4 of Tikorangi Formation has the lowest reservoir quality (av. porosity = 5.5%, av. permeability = 0.01 md, and nano pores, 0.07 μm). The PSRT2 (av. porosity = 4.17%, av. permeability = 0.26 md, and micro pores, 0.59 μm) and PSRT3 (av. porosity = 5.93%, av. permeability = 0.08 md, and micro pores, 0.22 μm) are petrophysically considered transitional rock types between the PSRT1 and the PSRT4.However, Tikorangi reservoir is already producing oil from the borehole scale fractures. This work represents the workflow applied during integrating seismic, petrographical and petrophysical data in order to characterize carbonate and clastic reservoirs for any further hydrocarbon development plans along the field.

Lithostratigraphic analysis and characterization of the upper miocene deformation of the Beni Bou Ifroure massif (Jbel Harcha Unit) eastern Rif Morocco

In the eastern Rif the unit of Jbel Harcha which is part of Beni Bou Ifroure massif, the latter belongs to the Rif chain which was formed during the Alpine orogeny. Lithostratigraphic analysis of the geological map and field investigations shows that this unit is constituted by carbonate facies of limestone attributed to the lower and middle Jurassic. At the level of upper Jurassic and Cretaceous we observe metamorphic terms presented by schists. The structural examination allows to distinguish two types of deformation the first one is penetrative which is materialized by a metamorphism of the formations of upper Jurassic and Cretaceous whose direction of the planes of schistosity varies between N125 and N140. This type is linked to a NE-SW shortening, attributed to the Tortonian and materialized by a set of open and normal faults of direction N040 to N045. The second type is generally characterized by brittle structures presented by dextral strike-slip faults of direction N120 to N140 that intersect the ancient accidents. This episode linked to a N-S to NW-SE shortening is responsible for the N070 thrusting of the Jurassic rocks in the study area.

Tectonic implication in the evolution of lake and Quaternary landforms in the Lohawati river basin, Kumaun outer Lesser Himalaya

The evolution of the Quaternary landforms in the Champawat area of the outer Kumaun Lesser Himalaya is reconstructed from the paleolake sections and the geometry of the landscape. Conjugate sets of normal faults are observed in both the bedrocks and Quaternary deposits at Banlek. The most prominent normal faults are those striking NE-SW and NW-SE and most of them are steeply dipping faults while some are vertical faults. Sediments akin to the lacustrine deposits are observed at four sites; while the contact between the bedrock and the lake sediments is observed at only one site in the peripheral side. The exposed sediments thicknesses vary from 8.30 m to 4.8 m and consist of an alternation of black carbonaceous mud and sandy horizons indicating different depositional regimes. The total thickness of the lake sediments appears to be more than 75 m as deduced from elevational differences between the exposed sites. From Site 1, two OSL samples collected from 2.5 m and 8 m from the present ground surface, were analyzed which give OSL ages of 16 ka and 17 ka, respectively; while one sample collected from Site 4 gives an OSL age of 13 ka. A total of 3653 lineaments were mapped encompassing 2,277.8 sq km from the eastern Kumaun Himalaya. Maximum of the lineaments trend ENE-WSW or almost E-W (∼46.5%); the major principal stress is deduced to be in NE-SW direction. Lake, mature topography and gentle stream gradient in the Champawat area are the result of highly weathered bedrocks and development of the normal faults.

Application of 3D Static Modelling in Reservoir Characterization: A Case Study from the Qishn Formation in Sharyoof Oil Field, Masila Basin, Yemen

AbstractThree‐dimensional (3D) static modelling techniques are applied to the characterization of the Qishn Formation (Fm.) in the Sharyoof oil field locating within the Masila basin, southeastern Yemen. The present study was initiated by the seismic structural interpretation, followed by building a 3D structural framework, in addition to analysing well log data and from these, 3D facies and petrophysical models are constructed. In the Sharyoof oil field, the Qishn Fm. exhibits depth values within the range of 400–780 m below sea level, with a general increase towards the SSE. A set of high dip angle normal faults with a general ENE–WSW trend dissect the rocks. The strata are also folded as a main anticline with an axis that is parallel to the fault trend, formed as a result of basement uplift. According to the facies models, the Qishn Fm. comprises 43.83% limestone, 21.53% shale, 21.26% sandstone, 13.21% siltstone and 0.17% dolomite. The Qishn Carbonates Member has low porosity values making it a potential seal for the underlying reservoirs whereas the Upper Qishn Clastics S1A and C have good reservoir quality and S1B has fair reservoir quality. The Upper Qishn Clastics S2 and S3 also have fair reservoir quality, while the Lower Qishn Clastics zone has good reservoir quality. The water saturation decreases towards the west and east and increases towards north and south. The total original oil in‐place (OOIP) of the Upper Qishn clastics is 106 million STB within the S1A, S1C and S2 zones. Drilling of development wells is recommended in the eastern study area, where good trapping configuration is exhibited in addition to the presence of a potential seal (Upper Qishn Carbonates Member) and reservoir (Qishn Clastics Member) with high porosity and low water saturation.

Effect of tectonic inversion on supra-salt fault geometry and reactivation histories in the Southern North Sea

High-resolution 3D seismic and borehole data in the Broad Fourteens Basin, Southern North Sea, are used to investigate the relationship between lithology and fault throw distribution, as well as to understand the reactivation and growth histories of faults developed due to tectonic inversion. Two (2) distinct tiers of faults are identified, and their geometry analysed in detail. Tier 1 faults comprise closely spaced sets of normal faults that resulted from the progressive buckling and stretching of Upper Mesozoic strata during Late Cretaceous to Paleogene tectonic inversion. They have been reactivated, but still show net normal throw separations, even though they were formed during a period of regional compression. Tier 2 faults comprise densely spaced sets of normal faults in Paleogene strata with a broad range of strikes, forming a polygonal pattern. These faults relate to early diagenesis but still record the effect of the Paleogene inversion episode. An important characteristic is that Tier 1 faults are highly segmented, and show differences in throw distribution between shale-rich and sandy intervals. These faults are more segmented with relatively small throw maxima of 14 ms (17.7 m) in shale-rich intervals, while sandy intervals are less segmented with larger throw maxima of 32 ms (40.3 m). Discrepancies in fault throw distribution and segmentation increase the chances of compartmentalisation or localised fluid flow through fault linkage zones, presenting at the same time significant risks when injecting CO2 in subsurface traps. Recognising the effect of tectonic inversion on supra-salt fault geometry, and reactivation histories, can be crucial to the characterisation of faulted hydrocarbon and carbon capture and storage (CCS) reservoirs in tectonically inverted basins such as the Southern North Sea.

영덕군 병곡면 해안에 형성된 단층에 대한 연구

In the southeastern part of the Korean Peninsula, the Yangsan Fault, an active fault zone, has developed. Many earthquakes occur around these faults, and the possibility of earthquakes occurring along the branch faults is being discussed. On the other hand, the Yeongdeok Fault is reported in Yeongdeok-gun, which is the northern part of the Yangsan fault. In this study, goemorphic characteristics of a set faults found on the outcrop of the gentle slope of the coast of Byeonggok-myeon were analyzed and granulometric and geochemical characteristics of sediments and other materials, including fault gouges were analyzed. The outcrop of Byeonggok-myeon is the part of the fault core and can be divided into two parts. Theses fault are formed on the upper part of the Mesozoic bedrock and the tertiary sedimentary layer of red sand-supported clasts are covered in several sedimentary units. The faults were normal fault sets, and a number of vertical cracks were developed, and glossy surfaces were observed in the fault area. It appears that these faults have occurred after alluvial deposition had been formed. In the case of samples from fault gouges, there were differences in particle size and geochemical characteristics from the surrounding area.

Seismic interpretation of the Late Albian-Early Cenomanian Bahariya reservoirs of Burg El Arab oil field for tectonic evaluation: a case study from Western Desert, Egypt

The evolution of different rift basins has been investigated tectonically and stratigraphically for decades using different geological and geophysical techniques based on data collected from outcrops and subsurface sequences. The tectonic subsurface evaluation of the so-called Bahariya sequence of Burg El Arab (BEA) oil field (Western Desert, Egypt) was studied using eleven seismic profiles showing the structural framework of the BEA oil field. The Late Albian-Early Cenomanian Bahariya Formation was dissected by a series of normal fault system, trending in NW-SE and WNW-ESE directions. This system was created due to the Cretaceous-Early Tertiary tectonic deformations related to the Tethyan plate tectonics. These tectonics lead to the presence of a symmetrical anticlinal fold dissected by a set of normal faults that is clearly dipping towards SSE and extending along the direction of NNW-SSE. The results of the structural seismic interpretation of the BEA oil field indicated that there are two main tectonic deformations affecting the subsurface rocks of the Mesozoic: the Jurassic and Early Cretaceous rifting and Late Cretaceous-Early Tertiary shortening deformation. Understanding and interpretation of such structural styles and tectonics are a key issue in hydrocarbon exploration and development in the study area.

Structural evolution and related implications for uranium mineralization in the Patterson Lake corridor, southwestern Athabasca Basin, Saskatchewan, Canada

The Patterson Lake corridor is situated along the SW margin of the Athabasca Basin and contains several basement-hosted uranium deposits and prospects. Drill core investigations during this study have determined that granite, granodiorite, mafic and alkali intrusive basement rocks are entrained in a deep-seated NE-striking subvertical heterogeneous high-strain zone defined by anastomosing ductile to semi-brittle shears and brittle faults. The earliest phases of ductile deformation (D 1 /D 2 ), linked with Taltson (1.94–1.92 Ga) orogenesis, involved interference between early fold sets (F 1 /F 2 ) and development of an associated ductile transposition foliation (S 1 /S 2 ). During subsequent Snowbird ( c. 1.91–1.90 Ga) tectonism, this composite foliation was re-folded (D 3 ) by NE-trending buckle-style folds (F 3 ), including a regional fold centred on the Clearwater aeromagnetic high. In continuum with D 3 , a network of dextral-reverse chloritic-graphitic shears, with C–S geometry, formed initially (D 4a ) and progressed to more discrete, spaced semi-brittle structures (D 4b ; c. 1.900–1.819 Ga). Basin development (D 5a ; < c. 1.819 Ga) was marked by a set of north-striking normal faults and related east- and NE-striking transfer faults that accommodated subsidence. Primary uranium mineralization (D 5b ; c . 1.45 Ga) was facilitated by brittle reactivation of NE-striking basement shears in response to WSW–ENE-directed compressional stress ( σ 1 ). Uraninite was emplaced along σ 1 -parallel extension fractures and dilational zones formed at linkages between NE- and ENE-striking dextral strike-slip faults. Uranium remobilization (D 5c ) occurred after σ 1 shifted to WNW–ESE, giving rise to regional east- and SE-striking conjugate faults, along which mafic dykes (1.27 and 1.16 Ga) intruded. Thematic collection: This article is part of the Uranium Fluid Pathways collection available at: https://www.lyellcollection.org/cc/uranium-fluid-pathways

Reservoir characterization and 3D modeling of the Aptian Alamein Formation in North Razzak area (North Western Desert, Egypt)

Improving exploration and development techniques of fossil fuels are essential for continuous reserves development. Although there are many oil discoveries in the Razzak Area (North Western Desert, Egypt), there are also many dry wells. Therefore, the tectonic setting and reservoirs characterization of the study area has to be fully understood. Twenty 2D highly filtered stack zero-phase seismic sections and logging data of four wells were analyzed. According to seismic sections and structure contour maps (both time and depth), there is one major structural high (horst). It is a part of the regional Jurassic rift system. The NE Jurassic rifts continued during the deposition of the Early Cretaceous strata as growth faults and have been rejuvenated or continued during the closure of the Neotethys Ocean. During the Late Cretaceous, the compressional stress resulting from the collision between African and Eurasian plates has led to the inversion of the Razzak basin, where some segments of the main faults are transformed from normal to reverse and the hanging walls formed plunging drag fold, which was dissected by a set of NW-SE normal faults. Four prospective closures in the Razzak Field were highlighted. Based on integrated petrophysical tools (Gamma Ray, Sonic Log, Resistivity Deep, Neutron Porosity, and Bulk Density) in four wells (NRZK-1, NRZK2, NRZK-3, and NRZK-4), the Aptian Alamein Formation (mainly dolomite) was interpreted to be a good reservoir and can be subdivided into two zones (Upper Alamein and Lower Alamein) with different reservoir quality. In addition, 3D structure, facies, and petrophysical models were built based on integrated geological and petrophysical data. The results indicated that integrating both seismic profiles with logging data, even from a small number of wells, is highly valuable in evaluating reservoir quality and defining future prospective.

Site selection and characterization for onshore 10,000-ton-class CO2 pilot storage in Early Miocene Janggi Basin, SE Korea: Storage potential and structural stability of siliciclastic-volcaniclastic storage combination

This paper presents the results of site selection and characterization for onshore 10,000-ton-class CO2 pilot storage in the Miocene Janggi Basin, SE Korea. The results were obtained from an integrated analysis of geological, geophysical, and geotechnical data, and indicated that Noeseongsan Subbasin is filled by >1-km-thick terrestrial sediments with dacitic to basaltic volcanic materials. Promising storage units are coarse siliciclastic sediments intercalated with mudstones in the lowermost Janggi Conlomerate, exhibiting suitable reservoir-caprock association for CO2 injection. The overlying Seongdongri Formation is composed of laterally extensive dacitic tuffs and fine-dominated tuffaceous sediments, forming a regional seal. The storage combination is characterized by a doubly sealed stratigraphic trap, and is laterally confined by juxtaposed seals formed by syndepositional normal fault sets. By considering the stratigraphic and structural features, the conglomerate and sandstone bodies at the boreholes JG-6 (940−971 m) and JG-7−1 (946−970 m) were selected as the optimal site for CO2 storage. It is expected that the stratigraphic and structural traps at the selected site minimize the leakage risk of injected CO2 due to the scarcity of surface and subsurface fractures, low fault intensity, and limited vertical extents of buried faults. The present study reveals that if multidisciplinary approaches involving careful synthesis of the basin were performed, an adequate storage site also can be obtained in this type of small-scale ancient sedimentary basin bearing abundant volcanic materials.

Lithologically controlled behaviour of the Dorozsma metamorphic hydrocarbon reservoir (Pannonian Basin, SE Hungary)

Numerous fractured hydrocarbon reservoirs occur in the metamorphic basement of the Pannonian Basin in Hungary, and among them, the Dorozsma field is one of the most productive. Here 66 boreholes penetrated the metamorphic massif, making detailed petrographic and microstructural evaluation possible. Well-log data (gamma-ray, density, neutron porosity and compressional slowness) are available for each well, which can be used to extend the petrographic information spatially.The data suggest three basic rock types in the study area, which align along a consequent rock column. In the deepest structural positions, amphibolite is typical, while the top of the basement is dominated by kyanite gneiss. Thermobarometric calculation results prove that the gneiss-rich realm was metamorphosed at a significantly higher temperature than the lowermost amphibolite, suggesting a post-metamorphic structural contact between them. The contact zone, observed in numerous boreholes, contains intensively deformed dolomite marble of a few tens of metres in thickness. The peak metamorphic temperature of this rock type is much lower than those typically seen in the two neighbouring blocks. Localising the position of the dolomite marble horizon in each well was accomplished using petrographic and well-log information, and through this investigation, a flat, low-angle shear zone became visible, cut by a set of younger normal faults. Hydrocarbon production data clearly shows that the best, most productive intervals in each well are strongly correlated to the shear zone between the gneiss- and amphibolite-dominated realms, namely the sheared dolomite marble zone.

Gas hydrate quantification in Walker Ridge block 313, Gulf of Mexico, from full-waveform inversion of ocean-bottom seismic data

The Gulf of Mexico (GOM) Joint Industry Project Leg 2 logging-while-drilling data in Walker Ridge lease block 313 (WR313) in the GOM detected gas hydrate in coarse- and fine-grained sediments at sites WR313-G and WR313-H. The coarse-grained units are thin ([Formula: see text]) and highly saturated, whereas the fine-grained unit is thick (approximately 200 m) with low saturation and fracture-filling gas hydrate. Unlike its coarse-grained counterpart, the seismic character of the fine-grained unit does not clearly indicate the presence of gas hydrate, which would likely have remained undiscovered in the absence of drilling. In this paper, through frequency-domain acoustic full-waveform inversion (FWI) of ocean-bottom seismometer data along a 2D multichannel seismic transect near sites WR313-G and WR313-H, we detect and quantify gas hydrate in the fine-grained unit. Key results are as follows: First, the base of the gas hydrate stability zone, which is not obvious in the reflection profile, can be discerned in the FWI results. Second, the gas hydrate in the fine-grained unit is mainly confined to the area between two sets of opposite-dipping normal faults implying that the fault architecture may be partially responsible for this gas hydrate accumulation and distribution.

Investigation of an oceanic plateau formation and rifting initiation model implied by the Caroline Ridge on the Caroline Plate, western Pacific

ABSTRACT The rifting of oceanic plateaus is an important mechanism for initiating lithospheric break-up and subsequent seafloor spreading. In this study, we present the latest multichannel seismic data investigating the Caroline Ridge and provide one of the typical cases for initial oceanic plateau evolution. We reveal that a smooth basement reflector (R2), as the top of the lava flows, is subparallel to the sediments with horizontal seismic reflections over the surface of the Caroline Ridge. Thick layer-parallel lava flows beneath the R2 appear within the crust. Large seamounts in the Sorol Trough possess abundant saucer-shaped intracrustal reflectors, and the overlying sediments were destroyed by intrusive bodies. The overlying sedimentary sequences, basement, and thick lava flows on the Caroline Ridge flanks were faulted by opposing normal fault sets, and the eruptions of the seamounts deformed the strata. A widespread bright horizontal reflector (R1), as an unconformity inside the Caroline Ridge sediments, truncates the lower tilted sediment layers and is itself cut by normal faults in the flank strata. Furthermore, we propose that subaerial lava flows extended laterally from the hotspot magmatism localizing in the Sorol Trough and led to Caroline Ridge formation. The initial rifting of the Caroline Ridge occurred during the Early-Middle Miocene. Limited volcanoes concentrate only in the Sorol Trough due to the attenuated thermal effect. It is suggested that dome uplifting and far-field force could have jointly caused initial rifting process of the Caroline Ridge.

Laramide Uplift near the Ray and Resolution Porphyry Copper Deposits, Southeastern Arizona: Insights into Regional Shortening Style, Magnitude of Uplift, and Implications for Exploration

AbstractThis study integrates new geologic mapping and structural analysis with previous work near Walnut Canyon and Telegraph Canyon to address the style and magnitude of shortening and the relationship between contractional structures and porphyry preservation and localization between the Ray and Resolution porphyry copper deposits. Cenozoic extensional structures were superimposed on earlier contractional structures formed during the Laramide orogeny, which dates from ~80 to 50 Ma. This superposition requires that Cenozoic normal faults be restored prior to analysis of Laramide contractional structures and their relationship to nearby porphyry copper deposits. Five distinct sets of normal faults within the study area progressively tilted the region 65° east. The amount of extension was 10.3 km or 276%. Using key constraints such as offset strata, cutoff angles between faults and various units, and Laramide fault geometries, the study area was structurally reconstructed and verified using 2-D kinematic modeling of reverse fault offset and related folding. Total shortening is 7.2 km or 98%. Laramide reverse faults are interpreted as thick-skinned basement-cored uplifts, because they restore to moderate angles, have related fault-propagation folds, and involve significant crystalline basement rock. The Telegraph Canyon reverse fault has at least 5.3 km of offset, and the Walnut Canyon reverse fault has 3.2 km. The preferred estimate of the total vertical uplift for the fault system is 5.2 km but could be several kilometers greater. The restored strike direction of these faults combined with mid-Cenozoic erosion surfaces throughout the region suggests that this fault system may be responsible for the Laramide uplift of the Tortilla Mountains and Black Hills. In addition, most major porphyry centers appear to have been intruded into the footwall of this large uplift, with local examples including Ray and Resolution, suggesting that topography generated from this uplift may have been critical to preservation of these ore systems. Though definitive crosscutting relationships do not exist in the immediate map area, geologic relationships in a broader area suggest that shortening here began after 74 Ma and, in the Ray area, had ended by ~69 Ma and that porphyry formation postdated reverse faulting by as much as 5 m.y. to as little as <1 m.y.