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Exploration Targets (exploration + target)
Selected AbstractsBEAM , Geoelectrical Ahead Monitoring for TBM-DrivesGEOMECHANICS AND TUNNELLING, Issue 5 2008Arnim Kaus Dr. rer.nat. BEAM is a non-intrusive focused-electrical induced polarisation ground prediction technique, permanently operating while TBM tunnelling. Main components of the survey system are the measuring unit placed in the TBM operator cabin and special adapted excavation tools which are used as electrodes. The unit is connected to the guidance system and receives the boring signal which allows fully automatic data acquisition and visualisation in real-time on an integrated monitor. Communication facilities transfer the forecast results to every accredited computer world wide simultaneously. Based on the measuring data the percentage frequency effect PFE and the resistivity R, an advanced evaluation software is established for geoelectrical-geological/hydrogeological classification and interpretation. Selected case studies from international TBM projects are outlined with prediction results of different kinds of exploration targets and geological situations. Since 2000 the geophysical probing system is fulfilling the practical demands under the rough and various conditions of TBM tunnelling work by indicating reliable results in hard rock as well as in soft ground. BEAM , Geoelektrische Vorauserkundung für TBM-Vortriebe BEAM ist eine zerstörungsfreie, vortriebsbegleitende Baugrund-Vorauserkundungs-Technologie auf Basis der fokussierend-elektrischen induzierten Polarisation. Das Monitoring-System besteht hauptsächlich aus einem Messgerät, das in der Steuerkabine aufgestellt werden kann, und aus speziell angepassten, bauseits vorhandenen Abbauwerkzeugen und Sicherungsmitteln, die als Elektroden dienen. Die Messeinheit wird mit dem bestehenden Vermessungssystem verbunden und empfängt das Bohrsignal, sodass vollautomatisierte Messungen durchgeführt werden, ohne die Tunnelvortriebsarbeiten zu stören, bei gleichzeitiger Datenauswertung und Visualisierung der Ergebnisse in Echtzeit auf dem integrierten Bildschirm der Einheit. Durch Anschluss an die Kommunikationseinrichtungen der Baustelle lassen sich die Vorauserkundungsdaten zeitgleich an jeden akkreditierten Computer weltweit transferieren. Eine innovative Auswertesoftware bewerkstelligt die geoelektrisch-geologische/hydrogeologische Klassifikation und Interpretation, die auf den Messparametern Prozent Frequenz Effekt PFE und dem Widerstand R basiert. Ausgewählte Fallbeispiele aus internationalen TBM-Projekten zeigen Vorauserkundungsergebnisse unterschiedlicher Explorationsziele und geologischer Situationen. Seit 2000 ist das Vorauserkundungssystem in der Anwendung und zeigt, dass es unter den schwierigen und unterschiedlichen Bedingungen im mechanisierten Tunnelbau sowohl im Hartgestein als auch im Lockergestein im Dauereinsatz zuverlässige Ergebnisse erbringt. [source] Near-surface models in Saudi ArabiaGEOPHYSICAL PROSPECTING, Issue 6 2007Ralph Bridle ABSTRACT A single-layer model of the near surface throughout the Kingdom of Saudi Arabia is available. While this simple model suffices for most areas and large subsurface structures, it fails in situations where the surface topography is complex, the base of weathering is below the datum, or where the time structural closure is less than the uncertainty in the static correction. In such cases, multiple-layered models that incorporate velocities derived from analysis of first arrivals picked from seismic shot records have proved to be successful in defining the lateral heterogeneity of the near surface. The additional velocity information obtained from this first-arrival analysis (direct as well as refracted arrivals) vastly improves the velocity,depth model of the near surface, regardless of the topography. Static corrections computed from these detailed near-surface velocity models have significantly enhanced subsurface image focusing, thereby reducing the uncertainty in the closure of target structures. Other non-seismic methods have been used either to confirm qualitatively or to enhance the layer models previously mentioned. Gravity data may be particularly useful in sandy areas to confirm general structure, while geostatistical modelling of vibrator base-plate attributes has yielded information that enhances the velocity field. In the global context, exploration targets of the oil and gas industry are seeking smaller and lower relief-time structures. Thus, near-surface models will need to enhance and integrate these methods, particularly in areas where the assumption of flat-lying near-surface layers cannot be met. [source] SEISMIC FACIES ANALYSIS BASED ON 3D MULTI-ATTRIBUTE VOLUME CLASSIFICATION, DARIYAN FORMATION, SE PERSIAN GULFJOURNAL OF PETROLEUM GEOLOGY, Issue 2 2006P. Farzadi Interpretation of recently acquired 3D seismic data from the adjacent Sirri C and D oilfields in the SE Persian Gulf indicates that a 3D interpretation of seismic facies is crucial to resolve the internal stratal geometries of the Aptian Dariyan Formation. This carbonate formation passes southward into the Shu'aiba Formation, a prolific reservoir rock of similar facies in the UAE. Lack of exposures and limited cored intervals have forced reliance on the seismic data for evidence of the depositional environment and the internal architecture of potential reservoir rocks. The progradational nature of the Dariyan Formation and the occurrence of carbonate build-ups within it make this stratal geometry complex. The complex internal heterogeneity of the build-ups and presence of seismic noise make mapping of the build-ups in 3D space using conventional seismic interpretation tools difficult, despite the availability of high-quality 3D seismic data covering the area. The high quality seismic and limited well data from this field is one of the few datasets of this kind presented in the literature. A procedure for the hierarchical multi-attribute analysis of seismic facies using Paradigm's Seis Facies software is used in this study to provide a 3D interpretation of the stratal patterns. Principal component analysis reduces the noise and redundant data by representing the main data variances as a few vector components in a transformed coordinate system. Cluster analysis is performed using those components which have the greatest contribution to the maximum spread of the data variability. Six seismic attribute volumes are used in this study and the result is a single 3D classified volume. Important new information obtained from within the Dariyan Formation gives new insights into its stratigraphic distribution and internal variability. This method of processing seismic data is a step towards exploring for subtle stratigraphic traps in the study area, and may help to identify exploration targets. [source] A REVIEW OF GEOLOGICAL DATA THAT CONFLICT WITH THE PARADIGM OF CATAGENIC GENERATION AND MIGRATION OF OILJOURNAL OF PETROLEUM GEOLOGY, Issue 3 2005H. Hugh Wilson The majority of petroleum geologists today agree that the complex problems that surround the origin, generation, migration and accumulation of hydrocarbons can be resolved by accepting the geochemical conclusion that the process originates by catagenic generation in deeply-buried organically-rich source rocks. These limited source rock intervals are believed to expel hydrocarbons when they reach organic maturity in oil kitchens. The expelled oil and gas then follow migration pathways to traps at shallower levels. However, there are major geological obstacles that cast doubt upon this interpretation. The restriction of the source rock to a few organically rich levels in a basin forces the conclusion that the basin plumbing system is leaky and allows secondary horizontal and vertical migration through great thicknesses of consolidated sedimentary rocks in which there are numerous permeability barriers that are known to effectively prevent hydrocarbon escape from traps. The sourcing of lenticular traps points to the enclosing impermeable envelope as the logical origin of the trapped hydrocarbons. The lynch-pin of the catagenic theory of hydrocarbon origin is the expulsion mechanism from deeply-buried consolidated source rock under high confining pressures. This mechanism is not understood and is termed an "enigma". Assuming that expulsion does occur, the pathways taken by the hydrocarbons to waiting traps can be ascertained by computer modelling of the basin. However, subsurface and field geological support for purported migration pathways has yet to be provided. Many oilfield studies have shown that oil and gas are preferentially trapped in synchronous highs that were formed during, or very shortly after, the deposition of the charged reservoir. An unresolved problem is how catagenically generated hydrocarbons, expelled during a long-drawn-out maturation period, can have filled synchronous highs but have avoided later traps along the assumed migration pathways. From many oilfield studies, it has also been shown that the presence of hydrocarbons inhibits diagenesis and compaction of the reservoir rock. This "Füchtbauer effect" points to not only the early charging of clastic and carbonate reservoirs, but also to the development of permeability barriers below the early-formed accumulations. These barriers would prevent later hydrocarbon additions during the supposed extended period of expulsion from an oil kitchen. Early-formed traps that have been sealed diagenetically will retain their charge even if the trap is opened by later structural tilting. Diagenetic traps have been discovered in clastic and carbonate provinces but their recognition as viable exploration targets is discouraged by present-day assumptions of late hydrocarbon generation and a leaky basin plumbing system. Because there are so many geological realities that cast doubt upon the assumptions that devolve from the paradigm of catagenic generation, the alternative concept of early biogenic generation and accumulation of immature oil, with in-reservoir cracking during burial, is again worthy of serious consideration. This concept envisages hydrocarbon generation by bacterial activity in many anoxic environments and the charging of synchronous highs from adjacent sources. The resolution of the fundamental problem of hydrocarbon generation and accumulation, which is critical to exploration strategies, should be sought in the light of a thorough knowledge of the geologic factors involved, rather than by computer modelling which may be guided by questionable geochemical assumptions. [source] MIDDLE MIOCENE DASHAVA FORMATION SANDSTONES, CARPATHIAN FOREDEEP, UKRAINEJOURNAL OF PETROLEUM GEOLOGY, Issue 4 2004I. Kurovets Middle Miocene (Sarmatian) sandstones in the Ukrainian Carpathian Foredeep are important exploration targets for natural gas. In this paper, we report on petrophysical studies on core samples of these sandstones with which we integrate wireline log data from 42 boreholes. Sarmation siltstones and sandstones in the study area are assigned to the lower part of the Dashava Formation. Seventeen units (LD 17 to LD 1:0.05 to 5m thick) are recognized in this formation on the basis of lithostratigraphy and log response. Sandstone content is highest within three lithostratigraphic complexes corresponding to units LD17-LD14, LD9-LD8 and LD5-LD3. During the Sarmatian, the Carpathian Foredeep was characterized by two depositional systems: a basinal turbidite system, and a second, more mixed system. Important controls on sedimentation included basin configuration and water depth, the occurrence of turbidity and other currents, and the location of provenance areas. Clastic material was delivered to the basin by rivers and ephemeral streams mostly from the Carpathian foldbelt. The content of sandy material within the Sarmatian succession increases from NW to SE, and from the central portion of the Krukenychy depression to the margins of the basin. [source] A REVIEW OF EOCENE NUMMULITE ACCUMULATIONS: STRUCTURE, FORMATION AND RESERVOIR POTENTIALJOURNAL OF PETROLEUM GEOLOGY, Issue 1 2001A. Racey Eocene nummulite accumulations, also referred to as nummullte "banks", form Important hydrocarbon reservoirs in Tunisia and Libya and may constitute exploration targets in other parts of North Africa, the Mediterranean and the Middle East. Porosities commonly average 10,20% and permeabilities 10,50md. Foraminifera of the genus Nummulites may comprise up to 98% of the bioclasts in these carbonate reservoirs, although only one or two species may be present. The absence of associated fauna is generally taken to indicate an oligotrophic depositional environment. In this paper, the palaeoecology of the genus Nummulites is discussed together with depositional models for two nummulitic carbonate reservoirs , the Middle Eocene Seeb Limestone of Oman and the Early Eocene El Garia/Jdeir Formation of Tunisia and Libya. The El Garia and Seeb Limestone Formations were deposited in ramp settings, and comprise a series of amalgamated sheets or low-relief banks. In the Hasdrubal field offshore Tunisia, where the El Garia Formation constitutes the reservoir rock, most of the nummulites have been redeposited from shallow into deeper waters whilst in the Bourri field (offshore Libya) they occur as an in situ "bank". Nummulite accumulations often show evidence that both physical reworking (scouring, winnowing and imbrication) and biological processes (reproduction strategies and bioturbation) have influenced their formation. A general model is outlined for discriminating between physically and ecologically produced biofabrics, and the implications for reservoir quality are discussed. [source] Maps for the planetary explorerASTRONOMY & GEOPHYSICS, Issue 5 2008Article first published online: 23 SEP 200 Planetary explorers may have the equivalent of SatNav to guide them, but to avoid ending up in the space equivalent of a double-decker bus wedged under a low bridge, they need proper maps. And the topographer who is mapping exploration targets has received an Exceptional Achievement medal from NASA for the quality of his work. [source] Towards ground truthing exploration in the central Arctic Ocean: a Cenozoic compaction history from the Lomonosov RidgeBASIN RESEARCH, Issue 2 2010M. O'Regan ABSTRACT The Integrated Ocean Drilling Program's Expedition 302, the Arctic Coring Expedition (ACEX), recovered the first Cenozoic sedimentary sequence from the central Arctic Ocean. ACEX provided ground truth for basin scale geophysical interpretations and for guiding future exploration targets in this largely unexplored ocean basin. Here, we present results from a series of consolidation tests used to characterize sediment compressibility and permeability and integrate these with high-resolution measurements of bulk density, porosity and shear strength to investigate the stress history and the nature of prominent lithostratigraphic and seismostratigraphic boundaries in the ACEX record. Despite moderate sedimentation rates (10,30 m Myr,1) and high permeability values (10,15,10,18 m2), consolidation and shear strength measurements both suggest an overall state of underconsolidation or overpressure. One-dimensional compaction modelling shows that to maintain such excess pore pressures, an in situ fluid source is required that exceeds the rate of fluid expulsion generated by mechanical compaction alone. Geochemical and sedimentological evidence is presented that identifies the Opal A,C/T transformation of biosiliceous rich sediments as a potential additional in situ fluid source. However, the combined rate of chemical and mechanical compaction remain too low to fully account for the observed pore pressure gradients, implying an additional diagenetic fluid source from within or below the recovered Cenozoic sediments from ACEX. Recognition of the Opal A,C/T reaction front in the ACEX record has broad reaching regional implications on slope stability and subsurface pressure evolution, and provides an important consideration for interpreting and correlating the spatially limited seismic data from the Arctic Ocean. [source] Geologic Characteristics of Volcanic Hydrocarbon Reservoirs and Exploration Directions in ChinaACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2010Caineng ZOU Abstract: Volcanic rocks are distributed widely in China, which are important exploration targets. By analyzing many discovered volcanic hydrocarbon reservoirs all over the world, the authors summarized the geologic characteristics of the formation of volcanic hydrocarbon reservoirs in China, and gave further exploration directions and advices. (1) There are mainly Carboniferous-Permian, Jurassic-Cretaceous, Paleogene-Neogene volcanic rocks in oil- and gas-bearing basins in China, which are mainly distributed in the Junggar Basin, Songliao Basin, Bohai Bay Basin, etc. There are mainly intermediate rocks and acidic rocks in east China, and intermediate rocks and basic rocks in west China. They primarily develop in intracontinental rift settings and island are environments. (2) Porefissure reservoirs are distributed widely in basins, which are volcanic rocks mainly in explosive and effusive facies. (3) Volcanic hydrocarbon reservoirs are chiefly near-source lithostratigraphic hydrocarbon reservoirs, and the oil and gas accumulation is predominantly controlled by lithotypes, faults and structural positions. (4) Deep-seated oil and gas reservoirs in the Songliao Basin and Carboniferous volcanic hydrocarbon reservoirs in the Junggar Basin are potential giant volcanic gas provinces, the volcanic hydrocarbon reservoirs in the Bohai Bay Basin and Santanghu Basin are favorable for oil and gas reserves increase, and volcanic rocks in the Turpan Basin, Sichuan Basin, Tarim Basin have exploration potentiality. (5) The technology series of oil and gas exploration in volcanic rocks have been preliminarily formed. [source] | ||||||||||