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Collaborating Authors
Exploration, development, structural geology
Abstract The present day collage of various Silurian basin fragments in Central and Eastern Europe is the result of several orogenic and rifting/drifting episodes. The proper paleogeographic reconstruction of a single, very large Silurian foredeep basin in the context of regional geology has a major impact on the ongoing unconventional shale gas exploration efforts in the broader region. The distal segments of a large Silurian foredeep basin, as the result of Caledonian orogeny, can be reasonably followed along strike from NW to SE, from Poland to Ukraine and Moldavia, all the way to the Black Sea coast. The foredeep basin sequence is onlapping to the NE on top of various Lower Paleozoic and basement units. The flexural origin of the basin, besides the typical subsidence curves, is also supported by the distribution of lithofacies such as deepwater shales in the center, neritic carbonates on the foreland perimeter and clastic turbidites on the southwestern flank. The proximal parts of the Silurian basin are much harder to reconstruct. Two major opening episodes are critical for restoring the Silurian paleogeography. One of them is the reconstruction of the conjugate Bohemian (Austria, Czechia, Slovakia and Poland) and Moesian (Romania and Bulgaria) passive margins prior to the opening of the Jurassic Magura Ocean. The other important step for any regional-scale Silurian reconstruction is the closing of the Cretaceous western Black Sea Basin between the conjugate margins of Moldavia/Romania/Bulgaria and Turkey.
- Europe > Romania (0.92)
- Europe > Poland (0.91)
- Asia > Middle East > Turkey (0.89)
- (4 more...)
- Phanerozoic > Paleozoic > Silurian > Llandovery (1.00)
- Phanerozoic > Mesozoic (1.00)
- Geology > Structural Geology > Tectonics > Plate Tectonics (1.00)
- Geology > Sedimentary Basin (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- North America > United States > Texas > Fort Worth Basin > Barnett Shale Formation (0.99)
- Europe > Slovakia > Pannonian Basin (0.99)
- Europe > Serbia > Pannonian Basin (0.99)
- (9 more...)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Shale gas (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
Abstract The Netherlands is a mature hydrocarbon province. EBN, the Dutch state participant for hydrocarbon exploitation and exploration, has identified shale plays as one of the contributors to add reserves and to maintain production at the current level. The main source rock for the limited amount of oil accumulations in The Netherlands are the Lower Jurassic (Toarcian) oil-prone shales. Lower Carboniferous (Namurian) hot shales have often been suggested as possible contributor to oil and gas Formation in The Netherlands as well, but this has not been proven to date. Recent discoveries of gas in the time-equivalent Bowland shales in the UK have encouraged interest in the production potential of these shales in North-western Europe. In this paper the geological and geomechanical properties of the Lower Jurassic and Lower Carboniferous are presented in a shale play context. The assessment methodology is subdivided in three sections: 1) the overall geology of the play, 2) the type and quantification of hydrocarbons present and 3) the production characteristics. New and specific measurements on core and cutting material include pyrolysis, methane adsorption, mineralogy, texture, porosity, permeability, static and dynamic geomechanical properties, hardness and fracture conductivity. The two identified plays show very distinctive properties. The Lower Jurassic samples indicate to be mostly thermally immature for dry gas implying that liquids can be expected. The Lower Carboniferous samples show areas that are overcooked. Mineralogical and geomechanical data suggest that different stimulation strategies may be necessary for these two plays to produce hydrocarbons effectively. The source rocks of Lower Jurassic age qualify as relatively soft while the Lower Carboniferous shales with high TOC content classify as very hard. Comparing the results of the assessment to known shale plays in the US, the plays position themselves in the opposite extremes of the productive shale play spectrum.
- Europe > Netherlands (1.00)
- North America > United States > Texas (0.68)
- Phanerozoic > Paleozoic > Carboniferous > Mississippian (1.00)
- Phanerozoic > Mesozoic > Jurassic > Lower Jurassic (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Petroleum Play Type > Unconventional Play > Shale Play (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- (2 more...)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (31 more...)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Shale oil (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Shale gas (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
- Management > Energy Economics > Unconventional resource economics (1.00)
Abstract A new approach, using stress functions, reveals how each component of the stress regime affects the stress pattern around the wellbore. The effect of tectonic far field stress on the stress trajectories in the host rock near a wellbore is visualized in a series of plots with the analytical stress trajectory solutions for a large range of net pressures on the wellbore. The deviatoric stresses around a wellbore result from the dynamic superposition of (1) far field tectonic stress, (2) near wellbore stress due to lithostatic pressure near the open hole, (3) pore over-pressure or under-pressure in the host rock, and (4) hydraulic pressure applied on the wellbore. The principal stress trajectory plots are used to determine the suitable options for well orientations and to delineate stress trajectory control of the incipient brittle failure patterns for hydrofracs and wellbore breakouts. Our approach provides fundamental insight, with an important practical application for improved understanding of the growth of hydrofractures.
- North America > United States (0.69)
- Europe > Netherlands (0.46)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Structural Geology > Tectonics > Plate Tectonics (0.37)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Mississippi Canyon > Block 252 > Macondo Field > Macondo 252 Well (0.99)
- Europe > United Kingdom > North Sea > North Sea Basin (0.99)
- Europe > Norway > North Sea > North Sea Basin (0.99)
- (2 more...)
Abstract Current well placement in unconventional shale ranges from simple geometric well placement to a gamut of patternrecognition systems and geosteering with geochemical and geomechanical analyses. The wide diversity of systems used leads to uncertainty in the effectiveness of any strategy, with confusion as to the true value or merit of a particular technique. Often, a well-placement strategy is based on what came before, with little regard as to the complexities or differences between reservoirs. This paper reviews the current common practices used in geosteering in shales, for both gas- and oil-producing reservoirs. A brief history of strategy development is outlined, with comments about its perceived effectiveness and value. Examples of successes and failures are examined to attempt to determine the viability of a particular strategy. Finally, alternative approaches and methodologies are reviewed and examined, with comments about the potential application, benefits, and value.
- North America > United States (1.00)
- Europe (1.00)
- Geology > Geological Subdiscipline > Stratigraphy (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.97)
Abstract This paper describes the key findings of a regional study that targeted the unconventional potential of exploration assets hold by OMV Petrom in Romania. Three unconventional plays have been evaluated, including the (1) Silurian and (2) the Dogger on the East European Margin (including Moesia), and the (3) Oligocene in Maramures (Pienides). The Silurian shales are at 2-4 km depth in the gas window on Western-Central Moesia. Maturity in most cases has been reached by the Late Paleozoic and it was followed by significant exhumation during the Hercynian Orogeny. The quality of Silurian shale represents a major uncertainty, due to the sparse dataset represented by old wells. The Dogger shales of Northern Moesia are in the oil and gas window under the most external thrusts of the Carpathians at depths that exceed 4 km. The shales have TOC values up to 6 %. Oligocene shales with TOC of up to 10 % in Maramures are in the oil window at depths of less than 2 km. This makes them a very attractive target for shale-oil exploration. However, major setbacks are the complex tectonic structure, rugged topography and large-scale exhumation. Ongoing exploration efforts for non-conventional plays are targeted to define the mechanical properties and the exploration sweet spots in the above mentioned plays, but also assessing the potential of the Late Paleozoic bituminous dolomites of Moesia and other black shales in the Carpathians.
- Phanerozoic > Paleozoic > Devonian (0.96)
- Phanerozoic > Mesozoic > Jurassic (0.95)
- Phanerozoic > Cenozoic > Paleogene > Oligocene (0.90)
- (2 more...)
- Europe > Slovakia > Pannonian Basin (0.99)
- Europe > Serbia > Pannonian Basin (0.99)
- Europe > Romania > Transylvanian Basin (0.99)
- (9 more...)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)
Abstract A multidisciplinary approach to shale characterization in a variety of North American gas- and liquids-rich shale plays has lead to improved understanding of the bulk physical, chemical and mechanical properties of these deposits and their geologic history. This effort is leading to successful exploitation of these enigmatic resources. Microfacies analysis of mudrocks provides a platform for upscaling from the "nano" to the regional scale, and results in comprehensive mudrock characterizations. Microfacies analysis of mudrock types within a select stratigraphic interval in a basin leads to the recognition of mudrock lithofacies. Lithofacies identification allows for calibration of petrophysical models, documentation of basin-specific variations in mudrock composition and microfabrics, the distribution of organic-rich members of these intervals, definition of the mechanical stratigraphy for completion design, and provides the litho-stratigraphic building blocks for predictive sequence stratigraphic models. Successful exploration and exploitation of mudrocks as resources can be advanced when the recognition of mudrock lithofacies provides a methodical means to tie together the geologic, chronostratigraphic, geochemical and petrophysical data from a diverse spectrum of physical scales and technical disciplines.
- Europe (1.00)
- North America > United States > Texas (0.94)
- Geology > Geological Subdiscipline > Stratigraphy (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.73)
- North America > United States > Texas > Fort Worth Basin > Barnett Shale Formation (0.99)
- Europe > United Kingdom > Kimmeridge Formation (0.99)
- Europe > United Kingdom > England > Southern England > Wessex Basin (0.99)
Effects of Pore Structure to Electrical Properties in Tight Gas Reservoirs: An Experimental Study
Liu, Xiao-Peng (Geological Exploration and Development Research Institute in Sichuan-Changqing Drilling and Exploration Engineering Corporation, CNPC, People’s Republic of China) | Hu, Xiao-Xin (Geological Exploration and Development Research Institute in Sichuan-Changqing Drilling and Exploration Engineering Corporation, CNPC, People’s Republic of China) | Xiao, Liang (China University of Petroleum, Beijing, People’s Republic of China)
Abstract The Archie’s equation lost its role in tight gas sands due to the complicated pore structure and strong heterogeneity. It’s a challenge to determine the input parameters in the Archie’s equation. In this paper, 36 core samples, which were drilled from tight gas sands in China, are chosen for resistivity and NMR laboratory measurements. Based on the experimental study of these core samples, the influence factors to electrical properties are concluded to reservoir porosity and the proportion of small pore components. When the porosity is higher than 25%, the relationship between the porosity and the formation factor illustrares a power function, this is coherent with the classical Archie’s equation. When the porosity is low, the statistic line of the porosity and the formation factor bend to the left. The relationship between the porosity and the formation factor is not a simple power function, the parameter of m is various and relevant to porosity. The relationship between the water saturation and the resistivity index is divergent, the saturation exponent n varies from 1.63 to 3.48. After analyzing the corresponding NMR laboratory measurement for the same core samples, an observation can be found that the saturation exponent is relevant to the proportion of small pore components. When core samples are dominant by the small core components, the corresponding saturation exponent is high, vice versa. To estimate reservoir initial water saturation accurately, the pore structure information must be considered.
- Research Report > New Finding (0.71)
- Research Report > Experimental Study (0.71)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Tight gas (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (0.93)
Abstract The paper highlights how key results from historical exploration for conventional hydrocarbons, dating back over 70 years, led to the discovery of a new shale oil resource play in the UK. Early conventional exploration in the West Lancashire sub-basin, conducted by D’Arcy Exploration, a forerunner of BP, was focussed on areas of surface seepage, and resulted in the discovery of the shallow Formby oilfield in 1939. In the late 1940s and early 1950s, a number of deeper wells were drilled, without success, targeting a proposed large Carboniferous conventional trap, leakage from which was thought to be source of the shallow accumulation. Exploration of the offshore East Irish Sea Basin, in the 1970s to 1990s, resulted in numerous oil & gas discoveries in Triassic reservoirs, sourced directly from Visean-to Namurian-age pro-delta shale source rocks (including the Brigantian-to Pendleian-age Bowland Shale Formation) precluding the requirement for secondary migration from Carboniferous traps. Regional studies highlighting poor poroperm preservation in Carboniferous clastic reservoirs led to the further downgrading of Carboniferous prospectivity. The recent identification of an unconventional shale gas play in the West Lancashire sub-basin by Cuadrilla Resources, within the Bowland Shale Formation, has led to a re-evaluation of the Formby area. New palynological and geochemical analyses of the early wells, presented in this paper, confirm the presence of a thick, prospective, Bowland Shale in the south of the West Lancashire sub-basin. Evidence that, locally, the Bowland Shale has generated liquid hydrocarbons is proven by the presence of the Formby shallow oilfield and the numerous oil seeps and relict hydrocarbon columns in the area; opening up a new shale oil resource play. The cumulative results from decades of exploration has revealed the true, unconventional, nature of the Carboniferous "mother lode" sought initially by D’Arcy, thereby heralding a new chapter in the hydrocarbon exploration of the basin.
- Europe > United Kingdom > England (1.00)
- Europe > United Kingdom > Irish Sea > East Irish Sea (0.46)
- Phanerozoic > Paleozoic > Carboniferous > Pennsylvanian > Lower Pennsylvanian > Bashkirian (0.49)
- Phanerozoic > Paleozoic > Carboniferous > Mississippian > Upper Mississippian > Serpukhovian (0.49)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Petroleum Play Type > Unconventional Play (1.00)
- Geology > Geological Subdiscipline (1.00)
- Europe > United Kingdom > Solway Basin (0.99)
- Europe > United Kingdom > Irish Sea > East Irish Sea > East Irish Sea Basin > Ormskirk Sandstone Formation (0.99)
- Europe > United Kingdom > Irish Sea > East Irish Sea > East Irish Sea Basin > Liverpool Bay > Block 110/15 > Lennox Field (0.99)
- (5 more...)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Shale oil (1.00)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Shale gas (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (1.00)