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NARROW
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commodities
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petroleum (1)
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geologic age
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Phanerozoic (1)
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petroleum (1)
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Abstract The Dino 9 Lifetime Achievement Award was bestowed upon Dr Robert A. Fensome of the Geological Survey of Canada in recognition of his outstanding research record in the field of dinoflagellate cysts. This is specifically his work on the classification, biostratigraphy, evolution, phylogeny and taxonomy of dinoflagellate cysts, his work on the geology of Canada, public outreach and as an organizer of conferences.
Abstract The extensive Cretaceous sedimentary sequence exposed within the James Ross Basin, Antarctica, is critical for regional stratigraphic correlations in the Southern Hemisphere, and also for our understanding of the radiation and extinction of a range of taxonomic groups. However, the nature and definition of Cenomanian-Turonian strata on the NW margins of James Ross Island has previously been difficult, due both to marked lateral facies changes and to stratigraphical discontinuities within the extensive Whisky Bay Formation. Facies variation and local unconformities were the result of fault-controlled deep-marine sedimentation along the basin margin. In this study the Albian–Cenomanian boundary is defined for the first time in the upper levels of the Lewis Hill Member of the Whisky Bay Formation. However, there is a Cenomanian–late Turonian unconformity between the Lewis Hill and Brandy Bay members of the Whisky Bay Formation. Equivalent lithostratigraphical units exposed further to the SW on James Ross Island appear to be more complete with the early Cenomanian–late Turonian interval represented by the upper parts of the Tumbledown Cliffs and the lower part of the Rum Cove members of the Whisky Bay Formation. The Turonian–Coniacian boundary is provisionally placed at the junction between the Whisky Bay and Hidden Lake formations. The revised stratigraphic ages for this section show that the Late Cretaceous radiations of a number of major plant and animal groups can be traced back to at least the Turonian stage. This raises the possibility that their dissemination might be linked to the global Cretaceous thermal maximum.
Abstract This volume in the Special Publication Series of The Micropalaeontological Society (TMS) is the result of an extremely successful joint meeting of TMS, the American Association of Strati-graphic Palynologists (AASP) and the North American Micropaleontology Section (NAMS) of SEPM that took place at University College London between 11 and 13 September 2002. The main theme of this international meeting was ’ Recent Developments in Applied Biostratigraphy’ and the vision was to encourage trans-Atlantic exchange of ideas, ultimately to seed new research initiatives. In particular, the aim was to develop an integrated multidisciplinary approach in both the academic and industrial realms. The editors hope that through publication of this volume, this goal will have been realized. The conveners of the meeting were: James Powell (Dinosystems) acting as TMS Secretary at the time; James Riding (British Geological Survey) acting as both TMS Treasurer and AASP President-Elect at the time; Chris Denison (ChevronTexaco) representing AASP; Tom Dignes (ExxonMobil) representing NAMS; Rachel Preece (ChevronTexaco) representing TMS in the USA; Alan Lord (UCL) acting as Local Secretary; Sue Mathews (UCL) providing Local Support. Over 200 delegates registered for the meeting from 25 countries (Argentina, Austria, Australia, Belgium, Brazil, Canada, Colombia, Denmark, France, Germany, India, Ireland, Italy, Jamaica, Mexico, Netherlands, Norway, Oman, Saudi Arabia, Spain, Switzerland, Trinidad, UK, USA and Venezuela). A group photograph of the delegates was published in the AASP journal Palynology (vol. 27, pp. 270, 271)
Morphostratigraphy: A new non-taxonomic biostratigraphical technique applied to a turbiditic deep-sea reservoir (Paleocene Maureen Formation, Fleming Field, UKCS)
Abstract This paper presents the results of a study that assesses a new non-taxonomic biostratigraphical technique as a tool for refining reservoir correlations. In this example from the Paleocene Maureen Formation, Fleming Field, UKCS, morphostratigraphy provides greater biostratigraphical resolution than a more conventional biozonation or bioevent approach and significantly improves reservoir correlation. As a result, a different reservoir sand connectivity model is proposed. This model explains production anomalies experienced in the field. The study also clearly demonstrates the applicability of morphostratigraphy to refine correlations within deep marine turbidite settings.
Mungo Field UK North Sea 22/20,23/16a: Stratigraphy, salt diapirs and reservoir development (or ‘The Riddle of the Sands’)
Abstract Mungo is an oil and gas field located within the Eastern Trough of the UK central North Sea. It comprises a salt diapir flank structure reservoired within Paleocene turbidite sandstones. Biostratigraphical data from early wells indicated extreme geological complexity; reworking, caving and injection were all invoked. Using the principle that the dinocystgenus Apectodinium did not migrate into the North Sea until Unit S1a of the Forties Sandstone Member, interpretation centred on the last downhole occurrence (LDO) of this genus. Once established, this ’golden spike’ became the key to interpreting well stratigraphy. The complexity thereby imposed fitted notional models of a ’Forties melange’ reservoir, with older sediments slumped off the growing diapir during the time of Forties deposition. Inter-well correlation was rendered doubtful and the role of biostratigraphy downgraded. Continued development drilling induced a further attempt to unravel this complexity. Emphasis was changed, downplaying the Apectodinium driven model, seeking instead any evidence of an in situ stratigraphy. Re-examination of biostratigraphical and core material, combined with heavy mineral analysis, has recognized a full ’normal’ Paleocene succession in which five layers can be correlated. The prime reservoir is now assigned to the Maureen Formation, albeit with significant volumes of the Forties Sandstone Member structurally emplaced, presumably by injection, entraining fossiliferous Forties muds. Possible mechanisms for injection are discussed.
The Ravenscar Group: A coeval analogue for the Middle Jurassic reservoirs of the North Sea and offshore Mid-Norway
Abstract A palynostratigraphical study of the Middle Jurassic Ravenscar Group, Cleveland Basin, northern England involving the integration of miospore and microplankton data with sedimentary facies data has resulted in improvements in the stratigraphical resolution of offshore hydrocarbon-bearing strata in the North Viking Graben and Mid-Norway. The Dogger Formation is of ‘earliest’ Aalenian age and is correlative with the uppermost Dunlin Group, Drake Formation and Båt Group, Ror Formation. The overlying Aalenian Saltwick and Eller Beck formations correlate with the Brent Group, Broom-Rannoch-Etive-Ness and the Fangst Group, Ile-Not–‘lower’ Garn genetic packages. The Cloughton Formation is either unrepresented or condensed in the Brent Province and Mid-Norway due to a regional unconformity, which truncates lower Bajocian sediments. The Scarborough Formation is of ‘latest’ early to ‘earliest’ late Bajocian age and correlative with the older part of the Tarbert-Heather and the ‘upper’ Garn-Melke genetic packages. These interpretations contrast markedly with the majority of those published.
Abstract The submarine fan/channel complex of the Eocene Ainsa System in the south-central Pyrenees, Spain is in the process of being analysed for its microfossil content. The aims of this analysis are to establish the age and palaeoenvironment of the system, and to investigate whether the different types of (channel axis, off-axis and levee/overbank) sub-environments that it contains can be discriminated using micropalaeontological criteria, thus contributing to a hydrocarbon reservoir analogue model. This paper presents some preliminary observations.
Micropalaeontological dissection of the Shu’aiba Reservoir, Saudi Arabia
Abstract Determination of the depositional architecture of carbonate hydrocarbon reservoirs is a necessary prerequisite for pre- and syn-development modelling and simulation. Such reservoirs are typically too thin for internal bedding geometries to be confidently determined from seismic and wireline log evidence, and this aim is best achieved by integrated palaeontological and sedimentological studies. Of these, micropalaeontological analysis and biofacies interpretation of closely spaced core samples can reveal cryptic, high-frequency depositional cycles and three-dimensional palaeoenvironmental information. In Saudi Arabia, the Shu’aiba Formation is the main reservoir in the Shaybah field, and has been subdivided into a number of biofacies (ShBf-1 to ShBf-10) within four main depositional units, of which the lower unit (Sh1) is regionally extensive, moderately deep marine and of non-reservoir significance. A thicker second unit (Sh2) displays significant lateral and vertical differentiation of a rudist-rimmed shallow carbonate platform in which discrete lagoonal, rudist bank complex and fore-bank biofacies have been determined. Deep platform sediments characterize the uppermost stacked unit (Sh3) of the main buildup, and are of early Aptian age. Flank carbonates onlap the former three units and are assigned a late Aptian age (Sh4). This fully integrated palaeontological approach to over 50 cored wells from the Shaybah Field has significantly provided a detailed stratigraphic and palaeoenvironmental interpretation that is currently being used to successfully develop this field with 14 billion barrels of crude oil and 25 trillion cubic feet of gas in place. A satisfactory sequence stratigraphic interpretation of the Shu’aiba Formation at Shaybah remains elusive, as neither detailed seismic evidence nor correlatively valuable wireline logs are available.
Saudi Arabian Permo-Triassic biostratigraphy, micropalaeontology and palaeoenvironment
Abstract The Khuff Formation of Saudi Arabia consists of a succession of shallow marine carbonates, mudstones and evaporites. It is exposed along the basement-flanking outcrop belt of central Saudi Arabia, and also forms important hydrocarbon reservoirs at depth in the east. Micropalaeontological evidence suggests that the Khuff Formation in Saudi Arabia is of latest Permian to early Triassic age. Of the four members, the Permo-Triassic boundary is located at, or slightly above, the boundary between the uppermost Midhnab and Khartam Members in the outcrop belt and within the lower part of the Khuff B carbonate reservoir in the subsurface. Accurate correlation between the exposed succession and the subsurface lithologies remains a tantalizing problem. Micropalaeontological biocomponents are sufficiently distinct within the late Permian carbonate succession to enable determination of a series of palaeoenvironmentally significant biofacies for which no previous interpretation has been suggested. Tiered biofacies reveal significant deepening and shoaling trends that assist in determining maximum flooding events and depositional cycle boundaries. The subsurface reservoir carbonates display subtle palaeoenvironmental variations of an extensive, generally shallow marine, carbonate platform that ranged from intertidal to depths within intra-shelf basins that probably rarely exceeded storm wave base. The problems of synonomy of the foraminifera have been resolved by a pragmatic approach justified by the analytical time constraints demanded by industrial micropalaeontology.
Abstract The Callovian to Volgian section in the Tyumenskaya superdeep well SDW-6 is very important for the development and improvement of Jurassic biostratigraphy in West Siberia. It was drilled with almost continuous recovery of core (about 200 m), which is characterized by rich assemblages of microfossils. In this paper the results of micropalaeonto-logical and palynological studies of the most complete Jurassic succession in the north of West Siberia are discussed, taking into consideration the problems of bio- and lithostratig-raphy of the region. The comprehensive analysis of the stratigraphical distribution of the different micro-fossil groups (foraminifers, microforaminifers, ostracods, dinoflagellate cysts, acritarchs, prasinophytes, spores and pollen) allows the creation of a detailed zonation. For the first time, an almost continuous sequence of dinoflagellate cyst zones for the Callovian-Middle Volgian has been established in the north of West Siberia, providing the basis for development of the Jurassic dinoflagellate cystzonation in West Siberia. Distinctive features of microbenthos communities and microphytoplankton associations reflecting biofacies have been studied. The pattern of distribution of microbenthic communities and microphytoplankton associations, depending on changes of transgressive-regressive events and palaeoenvironments in the Callovian to Volgian, has been established.
Abstract Oil exploration in Colombia has traditionally taken place in areas with relatively few structural complexities. However, in the last decade, exploration has moved to regions characterized by complex structural deformation, poor seismic resolution, and many stratigraphic problems, such as in the Llanos foothills. In this region, the major reservoirs occur in mostly continental Paleogene sequences, where palynomorphs are usually the only fossil group found. Thus, palynology has become an important tool in controlling the stratigraphic position of a well during drilling, in testing diverse seismic and structural interpretations, and correlating reservoirs. This study provides a biostratigraphic framework for the Cuervos Formation (Late Paleocene to earliest Eocene) of the Llanos and Llanos foothills, making use of graphic correlation. We used 14 sections with palynological information from outcrops, well cores, and well ditch cuttings. Five informal palynological zones are proposed. Based on the biostratigraphic model produced by this analysis, we reinterpreted a recently drilled well in the Llanos foothills upon which several previous interpretations had been made. A sidetrack of that well was subsequently drilled, validating the proposed model. This is a positive test that the biostratigraphic framework developed for the Cuervos Formation is reliable and can be successfully applied to exploration in the Llanos foothills.
Abstract: The Muglad Basin is part of the Central and West African Rift System that started to develop during late Jurassic/early Cretaceous time. The system evolved through three rift cycles spanning Berriasian to Cenomanian, Coniacian to Maastrichtian and Paleocene to Pliocene. In this work the results of a palynological study of selected wells from the Muglad Basin, Sudan are presented. The combination of samples from these wells has enabled a palynological analysis of a nearly complete Cenozoic section (Quaternary to Paleocene) which was developed during the last rift cycle. Five Zones have been recognized, most of which are further divided into two sub-zones. The Zones are (i) Gramineae - Chenopodipollis microporatus (Quaternary; Post-Adok Formation); (ii) Verrucato-sporites spp. (Pliocene-Miocene; Adok Formation); (iii) Cyathidites minor-Perfotricolpites digitatus (Miocene-Oligocene; Tendi Formation); (iv) Striatopollis spp. (Oligocene-Eocene; Nayil Formation); (v) Mauritiidites crassiexinus–Echimonocolpites rarispinosus (Paleocene; Amal Formation). The characteristics of each zone and corresponding sub-zones are discussed.
Abstract Research over the past few decades has shown that recent marine dinoflagellate cyst assemblages are strongly influenced by environmental factors, and statistical modelling of ecological signals (SMES) therefore has potential application for interpretation of fossil dinocysts in biostratigraphy. Towards this end a global database of recent cyst distributions from known environments has been developed using statistical methods that most accurately reflect and quantify the ecological signals expressed by the cysts. The first test is reported here of the application of SMES to industrial biostratigraphy using a palynology dataset from four wells along an onshore-offshore transect from the Norwegian North Sea provided by Statoil. The wells were part of a larger study on palaeoenvironments previously completed by Statoil on approximately 48 wells, where some of the traditional multivariate statistical methods had been tried but without success. The palaeoenvironment was thus partly understood, allowing the SMES method to be tested against a control. Correspondence analysis on the dinocyst data from each well allowed the identification of the statistically most important species, and the relative positions of these species along the two most important axes suggested ecological trends (the coastal/oceanic being most dominant). Tracking these down-hole showed two major shifts in each well that could be correlated between all wells; the shifts corresponded to major flooding surfaces previously identified, and suggested orientation of the well sites relative to a palaeo-shoreline. This first test strongly suggests that these methods offer a much quicker, and more robust application for palaeoenvironmental interpretations from the dinocysts in biostratigraphic datasets.
Abstract Biostratigraphical resolution has increased markedly over the past few decades. The use of origination and extinction data has been supplemented, particularly at the reservoir scale, by more subjective local ‘bioevents and biozones’ in the form of successions of unique abundance fluctuations of individual taxa and distinct faunal/floral assemblages. Herein, a methodology is described that uses a sample-by-sample multivariate similarity matrix of biostratigraphical census data to define a high-resolution correlation path between two wells. Three different similarity/dissimilarity metrics are used to calculate the matrix (cosine-theta, and Euclidean and Manhattan distance) for each of three transformations of the data: raw data (counts), presence-absence, and percent-range transformation. Recommendations are presented for use of various metrics and transformations, given different types of data sets and the objectives of the analyst. The correlation path through the matrix is monotonic and must increase in depth in one or both wells. The correlation path moves one sample-pair or matrix element at a time to an adjacent element that has the highest average, local path. After an adjacent element is selected it becomes the current state and the algorithm repeats the process until the matrix has been transited. The correlation path can be constrained using a priori information, if available (e.g. maximum flooding surfaces). Such events are established as tie-points, and the correlation path is required to go through these points. Additional steerage of the correlation path may be accomplished interactively, by graphical analysis of individual taxon abundance plots, followed by establishment of additional tie-points. The method also includes calculation and graphic representation of a 95% confidence interval about the calculated faunal/floral percentages. This enables the biostratigrapher to take into account the statistical confidence one has in a peak faunal abundance. The method is demonstrated on palynological data from two wells from the Blake Field, Outer Moray Firth, UKCS.
Non-acid wellsite palynology: Widening opportunities
Abstract Wellsite palynology is a geoscientific tool, which involves real time preparation and analysis of subsurface samples. Analysis of palynomorphs during drilling is used to identify the location of the drill bit in the geological succession, critical for reservoir prediction, biosteering, casing, coring and terminal depth determinations to be made. Until recently, extraction of palynomorphs was only considered possible with the use of highly toxic and hazardous chemicals (e.g. hydrofluoric acid) and technical support in a mobile laboratory, resulting in high costs, logistical problems and potential Health, Safety and Environment (HSE) risk. The development of new processing techniques has removed the bulk of the chemical component in the sample processing and allow a primarily mechanical extraction technique to be employed at wellsite, representing a major breakthrough that reduces cost and logistical problems and virtually eliminates any chemical HSE risk. As a result, the application of wellsite palynology has expanded, operational costs at wellsite have been reduced, the dependence on a limited market place for the hire of specialized laboratory equipment is alleviated and the global reach of this technique is enhanced. The technique has been used successfully at wellsite for sediments of Middle Jurassic to Palaeogene age, on over 60 offshore wells in the UK, Norway and Faroes. Laboratory testing has shown wider geographical and age applicability. The technique has enabled horizontal biosteering of wells, the maximization of mature field recoverable reserves and the application of wellsite palynology to areas with logistical limitations, with significantly lower HSE risks.
Abstract In recent years the application of biostratigraphy to hydrocarbon exploration and development has become increasingly important both scientifically and economically. The demand for higher stratigraphical resolution in field development studies has resulted in the utilization of new approaches. However, in under-explored areas with little reliable primary biostratigraphical data, conventional methods using relatively coarse biozonations still have relevance. The aim of this volume is to encourage an exchange of ideas and to seed new research initiatives particularly within integrated multidisciplinary teams. The papers are divided into four main themes which cover a broad range of modern applications of biostratigraphy. The first three themes are: UK North Sea field development; outcrop analogues; and international exploration and development. The final section discusses new methodologies, such as the application of correspondence analysis and multivariate correlation of wells, and palynological processing techniques applicable to the wellsite.