Mungo Field UK North Sea 22/20,23/16a: Stratigraphy, salt diapirs and reservoir development (or ‘The Riddle of the Sands’)
Published:January 01, 2005
S. N. J. Payne, P. A. Cornick, L. F. Draper, H. Nicholson, A. C. Morton, P. Huggins, R. Anderton, 2005. "Mungo Field UK North Sea 22/20,23/16a: Stratigraphy, salt diapirs and reservoir development (or ‘The Riddle of the Sands’)", Recent Developments in Applied Biostratigraphy, A. J. Powell, J. B. Riding
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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 insitu 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.
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Recent Developments in Applied Biostratigraphy
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.