Seismic stratigraphy and attribute analysis of an offshore field, Niger Delta, Nigeria
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ORIGINAL PAPER
Seismic stratigraphy and attribute analysis of an offshore field, Niger Delta, Nigeria Eniolayimika Jegede & Bankole Dayo Ako & Peter Adetokunbo & Paul Edigbue & Sunday James Abe
Received: 6 July 2014 / Accepted: 30 September 2014 # Saudi Society for Geosciences 2014
Abstract Three-dimensional seismic and composite well log data from three wells were used to carry out log sequence/ seismic stratigraphy and attribute analysis of an offshore field Niger Delta. The gamma ray and resistivity logs were used to delineate the reservoir sand bodies and carry out sequence analysis. From the log sequence analysis, two depositional sequences were delineated in wells 1 and 2 from 1,820 to 3,020 m and 1,860 to 3,000 m, respectively. The two depositional sequences were mapped on the seismic section at time windows 3.3 and 2.92 s for sequence 1, and for sequence 2 at 2.92 and 2.0 s, respectively. Time slice maps of sweetness attribute were generated to further investigate the hydrocarbon prospect of the field. The seismic facies analysis shows that the depositional setting in depositional sequence 1 is characterized by sheet- to lens-shaped variable amplitude and chaotic reflection characters while depositional sequence 2 is characterized by (i) sheet-like shaped medium to high amplitude, subparallel, continuous reflections, (ii) wedge-shaped low-to-medium amplitude, wavy, continuous reflections, and (iii) wedge-shaped high-amplitude, wavy, continuous reflections. Results from the seismic stratigraphy show that the depositional environment has prograded from the delta platform (delta front) in depositional sequence 2 down to the wave-dominated prodelta/slope (depositional sequence 1) in the shallow marine of the deltaic environment. The reservoir quality sand bodies within this field occur within the depositional sequence 2 and occur within all the systems tracts in this sequence. E. Jegede : B. D. Ako : S. J. Abe Department of Applied Geophysics, Federal University of Technology, Akure, Nigeria P. Adetokunbo (*) : P. Edigbue Earth Sciences Department, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia e-mail: [email protected]
Keywords Sequence stratigraphy . Attribute . Niger Delta . Seismic
Introduction For over 30 years, the oil and gas sector has been the mainstay of the economy of Nigeria. To this effect, oil and gas industries have been thriving so well in the nation, producing and exporting petroleum. In order to maintain the status quo, the oil and gas industries have intensified effort, exploring for more giant offshore oil fields. To embark on any reasonable exploration exercise, knowledge of the sedimentary package of the environment is a key factor. To achieve this, accurate techniques of stratigraphic analysis are needed. One of such techniques is sequence stratigraphy. In recent time, seismic stratigraphy together with attribute analysis has been proved to be a major tool in studying and analyzing the geology and petroleum system of an area (Nauman et al. 2010). The degree
