Identification of seismic attributes for hydrocarbon prospecting of Akos field, Niger Delta, Nigeria

Research Article Identification of seismic attributes for hydrocarbon prospecting of Akos field, Niger Delta, Nigeria Godwin Omokenu Emujakporue1 · Emmanuel Enifome Enyenihi1 Received: 5 December 2019 / Accepted: 18 March 2020 © Springer Nature Switzerland AG 2020 Abstract In this study, we have extracted and analyzed four seismic attributes of Akos oil field to obtain more information about the structures, stratigraphy and hydrocarbon potential of the Akos field from available seismic and a suite of well logs data. Two lithology and reservoirs were delineated from the well logs. Two horizons and growth faults were identified in the seismic sections. For a comprehensive analysis of the structural and stratigraphic understanding of the reservoirs, four seismic attributes variance edge, sweetness, root mean square and relative acoustic impedance were applied to the seismic data. The Variance edge analysis was used to delineate the prominent and subtle faults in the area. The high sweetness regions in the seismic data indicate high amplitude which indicates the presence of hydrocarbon-bearing sand units. The root mean square amplitude analysis also indicates the presence of hydrocarbon in seismic data. The relative acoustic impedance analysis was used for delineating lithology variation in the seismic sections. The result of the seismic attribute analysis has shown that the Akos field has good hydrocarbon prospects. Keywords Seismic attributes · Root mean square amplitude · Variance edge · Niger-Delta · Hydrocarbon prospects 1 Introduction Seismic attributes analysis involves the procedure used to extract corresponding subsurface geological information from seismic sections [5–7, 20]. Seismic attributes are extensively being used in the oil industry to predict subsurface reservoir properties [9, 28, 32, 35] . Seismic attributes are used in most seismic exploration and reservoir study to correctly image the subsurface geological structures, correctly characterize the amplitudes of the seismic data and to obtain information on reservoir properties [26, 27, 38, 39]. Seismic attributes analysis also offers clues to lithology typing, estimation of layer porosity, fluid content, mitigation of stratigraphic and structural features, drilling risk, reservoir characterization, and better identification and definition of sweet spots. Seismic attributes are quantities of geometric, kinematic, dynamic, or statistical features obtained from seismic data [11, 18, 24, 35]. The geometrical seismic attributes can enhance the visibility of the geometrical characteristics of seismic events and are sensitive to the lateral variation of azimuth, continuity, similarity, curvature, energy, and dip [3]. The geometrical attributes are used for structural and stratigraphic interpretations of seismic data. This study aims to determine the seismic attributes of the Akos field for the identification of potential hydrocarbon reservoirs and four seismic attributes: variance edge, sweetness, root mean square and relative acoustic impedance were applied to the seismic data. * Godwin Omokenu Emujakporue, ; Emmanuel Enifome Enyenihi, | 1Department of Physics, University of Port Harcourt, Choba, Rivers State, Nigeria. SN Applied Sciences (2020) 2:910 | https://doi.org/10.1007/s42452-020-2570-1 Vol.:(0123456789) Research Article SN Applied Sciences (2020) 2:910 | https://doi.org/10.1007/s42452-020-2570-1 2 Geological background The study area (Akos Field) is located in the onshore coastal swamp depositional belt in the eastern part of the Niger Delta (Fig. 1) and it lies on latitudes 4° 19′ 00″ N and 4° 50′ 00″ N and Longitudes 6° 02′ 30″ E and 7° 10′ 00″ E. The base map of the area showing the seismic lines and well locations are shown in Fig. 2. The Niger-Delta is located in the southern part of Nigeria, West Africa in the Gulf of Guinea. It is a major hydrocarbon province in the world. It covers an approximate area of about 75,000 with an average thickness of about 12 km. It is made up of an overall regressive clastic sequence [12, 30]. The Niger Delta resulted from the separation of the African and South American plates starting in the Late Jurassic and continuing into the Cretaceous. The Niger Delta has one identified petroleum system known as the Tertiary Niger Delta (Akata-Agbada) petroleum system [8, 12, 23, 30, 37]. Three lithostratigraphy (Akata, Agbada and Benin Formations) are present in the basin [13]. The Akata formation is the main source rock and it is made up of shale. The Agbada Formation, which is the main reservoir, lies on top of the Akata Formation and it is made up of alternation of sand and shale. The Benin Formation lies on top of the Agbada Formation and it made up of sand lithology. Most aquifers in the basin are found in the Benin Formation. The oil in geological structures in the basin may be trapped in dip closures or against a Synthetic or antithetic fault (Fig. 3). Fig. 1  Map Niger Delta showing the study area Vol:.(1234567890) Fig. 2  Schematic Base map showing the study area 3 Materials and methods The data provided for this research work are 3 D-seismic volume in SEG-Y format, composite well logs (ASCII), and check shot data: The logs include Gamma ray (GR), resistivity (LLD) and density (RHOB). The data were obtained from the Shell Petroleum Development Company of SN Applied Sciences (2020) 2:910 | https://doi.org/10.1007/s42452-020-2570-1 Research Article Fig. 3  Generalized dip section of the Niger Delta showing the structural provinces of the Delta. Adapted from [40] Nigeria (SPDC) in line with the Department of Petroleum Resources (DPR) and the federal government’s policy on education. Petrel® E&P software platform 2014 was used for the 3D seismic interpretation and attribute visualization, and well logs data analysis. Among the seismic attributes that have been used in the visualization of the geology of the subsurface are variance, root mean square amplitude, sweetness, and relative acoustic impedance. The seismic attribute analysis was applied to the seismic inline 6871. The procedure adopted for the research are; wells -to-seismic tie; seismic attribute analysis and prediction of reservoir properties from the seismic attributes. 4 Delineation of reservoir The available gamma-ray and resistivity logs from the oil wells in the field were used for lithologies and reservoirs delineation. The deflections of the gamma ray signature to the left (low values) indicate sandstone while the deflection to the right (high values) signifies shale. High resistivity values corresponding with sandstone zone is interpreted as a reservoir while low resistivity values represent shale or reservoir containing saltwater. 5 Generation of synthetic seismogram Synthetic seismogram was generated from sonic and density logs for one of the wells in the field. Well to seismic tie of the hydrocarbon reservoir was carried out using checkshot data, which helps in stu (...truncated)