IOSR Journal of Applied Geology and Geophysics (IOSR-JAGG) e-ISSN: 2321–0990, p-ISSN: 2321–0982.Volume 8, Issue 1 Ser. I (Jan – Feb 2020), PP 40-49 www.iosrjournals.org DOI: 10.9790/0990-0801014049 www.iosrjournals.org 40 | Page Post-Stack Reflectivity Inversion for Hydrocarbon Prospectivity in the Niger Delta Field Ekone, N.O 1 ; Ehirim, C. N. 2 ; Nwosu, J.I. 3 andDagogo, T. 2 . 1 World Bank Africa Centre of Excellence (Centre For Oilfield Chemical Research), University Of Port Harcourt. 2 Department of Physics, University of Port Harcourt, Nigeria. 3 Department of Geology,University of Port Harcourt Abstract: The present study describes the use of seismicinversion process to optimize the reservoir characterization of a field in the Niger Delta basin of Nigeria. The purpose of the study was to use post-stack reflectivity inversionto predict the lithology, porosity and presence hydrocarbon within the field away from well control. The reservoir interval were discriminated and evaluated to show characterize lithology and identified fluid. The estimated average porosity in B20 reservoir varies from 28% to 31% whilethe volume of shale and water saturation ranges from 6% to 8% and 19% to 27% in Niger Delta reservoir respectively. Theinversionresult and the RMS attribute was used to predict lithology variationin the field. The sand facies indicate high RMS amplitudecorresponding to low acoustic impedance at the top of the reservoir. Higher- quality areas of Niger Deltareservoir were spotted and specific consideration were dedicated to some deep geological structures that have favored hydrocarbon accumulation. Keywords: Well log analysis, Structural interpretation,Acoustic impedance, Seismic inversion --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 08-01-2020 Date of acceptance: 23-01-2020 --------------------------------------------------------------------------------------------------------------------------------------- I. Introduction The reflection of seismic waves from subsurface layers reveal potential hydrocarbon accumulations. As waves reflect, their amplitude change to uncover significant information about the subsurface. Petroleum geoscientists use amplitudes to foresee variation in lithology and presence of fluids (Hampsonet al 2001). However, extracting reservoir information poses great difficulty for seismic interpreter. Seismic inversion serves as one of the powerful tools for estimating detailed characteristics of the reservoir (Krebs et al., 2009). Seismic inversion method converts the seismic reflection amplitude (reflectivity) into impedance values which is a characteristics of the geologic layer. Inversion could be pre- or post-stack where acoustic and shear impedances and acoustic impedance are estimated, respectively. Inversion results demonstrate high resolution and diminishes the risk involve in drilling (Pendrel, 2006). Post-stack inversion is the most used inversion method because it is fast, reliable and yields acoustic impedance property from the reflection amplitudes. Acoustic impedance is a quantitative seismic attribute used for reservoir characterization. It is closely related to lithology, porosity, pore fill and pressure. The significance of this property is that it contains greater subsurface information than seismic data (Latimaret al. 2000). Post stack inversion has been adopted by several authors (Ebeniroet al., 2003;Adekanle and Enikanselu,2013; Rahim et al., 2014; Sinha and Mohanty 2015;Kumar et al., 2016;Dagogoet al.,2016;Aamiret al., 2018) in reservoir characterization. Their study reveals acoustic impedance in combination with other pertinent seismic attributes are used for prediction of reservoir lithology, hydrocarbon potential prediction, as well as reservoir property estimation. The study area is located in the eastern Niger delta, Nigeria (Figure 1). Niger delta is a basin of 12km sedimentary thickness developed by rift faulting during the Precambrian (Weber, 1971), rich in hydrocarbons. Physiographically, the region is characterized by low-lying, flat geomorphic units with dense network of meandering rivers and creeks with abundant rainfall. The vegetation is dominantly mangrove typical of the zone. The study is aimed at integrating 3-D seismic and well data for post- stack reflectivity inversion in order to analyze reflection characteristics that are favourable to probable hydrocarbon accumulations in the field.