Ahmad, J Geol Geosci 2013, 2:3 DOI: 10.4172/2329-6755.1000123 Open Access Review Article Volume 2 • Issue 3 • 1000123 J Geol Geosci ISSN: 2329-6755 JGG, an open access journal Mitigation Exploration Risk of Jurassic Reservoir by Seismic Inversion, Penobscot Area, Sable Sub Basin Nova Scotia, Offshore, Canada Qadeer Ahmad* Bahria University Islamabad, Pakistan *Corresponding author: Qadeer Ahmad, Bahria University Islamabad, Pakistan, E-mail: qadeer_ahmad2009@yahoo.com Received March 14, 2013; Accepted July 26, 2013; Published July 30, 2013 Citation: Ahmad Q (2013) Mitigation Exploration Risk of Jurassic Reservoir by Seismic Inversion, Penobscot Area, Sable Sub Basin Nova Scotia, Offshore, Canada. J Geol Geosci 2: 123. doi: 10.4172/2329-6755.1000123 Copyright: © 2013 Ahmad Q. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Introduction High exploration costs require that you achieve your target in the frst attempt. Optimization technology innovate higher-value solutions. Inversion is one of those techniques which mitigate the exploration risk by reservoir prediction. It is a process of transforming impedance into quantitative rock properties like porosity, saturation and pore pressure. Area Penobscot is located in the Sable Island, Sable sub basin Canada. Te Scotian Basin lies on the North American Plate. It is a classic passive, non-volcanic conjugate margin. It represents over 250 million years of continuous sedimentation recording the region’s dynamic geological history from the initial opening of the Atlantic Ocean to the recent post-glacial deposition. It contains the lithology ranging from Mesozoic era to Cenozoic era (Figure 1) [1]. Geology of area is complex due to presence of salt (Agro formation) of Late Triassic to Early Jurassic age. Te source rock present in the study area is Mohican and Verril Cannyon formation of Jurassic age. Te reservoir rocks are the Mississauga Formation (clastic) of Early Cretaceous age and Abenaki Formation (carbonate) of Jurassic age (Baccaro member). Mainly trap formed in Late Jurassic to Early Cretaceous age [2]. Inversion Inversion is a process of calculating impedance from seismic data. Te input data is the seismic cube. By applying inversion algorithm, seismic data is transformed into impedance cube [3]. Basis of the calculation is the ‘convolution model. Te model assumes that the Earth has discrete changes in impedance with changing depth and that the seismic wavelet convolves with these points of diferent impedance contrast to produce the seismic trace. Te challenge that seismic inversion face is, to locate and then quantify the impedance contrasts and then compute the impedance itself. It provides quantitative values. Tese quantitative values, attributed to impedance, are derived by multiplying the velocity of sound energy in a medium by the density of the medium. Te refection coefcient of a refecting interface can be calculated. Te value of impedance for the medium below the refecting interface can be calculated if one knows the impedance above the refecting interface or the refection coefcient of the refecting interface. Seismic inversion computed in this way is known as “recursive inversion.” Tis is used here to identify the porosity of Jurassic reservoir [4]. Methodology and Interpretation Te main steps in an inversion study are: • QC of the input data. • Generation of synthetic seismogram and extraction of the wavelet. • Running of the inversion algorithm to generate Acoustic impedance cube • Well–to-seismic calibration • Visualization and interpretation of the results in terms of reservoir development • By using 3D PSTM data, impedance is computed by calculating the ‘refection coefcient’ at refecting interface Ri = (Ii+1 - Ii) / (Ii+1 + Ii) • Where Ii and Ii+1 are, the impedance values of the media above and below the refection interface, respectively. Te equation above can be inverted to produce Ii+1 = (Ri + 1) / (1- R1) I1 • Te value of impedance for the medium below the refecting interface can be computed if the value of impedance for the upper layer is known, then hypothetical velocity value of upper layer is given to calculate the impedance of upper layer until the relative impedance calculated at the zone of interest matched with the absolute impedance calculated from well (Figure 2). Cross plot analysis • Aim of cross plot analysis is to develop the relation between impedance and porosity and indicate the separation of the producing Study Area Penobscot 200 km Figure 1: Geographic map of study area. Journal of Geology & Geosciences J o u r n a l o f G e o l o g y & G e o p h y s i c s ISSN: 2381-8719