Classification of Litho-Facies using Simultaneous Inversion Technique, Geomechanical Properties Prediction and Pore Pressure Calculation of Badin Gas Field, Lower Indus Basin, Pakistan

Abstract

The Badin reg ion is extreme ly productive, hav ing a decent hydrocarbon potent ial situated in the Lower fndus Bas in, Pakistan. Number of discoveries have been made in the investigation reg ion based on structural interpretation. There is a need to carry advanced seismic investigations on the Badin area, to upgrade the production profile of hydrocarbons fi'om the Badin fi e ld . For this reason, advanced se ismic techniques are applied for the exhaustive investigation of thi s zone. In this research work, the characterization of lithology and fluid is done utiliz ing different strategies, alongs ide the 3D geomechanical mode ling and pore pressure prediction at reservo ir leve l. This coordinated investigation can be divid ed into different parts. As a matter offirst importance to enhance the frequency bandwidth and to improve the spatial and temporal resolution of 3D se ismic data, continuous wave let transform technique is applied. This method improve the reso lut ion of seismic data by enhanc ing the fi'equency co ntent fi'om 30 to 45 Hz. To remove any undesirable no ise content, which was enhanced by applying continuous wavelet transform, 3D prediction filtering is applied which has not just expelled the undes irab le random noises fi'om seismic data, yet it has additiona lly smoothened the 3D seismic data. The preconditioning of the seismic data is very crit ical for applying the simultaneous invers ion studies to 3D Seismic data and fo r litho-fluid c lass ification as well. After the preconditioning of the 3D se ismic cube, the data is interpreted to get the information of subsurface stru ctural patterns. For this reason the synthetic se ismograms are prepared fi'om the access ible well log informat ion of well s Bukhari-Ol , Bukhari-04, Zaur Deep-Ol and Zaur Deep-03. The exact tie of Upper Sand s, Middle Sand and Basal Sands was set up for the interpretation reason. The sort of subsurface structure deciphered is tilted fault blocks with the presence of horst and graben structures in subsurface. After se ismic data interpretation, simultaneous se ismic invers ion is applied over the entire 3D seismic cube at Upper Sand s, Middle Sand and Basa l Sands level. For simultaneous se ismic invers ion, as a matter of fir st importance the low frequency model is produced to recuperate the frequencies and amplitudes of se ismic data. The accessible ang le stacks are inverted to compute P and S impedances. These impedances are addit ionally used to figure the elast ic parameters, for example, mu-rhu, lamda-rho, poisson's ratio and so forth . These e last ic parameters are further used to compute the reservo ir propelt ies, for example, litho logy type, fluid type, its content and saturation. To compute these reservoir propert ies away from the we ll bore and for litho -fluid c lass ification, differe nt comparative strategies are applied which incorporate cro ss-plot method, weighted stack section technique and Bayesian Class if ication technique. Of the three strategies the Bayesian Class ification de livered the best outcomes for litho-fluid c lass ification. At that point the pore pressures for the Badin f ie ld are assessed by utiliz ing the well log information and the se ismic data. The outcomes of both techniques did not show any unusual pore pressure cond itions in the region and drilling of new well can be co mpleted by utilizing ordinary mud weight windows. The stress magnitude and orientation is figured by utiliz ing the geomechanical investigation. The geomechanical investigation of Badin area demonstrate the presence of normal stresses a ll through the examination region with no abnormal stresses. The minimum horizontal stresses are computed, and from the extents of minimum horizo ntal stresses, the maximum horizontal stresses are processed. The heading of maximum horizontal stresses is NW and SE. After the computation of geomechanical mode l, the se ismic inversion is applied to figure the three dimens ional mechanical earth model to get the data of geomechanical properties over entire of the 3D seismic cube. From this research work, it is reasoned that the Upper Sands and Middle Sands go about as good hydrocarbon producers in Badin region, however Basal Sands don't act as good hydrocarbon producer on account of more sha le to sand ratio . The quality of sand is good for Upper Sands and Midd le Sands in the center and western part ofthe study area with more hydrocarbon saturation, while the eastern part of survey don't demonstrate much potential. The pore pressures computed utiliz ing the well and se ismic data don't demonstrate any abnorma l behav ior. While stresses are oriented in NW and SE bearing with no anomalous behavior.