Unconvectional And Conventional Reservoir Characterization Of Lower Goru Formation In Gambat-Latif Block Lower Indus Basin Pakistan

Abstract

The demands in the energy production over the globe is increasing day by day. Subsequently demands in exploration and production of conventional and unconventional hydrocarbon reservoir have increased over the past decades. For hydrocarbon exploration, seismic surveys are the most apposite method because it provides precise and detailed spatial coverage of the subsurface. This study pertains to explore the hydrocarbon within the both conventional and unconventional domains. The methodology to carry out this research work includes 3D seismic data interpretation, petrophysical analysis, seismic inversion analysis, 3D static modeling and TOC estimation. The 3D seismic data interpretation is done by marking major and minor faults, and marking horizons. This information is then used to map the contour. The structural analysis from assigned 3D seismic cube show that normal faulting is present within the study area and the horizons are marked on the basis of the well tops after correlation with seismic data. The petrophysical analysis is done by using the well log data to estimate the effective porosity, lithofacies identification, saturation of water and this information will lead to mark the promising hydrocarbon zone within the reservoir. The petrophysical analysis is performed on all Tajjal wells available. This analysis is used to delineate the lithology, effective porosity and hydrocarbon saturation. The average effective porosity ranges are from 6 to 14%, 9.1% and average hydrocarbon ranges is from 50-74 %, 74% within zone of interest of B Interval and C Interval sands for Tajjal-01.. For Tajjal-02 (water wet), the average effective porosity is 8.30-9.30% and 7% and average hydrocarbon ranges from 47% and 55% within both the B and C intervals of the Lower Goru Formation, respectively. In inversion analysis, various algorithms and techniques were opted to analyses for better understanding of lower Goru sands and shales. The acoustic impedance (AI) sections are the end results of seismic inversion. The acoustic impedance (Al) is the property of the layer, and this property of the layer is used to make quantitative interpretations of seismic data. Model-based Inversion uses a forward model to figure out how to make the synthetic seismic data that is used in the inversion process. Sparse spike inversion gives best result as compare to all other inversion types. 3D static reservoir modelling is used to define reservoir properties in a more realistic 3D geological model in the subsurface. The primary goal of the static type modelling is to determine the accurate amount of hydrocarbons that are contained in the subsurface. These hydrocarbon volume calculations can be performed for the entire reservoir or separately for a fault segment or any layer that was designated as a zone of interest during the model's building. Another important outcome is to DRSML QAU 8 accurately locate the hydrocarbon bearing zones in the subsurface for further developments of study area. Modelling was carried at B and C-intervals both for conventional reservoir parameters and unconventional reservoir parameters like porosity, permeability, water saturation, and TOC content along with facies distribution on whole reservoir intervals. Some promising zones were also identified based on static reservoir modelling study. TOC (total organic content) is calculated using the Passey et al (1990) equation. The ΔLogR technique is used to determine total organic content of the shale portions in the lower part of Goru formation. The results show that in B interval (Talhar shale) has a greater organic content than the C interval shale part. Total organic carbon content all show that the B interval shale (Talhaar shale) has potential for shale gas based on high values of total organic carbon content.