Surajit Gorain - Academia.edu (original) (raw)

Papers by Surajit Gorain

Journal of Geosciences Insights

Hydrocarbon exploration entails complex and costly endeavors, with drilling activities accounting... more Hydrocarbon exploration entails complex and costly endeavors, with drilling activities accounting for the highest expenses. To facilitate informed decision-making for geoscientists and investors, this study presents a template highlighting the average rig days and drilling ease in Indian sedimentary basins. Leveraging data from over 19,000 wells across these basins, a comprehensive analysis was conducted. While the physics and chemistry of drilling are well understood, uncertainties arise from local geological conditions, well specifications, contractor expertise, timely rig availability, market factors, and local regulations. By filtering out extreme rig times affected by these factors, average rig time (ART) and average total depth (ATD) were calculated for each basin using a simple averaging approach. ART was visualized as a basin-wise bubble map, providing an overview of the drilling duration required to reach total depth. This aids in estimating drilling costs for future wells ...

International Journal of Petroleum Technology

Carbonate reservoirs present significant challenges in characterizing and extracting hydrocarbons... more Carbonate reservoirs present significant challenges in characterizing and extracting hydrocarbons due to their low permeability, matrix heterogeneities, fractures, and dissolution patterns. Accurately predicting the facies architecture and reservoir properties in such complex formations has been a persistent challenge for geoscientists. This paper proposes an integrated approach that combines geo-body extraction and geostatistical modeling to accurately predict the facies architecture and reservoir properties in carbonate reservoirs. The methodology begins by generating 3D seismic root mean square amplitude (RMS) attributes, which are then used to extract geo-bodies along the pay sequences. The extracted geo-bodies are then subjected to geostatistical modeling to analyze reservoir properties to facilitate the optimization of drilling and production strategies. To validate the effectiveness of the proposed approach, a small field in the Mumbai offshore basin is chosen as a case study. This field is located on the Mumbai High-Deep Continental Shelf and exhibits westerly dipping structures. Structural mapping confirms the presence of an antiformal structure, with one particular well (D-8) at the crest showing the absence of hydrocarbons. The proposed approach mapped two seismic reflectors within the reservoir zones and generated window-based 3D seismic RMS attributes to extract three geo-bodies within the reservoir. Facies and property modeling revealed the presence of distinct nonreservoir facies with poor reservoir properties near dry wells (D-8, D-4, and D-7), which is in line with the production performance observed in the drilled wells. The proposed integrated approach of geo-body extraction and geostatistical modeling is effective in delineating the facies architecture and reservoir heterogeneity of carbonate reservoirs. It enables the identification of favorable reservoir facies and facilitates a comprehensive assessment of the remaining potential.

Journal of Asian Earth Sciences: X, 2023

Gas discovery in Nohta-2 well from Proterozoic Rohtas plays in Vindhyan Basin, south of Ganga Bas... more Gas discovery in Nohta-2 well from Proterozoic Rohtas plays in Vindhyan Basin, south of Ganga Basin has been a significant lead to suggest that Proterozoic sediments underneath Ganga Basin could be prospective. With this in view, the Govt. of India (GOI) acquired 1350 LKM (Line kilometer) of 2D regional seismic lines to image the Proterozoic sediments for the first time within the basin under National Seismic Program (NSP). The present study is carried out to understand the paleo structures, the nature of the sedimentary sequences, and the trapping mechanism to further visualize the prospectivity of the Proterozoic sequence within the basin. The paleo-tectonic and seismic sequence stratigraphy analysis reveals that the Proterozoic sediments were deposited in the passive margin setting in shallow marine and tidal conditions with several progradations and retrogradation cycles. Precisely, it is noticed that the Proterozoic sediments experienced two stages of progradations and retrogradations. That was followed by a long non-depositional hiatus (>500 Ma) spanning from the Paleozoic to Mesozoic ages which led to a regional unconformity throughout the basin as well as other local unconformities and hydrocarbon traps within the Proterozoic sediments. Four giant structural traps (>300 km2) and one combination trap (>500 km2) are identified within Neo-Proterozoic to Meso-Proterozoic sequence and are expected to be prospective. However, with more exploration efforts and additional data, these traps may lead to a paradigm shift in exploration strategy and discoveries in near future within the basin.

Journal of Asian Earth Sciences: X

In general, standard distribution functions (normal, log normal, gamma etc.) of reservoir propert... more In general, standard distribution functions (normal, log normal, gamma etc.) of reservoir properties (porosity (Φ), water saturation (Sw), net pay (h) etc.) are taken as inputs in Monte-Carlo Simulation for volume estimation. Though this method takes care of the variability in input data set, it is likely that assumed standard distribution functions will not always fit to the actual variation of data. Therefore a customized distribution function which fits to the actual variation of reservoir properties is crucial for better accuracy in volume estimation.

Acta Geodaetica et Geophysica, 2014

With major oil and gas discoveries diminishing in number, industry is turning its attention to re... more With major oil and gas discoveries diminishing in number, industry is turning its attention to redevelop fields with reservoirs (Res) like silts which have otherwise been accorded lower priority earlier. It has always been a challenge to identify the locales with better Re facies development in un-drilled areas of a field and most often many development wells either go dry or turn out to be poor producers, significantly increasing the cost of production from a given field. Kalol Field, Cambay Basin, India is a several decade old discovery with a significant number of development wells. However, the oil recovery remained hardly around 10 %. Most often, the contributing factor for this low recovery is poor Re facies (tight silts) within the major producing sequences like Kalol IX and Kalol X. Hence identifying areas of better Re facies remained a challenging task before the geo-scientists. To overcome this challenge a workflow has been developed for Re characterization based on an "Attribute based Inversion" technique, in which 3D attribute volume of petrophysical properties are calculated through genetic inversion algorithm using a nonlinear correlation between seismic property and log property. Calculated 3D attribute volume of petrophysical properties are utilized further for Re classification and finally geostatistical modeling is performed for Re modeling. The adopted approach is operative even if the Re is very thin (beyond seismic resolution) and can provide a way to generate 3D attribute volumes of log property from seismic and well log data. This approach is also effective in determining the Re geometry and quality of Re, which may help in planning future drilling locations. The application of the workflow has been illustrated with a case study from Kalol Field, Cambay Basin. The obtained results shows that the proposed approach is effective enough in resolving 2-8 m thick Re within Kalol formation. It gives an idea about the Re quality (good or bad Re) and geometry of the Kalol Reservoir in the field. Volumetric calculation shows that there is still

Sanand Structure evolved during Paleocene due to fault block tectonics related to rifting. As rif... more Sanand Structure evolved during Paleocene due to fault block tectonics related to rifting. As rifting continued, the size of structure grew with faulting; grabens formed were filled with syn-rift sedimentation. Kalol Formation was deposited post cessation of rift activity. It is likely that drape structure at Kalol level was formed due to differential compaction with underlying basement rock and Deccan Trap remained uncompact being more competent.

Kalol Field, Cambay Basin India, was discovered in June 1961 and put on production in 1964. But t... more Kalol Field, Cambay Basin India, was discovered in June 1961 and put on production in 1964. But the production history reveals that oil recovery remained hardly around 10% (Jena, 2008). Most often, the contributing factor for this low recovery is poor reservoir facies (tight silts) within the major producing sequences like Kalol IX and Kalol X. Identifying areas of better reservoir facies remained a challenging task before the geo-scientists. to tackle the above challenge, geo-scientists evolved seismic inversion. Inversion through sonic log has been a trend for many years as a litho-prediction tool. But it is often observed that sonic log alone is not fully effective in resolving the subtle differences between clastic facies like silty sand and silty shale. Conventional seismic inversion approach has been modified and a “Multi-litho Attribute based Inversion” has been developed to overcome this challenge of reservoir classification in which 3D attribute volume of petrophysical prop...

Magnetotelluric (MT) data can be particularly useful for delineating potential hydrocarbon traps ... more Magnetotelluric (MT) data can be particularly useful for delineating potential hydrocarbon traps (sediments which are conducting) below volcanic (which are resistive) which give rise to multiple reflection and scattering of seismic energy. The diffusive signal propagation used in MT can be an advantage in a region of intense heterogeneity while seismic signals will be scattered, the MT signals diffuse and give a reliable estimate of the physical property of the medium.

SEG Technical Program Expanded Abstracts 2018