Dr. Rima Chatterjee | Indian School of Mines, Dhanbad (original) (raw)
Books by Dr. Rima Chatterjee
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Papers by Dr. Rima Chatterjee
We prove that Legendrian and transverse links in overtwisted contact structures having overtwiste... more We prove that Legendrian and transverse links in overtwisted contact structures having overtwisted complements can be classified coarsely by their classical invariants. We further prove that any coarse equivalence class of Legendrian loose links has support genus zero. We also find a relationship between the support genus of the transverse link and its Legendrian approximation. As a corollary to this, we show that loose, null-homologous, transverse knots have support genus zero and also give a condition when non-loose Legendrian knots have non-loose transverse push offs.
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... The corresponding wells in the peri-cratonic area are: wells l, 2, 3 and 4 at or near the Rav... more ... The corresponding wells in the peri-cratonic area are: wells l, 2, 3 and 4 at or near the Ravva prospect; well 5 for the GS-38 field; well 6 near the dry fields GS-I 1 and GS-12 in front of the bight of the Masuli-patnam Bay; well 7 in the MORI-I oil field; wells 11 and Rz4 in the ...
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The study area belongs to the marine geological setup of Surat depression of Mumbai Offshore Basi... more The study area belongs to the marine geological setup of Surat depression of Mumbai Offshore Basin, India. The lithology of three wells in Mumbai offshore is analyzed using Gamma-Ray (GR) log, Density (ρ) log, Resistivity (Rt) log and Neutron Porosity (Φ) log. This analysis makes the identification of the lithology difficult. DSI log is recorded only for wells W-1 but for W-2, W-3 shear wave velocity data is not available. Major lithologies found in this area are sandstone, siltstone, shale, limestone and mixed lithologies of sand, silt, shale. This study aims to construct a lithology indicator parameter which is better in the identification of lithologies. This lithology indicator parameter is named as Lithology Impedance (LI). This parameter is calculated using density, P wave (Vp) and S wave (Vs) velocity. This indicator shows a better contrast for different lithology and also follows a specific range. To estimate the LI log value for W-2 and W-2, the Vp-Vs relation from W-1 is u...
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Prediction of permeability from well logs in heterogeneous formation is a difficult and complex p... more Prediction of permeability from well logs in heterogeneous formation is a difficult and complex problem to solve by conventional statistical methods. The correlation between parameters like porosity with permeability for different we lls alone may be a crude approximation for permeability estimation, even for homogeneous formations. Recently artificial neural networks have been successfully used for solving many complex problems in reservoir permeability estimation. In this work, the neural network technique is utilized for the permeability estimation of coal formations. The back propagation neural network (BPNN) permeability prediction model has been developed from a data set consisting of well test permeability and well log data from “well A” located in the Damodar valley coalfield, India. The bulk density, gamma ray, long normal resistivity and neutron porosity logs have been used as the inputs for the modelin g. The model is tested with well log data from the “well A” as well as...
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Journal of Geophysics and Engineering
The Miocene reservoirs in prolific Krishna-Godavari basin are mostly fluvial deposits and laminat... more The Miocene reservoirs in prolific Krishna-Godavari basin are mostly fluvial deposits and laminated or blocky in nature. The type of reservoir quality depends on associated geological environments. Due to several lateral variations in reservoir properties, a similar kind of workflow for reservoir characterisation does not work. Customised workflow needs to be applied in this area for estimation of petrophysical properties or rock physical analysis for reservoir quality prediction. As the major input of rock physical analysis is petrophysical properties, it is crucial to estimate these properties accurately. Meanwhile, it is also important to check the seismic sensitivity to change in fluid saturation in the reservoir characterisation process. The analysis assures the presence of reservoir and hydrocarbon contact in seismic sensitivity, which is essential for removing risk. Integrating the geological model with rock physical analysis for reservoir characterisation at the drilled well...
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Natural Resources Research
Well log analysis and production testing in coal are the initial requirements to judge the prospe... more Well log analysis and production testing in coal are the initial requirements to judge the prospectivity of a coalbed methane (CBM) reservoir. The process of prospect identification through laboratory studies is accurate although it is time-consuming and expensive. Therefore, we developed a methodology to identify prospective coal seam by establishing multiple regression models of geophysical well log parameters vs. organic/inorganic contents from laboratory-tested core samples for one seam. The Langmuir’s equation and methane adsorption isotherm were used to estimation of gas and saturation content by developing a regression model from organic content. Gas and coal contents (ash, moisture, fixed carbon, and volatile matter) were obtained from the subsequent propagation of the established equations to other wells. Gas saturation increased with depth from 60 to 69%. Mapped seam thickness and gas content were in the ranges of 10.0–54.0 m and 6.1–28.2 cc/g, respectively. Overlaying of seam thickness and gas content identified the sweet spots in releasing potential future well locations. Errors within the permissible limit between the predicted and observed values indicate the gas estimation to be reliable. Another application for electro-facies classification was demonstrated by applying multi-resolution graph-based clustering architecture to capture texture parameters from histogram and auto-covariance function in resistivity image log. Determination of lithology by correlation of resistivity image and geophysical well log corroborated with the depositional environment having fining upward formational sequence. Thus, this study helps in estimating proximate components, gas content, and saturation with depth in coal seam for production optimization to better understand its implications on the dewatering and gas production periods in the Bokaro CBM reservoir situated in India.
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Near Surface Geophysics
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Journal of Petroleum Science and Engineering
Abstract Geomechanics plays a critical role in the different stages of coal bed methane (CBM) ope... more Abstract Geomechanics plays a critical role in the different stages of coal bed methane (CBM) operations, starting from its development through production to its abandonment as in Sohagpur field of central India. In general, higher gas production has been observed from the coal seams in low-stress regimes compared to high-stress regimes; however, during the CBM development planning, stress information has been overlooked. The need for inclined and horizontal wellbores in coal seams has increased due to their many-fold rise in production when compared to vertical wells with a minimum surface footprint. However, these non-vertical wells have wellbore instability issues leading to high nonproductive time (NPT) during drilling and completion operations. Prolong challenges exist in achieving the desired half-length from hydraulic fracturing (HF) stimulation due to the limited understanding of the stress contrast between target coal and bounding lithology. The permeability of the coal reservoir varies greatly during depletion due to the combined effects of effective stress and matrix shrinkage. These effects directly impact productivity and hence, require a detailed understanding of how permeability varies during production life. In many instances, production from coal seams is complicated and unpredictable because of the influence of stress induced natural fractures. A geomechanical earth model is focused on understanding and mitigating the aforementioned challenges. In addition to coal thickness and gas content, stress-permeability maps are prepared to assist in the development program to prioritize wells in lower and moderate stress areas. Wellbore stability analysis has been carried out using calibrated stress and strength profiles along with other rock mechanical inputs to successfully drill high angle wells. This analysis indicates that with a slightly higher mud weight, high angle and horizontal wells can be drilled successfully. Hydraulic fracturing design incorporating the available stress contrast can help in achieving the desired fracture parameters without height growth. The coal permeability model suggests that during depletion, coal permeability is expected to increase by about 1.2–3.5 times with a positive impact on productivity. Critically stressed fracture analysis has been carried out on mapped fractures, which suggest that about 48% of the natural fractures are in a stressed state. Presence of these natural fractures has a positive (faster dewatering) as well as a negative (external water) impact on productivity at different places in the study area.
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Journal of Applied Geophysics
Abstract Rock physical crossplots from different geological setup along eastern continental margi... more Abstract Rock physical crossplots from different geological setup along eastern continental margin of India (ECMI) represent diversified signatures. To characterize the reservoirs in rock physics domain (velocity/modulus versus porosity) and then connecting the interpretation with geological model has been the objectives of the present study. Petrophysical logs (total porosity and volume of shale) from five wells located at sedimentary basins of ECMI have been analyzed to quantify the types of shale such as: laminated, dispersed and structural in reservoir. Presence of various shale types belonging to different depositional environments is coupled to define distinct rock physical crossplot trends for different geological setup. Wells from three different basins in East Coast of India have been used to capture diversity in depositional environments. Contact model theory has been applied to the crossplot to examine the change in rock velocity with change in reservoir properties like porosity and volume of shale. The depositional and diagenetic trends have been shown in the crossplot to showcase the prime controlling factor which reduces the reservoir porosity. Apart from that, the effect of geological factors like effective stress, sorting, packing, grain size uniformity on reservoir properties have also been focused. The rock physical signatures for distinct depositional environments, effect of crucial geological factors on crossplot trends coupled with established sedimentological models in drilled area are investigated to reduce the uncertainties in reservoir characterization for undrilled potentials.
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Journal of Earth System Science
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SEG Technical Program Expanded Abstracts 2018
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Journal of Applied Geophysics
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Journal of Asian Earth Sciences
Abstract Estimation of pore pressure and in-situ vertical stress magnitude is essential for under... more Abstract Estimation of pore pressure and in-situ vertical stress magnitude is essential for understanding the geomechanical behavior of the gas hydrate sediments in deep offshore of the Mahanadi basin. The basin located at northern side of eastern continental margin of India (ECMI) contains gas hydrate in clay/silt sediments. The pore pressure and vertical stress are mapped on two 2D-multi channel seismic data of lines (MH-38A and MH-38B) with aid of information of three wells (namely NGHP-01-19, NGHP-01-09 and NGHP-01-08). Initially, the coefficients of best fit curve have been computed from velocity-effective stress plot for the individual wells and applied on the seismic velocity to transform into the effective stress. The vertical stress has been computed from both the seismic and log data. Therefore, the pore pressure is predicted by subtracting the effective stress from the vertical stress. The pore pressure have been mapped in gas hydrate stability zone (GHSZ) and sediments below bottom simulating reflector (BSR). The pore pressure and vertical stress gradient are 10.11 MPa/km and 10.67 MPa/km, respectively. The pore pressure and vertical stress from seismic data are closely matched at well location with excellent goodness of fit (R2) varying from 0.82 to 0.95. Normal pressure is observed in the gas hydrate bearing sediments but slightly high pressures are noticed below the BSR indicating presence of free gas. The pore pressure from seismic data will guide drillers for choosing the mud weight during well drilling and casing optimizing in other part of deep offshore in the Mahanadi basin.
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SPE Asia Pacific Oil and Gas Conference and Exhibition
Numerical analyses are carried out to obtain the understanding of stressdistribution near and aro... more Numerical analyses are carried out to obtain the understanding of stressdistribution near and around a drilled circular wellbore into the rock masses.The seven numerical twodimensional models are generated using the ANSYS finiteelement software. The models are analysed to investigate the effects of theequal and differential far-field stresses on and around the drilled wellbore, to study the contrast in Young's modulus for rocks inside and outside thewelbore as well as to study the effects of fluid pressure during drilling.Stress magnitudes and orientation is varying uniformly around the wellboreunder the equal far-field stresses. Differential farfield stresses are the maincause of deformation of stress trajectories. Stress trajectories becomeelliptical around the wellbore. Differential far-field stresses and contrast inrock strength parameter like, Young's modulus are playing important role inmodifying the stress contour pattern near and around the wellbore. The drillingflui...
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Geophysical Prospecting
Sands belonging to Kamalapuram Formation of Paleocene-Eocene age are deposited in Cauvery basin a... more Sands belonging to Kamalapuram Formation of Paleocene-Eocene age are deposited in Cauvery basin as incised valley fill during a regressive cycle. Here we attempt to quantify the influence of diagenesis on pore-filling materials using rock physics template constrained by geohistory modelling. Primarily, porosity–velocity and acoustic impedance – the ratio of P-wave and S-wave velocity (VP/Vs) cross-plots are used as rock physics templates. Rock physics template has efficiently quantified pore-filling materials namely; contact cement and non-contact cement. The estimated contact cement and non-contact cement are correlated with conventional petrophysical logs within the selected depth interval. Further, this correlation is used to interpret the composition of pore-filling materials. Shallower depth intervals (I and II) exhibit moderate non-contact cement (4–5%) and insignificant contact cement (1–2% approx.) depositions. However, deeper interval (III) records a significant amount of pore-filling materials amounting average of 12% non-contact cement and 4% contact cement. Pore-filling materials demonstrate a positive correlation with the depth of burial. The fluid response is substantially affected by the degree of diagenesis, composition and spatial distribution of pore-filling materials. Shallower depth intervals (1770– 1786 m and 1858–1878 m) are relatively more sensitive to fluid changes as it is affected by insignificant contact cement. The depth interval 1770–1786 m shows class II (oil) and class III (gas) amplitude variation with offset anomalies. The sand occurring in depth interval 1858–1878 m demonstrates class IIP (oil) and II (gas) anomaly. The deeper interval (2118–2170 m) is comparatively stiffer and demonstrates class I amplitude variation with offset (oil and gas sand) anomaly.
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SEG Technical Program Expanded Abstracts 2009
Summary Characterization of coal in term of its physical properties like porosity and permeabilit... more Summary Characterization of coal in term of its physical properties like porosity and permeability has generally been performed on limited sample volumes such as plugs or cores. A methodology is proposed for estimation of permeability for a macro-cleat system of coal from well log derived porosity and from known cleat spacing for Rangamati area of Raniganj Coalfield, India. Data of seven numbers of wells were available from the study area. Geological logs of these boreholes recorded occurrence of four major consistent coalseams (A, B, C & D) at different depths, varying between 53 to 200m in the area. Permeability values of four coalseams with thickness varying between 2-5 m encountered in the seven wells have been correlated with vertical (overburden) stress. Permeability value ranges from 0.5 md at depth of 200 m to 18 md at shallower depth of 53 m while vertical stress decreases from 4.566 MPa to 1.254 MPa respectively. Permeability value of coalseam decreases with increase in vertical stress. Regression analysis between permeability & vertical stress of the coalseams show 2 nd order polynomial, as the best fit curves. Goodness of fit (R 2 ) for the 2 nd order regressions between vertical stress and permeability for individual coalseams varies between 0.86 and 0.99.
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Energy & Fuels
Conventional well logs from three wells in South Karanpura coalfield are analyzed to correlate 10... more Conventional well logs from three wells in South Karanpura coalfield are analyzed to correlate 10 major coal seams belonging to the Barakar formation for coalbed methane (CBM) exploration. Face cleat orientations are studied for the Simana and Argada coal seams from the Sirka and Argada mines. It varies from 130 to 140°N for a total 349 face cleats observed from Simana and Argada coal seams. Cleat identification and its orientation have also been analyzed from simultaneous acoustic and resistivity (STAR) log from two CBM wells located 20–22 km away from the Sirka and Argada mines. Total number of fractures is found to be 1118 from two wells. Face cleats are not distinguishable from STAR image. Fracture density in coal is varying from 2.48 fractures per meter to 23.8 fractures per meter with a maximum density in the Banasgarah seam. Fracture orientations observed in Saunda, Sayal, Balkudra, Kurse, Hathidari, Banasgarah, and Argada vary from 10°N to 115°N. The in situ maximum horizontal stress (SH) is compu...
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We prove that Legendrian and transverse links in overtwisted contact structures having overtwiste... more We prove that Legendrian and transverse links in overtwisted contact structures having overtwisted complements can be classified coarsely by their classical invariants. We further prove that any coarse equivalence class of Legendrian loose links has support genus zero. We also find a relationship between the support genus of the transverse link and its Legendrian approximation. As a corollary to this, we show that loose, null-homologous, transverse knots have support genus zero and also give a condition when non-loose Legendrian knots have non-loose transverse push offs.
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... The corresponding wells in the peri-cratonic area are: wells l, 2, 3 and 4 at or near the Rav... more ... The corresponding wells in the peri-cratonic area are: wells l, 2, 3 and 4 at or near the Ravva prospect; well 5 for the GS-38 field; well 6 near the dry fields GS-I 1 and GS-12 in front of the bight of the Masuli-patnam Bay; well 7 in the MORI-I oil field; wells 11 and Rz4 in the ...
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Bookmarks Related papers MentionsView impact
The study area belongs to the marine geological setup of Surat depression of Mumbai Offshore Basi... more The study area belongs to the marine geological setup of Surat depression of Mumbai Offshore Basin, India. The lithology of three wells in Mumbai offshore is analyzed using Gamma-Ray (GR) log, Density (ρ) log, Resistivity (Rt) log and Neutron Porosity (Φ) log. This analysis makes the identification of the lithology difficult. DSI log is recorded only for wells W-1 but for W-2, W-3 shear wave velocity data is not available. Major lithologies found in this area are sandstone, siltstone, shale, limestone and mixed lithologies of sand, silt, shale. This study aims to construct a lithology indicator parameter which is better in the identification of lithologies. This lithology indicator parameter is named as Lithology Impedance (LI). This parameter is calculated using density, P wave (Vp) and S wave (Vs) velocity. This indicator shows a better contrast for different lithology and also follows a specific range. To estimate the LI log value for W-2 and W-2, the Vp-Vs relation from W-1 is u...
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Prediction of permeability from well logs in heterogeneous formation is a difficult and complex p... more Prediction of permeability from well logs in heterogeneous formation is a difficult and complex problem to solve by conventional statistical methods. The correlation between parameters like porosity with permeability for different we lls alone may be a crude approximation for permeability estimation, even for homogeneous formations. Recently artificial neural networks have been successfully used for solving many complex problems in reservoir permeability estimation. In this work, the neural network technique is utilized for the permeability estimation of coal formations. The back propagation neural network (BPNN) permeability prediction model has been developed from a data set consisting of well test permeability and well log data from “well A” located in the Damodar valley coalfield, India. The bulk density, gamma ray, long normal resistivity and neutron porosity logs have been used as the inputs for the modelin g. The model is tested with well log data from the “well A” as well as...
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Journal of Geophysics and Engineering
The Miocene reservoirs in prolific Krishna-Godavari basin are mostly fluvial deposits and laminat... more The Miocene reservoirs in prolific Krishna-Godavari basin are mostly fluvial deposits and laminated or blocky in nature. The type of reservoir quality depends on associated geological environments. Due to several lateral variations in reservoir properties, a similar kind of workflow for reservoir characterisation does not work. Customised workflow needs to be applied in this area for estimation of petrophysical properties or rock physical analysis for reservoir quality prediction. As the major input of rock physical analysis is petrophysical properties, it is crucial to estimate these properties accurately. Meanwhile, it is also important to check the seismic sensitivity to change in fluid saturation in the reservoir characterisation process. The analysis assures the presence of reservoir and hydrocarbon contact in seismic sensitivity, which is essential for removing risk. Integrating the geological model with rock physical analysis for reservoir characterisation at the drilled well...
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Natural Resources Research
Well log analysis and production testing in coal are the initial requirements to judge the prospe... more Well log analysis and production testing in coal are the initial requirements to judge the prospectivity of a coalbed methane (CBM) reservoir. The process of prospect identification through laboratory studies is accurate although it is time-consuming and expensive. Therefore, we developed a methodology to identify prospective coal seam by establishing multiple regression models of geophysical well log parameters vs. organic/inorganic contents from laboratory-tested core samples for one seam. The Langmuir’s equation and methane adsorption isotherm were used to estimation of gas and saturation content by developing a regression model from organic content. Gas and coal contents (ash, moisture, fixed carbon, and volatile matter) were obtained from the subsequent propagation of the established equations to other wells. Gas saturation increased with depth from 60 to 69%. Mapped seam thickness and gas content were in the ranges of 10.0–54.0 m and 6.1–28.2 cc/g, respectively. Overlaying of seam thickness and gas content identified the sweet spots in releasing potential future well locations. Errors within the permissible limit between the predicted and observed values indicate the gas estimation to be reliable. Another application for electro-facies classification was demonstrated by applying multi-resolution graph-based clustering architecture to capture texture parameters from histogram and auto-covariance function in resistivity image log. Determination of lithology by correlation of resistivity image and geophysical well log corroborated with the depositional environment having fining upward formational sequence. Thus, this study helps in estimating proximate components, gas content, and saturation with depth in coal seam for production optimization to better understand its implications on the dewatering and gas production periods in the Bokaro CBM reservoir situated in India.
Bookmarks Related papers MentionsView impact
Near Surface Geophysics
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Journal of Petroleum Science and Engineering
Abstract Geomechanics plays a critical role in the different stages of coal bed methane (CBM) ope... more Abstract Geomechanics plays a critical role in the different stages of coal bed methane (CBM) operations, starting from its development through production to its abandonment as in Sohagpur field of central India. In general, higher gas production has been observed from the coal seams in low-stress regimes compared to high-stress regimes; however, during the CBM development planning, stress information has been overlooked. The need for inclined and horizontal wellbores in coal seams has increased due to their many-fold rise in production when compared to vertical wells with a minimum surface footprint. However, these non-vertical wells have wellbore instability issues leading to high nonproductive time (NPT) during drilling and completion operations. Prolong challenges exist in achieving the desired half-length from hydraulic fracturing (HF) stimulation due to the limited understanding of the stress contrast between target coal and bounding lithology. The permeability of the coal reservoir varies greatly during depletion due to the combined effects of effective stress and matrix shrinkage. These effects directly impact productivity and hence, require a detailed understanding of how permeability varies during production life. In many instances, production from coal seams is complicated and unpredictable because of the influence of stress induced natural fractures. A geomechanical earth model is focused on understanding and mitigating the aforementioned challenges. In addition to coal thickness and gas content, stress-permeability maps are prepared to assist in the development program to prioritize wells in lower and moderate stress areas. Wellbore stability analysis has been carried out using calibrated stress and strength profiles along with other rock mechanical inputs to successfully drill high angle wells. This analysis indicates that with a slightly higher mud weight, high angle and horizontal wells can be drilled successfully. Hydraulic fracturing design incorporating the available stress contrast can help in achieving the desired fracture parameters without height growth. The coal permeability model suggests that during depletion, coal permeability is expected to increase by about 1.2–3.5 times with a positive impact on productivity. Critically stressed fracture analysis has been carried out on mapped fractures, which suggest that about 48% of the natural fractures are in a stressed state. Presence of these natural fractures has a positive (faster dewatering) as well as a negative (external water) impact on productivity at different places in the study area.
Bookmarks Related papers MentionsView impact
Journal of Applied Geophysics
Abstract Rock physical crossplots from different geological setup along eastern continental margi... more Abstract Rock physical crossplots from different geological setup along eastern continental margin of India (ECMI) represent diversified signatures. To characterize the reservoirs in rock physics domain (velocity/modulus versus porosity) and then connecting the interpretation with geological model has been the objectives of the present study. Petrophysical logs (total porosity and volume of shale) from five wells located at sedimentary basins of ECMI have been analyzed to quantify the types of shale such as: laminated, dispersed and structural in reservoir. Presence of various shale types belonging to different depositional environments is coupled to define distinct rock physical crossplot trends for different geological setup. Wells from three different basins in East Coast of India have been used to capture diversity in depositional environments. Contact model theory has been applied to the crossplot to examine the change in rock velocity with change in reservoir properties like porosity and volume of shale. The depositional and diagenetic trends have been shown in the crossplot to showcase the prime controlling factor which reduces the reservoir porosity. Apart from that, the effect of geological factors like effective stress, sorting, packing, grain size uniformity on reservoir properties have also been focused. The rock physical signatures for distinct depositional environments, effect of crucial geological factors on crossplot trends coupled with established sedimentological models in drilled area are investigated to reduce the uncertainties in reservoir characterization for undrilled potentials.
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Journal of Earth System Science
Bookmarks Related papers MentionsView impact
SEG Technical Program Expanded Abstracts 2018
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Journal of Applied Geophysics
Bookmarks Related papers MentionsView impact
Journal of Asian Earth Sciences
Abstract Estimation of pore pressure and in-situ vertical stress magnitude is essential for under... more Abstract Estimation of pore pressure and in-situ vertical stress magnitude is essential for understanding the geomechanical behavior of the gas hydrate sediments in deep offshore of the Mahanadi basin. The basin located at northern side of eastern continental margin of India (ECMI) contains gas hydrate in clay/silt sediments. The pore pressure and vertical stress are mapped on two 2D-multi channel seismic data of lines (MH-38A and MH-38B) with aid of information of three wells (namely NGHP-01-19, NGHP-01-09 and NGHP-01-08). Initially, the coefficients of best fit curve have been computed from velocity-effective stress plot for the individual wells and applied on the seismic velocity to transform into the effective stress. The vertical stress has been computed from both the seismic and log data. Therefore, the pore pressure is predicted by subtracting the effective stress from the vertical stress. The pore pressure have been mapped in gas hydrate stability zone (GHSZ) and sediments below bottom simulating reflector (BSR). The pore pressure and vertical stress gradient are 10.11 MPa/km and 10.67 MPa/km, respectively. The pore pressure and vertical stress from seismic data are closely matched at well location with excellent goodness of fit (R2) varying from 0.82 to 0.95. Normal pressure is observed in the gas hydrate bearing sediments but slightly high pressures are noticed below the BSR indicating presence of free gas. The pore pressure from seismic data will guide drillers for choosing the mud weight during well drilling and casing optimizing in other part of deep offshore in the Mahanadi basin.
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SPE Asia Pacific Oil and Gas Conference and Exhibition
Numerical analyses are carried out to obtain the understanding of stressdistribution near and aro... more Numerical analyses are carried out to obtain the understanding of stressdistribution near and around a drilled circular wellbore into the rock masses.The seven numerical twodimensional models are generated using the ANSYS finiteelement software. The models are analysed to investigate the effects of theequal and differential far-field stresses on and around the drilled wellbore, to study the contrast in Young's modulus for rocks inside and outside thewelbore as well as to study the effects of fluid pressure during drilling.Stress magnitudes and orientation is varying uniformly around the wellboreunder the equal far-field stresses. Differential farfield stresses are the maincause of deformation of stress trajectories. Stress trajectories becomeelliptical around the wellbore. Differential far-field stresses and contrast inrock strength parameter like, Young's modulus are playing important role inmodifying the stress contour pattern near and around the wellbore. The drillingflui...
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Geophysical Prospecting
Sands belonging to Kamalapuram Formation of Paleocene-Eocene age are deposited in Cauvery basin a... more Sands belonging to Kamalapuram Formation of Paleocene-Eocene age are deposited in Cauvery basin as incised valley fill during a regressive cycle. Here we attempt to quantify the influence of diagenesis on pore-filling materials using rock physics template constrained by geohistory modelling. Primarily, porosity–velocity and acoustic impedance – the ratio of P-wave and S-wave velocity (VP/Vs) cross-plots are used as rock physics templates. Rock physics template has efficiently quantified pore-filling materials namely; contact cement and non-contact cement. The estimated contact cement and non-contact cement are correlated with conventional petrophysical logs within the selected depth interval. Further, this correlation is used to interpret the composition of pore-filling materials. Shallower depth intervals (I and II) exhibit moderate non-contact cement (4–5%) and insignificant contact cement (1–2% approx.) depositions. However, deeper interval (III) records a significant amount of pore-filling materials amounting average of 12% non-contact cement and 4% contact cement. Pore-filling materials demonstrate a positive correlation with the depth of burial. The fluid response is substantially affected by the degree of diagenesis, composition and spatial distribution of pore-filling materials. Shallower depth intervals (1770– 1786 m and 1858–1878 m) are relatively more sensitive to fluid changes as it is affected by insignificant contact cement. The depth interval 1770–1786 m shows class II (oil) and class III (gas) amplitude variation with offset anomalies. The sand occurring in depth interval 1858–1878 m demonstrates class IIP (oil) and II (gas) anomaly. The deeper interval (2118–2170 m) is comparatively stiffer and demonstrates class I amplitude variation with offset (oil and gas sand) anomaly.
Bookmarks Related papers MentionsView impact
SEG Technical Program Expanded Abstracts 2009
Summary Characterization of coal in term of its physical properties like porosity and permeabilit... more Summary Characterization of coal in term of its physical properties like porosity and permeability has generally been performed on limited sample volumes such as plugs or cores. A methodology is proposed for estimation of permeability for a macro-cleat system of coal from well log derived porosity and from known cleat spacing for Rangamati area of Raniganj Coalfield, India. Data of seven numbers of wells were available from the study area. Geological logs of these boreholes recorded occurrence of four major consistent coalseams (A, B, C & D) at different depths, varying between 53 to 200m in the area. Permeability values of four coalseams with thickness varying between 2-5 m encountered in the seven wells have been correlated with vertical (overburden) stress. Permeability value ranges from 0.5 md at depth of 200 m to 18 md at shallower depth of 53 m while vertical stress decreases from 4.566 MPa to 1.254 MPa respectively. Permeability value of coalseam decreases with increase in vertical stress. Regression analysis between permeability & vertical stress of the coalseams show 2 nd order polynomial, as the best fit curves. Goodness of fit (R 2 ) for the 2 nd order regressions between vertical stress and permeability for individual coalseams varies between 0.86 and 0.99.
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Energy & Fuels
Conventional well logs from three wells in South Karanpura coalfield are analyzed to correlate 10... more Conventional well logs from three wells in South Karanpura coalfield are analyzed to correlate 10 major coal seams belonging to the Barakar formation for coalbed methane (CBM) exploration. Face cleat orientations are studied for the Simana and Argada coal seams from the Sirka and Argada mines. It varies from 130 to 140°N for a total 349 face cleats observed from Simana and Argada coal seams. Cleat identification and its orientation have also been analyzed from simultaneous acoustic and resistivity (STAR) log from two CBM wells located 20–22 km away from the Sirka and Argada mines. Total number of fractures is found to be 1118 from two wells. Face cleats are not distinguishable from STAR image. Fracture density in coal is varying from 2.48 fractures per meter to 23.8 fractures per meter with a maximum density in the Banasgarah seam. Fracture orientations observed in Saunda, Sayal, Balkudra, Kurse, Hathidari, Banasgarah, and Argada vary from 10°N to 115°N. The in situ maximum horizontal stress (SH) is compu...
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International Journal of Rock Mechanics and Mining Sciences, 2017
Abstract Analysis of wellbore instability contains evaluation of rock mechanical properties and t... more Abstract Analysis of wellbore instability contains evaluation of rock mechanical properties and the state of in-situ stresses. In this analysis the only convenient factor is the mud weight i.e. the fluid density of the drilling fluid. If the mud weight is greater than the predicted, the mud will enter into the formation, causing tensile failure (fracture stress). Conversely a lower mud weight can result in shear failure (collapse stress) of rock, which is known as borehole breakout. Here we present three types of failure criteria - Mohr–Coulomb, Mogi–Coulomb and Modified Lade. Rock mechanical rocks such as: Poisson’s ratio, Uniaxial Compressive Strength, Cohesion have been computed from compressional and shear wave velocities. Internal friction angle is obtained from gamma ray log. The failure criteria have been applied to two wells located at Krishna-Godavari (K-G) onshore and three wells at offshore to obtain minimum mud weight required to sustain its stability. The caliper log for above-mentioned wells have experienced complete to moderate failure, considered as a lower bound of onset of failure at selected depth intervals. It is observed that Mohr – Coulomb failure criteria overestimates the predicted mud weight for the safe drilling. On the contrary Mogi – Coulomb failure criteria is closer to the expected result.
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Energy & Fuels, 2016
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