10 research outputs found
CO2 sequestration potential in Indian basalts
Get PDFIndia currently produces 7 – 8% of annual global CO2 emissions, with energy production accounting for 69% of India’s emissions. As such there is growing interest in the potential for emissions reductions through Carbon Capture and Storage (CCS). Vishal et al., (2021) estimated the theoretical storage capacity of India. However, many large emission sources are located distant from sedimentary basin settings where CO2 storage may conventionally be considered. Continental flood basalts of the Deccan Traps cover an estimated 500,000 km3 in west-central India, and have been identified for potential CO2 storage.
The concept of CO2 storage in basalt relies on CCS by mineralisation (CCSM) as basalt can act as a ready source of divalent cations such as Mg2+ and Ca2+. These can combine with carbonate, CO32-, from dissolved CO2, to produce carbonate minerals such as Magnesite (MgCO3). The CarbFix project in Iceland is a successful example of CCSM in basalt. CO2 is captured from the industrial emission site and piped to the CarbFix operation, where CO2 gas is dissolved in water to produce carbonated water and injected into the basalt (Matter and Kelemen, 2009). A key point to note is that a successful basalt storage scheme requires a target formation with sufficient porosity and permeability to sustain the required injection rates. We present an experimental study focused on characterising basalt of the Ambenali and Poladpur formations sampled from the Killari-1 borehole to assess the storage potential of Deccan Trap basalts. A density log for the Killari-1 borehole is shown in Figure 1, illustrating significant physical property variations throughout the site. Rubbly flow tops and vesicular layers which may be considered as potential injection intervals can be identified from the density log. Higher density layers may act as low permeability top seals.
X-ray computed tomography (CT) was performed on six selected core samples (c. 120 mm in length and 54 mm in diameter) using a Geotek rotating X-ray computed tomography (RXCT) core scanner at the British Geological Survey’s (BGS) Core Scanning Facility (CSF). Sample depths are shown on Figure 1. Total and connected porosity was calculated using digital rock analysis (PerGeos by ThermoFisher). Figure 2 illustrates the porosity network for sample KIL-110 taken from a low-density zone at a depth of 231 m. The left image (blue) shows total porosity, while the right image (purple) shows total connected porosity which is 15.57%. For comparison, KIL-123, at a depth of 168 m has no porosity and is therefore unlikely to contribute to fluid flow unless open fractures or joint networks are present.
Previous geochemical experiments carried out on Deccan Trap samples have indicated that major dissolution of primary carbonates and precipitation of secondary minerals such as siderite occurs
during CO2 exposure. This confirms the potential for mineral trapping of CO2. Using samples from the Killari-1 borehole, a new series of experiments has been initiated to explore these geochemical processes more fully, including the reaction rates and implications for CO2 storage. An ongoing series of batch experiments using powdered basalt samples at a range of temperatures is currently underway, with regular fluid sampling and monitoring to provide valuable information on reaction rates. The experiments are conducted under 100 bar CO2 headspace and at temperatures of 50°C, 100°C and 150°C. As well as providing some relatively high temperature data points where reactions will progress more rapidly, the selected temperature range reflects the significant variation in geothermal gradient across the Deccan Volcanic Province. SEM and XRD reacted solids will provide information on changes from pre to post experiment. The experiments will be complemented by additional batch experiments conducted at similar conditions using cut, rather than powdered sample material. As well as generating more realistic data on reaction rates, this approach will enable detailed characterisation of the reacted material surfaces through a before and after comparison of specific surface sites via SEM.
A subsequent suite of flow-through experiments will be conducted on core samples to investigate the impact of flowing water with a high dissolved CO2 content through the basalt. These experiments will enable the assessment of the dissolution and precipitation potential of porous basalt systems, and, therefore, the potential impacts on flow within a representative flow zone. Effluent chemistry will be monitored to assess directions and rates of reaction within the system, allowing an assessment of the storage potential of Deccan Trap basalts. The experiments will be conducted under pressure and temperature appropriate to potential storage depths.
Acknowledgements
The research was part of the BGS International NC programme ‘Geoscience to tackle Global Environmental Challenges’, NERC reference NE/X006255/1. Nimisha Vedanti acknowledges ECCSEL-ERIC for supporting transnational access to ECCSEL research infrastructure at the British Geological Survey. The Director, NGRI is acknowledged for permission to conduct research on NGRI Basalt samples. The extended abstract is published by permission of the Director of the British geological Survey.
References
Gupta, H.K., Srinivasan, R., Rao, R.U.M., Rao, G.V., Reddy, G.K. and others. 2003. Borehole investigations in the surface rupture zone of the 1993 Latur SCR earthquake, Maharashtra, India: Overview of results. Memoir of the Geological Society of India, 54, 1–22.
Matter, J., Kelemen, P. 2009. Permanent storage of carbon dioxide in geological reservoirs by mineral carbonation. Nature Geosci 2, 837–841.
Vishal, V., Verma, Y., Chandra, D. and Ashok, D. 2021. A systematic capacity assessment and classification of geologic CO2 storage systems in India. International Journal of Greenhouse Gas Control, 111, 103458
Fractal behavior of electrical properties in oceanic and continental crust
No full text273-278The fractal behavior of electrical properties of oceanic and upper continental crust was examined for different lithological units encountered in boreholes of Ocean Drilling Program (ODP) and German Continental Deep Drilling Program (KTB), using wavelet transform and Welch averaged periodogram methods. Results obtained from both the sites reveal that the electrical properties in oceanic as well as upper part of continental crust are fractal in nature. The scaling exponent obtained by periodogram analysis has shown variation with lithology and for continental crust it decreases with an increase in depth, which reveals that the electrical crust is more homogeneous at deeper levels than at shallow levels
An integrated geophysical study for the assessment and monitoring of CO2 sequestration in Gandhar Oilfield, Cambay Basin, India
No full textIntroduction
Gandhar oilfield, Cambay Basin, Gujarat is one of the Oil and Natural Gas Corporation Limited's (ONGC) major brownfields and a pilot candidate for India’s first large-scale CO2 sequestration project. The field which has been produced from multilayered sand bodies of Hazad Member, Ankleshwar formation has undergone various phases of production, and currently, it has reached a highly matured stage of its production life. ONGC has planned to implement the CO2 EOR technique in this field to recover an extra 15% of residual oil based on recent studies of source-sink matching, petrophysical properties analysis, current reservoir pressure, minimum miscibility pressure (MMP), and other laboratory experiments. The field is being studied for the assessment of CO2 storage potential and the feasibility of seismic techniques to monitor injected CO2 in Hazad sands (reservoir) and overlying brine saturated Ardol sands of Ankleshwar formation. For such a study, an integrated geophysical approach is performed with seismic, petrophysical, and geophysical well-log data provided by the National Data Repository-DGH (Govt. of India) and ONGC.
Prediction of unrecorded P-sonic logs using Gradient Boosting Regressor algorithm in Gandhar oilfield
A total of 15 wireline geophysical well log data from a 50 sq. km. block of the Gandhar oilfield for this study were provided but only 12 out of the 15 wells had P)-sonic logs. The sonic log (DT) is one of the essential logs required to perform petrophysical analysis, to aid in missing check-shot profiling, fluid substitution modeling, and seismic modeling & inversion studies. Therefore, the prediction of unrecorded P-sonic logs was required to reduce the uncertainty in reservoir characterization at the field scale by reducing the scarcity of sonic log data over an area. To overcome this problem, we implemented the Ensemble machine learning technique named Gradient Boosting Regressor (GBR) (J.H. Friedman, 2001, 2002) algorithm to predict the unrecorded P-sonic logs in the Gandhar oilfield. The GBR has unique functionality to reduce bias and variance problems by converting weak learners to strong ones. Also, GBR can optimize different loss functions and provides several hyperparameter tuning options that make the prediction function fit very flexibly. The predicted P-sonic log correlates very well with the original P-sonic log. The predicted sonic logs are then used in the geomodel building process and fluid substitution modeling for CO2 sequestration.
Gandhar Oilfield Geomodel Building
We interpreted the 3D seismic data of the Gandhar oilfield with the help of the geophysical well logs including the predicted one and prepared a structural and stratigraphic geomodel of the Gandhar oilfield. The geomodel consists of 12 sand layer units (multi-stratigraphic pay sands) with thin intercalated shales in between them. The shales are as thin as 1.5 m and incorporating them in the geomodel was a hectic task that required several updates (well-tie tomography) in the building process to reduce mistie to avoid the crosscut between layers. We first displayed the prepared geomodel on 3D seismic data and it is observed that it honors the seismic data very well. The geomodel was flooded with facies interpreted from the geophysical well logs, effective porosity, and water saturation for the purpose of CO2 storage capacity assessment.
Synthetic seismogram generation for monitoring CO2 sequestration in Gandhar oilfield
The feasibility of seismic data to monitor CO2 sequestration in the overburden of the reservoir, which is brine saturated Ardol sands of the Ankleshwar Formation, is demonstrated through convolutional synthetic seismic modeling and seismograms. The evolution of an expanding CO2 plume in Ardol sands was calculated through the analytical approximation of axisymmetric gravity currents in a brine-CO2-saturated medium by using an injection rate of ∼0.5 Mt/year for a period of 6 years. CO2-saturated rock properties were determined using Gassmann fluid substitution and monitoring of CO2 plume was imaged by a time-lapse convolutional synthetic seismogram. Random noises were added to the synthetic seismogram and then NRMS and repeatability metrics were performed which established the detection threshold of 30 days since CO2 injection. The results are shown in Figure 1.
Now, we don’t have the geomodel ready for the full-wavefield seismic modeling as it is in the development process. The Poroviscoelastic wave equation was solved numerically and was tested on the Sleipner field geomodel for monitoring the CO2 sequestration. Full-wavefield synthetic seismograms were generated for the pre-and post-CO2 injection cases. The poroviscoelastic theory models realistic amplitude attenuated due to squirt-flow (viscoelasticity) and Biot-flow (poroelasticity) related to matrix fluid coupling relaxation mechanisms. The prediction of more realistic amplitudes subject to CO2 sequestration signifies the success of the poroviscoelastic theory in monitoring CO2 sequestration in geological formations.
Conclusions
Gradient Boosting (ML) can be used for the prediction of logs, and it clearly demarcates the lithological boundary changes in Gandhar by preserving the amplitude. Fine scale geomodel of Gandhar oilfield (Hazad sands, Ankleshwar Formation) will give more accurate estimation of CO2 storage capacity. We anticipate that monitoring of CO2 sequestration on synthetic seismogram by poroviscoelastic theory will be more enhanced due to realistic amplitude attenuation attributed to interplay of squirt-flow and Biot-flow relaxation mechanisms. In addition to Hazad Sands (reservoir), brine saturated Ardol Sands is studied for the possibility of CO2 sequestration. The detection threshold is obtained for 30 days since CO2 injection in Ardol sands
CO2 Mineralization of Deccan Trap Basalts
No full textIntroduction
Many of India’s large emission sources are located far from sedimentary basin settings where CO2 storage might otherwise be considered. Continental flood basalts of the Deccan Traps cover an estimated 500,000 km3 in west-central India, and there is much interest in their potential to permanently store and trap CO2 through mineral carbonation processes. The Deccan Traps consist of layers of solidified flood basalt more than 2,000 m in thickness. The volume of basalt exceeds 1,000,000 km3 and provides a significant theoretical potential for high-volume storage of CO2. Carbon capture and storage by mineralization (CCSM) has been studied in several regions, including the Wallula Basalt Project in Columbia River, USA, and the Carbfix project in Iceland. Although some previous studies on the trapping potential of basalts have shown promising results, there remains significant uncertainty as to the practicality of storing CO2 volumes at industrial scale in the Deccan Traps.
Theory and/or Method
To gain a preliminary insight into the types of reactions that may be expected during CCSM in Deccan Trap basalts, a core sample taken from the Killari borehole was reacted with CO2-rich water. Prior to reaction the sample was crushed to produce a 125 to 250 μm fraction, which increases the mineral surface area and enhances the rate at which the reactions occur. Future experiments using whole-rock samples will provide more realistic reaction rates, requiring the experiments to be run over a longer period of time to produce detectable mineralogical reactions. To produce basalt-equilibrated fluid for the experiment, this powder was placed in a 1 liter container of deionized water at 70°C for one week. A preliminary study was conducted using three batch vessels containing crushed starting material and the equilibrated fluid pressurized first with nitrogen, and then with CO2 to 90 bar. Each vessel was subjected to a different temperature (50, 100, and 150°C), and reacted for up to 43 days. The selected temperature range reflects the significant variation in geothermal gradient across the Deccan Volcanic Province. Fluid samples were collected at regular intervals for geochemical analysis, while post-reaction solids were examined using Scanning Electron Microscopy (SEM) to provide evidence for mineral dissolution and precipitation.
Example
Little evidence of mineral dissolution or precipitation was observed in the 50˚C experiment, whereas notable dissolution of plagioclase was observed in the 100˚C experiment. There was no clear evidence of carbonate precipitation in either experiment. In contrast, the 150˚C experiment resulted in significant dissolution of plagioclase and precipitation of secondary phases, including rhombohedral crystals of siderite (40-50 μm) and silicate minerals, likely smectite and phases belonging to the zeolite mineral group based on SEM qualitative analysis. Figure 1 shows evidence of the rhombohedral siderite crystals and Figure 2 shows fibrous silicate minerals formed during the 150˚C experiment. Platy silicate minerals were also observed which may be smectite. A significant amount of calcium carbonate and amorphous silica precipitate eventually blocked the fluid sampling tube.
Conclusions
The preliminary data indicates that while dissolution and carbonate mineral precipitation occurred during experiments at 150˚C, the reaction rates were significantly reduced at lower temperatures resulting in less CO2 trapped in mineral form. This indicates that targeting of regions with higher geothermal gradients might be worthwhile for future laboratory and field studies. Ongoing work continues to analyze the fluid geochemistry data, which provide a sensitive analytical means of determining the relative timing and rates of reactions
A feasibility study to assess seismic detectability of CO2 sequestration in Gandhar Oilfield, Cambay basin: India’s first CO2 Project
No full textThe Gandhar oilfield is one of the major hydrocarbon fields of the Cambay Basin and a pilot candidate for India’s first large-scale CO2 injection project. The feasibility of seismic data to monitor CO2 sequestration in the Ardol Member of the Ankleshwar Formation is demonstrated through synthetic seismic modeling. The evolution of an expanding CO2 plume was calculated through the analytical approximation of axisymmetric gravity currents in a brine-CO2-saturated medium. CO2-saturated rock properties were determined using Gassmann fluid substitution. Seismic modeling was carried out for both pre-CO2 and post-CO2 injection models to determine the potential value of time-lapse seismic monitoring.
It was observed that the CO2-saturated layers were readily detected, and seismic data would provide a suitable monitoring tool for a future CO2 storage complex. We anticipate that monitoring of CO2 sequestration on synthetic seismogram by poroviscoelastic theory will be more enhanced due to realistic amplitude attenuation attributed to interplay of squirt-flow (viscoelasticity) and Biot-flow (poroelasticity) mechanisms associated with matrix-fluid coupling relaxation.
In addition to Hazad Sands (reservoir), brine-saturated Ardol Sands is studied for the possibility of CO2 sequestration. The enhanced impedance contrast between CO2 saturated Ardol Sand sand layers below it brightens the amplitude of the underburden. If the injection point is on the top of Ardol Sands, we see that it is easier to detect the CO2 saturated layer. Detection threshold is obtained for 30 days since CO2 injection in Ardol sands
First observation of microspherule from the infratrappean Gondwana sediments below Killari region of Deccan LIP, Maharashtra (India) and possible implications
No full textA rare occurrence of a microspherule has been found in the infratrappean sediments, encountered below 338 m thick Deccan volcanic cover in KLR-1 scientific borehole, drilled in the epicentral zone of the 1993 Killari earthquake (Maharashtra, India). Palynological studies of the sediments indicate their age as Early Permian (Asselian, 298-295 Ma) for deposition. Transmission electron microscope studies reveal that the spherule from the infratrappeans, is having a similar composition to that of the Neoarchean amphibolite to granulite facies mid crustal basement. The spherule is non-spherical in nature, containing mostly FeO (10.70 +/- 0.20 wt.%), CaO (13.8 +/- 0.5 wt.%), Al2O3 (7.78 +/- 0.30 wt.%), MgO (6.47 +/- 0.3 wt.%), SiO2 (47.46 +/- 0.50 wt.%), TiO2 (2.47 +/- 0.3 wt.%), K2O (1.89 +/- 0.20 wt.%), and Cl (0.33 +/- 0.05 wt.%). Since the Fe composition of the spherule is almost same as the basement rock (10.5 wt.%), and the chlorine content is also in the same range as the basement (0.04-0.24 wt.%), it would suggest possibility of an extraterrestrial impact over the Indian terrain during the erstwhile Gondwana sedimentation period that may be associated with the Permian-Triassic mass extinction, the most severe one in the Earth's history
