National Gas Research Articles

Prediction of reservoir parameters in gas hydrate sediments using artificial intelligence (AI): A case study in Krishna–Godavari basin (NGHP Exp-02)

The estimation of accurate reservoir parameters is essential for conventional and non-conventional hydrocarbon prospects. An artificial neural network has been developed to predict the reservoir parameters (porosity and saturation of gas hydrates) in a silty-sand, sandy-silt and pelagic-poor clay reservoir at two neighbour wells using the petrophysical information at another well in the Krishna–Godavari basin. The well log data were acquired during the Expedition-02 of Indian National Gas Hydrates Program (NGHP Exp-02). The estimation of gas hydrate saturation using Archie’s equation may be erroneous, as it is valid for the quantification of conventional hydrocarbons in the clean sand reservoir. Since the study area is clay dominated, it is subjective to adjust Archie’s exponents so that it matches with the saturation, measured from the core data. To overcome this problem of estimating the reservoir parameters in such a scenario, first of all we have derived porosity from the density log data and estimated saturation by employing modified Archie’s equation to the resistivity log data at one well. In order to train the network, the log data at one well are taken as inputs and corresponding porosity and saturation are taken as outputs. The reservoir parameters are then predicted at two neighbour wells using the wireline log data as input in those two wells. The predicted porosity and saturation of gas hydrates are alike to the traditionally estimated porosity and saturation at the neighbour wells. The predicted porosity in the studied region varies between 33 and 76%, whereas the saturation of gas hydrates ranges between 3.39 and 86.92%. This shows that the designed network can be used to estimate the reservoir parameters directly from the well log data in the same reservoirs.

India National Gas Hydrate Program Expedition 02 Summary of Scientific Results: Gas hydrate systems along the eastern continental margin of India

Abstract The primary objectives of the India National Gas Hydrate Program Expedition 02 (NGHP-02) were to obtain new data on the occurrence of gas hydrate systems and to advance the understanding of the controls on the formation of gas hydrate accumulations in the offshore of India. In accordance with the ultimate overall goal of the NGHP effort to assess the energy resource potential of marine gas hydrates in India, particular focus was placed on the exploration and evaluation of gas hydrate occurrences at high saturations in sand-rich systems. NGHP-02 operations were conducted from 3-March-2015 to 28-July-2015 off the eastern coast of India and included logging while drilling (LWD) operations at 25 locations, and coring and wireline logging operations at 10 locations, in the Krishna-Godavari and Mahanadi Basins. The formation of highly concentrated gas hydrate accumulations, which are more suitable for energy extraction, requires the presence of relatively coarse-grained sediments with porosity needed to support the migration and accumulation of gas, and the nucleation of gas hydrate. The results of downhole logging, coring and formation pressure testing operations during NGHP-02 have confirmed the presence of extensive sand-rich depositional systems throughout the deepwater portions of the Krishna-Godavari and Mahanadi Basins. Two areas of the Krishna-Godavari Basin, referred to as Areas B and C, contain substantial gas hydrate accumulations in sand-rich systems and therefore represent ideal candidate sites for future gas hydrate production testing. This summary and technical report includes a comprehensive synthesis of the geologic, geophysical, geochemical, and physical property data acquired during NGHP-02 as it relates to the controls on gas hydrate occurrence, particularly with regards to sand-hosted accumulations. In the Mahanadi Basin, despite the confirmation of extensive reservoir capacity, gas supply at the NGHP-02 sites was insufficient to charge the reservoirs with gas hydrates. In the Krishna-Godavari Basin, extensive reservoir systems were confirmed with sediment grain-sizes ranging from coarse-silts to gravels. These reservoirs range from fully- to partially-filled with gas hydrate. The gas is determined to be from only microbial sources, and in part migrated into the reservoirs from deeper systems. The controls on gas hydrate occurrence are complex and varied; and include substantial reservoir heterogeneity and sufficient permeability throughout the reservoirs and seals that allowed pervasive fluid flow into and through the hydrate-bearing systems. These discoveries are the most significant confirmation of the exploration approach that focuses on direct detection of hydrate reservoirs supported by comprehensive petroleum systems analyses.

The achievement of regulatory excellence in the oil and gas industry in Nigeria: the 2017 National Oil and Gas Policy

This article critically assesses the regulatory landscape for oil and gas development proposed under the 2017 Nigeria gas and petroleum policies, which are together referred to as the Nigeria Oil and Gas Policy (NOGP) 2017, to highlight its capacity to lead to the achievement of regulatory excellence in the oil and gas industry in Nigeria. The assessment is based on a conceptual framework developed by the Penn Program on Regulation (PPR) at the University of Pennsylvania Law School in 2015 to assist the Alberta Energy Regulator – the body responsible for regulating energy development in Alberta, Canada – to identify the best regulatory approach to overcome the challenges of regulating energy development in the province. The PPR framework is selected not only because it is based on a detailed and systematic review of earlier frameworks but also because it is the only framework prepared primarily for the energy sector, though its elements can be easily adapted to other sectors as well. The article’s central argument is that while the NOGP 2017 represents an important step forward in the efforts to effectively regulate the oil and gas industry, there are significant gaps in the regulatory landscape proposed in the policy for the achievement of regulatory excellence. The article identifies those gaps and notes, however, that the achievement of regulatory excellence depends considerably on the implementation framework adopted by the new yet-to-be-established regulator when it comes into operation.

Estimating country-specific space heating threshold temperatures from national gas and electricity consumption data

Space heating in buildings is becoming a key element of sector-coupled energy system research. Data availability limits efforts to model the buildings sector, because heat consumption is not directly metered in most countries. Space heating is often related to weather through the proxy of heating degree-days using a specific heating threshold temperature, but methods vary between studies. This study estimates country-specific heating threshold temperatures using widely and publicly available consumption and weather data. This allows for national climate and culture-specific human behaviour to be captured in energy systems modelling. National electricity and gas consumption data are related to degree-days through linear models, and Akaike’s Information Criteria is used to define the summer season in each country, when space heating is not required. We find that the heating threshold temperatures computed using daily, weekly and monthly aggregated consumption data are statistically indifferent. In general, threshold temperatures for gas heating centre around 15.0 ± 1.7 ∘C (daily averaged temperature), while heating by electricity averages to 13.4 ± 2.4 ∘C. We find no evidence of space heating during June, July and August, even if heating degree-days are present.

Obstacles to Improve Human Resources Performance from Employees Point of View - Case Study of the National Electricity and Gas Distribution Corporation, Mila

In this research, we discussed the subject of obstacles to improve the performance of human resources from its point view- a study of the human resources situation working in the National Electricity and Gas distribution Corporation in Mila.
 We have divided the research into three axis: The first one to highlight the fact that human resource performance has improved, and the various steps of this process. The second one we devoted to talk about the obstacles that hinder the improvement of the human resources performance, where we divided the obstacles to the source of human resources, and other sources of institutions. The third one includes a field study of the reality of the human resources performance improvement where we found that there are constraints on the jobs and working conditions, especially the incentive system and the lack of means. This requires the intervention

Legal and institutional aspects of public forms of electricity or gas fuel trading in Poland versus the conditions in the common energy market

Abstract This study aims at presenting the legally, technically, and economically empowered suggestion for a clear definition of a competitive market of gas fuels and electricity of a Member State in order to be utilized within trans-border trade of these utilities, as required by the European Union (EU) legislation. Thus, this study addresses, first of all, the issue of the division of the national gas fuel and electricity market into sections and separating these market segments that are more susceptible to the existence of competition in the trans-border dimension. This division is a model that reflects every internal market that is self-sufficient and distinguished in technical terms which has been established and is functioning within one or more Member States. The suggested structural, subject-related division of the market into sections, a competitive one (with its segments), a balancing one, and a technical one, makes it possible to determine which fragments of the market prevail over merely the technical security of ensuring continuity and quality of electricity supplies at the national level. Public forms of electricity and gas fuel trading take first place. Thus, second, the issues of legal and business conditions for operation in the energy section of the commodity exchange, regulated market, or open tenders for purchase of energy and interdependence between public forms of electricity or fuel gas trading and standards in the common electricity market have become the subject of this study. The advantage of a commodity exchange that establishes transparent conditions for public trading transactions involving these goods and provides pricing information for actors in the market cannot be overestimated. A commodity exchange enhances competition and is instrumental in the reduction of prices for ultimate clients. The completed analysis aims at reviewing public forms of trading as the instruments for achievement of the objectives of the national energy law and a component for a common energy market in the perspective of development of trans-border transmission capabilities. Legal multi-centricity and multi-aspectual nature of the addressed issues form a structure of relations that has affected the selection of the research methodology. Three research methods were adopted as the main principles that, bearing in mind a different context in which they are used, are treated to be complementary. The first one is an interdisciplinary research analysis, taking account of the context of functioning in the EU law environment in the interpretation of the national law provisions and technical sciences (and thus, e.g., laws of physics, properties of energy, technical aspects of functioning of the power industry as a system of interdependent relations of installations and grids) and economic sciences (e.g., a concept of the market, competition, operation of the commodity exchange). References to technical or economic sciences allowed to maintain the clarity of the above considerations and render the addressed issues better in practice. The legal and dogmatic method is an indispensable supplement of the above method; in this method, the process of interpretation of legal regulations is based on the jurisprudence and case law which should be referred, in particular, to the national law; it is made complete by the analysis of the economic practice. The selection of the concept analysis method (a linguistic one) as the third method should be justified by the undertaken attempts to define in a precise manner the content and the scope of meaning of general, generic concepts making references, as a rule, to a broad spectrum of business operations, the application of which in the EU legislation is a feature of this legal order established on the basis of the elements of the continental (established, statute) law and flexible common law.

Numerical investigation of rock-pile based waste heat storage for remote communities in cold climates

Remote communities in arctic climates are solely dependent on diesel generators for continuous power supply due to their detached loci from national power gridlines or natural gas pipelines. Moreover, to get along with the harsh, long winters, these communities directly or indirectly depend on fossil-fuel based heating systems. Due to the lower efficiency of the conventional diesel engines, these generators discard a significant amount of heat through the exhaust. Occasionally, during the wintertime, this waste heat from the exhaust is used directly as a heat source after recovery. However, during summer, when the heating demand is lower or nil, this heat is commonly discarded, and its energy potential wasted. A rock-pile based seasonal thermal energy storage is a viable solution that can sustainably resolve this issue. This paper presents a validated numerical study that focuses on the coupling of a waste heat recovery system to a diesel exhaust stream offering a performance assessment of the proposed rock-pile waste heat storage system in a remote, off-grid community located in northern Canada. It examines the impacts of local thermal equilibrium versus non-equilibrium approaches as well as temperature-dependent properties, variation of air mass flow rate, particle size and finally the thermo-physical properties on the proposed model. The presented results show that air should be treated as an ideal gas and that the local thermal non-equilibrium approach should be used for its considerably higher accuracy. Techno-economic assessment of the system resulted in a relatively short payback period of less than six years.

Estimation of gas hydrate saturation using isotropic and anisotropic modelling in the Mahanadi basin

A base of gas hydrate stability zone was established after coring and drilling under the National Gas Hydrate Program (NGHP) Expedition-01 in the Mahanadi basin. At two sites, logging-while-drilling log data, and, at one site, wireline log data, were acquired during the NGHP Expedition-01. Gas hydrate reservoirs modelling can be performed in two different ways. One way is isotropic (load bearing) and, on the other hand, anisotropic media (fracture filling with gas hydrate). Here, we have performed anisotropic modelling and estimated gas hydrate saturation using P-wave velocity, assuming an incidence angle of 75\(^{\circ }\) represents the vertical fracture. The estimated gas hydrate saturation at sites NGHP-01-08 and NGHP-01-09, assuming anisotropic media, reduces the estimate by half compared to the saturation estimation by assuming isotropic media. The saturation at site NGHP-01-19 estimated from the isotropic and anisotropic P-wave velocity models are more or less similar except in the zone (175–210 m) just above the bottom simulating reflector depth, and this zone shows similar reduction in saturation as estimated at sites NGHP-01-08 and NGHP-01-09. Observations show that average gas hydrate saturations are relatively low (up to 5% of the pore space). The saturation of a gas hydrate estimated from an isotropic P-wave model varies from 5% to 20%. However, the saturation estimated from the anisotropic P-wave model shows a variation up to 10% of the pore spaces at three sites.

Diffusion of the Ethical Philosophy of Good Governance at the National Oil Company of South Africa

This article seeks to examine challenges affecting the ethical philosophy of senior management at South Africa’s national oil and gas company. South Africa’s economy has been downgraded to junk status due to mismanagement of public funds in public enterprises. Government parastatals have come under major scrutiny in recent years for transgressing the code of good conduct prescribed by the King Report. The article presents a conceptual exploration of corporate governance challenges and is underpinned by diffusion of responsibility and moral hypocrisy which has roots in social psychology. Social psychology can be used as an overlap for strategy and institutional concepts, which encourages new ways of addressing corporate responsibility. The research reveals the impact on state enterprises financial stability when senior management diffuses responsibility and is not prosecuted or held accountable under the constitutional Act 108 of 1996. The article highlights one of the many corporate responsibility transgressions by state-owned enterprises who should be responsible for building the economy rather than destroying public value.

Enrichment laws and scale effective development of shale gas in the southern Sichuan Basin

Based on the newest understandings of geological assessment and new progresses in engineering technologies in the development of shale gas rich in the southern Sichuan Basin, this paper analyzed the shale gas enrichment laws and the key factors of its commercial production, discussed the scale and efficient development modes, and clarified the further developing orientation. The following findings were concluded. (1) The Lower Silurian Longmaxi shale is the sweetest spot in this study area with a low density and a high uranium/thorium (U/Th) ratio, TOC content, quartz content, and free gas content. Besides, its distribution laws are mainly controlled by the sedimentary facies of deep water shelf. (2) The overpressured zones away from the ancient (present) erosion zones and large faults, mainly controlled by multi-stage tectonic evolution, belong to the most favorable sweet spots not only because there are well-developed organic matters and pores but the produced gas there is mainly of secondary cracking retention oil. (3) Layout, drilling, completion (fracturing) and management of wells will be essential to achieve high productions in the shale gas production. (4) The existing main technologies have helped achieve efficient development of quality shale gas resources underground less than 3500 m in such national shale gas demonstration zones as Changning–Weiyuan, Zhaotong, etc. Also, there shows a good potential of shale gas resources in those shallower strata and the strata with the burial depth of 3500–4000 m. In conclusion, with the help of continuous progress in technologies, an annual shale gas production rate of 40 billion cubic meters will be possibly achieved in this study area.

Convergence of European natural gas prices

Over the period 2015–2050 the consumption of natural gas of European OECD countries is expected to grow more than the consumption of any other energy source. Although these countries are interconnected and in most cases share a common currency, their wholesale national gas markets are highly heterogeneous. We study the determinants of cross-country convergence of natural gas prices for industrial consumers in fourteen European countries. Our empirical analysis is based on the notions of pairwise, relative and σ-convergence. We show that there is evidence of pairwise price convergence and that some key characteristics of gas markets, such as the existence of trading hubs and the degree of interconnection, are positively associated with the existence of a convergence process. This result carries over to the notion of σ-convergence and is robust to a number of changes in the implementation of the statistical tests. The analysis of relative convergence points to the existence of price-growth convergence, while price-level convergence is not supported by the data. Lastly, we assess the short-run implications of price convergence focusing on the speed of reversion to equilibrium after a system-wide shock hits the cointegrating relation.

Effects of Model Horizontal Grid Resolution on Short- and Medium-Term Daily Temperature Forecasts for Energy Consumption Application in European Cities

A short-term forecast of energy consumption is affected by different factors related to the demand in residential, commercial, thermoelectric, and industrial sectors. This demand can be strongly constrained by weather variables, especially temperatures, whose forecast may be very useful to predict the balances between supply and demand, minimizing the risk of price volatility. Energy companies use the relationship between meteorological forecast output and energy request to provide an effective scheduling of national gas and power grids and reduce operational costs in critical periods. This work reports a comparison analysis for short- and medium-term daily temperature forecasts during the period 2013-2014 by using the weather model e-kmf™ (eni-kassandra meteo forecast), currently adopted in gas and power applications where meteorological output has a key role. This weather forecast system uses different models and initial data to develop probabilistic predictions from a perspective of eleven days ahead. In particular, a set of model runs with horizontal grid spacing of 5.5, 8, 13, and 18 km with the same domain size are undertaken to assess the sensitivity of temperature to horizontal resolutions. A nonlinear Kalman filter has been also applied to postprocess forecasted data in eight European cities (Milano, Roma, Torino, Napoli, Munich, Paris, Brussels, and London). Filtered forecasts over these cities have been compared to local observations taken from SYNOP (surface synoptic observations) and METAR (meteorological Aerodrome Report) stations. Skill scores of performance have been used to generally assess the forecast reliability up to day +11. In order to understand the sensitivity to the horizontal resolution, investigations have been carried out even during four specific periods of two weeks with stable and unstable weather conditions.

Resistance to Organizational Change: A Case of Yemen National Oil and Gas Sector

The purpose of this study was to evaluate barriers in understanding different sets of culture, which can arise in an organization. This study was also done to comprehend how resistance can be managed or reduced by discussing the significance of effective communication between management and employees. Trust in management and employee participation during the process of managing changes in National Oil and Gas Company was also identified. We conducted a case study as an investigative tool. In terms of the research site, we focused on one of the national oil and gas companies to highlight some of the issues and outcomes of recent management change. To collect data, questionnaires were distributed within the company. Bivariate correlation analysis and regression analysis were then used to test the proposed hypotheses. The results empirically showed that there are several parameters involving resistance to organizational changes. These parameters can be classified as communication between management and employees, trust in management, and employee participation. These parameters gave a positive impact as employee participation has the highest impact of the three examined factors.

Operational Experience of HiPACT Process

We would like to share some of the challenges faced during the first commercial use of the HiPACT® technology. HiPACT® is a technology jointly developed by JGC and BASF, which has now been successfully implemented by NIS, a Serbian multinational oil and gas company. HiPACT® is an advanced solvent based CO2 capture technology that contributes to improving the economics of Carbon dioxide Capture and Storage (CCS) in natural gas processing plants as well as Carbon dioxide Capture, Utilization and Storage (CCUS) projects such as Enhanced Oil Recovery (EOR). The solvent has excellent stability against thermal degradation, which enables operation at high pressure and elevated temperatures during solvent regeneration to reduce CO2 compression costs downstream. In addition, it also has a higher CO2 absorption capacity than other commercially available solvents which results in decreased solvent circulation rates and lower Acid Gas Removal Unit (AGRU) capital and operating costs. As the first commercial implementation, a HiPACT® unit was installed at the Elemir site which is owned by NIS with the aim of meeting the technical requirements of the national gas distribution network in Serbia. The natural gas was firstly introduced in January 2015 and continued for a trial run period until July 2015. The gas processing plant was then successfully commissioned and has been in commercial operation ever since this time. This paper presents i) operational experience with the HiPACT® unit and ii) economic evaluation including the compressor section to show the advantage of HiPACT® over state-of-the-art technology currently used worldwide.

US LNG Exports—How We Got Here and Where We Are Going

Return with us now to the thrilling days of 2005–2008. Qatar Petroleum, the national oil and gas company of the State of Qatar, was preparing to become the largest importer of liquefied natural gas (LNG) into the United States. The gas industry was excited about the growth prospects from all of this LNG, but also concerned about the cost—approximately $20 per million Btu's, as opposed to around $5 per million Btu's for domestic gas. The U.S. Energy Information Administration (EIA) projected imports of LNG would grow steadily until 2030, when the United States would then be importing 8 billion cubic feet per day (bcf/d) of LNG, amounting to more than 10 percent of the total US gas supply. The EIA's forecast is shown in Figure 1.

Lithofacies characterization of gas hydrate prospects discovered during the National Gas Hydrate Program expedition 02, offshore Krishna-Godavari Basin, India

Abstract Lithofacies of host sediments associated with gas hydrate reservoirs may have a significant influence on the formation of hydrates. The type of sediments and the depositional processes responsible for the gas hydrate-bearing sediments along the eastern margin of the India have been studied by integrating core data and logging-while-drilling downhole logs. Borehole data correlated with seismic data were used for the interpretation of geological process responsible for gas hydrate formation. The acquired seismic profiles were correlated with the downhole logs by identifying the shape of the well logs curves that indicate finning up and blocky patterns. Turbidite sands and debris flows were also identified from the log and core sediment studies. This study identified two prominent types of depositional systems: (1) turbidity currents and (2) debris flows were mainly responsible for the deposition of gas hydrate-bearing reservoirs in the study area. Based on these studies two well-developed gas hydrate systems have been identified in the Krishna-Godavari Basin and hydrates were determined to be distributed mostly in sand dominated facies. Fine-grained sand in the identified turbidite deposits were shown to be a good hydrate reservoir. The hydrate-bearing sediments in the central part of the Krishna-Godavari Basin (Area C in D6 block) consist of mostly debris flows, which is consistent with scattered gravel- and sand/silt-sized grains in channel-levee systems.

Life cycle environmental and economic assessment of coal seam gas-based electricity generation

PURPOSE: A large portion of coal seam gas is directly wasted and emitted to the environment, especially China, which is the world’s largest global warming gas emitter and energy consumer. Such emissions place heavy pressure on the Chinese government to achieve its global carbon reduction goals. This study quantified the economic and environmental impacts of coal seam gas-based power generation in China through a cost-combined life cycle assessment to systematically quantify the emission, impact, and mitigation measures caused by coal seam gas release in China. METHODS: Cost-coupled life cycle assessment analysis was conducted with SimaPro 8.4 in accordance with ISO 14040 series standards. Specifically, life cycle assessment was conducted with the IMPACTWorld+ method, and internal (e.g., raw materials, energy, labor, maintenance, infrastructure, and taxes) and external costs (e.g., land eco-remediation cost, human health economic burden, and environmental emission cost) were used to quantify the life cycle cost. RESULTS AND DISCUSSION: Approximately 11.8 kg of CH₄ and 19.8 kg of CO₂ were emitted per ton of coal mining in China in 2015. The direct global warming emission of coal seam gas at the national level accounted for 12% of the national carbon emission in 2015 in China. Coal seam gas-based electricity generation significantly reduced environmental impacts in the key categories of fossil depletion, non-carcinogens, global warming, and respiratory inorganics because of the substitution of coal power. Approximately $ 0.04/kWh of cost benefit was achieved due to the profit from concomitant coal during coal seam gas production. CONCLUSIONS: A win-win situation from economic and environmental perspectives was observed in electricity and freshwater consumption, pollutant emission cost, and human health economic burden. Effective measures to reduce the overall economic and environmental burdens from national coal seam gas-based power generation include alleviation of atmospheric carbon dioxide and dinitrogen oxide emissions, improvement of coal seam gas-based electricity generation and utilization efficiency, intensification of national coal seam gas utilization, and reduction of electricity and freshwater consumption.

New air speed calibration system at NMIJ for air speeds up to 90 m/s

National Metrology Institute of Japan (NMIJ) has established a high air speed standard facility and has been providing a calibration service since 2015. The facility has an air speed range of 40 m/s to 90 m/s with a relative expanded uncertainty (k = 2) of 0.63%. The purpose of this primary standard is mainly to contribute to the improvement of meteorological observation research and to the evaluation of flow field inside a turbo machine and around a high speed vehicle. The reference air speed is derived from the national primary gas flowrate standard of Japan. A conversion device from flowrate to air speed is installed in the test line of the closed-loop calibration facility. The reference air speed at the nozzle exit of the conversion device is obtained by comparing the integral of the air speed profiles and the reference volume flowrate. The total pressure tube used as a transfer standard is then calibrated against the reference air speed at the center of the nozzle exit. The Eiffel-type wind tunnel, which is a working standard for the daily calibration service, is calibrated using this total pressure tube. The present paper describes the calibration system, the traceability chain, and an uncertainty analysis using a validation method.

Assessment of gas hydrate accumulations using velocities derived from vertical seismic profiles and acoustic log data in Krishna-Godavari Basin, India

The second Indian National Gas Hydrate Program Expedition (NGHP-02) was executed in 2015 in four areas termed as Areas A, B, C and E. During this expedition, twenty five research sites were drilled and/or cored in Krishna-Godavari (KG) and Mahanadi Basins, eastern Indian offshore. During NGHP-02, zero offset vertical seismic profile (VSP) data were acquired at three sites: Sites NGHP-02-17, −19 and −22 in Area B of the KG Basin. In this study, we focus on the three sites in Area B of the KG Basin, where, zero-offset VSP and downhole acoustic log data are used to assess and characterize the gas hydrate deposits. Zero-offset VSP data are correlated with wireline log, surface seismic and synthetic seismic data to characterize and delineate gas hydrate accumulations in the KG Basin. Low velocities ranging from 1500 to 1650 m/s are observed in the unconsolidated shallow sedimentary section above gas hydrate-bearing units, whereas, very high velocities are observed in the acquired acoustic log and VSP data. In the gas hydrate-bearing sedimentary sections, the VSP derived interval velocities range from 2000 to 3000 m/s in the depth interval between 267 and 287 m below sea floor (mbsf) at Site NGHP-02-17, between 1650 and 1750 m/s in the depth interval between 306 and 366 mbsf at Site NGHP-02-19 and between 1700 and 1800 m/s in the depth interval between 198 and 290 mbsf at Site NGHP-02-22. Gas hydrates are distributed both as pore-filling and fracture-filling at all three sites, however, high concentrations are only observed as pore-filling morphology. We estimate the amount of gas hydrate considering both isotropic (pore-filling) and anisotropic (fracture-filling) acoustic reservoir models. Our estimations of gas hydrate saturation match well with the available pressure core data and suggest that high gas hydrate concentrations (to nearly 85% of pore space) are distributed in a load bearing morphology.

Culture based investigations of key microbial functional groups in gas hydrate bearing sediments of the Krishna-Godavari Basin in offshore India

Abstract Results of National Gas Hydrate Program-02 (NGHP-02) expedition have confirmed the resource potential of sand-hosted gas hydrate accumulations in the deep offshore of Krishna-Godavari Basin (KG Basin). NGHP-02 has identified two types of gas hydrate accumulations: one is thick, layer-type units developed in sand-rich facies at depths of a few 100 m below sea floor (mbsf), and the other, fracture type unit of variable thickness at shallow depths. Fracture-type and Layer-type gas hydrates were observed in Areas B, C, and E in the KG Basin as defined under NGHP-02. The importance of each type of gas hydrate occurrence as discovered during NGHP-02 has led to the need for microbial profiling. Different classes of microbes, anaerobic fermentative microbes (AFM), methanotrophs and sulphate reducing bacteria (SRB) were studied to understand the microbial system for biogenic gas generation in sedimentary sequences encountered in eight core holes (4 in Area B, 3 in Area C and 1 in Area E) as established during NGHP-02. This study reveals the availability of highest concentration of methane generating microbes that are closely associated with high total organic carbon (TOC) content in the identified gas hydrate bearing sedimentary units cored in each borehole. The presence of microbial consortia for methane generation through both processes, of reduction of CO2 and fermentation of formate/acetate has been confirmed. Stratigraphic correlation between drill sites have also been generated to better understand the spatial relationship of various microbial processes. An observation from the study, is that the entire late Miocene age sediments has potential to generate biogenic gas in Holes NGHP-02-05B, −17B, −22B and −23B. Late to early Pleistocene age sediments are showing methane generating activity in Holes NGHP-02-01C, −08B and −09B, while early Pleistocene to late Pliocene age sediments contains methane generating microbes in Holes NGHP-02-05B, −17B, −19B, −22B and −23B. The existence of methane generating biogenic microbial system in Areas B, C and E of KG Basin has been confirmed.