Gas production from shale formations is growing, especially in the USA. However, the origin of shale gases remains poorly understood. The objective of this study is to interpret the origin of shale gases from around the world using recently revised gas genetic diagrams. We collected a large dataset of gas samples recovered from shale formations around the world and interpreted the origin of shale gases using recently revised gas genetic diagrams. The dataset includes >2000 gas samples from the USA, China, Canada, Saudi Arabia, Australia, Sweden, Poland, Argentina, United Kingdom and France. Both free gases collected at wellheads and desorbed gases from cores are included in the dataset. Shale gas samples come from >34 sedimentary basins and >65 different shale formations (plays) ranging in age from Proterozoic (Kyalla and Velkerri Formations, Australia) to Miocene (Monterey Formation, USA). The original data were presented in >80 publications and reports. We plotted molecular and isotopic properties of shale gases on the revised genetic diagrams and determined the origin of shale gases. Based on the distribution of shale gases within the genetic diagram of δ13C of methane (C1) versus C1/(C2+C3), most shale gases appear to have thermogenic origin. The majority of these thermogenic gases are late-mature (e.g., Marcellus Formation, USA and Wufeng-Longmaxi Formation, China) and mid-mature (associated with oil generation, e.g., Eagle Ford Formation, USA). Importantly, shales may contain early-mature thermogenic gases rarely found in conventional accumulations (e.g., T⊘yen Formation, Sweden and Colorado Formation, Canada). Some shale gases have secondary microbial origin, i.e., they originated from anaerobic biodegradation of oils. For example, gases from New Albany Formation and Antrim Formation (USA) have secondary microbial origin. Relatively few shale gases have primary microbial origin, and they often have some minor admixture of thermogenic gas (e.g., Nicolet Formation, Canada and Alum Formation, Sweden). Two other revised gas genetic plots based on δ2H and δ13C of methane and δ13C of CO2 support and enhance the above interpretation. Although shales that contain secondary microbial gas can be productive (e.g., New Albany Formation, USA), the resource-rich, highly productive and commercially successful shale plays contain thermogenic gas. Plays with late-mature thermogenic gas (e.g., Marcellus Formation, USA and Wufeng-Longmaxi Formation, China) appear to be most productive.
One of the most secure storage sites for CO2 injection is in depleted gas reservoirs. To ensure that the CO2 is trapped securely and will not escape to the surface, storage in such formations must be study carefully prior to injection in such formations. After the injection, the injected CO2 will undergo several trapping mechanisms; namely: hydrodynamic, solubility and mineral trapping. The extend of geochemical reactions involved depend on the composition of the injected fluid introduced in the aquifer, the composition of the initial minerals assemblage and the aquifer brine. In this paper, the importance of biological/microbial mechanisms towards the impact on the storage capacity was studied using reactive transport modelling. The results obtained shows that the presence of microbial compound such as organic matter contributes to the enhancement of mineral precipitation, resulting in secure long-term storage.
Design of offshore structures for arctic and subarctic regions requires consideration of wave, wind and ice actions. If individual actions are not mutually exclusive, then combined actions also need consideration. ISO 19906 recommends that, when possible, extreme level combined actions should be determined based on the joint probability distribution of the actions. As an alternative, ISO 19906 provides a framework where a user can determine principal and companion extreme actions independently, and sum these with calibrated combination factors applied. While the combination factors in ISO 19906 were calibrated over a range of conditions and platforms, site-specific information is not taken into account when applying the method. In this paper, a procedure is presented for determining extreme level combined actions for sea ice and waves based on site-specific sea ice and wave information, accounting for the joint probability distribution of the actions. The procedure is demonstrated for an example fixed structure on the Grand Banks off Canada's east coast. The results are compared with extreme actions determined using the ISO 19906 combination factors.
Dewatering of groundwater resources induced by leakage into underground constructions can cause land subsidence, damage to constructions and their foundations and disturbances of groundwater dependent ecosystems. To reduce the environmental impacts, safety measures, e.g. sealing fractures by grouting to reduce inflow of groundwater or artificial recharge to maintain groundwater levels, must be implemented. Site investigations of the total geological and hydrogeological conditions at a site before construction is, due to financial aspects, most often not possible. To handle these uncertainties in the design- and construction process, it is suitable to use the observational method, which include the idea of identification, confirmation or rejection, and revision of the most probable and unfavorable conditions, and predefined technical design solutions for conditions that can reasonable be anticipated or foreseen. To assess the geological and hydrogeological conditions at an early stage of a project we suggest that geological and related hydrogeological reference conditions are used. Fundamental to our approach using reference conditions is the grouping of materials with similar geological and hydrogeological conditions and engineering characteristics. In this paper, we present conceptualizations of five reference conditions common in western Sweden and two examples of reference conditions in Singapore. The conceptualization of reference conditions includes a description of: the geological material; the hydrogeological properties and behavior within the environment; and the engineering characteristics related to water control and grouting. Examples of technical design solutions used to adopt to project specific requirements for inflow and drawdown for underground constructions constructed in environments representing one of the suggested reference conditions in western Sweden are also presented to exemplify the application of reference conditions for technical design.
As demand for land above the ground surface increase, it becomes more attractive with underground facilities. Dewatering of groundwater resources induced by leakage into underground constructions is known from several underground projects around the world (Kvӕrner and Snilsberg, 2013; López-Fernández et al., 2012). A lowered water table may result in land subsidence and damage to buildings and their foundation (Roy and Robinson, 2009; Xue et al., 2005), impacts on groundwater dependent ecosystems such as peatlands, streams, springs and lakes (Kvӕrner and Snilsberg, 2008) and changes of the groundwater chemistry (Mossmark et al., 2008). Furthermore, large inflows of water into underground constructions can cause casualties, economic losses and adverse working conditions (Coli and Pinzani, 2014; Hou et al., 2016).
According to Chapter 11 in the Swedish Environmental Code, all water operations (change of water level, land drainage, groundwater drainage or groundwater infiltration) needs an environmental court ruling from the Land- and Environment court (Naturvårdsverket, 2008). The project specific court rulings often include requirements regarding maximum allowed groundwater drawdown or inflow into the underground space. To be able to state relevant requirements in the environmental court ruling, it must be ensured that the requirements are both technically relevant, achievable and measurable. Therefore, the hydrogeological descriptions must closely link to possible technical solutions for project specific requirements and to the monitoring set up.
The paper introduces design principles of ground support. The topics include underground loading conditions, the natural pressure arch in the rock mass, design methodologies, determination of the factor of safety and compatibility between support elements. A natural pressure arch is formed in the rock mass in a certain distance behind the tunnel wall. The methodology of ground support in an underground opening is dependent on the size of the failure zone and the boundary depth of the natural pressure arch. In the case of a small failure zone, rockbolts should be long enough to reach the natural pressure arch. In the case of a vast failure zone, an artificial pressure arch could be established in the failure zone with tightly spaced rockbolts and the artificial pressure arch is stabilised with long cables anchored on the natural pressure arch and/or by external support elements like shotcrete liners, girdles, steel arches and shotcrete arches. In addition to the factor of safety, the maximum allowable displacement in the tunnel and the ultimate displacement capacity of support elements should be also taken into account in the design. Finally, the support elements in a ground support system should be compatible in terms of displacement and energy absorption.
Ground support design is associated with the rock mass quality, the in situ stresses and the size and geometry of the underground opening. Knowledge of the in situ loading condition is crucial for the design of ground support. The methodology and design principles of a ground support program are determined by the potential failure mode and failure extent of the rock mass as well as the engineering requirements to the maximum allowable displacement. In this paper, some key parameters for ground support design are presented which include the natural pressure arch, the artificial pressure arch established in the failure zone, support layers, the factor of safety, and the compatibility between support elements.
Fractures have a significant impact on rock mass mechanical and hydraulic properties, which is a concern for rock engineering applications like excavation or repository design, support design, slope stability and caving in mines. To address this issue, a sound description of the fracturing pattern is required. DFN models are statistical models which define the density of fractures having given geometrical properties (size and orientation) and which include an intrinsic variability term. One of the main challenging task is to combine all available data. Data remain sparse and scarce and are acquired at different scales and from different support shapes and dimension (1D, 2D). We present a 3D modelling approach combining data from borehole logs, outcrop trace maps and tunnel walls mapping. It is applied to the Äspö site in Sweden, for which a large database is available, containing tens of thousands of records. Using stereological rules and assumptions about the underlying DFN scaling model, we are able to integrate all data to define the fracturing properties from the borehole scale (ten centimeters) to the repository scale (several kilometers). An advanced DFN modeling framework is applied, accounting for fractures mechanical interactions. This model has proved to be almost universal in crystalline rocks and reproduces, with very few parameters, the scaling properties of fractures. We show that this modelling framework better reproduces observations at all available scales and yields DFN, which structure and associated properties have a better consistency with natural cases than for simple DFN approaches.
Studying fractured systems is a requirement for many industrial applications including nuclear waste deep repositories, geothermal energy exploitation in crystalline hard rocks and oil and shale gas extraction. In these fields, fractures are key factors for rock masses flow and mechanical properties. Fracture networks are complex systems arising from the physics of fracture development and from complex interactions between fractures. Because of this intrinsic complexity, fracture systems present the classical characteristics of complex systems with power-law scaling relationships . This is now widely recognized from geological studies [2-4].
The major difficulty for defining Discrete Fracture Network (DFN) models is the limited amount and the nature of available data. Despite constant technical improvements, high-resolution measurements of fracture patterns are mostly limited to borehole and surface mapping, thus raising both under-sampling and stereological issues. The fracture system is defined at best from statistical distributions, which are the basic ingredients for interpolating local measurements at the site scale. The precise knowledge of these distributions, including scaling, is a critical issue for site modeling.
This paper shares results from three DeepStar® Phase XII efforts championed by the X800 Metocean Committee. The first project, 12801, examined marine growth profiles for the Gulf of Mexico. The profile presently used by industry is based on limited data collected nearly thirty years ago, and was shown by the study to under-represent the amount of growth that should be expected on platforms in the Gulf. In addition, flaws in the survey processes currently used to evaluate growth as part of inspections were identified and documented. The second project, 12802, evaluated the design wind speed relationships used by industry to characterize extra-tropical storms, through analysis of high-quality overwater wind measurements collected for elevations up to 100 m made at three locations in the North Sea and Baltic Sea. The evaluation demonstrated the present NORSOK relations are adequate for extra-tropical storms, and hence going forward, industry will use separate design wind speed relationships for extra-tropical storms and tropical cyclones, a revised set for the latter being developed previously under project 11802. The third and final project, 12803, sponsored the development of an updated 54-year free-running simulation of currents in the Gulf of Mexico, with refined modeling of bottom currents in areas near steep bathymetry such as the Sigsbee Escarpment, in order to better represent topographically-enhanced Rossby waves (TRWs), which are a critical design consideration for risers and tendons. The resulting database provides an excellent basis for the development of Loop Current and TRW criteria for use in deepwater Gulf of Mexico projects.
Wang, Guanxue (Huazhong University of Science and Technology) | Xu, Guohua (Huazhong University of Science and Technology) | Shen, Xiong (Wuhan Second Ship Design and Research Institute) | Xu, Han (Huazhong University of Science and Technology) | Liu, Chang (VTT Technical Research Centre of Finland) | Wang, Wenjin (Huazhong University of Science and Technology)
This paper focuses on design and experiment of an abdominal operation ROV. Firstly, overall design for system of abdominal operation ROV which consists of surface unit, power module, umbilical cable and ROV body is introduced. Secondly, the design of ROV body is described in detail to give a further study on body frame, buoyancy, thrusters, locking mechanism, underwater camera, lamps, navigation sensor and control cabin. Thirdly, research on control system which is the key part of ROV is presented. Finally, based on designed ROV a number of experiments are conducted to verify and test the functions and performances of abdominal operation ROV.
With the increasing attention of human beings to marine resources, ROV has been growing as a major vehicle in ocean exploration. Due to the complex and uncertain underwater environment, ROV need to be equipped with operating system, power system, observation system and control system to complete a series of missions. It`s significant to design and manufacture new type of ROV to adapt different working conditions while realizing various functions and high performances.
The shape and the appearance of the ROV proposed in this paper is shown in Fig. 1. It weighs 52.25kg in air. Main dimensions are 700mm in length, 550mm in width and 425mm in height. The velocity is up to 4kn and it is capable of dividing to the depth of 300m under water. ROV is open frame equipped with thrusters, a linear actuator, an underwater camera, lamps and a navigation sensor. It is able to complete 3-DOF motion maneuvers: along axes X and Y, as well as rotate around Z by sending commands from the surface unit to the underwater main controller. To execute docking tasks, ROV will hover in order to search for the rod which is the object to be docked. When the rod came into the view of camera, ROV approaches to it and tilts its camera to identify the relative position between them. At the same time, ROV adjusts its attitude to let the rod insert into its abdominal operation mechanism with the help of the guidance conic. At last, the linear actuator extends out to lock the rod which means rigid connection between the ROV and the rod is completed, that is to say, docking tasks are achieved.
Li, Peng (Chinese Academy of Sciences) | Zhang, Xuhui (Chinese Academy of Sciences) | Lu, Xiaobing (Chinese Academy of Sciences) | Liu, Lele (China Geological Survey) | Liu, Changling (China Geological Survey)
High efficiency, economic, and safe exploitation of natural gas hydrate is an important researching topic. Mechanical-Thermal exploitation is new presented potential efficient method for shallow marine hydrate exploitation, and contains the following procedures: In-situ mining o: hydrate-bearing sediments, cutting the sediments into small bodies mixing the sediments with surface injected seawater, transporting the multiphase fluid with hydrate dissociation in the exploitation well, and backfilling the sediments, etc. The physical processes of small bodies of hydrate-bearing sediments and water flow accompanying hydratt dissociation are described in the main controlling parameters. Ther some trial observational tests are conducted to obtain information or the dissociation process of gas hydrate in small bodies under water. heating condition.
Gas hydrate (GH) is a solid compound of hydrocarbon gas and water molecules. Gas hydrate-bearing sediments (GHBS) consist of hydrate water or/and gas, sand/clay etc. GH exists in cementing or filling status with soil skeleton, and widely distributes in the sea, permafrost and deep lakes (Kvenvolden and Lorenson, 2001; Koh, 2002; Song et al. 2014).
Countries such as Russia, Canada, America and Japan have carried ou trial productions of GH in the permafrost (Makagon et al., 2005, 2013 ConocoPhillips, 2012a, b; Collett et al., 2012;) and deep marine (Fuji et al., 2013; Chee et al., 2014; Terao et al., 2015). The methods of GI-exploitation include thermal injection, depressurization, and CO2 displacement. The trial production of GH gives the confidence tha increasing temperature or/and decreasing pressure could release methane from GHBS in a short period, but the efficiencies of these productions are hard to satisfy a commercial-viable application.
The physical processes in the production contain heat conduction, phase transformation, multiphase seepage and soil deformation (Moridis et al., 2009). The ratio of the characteristic times is 109:107:106:1. The heat conduction is the slowest physical effect, and controls the coupling processes. Lack lasting supply of heat into the GHBS leads to the low efficiencies of the in-situ trial production, and constrains the utilization of the methods such as depressurization and thermal injection (Hong et al., 2003; Zhang et al., 2014a).
The formation and geological characteristics of GHBS in South China Sea are more complex and inhomogeneous. The reserve is large but in a scattered spatial distribution. The sediment is soft and the permeability is low. Through a preliminary estimation of thermal injection, the expansion length of hydrate dissociation zone gets to merely about 30 m after 20 years, leading to a serious situation of high investment and low profit, especially at the period of low price of international oil and natural gas (Zhang et al., 2014a, b).
Growing commercial activities in the High North increase the possibility of unwanted incidents. The vulnerability related to human safety and environment as well as a challenging context, call for a strengthening of the maritime preparedness system, cross-border and cross-institutional collaboration. In this paper, we look into the different stressors and risk factors of the sea regions in the High North. We elaborate on emergencies where integrated operations like mass evacuation is needed. We build upon in-depth studies of two cruise ship incidents close to the Spitsbergen Islands, and full-scale exercises in the Arctic region. We claim that coordination of such operations where several institutions and management levels are included demands significant integration and communication efforts. Implications for the training of key personnel responsible for coordinating such operations are discussed.
Emergency situations are often characterized by lack of overview and uncertainty about cause, consequences and suitable safety barriers. In areas like the High North, due to limited infrastructure and the scarcity of emergency capacities, a simple emergency situation can quickly turn into a crisis involving significant risk for people, nature and vulnerable societies. The turbulent weather conditions facing emergency actors, makes rescue and relief operations a challenging and time consuming task. In this paper, we examine how the emergency management has to be configured to overcome challenges related to large-scale emergencies with limited local infrastructure, long distances and harsh weather conditions in icy waters. In addition, we consider the limited availability of emergency support systems and the time delays caused by the geographical distances.
By examining the various emergency situations we reflect on suitable composition of the infrastructure, emergency groupings, and coordination mechanism.
Emergency Management and Emergency Response Pattern
High levels of uncertainty combined with a need for fast and reliable action are the main characteristic of emergencies (Kyng, Nielsen, and Kristensen 2006). Major incidents like shootouts and terror action, or cruise ship groundings with mass rescue operations (MRO) are categorized by lack of sufficient resources to meet the emergency situation. These situations are often chaotic and stressful with a large number of causalities, and a mix of SAR capacities. Thus, obtaining and maintaining an overview for such an incident become extremely hard for the coordinators and the different levels of command.