Fakultet for naturvitenskap og teknologi

Modeling of seismic amplitude anomalies associated with CO2 underground storage

Mon, 01 Jun 2015 00:00:00 GMT

Nordahl, Janita Louise
Higher amounts of CO2 in the atmosphere has contributed to finding techniques to mitigate the emissions of CO2. One of those techniques is Carbon Capture and Storage (CCS). CO2 can be stored in subsurface reservoirs over time. Monitoring and modeling of reservoirs is important to avoid leakage and to predict how the CO2 could migrate. Modeling is also useful when the seismic interpreter has problems, then seismic from modeling with known parameters can be useful. The first place in the world to inject CO2 was in the Sleipner field in the Norwegian North Sea. The injection found place in 1996 in the Sleipner East field into the Utsira formation. The reservoir is estimated to have a vertical thickness about 200 m at the injection point, and the estimated caprock for the CO2 is about 100 m thick. This thesis shows modeling of the seismic response from different synthetic models associated with CO2 underground storage. The parameters is based on data from the Sleipner field to get a realistic view of the result. Incident angle, input frequency, CO2 saturation and geometry of the models are all important parameters affecting the seismic result. Modeling with various incident angles and input frequencies has been done. It showed that higher frequencies gives the best resolution as expected, and that smaller incident angle makes it easier to distinguish interfaces. A frequency of 70 Hz and an incident angle of 20°, made it possible to detect both interfaces of a layer with vertical thickness of 1 m. Several models with varying vertical and horizontal thicknesses of the plume have been made. The results shows that an incident angle of 20° with 60 Hz and realistic migration options turned on (aperture range and traveltime range) will not create any vertical reflections. Horizontal plumes with an incident angle of 20° using 30 Hz and 60 Hz, is visible with no interference for vertical thickness equal and greater than 40 m and 20 m, respectively. Tuning thickness occurred with a vertical thickness of 20 m and 10 m for respectively 30 Hz and 60 Hz. A stronger reflection in the area the plume is located is visible for vertical thicknesses equal to and greater than 3 m when using both 30 Hz and 60 Hz.

Synthetic aperture radar compact polarimetry for sea ice surveillance

Fri, 26 Jun 2015 00:00:00 GMT

Espeseth, Martine Mostervik
The focus of this thesis is to investigate the use of synthetic aperture radar (SAR) compact polarimetry for studies of sea ice. Data obtained from quad-polarimetric SAR systems have already been studied extensively for sea ice monitoring. This thesis focuses on finding parallels to quad-polarimetric features from the compact-polarimetric data. This is achieved through the reconstruction of a pseudo quad-polarimetric sample covariance matrix. The main contribution of this thesis is the suggestion of new reconstruction techniques for sea ice covered SAR scenes. Most of the estimated polarimetric features relevant to sea ice monitoring are successfully reconstructed. Furthermore, a comparison between the different reconstruction techniques is presented for different sea ice types. It is shown that the cross-polarization intensity can be reconstructed for different sea ice types, but that the performance is strongly affected by the choice of reconstruction method. The proposed modified Souyris' reconstruction technique turns out to be the best method for achieving high performance for different polarimetric features representing different sea ice types. Additionally, three other methods are suggested, namely a model-based, an eigenvalue-based, and a DoP-based reconstruction method. Each of these methods produce a higher accuracy than the existing reconstruction methods for most of the polarimetric features. Remote sensing instruments have been extensively used as a tool for sea ice monitoring. Information about sea ice is important for multiple industries like oil and gas, fishing, research communities, and tourism. Full- and dual polarimetric SAR instruments have been used to extract useful information about the sea ice surface, but now a new polarimetric mode has been invented. In its infancy, the theoretical foundation of compact polarimetry was presented by Souyris, Nord, and later Raney with the hybrid-pol mode. However, compact polarimetry—especially the hybrid-pol mode—has proved valuable, and has in later years found its way into operational satellite systems such as the RISAT and the ALOS-2 satellites. The work presented in this thesis adds to the on-going discussion on the potential of compact polarimetry, and is the first comprehensive analysis of reconstruction methods for specified application to sea ice.

Reservoir structure and geological setting of the shallow PEON gas reservoir

Mon, 01 Jun 2015 00:00:00 GMT

Mikalsen, Håkon
In recent years, the petroleum industry started to look for new, unconventional energy resources. Peon, a shallow gas discovery in the northern North Sea, are being assessed as a possible energy resource. However, there are challenges related to reservoir pressure, sealing mechanism, and fluid migration. In this regard, geophysical and well log analyses is figured out to get a better understanding of the depositional regime and stratigraphy in the Peon area, as well as the structure of Peon and the dipping nature of the gas-water contact. During the last 1.1 million years, the Norwegian Channel Ice Stream have fed the Norwegian Continental Shelf with enormous amounts of sediments. Peon is located at the base of a regional unconformity in the outer part of Norwegian Channel. The overburden and the reservoir reveal several prominent surfaces, distinguishing sub-horizontal bedded units. The presence of iceberg plough marks and mega-scale glacial lineations on these surfaces and several till units interbedded, testifies what great actor the ice streams had during deposition. Peon reservoir deposited likely during a glacial retreat. Orientation of reservoir, erosional truncations and structures in the top reservoir indicate a glacial advance has remobilized and cut the reservoir, forming a lensoid-shaped reservoir.

RAM analysis of mining equipment and framework for data collection

Mon, 01 Jun 2015 00:00:00 GMT

Sneve, Terje
In the mining industry, equipment are continuously increasing in size and complexity. At the same time, the demand for available plants and continuous production has never been higher. The performance of equipment depends on the reliability and maintainability performance of the equipment along with the maintenance supportability, operational conditions, and environmental conditions. In order to improve plant availability, fully utilize equipment performance, avoid equipment breakdowns and optimize operation and maintenance (O&M), the concept of reliability, availability and maintainability (RAM) analysis is required. In most industries, the only collected explanatory variables used in RAM analysis have been time to failure (TTF) and time to repair (TTR). For a more precise estimation of the reliability and maintainability characteristics of mining equipment, factors influencing the reliability and maintainability of equipment should be collected and included in the analysis. In this thesis, the concept of RAM analysis is applied for availability improvement in the mining industry as a quantitative case study. Furthermore, a framework for data collection including influence factors has been developed, which highlights important steps in the data collection process. For including the effects of influence factors in RAM analysis, the Proportional Hazard Model (PHM) with the modified Proportional Repair Model (PRM) are discussed. Finally, a qualitative case study is conducted to demonstrate the application of the framework for data collection for RAM analysis. The result of the RAM analysis have been used to determine optimum preventive maintenance interval in order to improve availability performance. Furthermore, aspects for improvement of reliability performance and maintainability performance have been assessed in order to improve overall system availability. The framework developed for data collection is considered general enough to cover several industries. However, the framework is especially suited for the mining industry with the use of the PHM and PRM for including influence factors in reliability and maintainability analysis. The work in this thesis, the framework for data collection especially, is considered valuable and necessary as it addresses an area that has received less focus in today's mining industry. Keywords: RAM, mining, O&M optimization, data collection, influence factors, Proportional hazard model, Proportional repair model

A detailed investigation of a geological CO2-storage reservoir

Sun, 31 May 2015 00:00:00 GMT

Hatland, Anna Maria
Increased CO2-concentrations within the atmosphere of the Earth have encouraged development of “carbon capture and storage” (CCS). It is important to avoid global warming, and CO2 may be stored within geological formations in the subsurface. This thesis focuses on the possibilities of storing CO2 in a reservoir of Middle Triassic-Middle Jurassic age in The Nordkapp Basin, The Southern Barents Sea. The thesis tries to map out the extent of a reservoir and a cap rock, calculate the amount of injectable CO2, and assess the potential risks of leakage for the CO2-storage complex. The evaluation is based on a migrated 3D-seismic dataset, ST9403, with 7228/7-1A as a reference well. The well penetrates several formations, where the formations of Stø-Tubåen are considered the best reservoir unit, consisting of a homogenous sandstone with good properties. The cap rock constitutes the formations of Hekkingen and Fuglen, which is tight, covering and homogenous. The trap type is linked to extensive salt domes, enclosed by faulted structures. The salt domes are stable and the faults inactive and tight. Possible hazardous, chemical reactions between the salt, the injected CO2 and a Permian carbonate are considered the largest safety risks for the CO2-storage complex.

Evaluation of probability of failure of static equipment in pressurized mud systems on an offshore drilling installation

Mon, 01 Jun 2015 00:00:00 GMT

Rød, Bjarte
Degradation of pressurized topside static mud equipment is a very complex process. Inspection is a helpful tool to monitor degradation and helps reduce the number of critical failures. If it is left undetected and unchecked, it can lead to leakage resulting in accidents. To set up an effective inspection program, the concepts of Risk-Based Inspection (RBI) can be utilized. RBI helps to develop an optimum inspection program by evaluating the probability of failure (PoF) and consequence of failure (CoF), and combining them to estimate risk. The parts that have risk higher than the acceptable limit are then prioritized for inspection. This thesis studies the probability of failure in static equipment in pressurized mud systems on an offshore drilling installation, due to different degradation mechanisms and its influencing factors. Det Norske Veritas (DNV), suggests a number of models to estimate internal and external degradation. By analyzing inspection data from the industry, it is observed that the models can at times be inconvenient to use when the degradation process is complex. For example, it is difficult to develop a simple, yet reliable, model that can accurately predict rate of degradation in situations where corrosion and erosion are simultaneously taking place. In static equipment in high pressurized mud systems, inspection have shown that the main reason for internal degradation is high amounts of solids in the fluid, high velocity, presence of seawater, and corrosive chemicals. DNV-RP-G101 does not present any model for this situation. For external corrosion, the current models presented in DNV-RP-G101 can be used to analyze inspection data. In an old installation, the accurate quantitative records are often not available due to a number of reasons, like difficulty in measuring, old data management system, unsystematic inspections or lost records. Thus, it often becomes difficult to develop any qualitative model. On the other hand, the inspection and maintenance engineers have extensive experience that may be utilized for developing effective subjective models. In this thesis, based on some simplified parameters, a methodology for evaluating probability of failure is established. The methodology is divided into external and internal degradation, where the subjective judgments are more evident for internal degradation. Simplified flowcharts and tables are developed to easily evaluate probability of failure.

A study of the potential improvement of Sydvaranger Gruve´s process water treatment through experiments with different flocculants and coagulants

Mon, 01 Jun 2015 00:00:00 GMT

Floer, Ida Katrine
Mining is the process or industry of extracting valuable minerals or other geological materials from the earth. The nature of mining creates a potential negative impact on the environment both during the mining operations and several years after the mine is closed. Over the years regulations designed to moderate the negative effects are adopted, and environmental issues and challenges have gotten more attention. The mining industries aim to improve production efficiency and at the same time take care of the environment according to best practice. The latter is the subject in this thesis, which aims to look at Sydvaranger Gruve AS’s use of chemical treatment of process water within the mining industry. Flocculants and coagulants are chemicals that are used in water treatment in many industries. In this approach the water resource is limited and the aim is to treat the process water in order to recirculate it. Despite the same mineral being processed the process water will not have the same properties due to the huge variations of influencing factors. Some theory regarding water treatment with chemicals exists, but there are still many assumptions and a lack of understanding. There are many chemicals on the market and it requires a lot of testing to assure that the most efficient chemical is used in the process water treatment. Sydvaranger Gruve AS is a mining company located North in Norway close to the Russian border. The company has a history that dates back over a hundred years and it is known for its pioneering development of technology to process taconites, which is a low-grade ore. Sydvaranger Gruve AS is currently using a cationic coagulant with low molecular weight, Magnafloc LT 38, in combination with a slightly anionic flocculent with a medium molecular weight, Magnafloc 10. The study presented in this thesis is based on existing literature, though the previous work in this area has proved to be limited. It is challenging to conclude the specific chemical reaction due to lack of literature, but assumptions will be made based on theory. In this thesis the process is presented in the form of description and flowcharts. Influencing factors regarding the process and geology are identified and discussed. The existing theory regarding chemical water treatment is presented and various chemical products for water treatment are gathered from different suppliers. The procedure for testing is presented, the testing is performed in three main stages and are evaluated both quantitative and qualitative. A lot of effort has been put into finding a suitable chemical or a combination of chemicals and many chemicals were tested through experimental work. Zetag 8187, a strongly cationic flocculent with a medium high molecular weight, is the chemical that has shown the best result and has been examined further to compare its behavior against the chemicals in use today. A quality assurance has been performed to illustrate the reliability of the test methods and procedures despite the large variations in the influencing factors. A risk assessment based on environmental issues has been done on the final chemical recommendation, Zetag 8187, versus the chemicals that are in use today, Magnafloc 10 and Magnafloc LT 38, in order to see if there are any environmental benefits by substitution of chemicals, other than performance. The results are presented and final recommendations are made based on the tests and other observations. Despite proving good results in small-scale tests, extensive plant scale tests should be carried out to verify the results shown in the thesis.

QRA techniques on dynamic positioning systems during drilling operations in the Arctic: With emphasis on the dynamic positioning operator

Mon, 01 Jun 2015 00:00:00 GMT

Pedersen, Runar Nikolai
With the Norwegian government moving the ice edge farther north than ever before, opening for new areas for petroleum exploration, it will need research on how these areas can affect oil and gas operations. A sensitive environment along with the harsh Arctic climate and remote distances means that severe accidents, like blowouts, will have serious impacts and make cleanup and rescue actions to challenging operations. Additionally, humans working under these conditions are prone to be affected with regards to their reliability, which means that human errors are more likely to occur. The use of dynamic positioning systems as position-keeping solutions on mobile offshore drilling units is becoming increasingly popular as it is quick and easy to change position, independent on seabed conditions and does not need handling of anchors. The dynamic positioning operation is managed by an operator who is responsible for keeping the vessel in position, in addition to being a barrier for safely shutting in the well and disconnecting the riser configuration from the BOP when position-keeping is not possible. Quantitative risk assessment techniques have been used in the offshore industry for decades. They are usually applied to operations and systems, but are also possible to utilize for analyzing humans and their contribution in a risk picture. Based on a set of precautions, a model for analyzing dynamic positioning systems during loss-of-position events in the Arctic, with the focus particularly on the dynamic positioning operator, is in this thesis developed. A fictional comparison between a dynamic positioning drilling operation influenced by Arctic conditions and a similar operation in an area not exposed to such conditions is also provided. The comparison will indicate to which extent the reliability of the dynamic positioning operator is decreased by influence of Arctic conditions, and the role this plays in the recovery phase of loss of position events. Hopefully the findings in this thesis can contribute to safer oil and gas operations in the Arctic.

Risk analysis of well control operations considering Arctic environmental conditions

Mon, 01 Jun 2015 00:00:00 GMT

Bergan, Håvard Hegg
Oil and gas development in the Arctic is becoming a major focus in the industry today. However, compared to other regions, there is less experience regarding drilling operations in the Arctic environment. This fact raises concerns about high-risk scenarios, which might take place because of the harsh environmental conditions and the effects they have on various phases of operations, equipment and human performance. The operating conditions depend on the location in the Arctic, but sea ice, spray and atmospheric icing, low temperatures, seasonal darkness, winds, and polar lows, are considered as important Arctic environmental factors. In any offshore drilling setting, well control operations are among the most crucial activities taking place, from risk perspective. A failure to control the wellbore can lead to devastating scenarios such as oil spills, explosions and major fatalities. There are mainly two safety barriers in place to prevent the loss of well control: primary and secondary well control barriers. The former refers to maintaining the wellbore pressure greater than formation pore pressure and less than formation fracture pressure, using the mud column pressure. The latter refers to mechanically securing the wellbore utilizing the blowout preventer (BOP) stack. This study aims to develop a risk model for a well control operation, based on which the effects of the operating conditions in the Arctic offshore can be assessed. This aim is achieved through a stepwise procedure. By identifying the causes and consequences of failures in different phases of a well control operation, the risk model is built. Furthermore, the potential impacts of Arctic operating environment are investigated. Finally, how such impacts can be quantified and applied to the model is discussed. The analyses performed in this study indicate that Arctic operating conditions can negatively affect human performance and reliability performances of well control procedures. The potential impacts are accounted for in the developed risk model through an expert-based approach, based on linear aggregation of expert opinions, through which the decision-maker's distribution is estimated using a Monte Carlo simulation method. A sensitivity analysis of well control safety barriers is performed, using Birnbaum's importance measure, to prioritize such barriers from reliability performance perspective. Moreover, a Monte Carlo simulation technique is used for the propagation of parameter uncertainties, to evaluate the resulting probabilities of near miss and blowout.

The role of safety culture in establishing an effective safety information system in the oil and gas industry. A case study of an onshore facility

Mon, 01 Jun 2015 00:00:00 GMT

Wolff, Steffen Hauge
The main purpose of this study was to contribute to understanding of how safety culture affects the performance of safety information systems (SISs). More particularly, to investigate how safety culture can both facilitate and inhibit a SIS to function effectively. The thesis has been carried out as a qualitative, single case study of an onshore facility in the oil and gas industry. Seven semi-structured qualitative interviews were conducted. Informants included employees from the operational, line-management and management level. In addition, textual analysis of internal management system documents was used. Analysis has revealed that safety culture both facilitates and inhibits performance of a SIS. The facility has implemented multiple organizational measures directed at safety that together influences the development of safety culture. This safety culture further affects performance of the established SIS. Facilitating factors to several of the SIS’ phases were: personal reporting in combination with a mutual established trust between the management and operative personnel. In addition, there is an established practice of asking the operative personnel follow-up questions related to reported incidents, which enhances the understanding and accuracy of conducted risk analysis in the system. At last, there is a continuous monitoring of incoming reports in the SIS, seeking to avoid particularly personnel injuries and facilitating response time. However, several inhibiting factors have also been identified: there is a strong belief that under-reporting is happening with the facility, which potentially inhibits the performance of the whole SIS. There is also a need to use the operative personnel’s expertise more in cases when they possess the best knowledge. In addition, the multiple workshops within the facility know little about each other’s preventive work. At present, lack of experience transfer internally inhibits performance of the SIS. The facility is moving towards having an effective SIS. However, there needs to be continuous improvement, starting by acting upon the identified inhibiting factors. Overall, a basis has been already established. The future is about developing the safety culture further.