Safety analysis of plugging and abandonment of oil and gas wells in uncertain conditions with limited data

Well plugging and abandonment are necessitated to ensure safe closure of a non-producing offshore asset. Little or no condition monitoring is done after the abandonment operation, and data are often unavailable to analyze the risks of potential leakage. It is therefore essential to capture all inherent and evolving hazards associated with this activity before its implementation. The current probabilistic risk analysis approaches such as fault tree, event tree and bowtie though able to model potential leak scenarios; these approaches have limited capabilities to handle evolving well conditions and data unavailability. Many of the barriers of an abandoned well deteriorates over time and are dependent on external conditions, making it necessary to consider advanced approaches to model potential leakage risk. This paper presents a Bayesian network-based model for well plugging and abandonment. The proposed model able to handle evolving conditions of the barriers, their failure dependence and, also uncertainty in the data. The model uses advanced logic conditions such as Noisy-OR and leaky Noisy-OR to define the condition and data dependency. The proposed model is explained and tested on a case study from the Elgin platform's well plugging and abandonment failure

Dynamic safety analysis of decommissioning and abandonment of offshore oil and gas installations

The global oil and gas industry have seen an increase in the number of installations moving towards decommissioning. Offshore decommissioning is a complex, challenging and costly activity, making safety one of the major concerns. The decommissioning operation is, therefore, riskier than capital projects, partly due to the uniqueness of every offshore installation, and mainly because these installations were not designed for removal during their development phases. The extent of associated risks is deep and wide due to limited data and incomplete knowledge of the equipment conditions. For this reason, it is important to capture every uncertainty that can be introduced at the operational level, or existing hazards due to the hostile environment, technical difficulties, and the timing of the decommissioning operations. Conventional accident modelling techniques cannot capture the complex interactions among contributing elements. To assess the safety risks, a dynamic safety analysis of the accident is, thus, necessary. In this thesis, a dynamic integrated safety analysis model is proposed and developed to capture both planned and evolving risks during the various stages of decommissioning. First, the failure data are obtained from source-to-source and are processed utilizing Hierarchical Bayesian Analysis. Then, the system failure and potential accident scenarios are built on bowtie model which is mapped into a Bayesian network with advanced relaxation techniques. The Dynamic Integrated Safety Analysis (DISA) allows for the combination of reliability tools to identify safetycritical causals and their evolution into single undesirable failure through the utilisation of source to-source variability, time-dependent prediction, diagnostic, and economic risk assessment to support effective recommendations and decisions-making. The DISA framework is applied to the Elgin platform well abandonment and Brent Alpha jacket structure decommissioning and the results are validated through sensitivity analysis. Through a dynamic-diagnostic and multi-factor regression analysis, the loss values of accident contributory factors are also presented. The study shows that integrating Hierarchical Bayesian Analysis (HBA) and dynamic Bayesian networks (DBN) application to modelling time-variant risks are essential to achieve a well-informed decommissioning decision through the identification of safety critical barriers that could be mitigated against to drive down the cost of remediation.The global oil and gas industry have seen an increase in the number of installations moving towards decommissioning. Offshore decommissioning is a complex, challenging and costly activity, making safety one of the major concerns. The decommissioning operation is, therefore, riskier than capital projects, partly due to the uniqueness of every offshore installation, and mainly because these installations were not designed for removal during their development phases. The extent of associated risks is deep and wide due to limited data and incomplete knowledge of the equipment conditions. For this reason, it is important to capture every uncertainty that can be introduced at the operational level, or existing hazards due to the hostile environment, technical difficulties, and the timing of the decommissioning operations. Conventional accident modelling techniques cannot capture the complex interactions among contributing elements. To assess the safety risks, a dynamic safety analysis of the accident is, thus, necessary. In this thesis, a dynamic integrated safety analysis model is proposed and developed to capture both planned and evolving risks during the various stages of decommissioning. First, the failure data are obtained from source-to-source and are processed utilizing Hierarchical Bayesian Analysis. Then, the system failure and potential accident scenarios are built on bowtie model which is mapped into a Bayesian network with advanced relaxation techniques. The Dynamic Integrated Safety Analysis (DISA) allows for the combination of reliability tools to identify safetycritical causals and their evolution into single undesirable failure through the utilisation of source to-source variability, time-dependent prediction, diagnostic, and economic risk assessment to support effective recommendations and decisions-making. The DISA framework is applied to the Elgin platform well abandonment and Brent Alpha jacket structure decommissioning and the results are validated through sensitivity analysis. Through a dynamic-diagnostic and multi-factor regression analysis, the loss values of accident contributory factors are also presented. The study shows that integrating Hierarchical Bayesian Analysis (HBA) and dynamic Bayesian networks (DBN) application to modelling time-variant risks are essential to achieve a well-informed decommissioning decision through the identification of safety critical barriers that could be mitigated against to drive down the cost of remediation

80,000 Inactive Oil Wells: A Blessing or a Curse?

For a century, oil and gas wells have been Alberta’s economic pride. That there could be a hidden cost in maintaining these wells past their productive life is difficult to imagine, much less accept. The financial burden of abandoning a well officially is no doubt why Alberta producers delay doing so as long as possible. Turning a blind eye, they routinely keep non-producing wells in a state of “inactive” suspension and refuse to rule out the possibility that someday oil prices or technology, or both, will change significantly enough to make those wells profitable again. In most cases that will never happen, but the province plays along anyway: It enforces no limit on how long a well can be kept inactive before it must be reactivated or abandoned. While a convenience for well owners, there is no benefit to Albertans. They are exposed to the risk of thousands of inactive wells becoming a hazardous threat to public safety. The longer a well is inactive, the higher the likelihood that its owner may no longer be around to arrange and pay for its official abandonment, a process whereby wells are permanently sealed using regulated methods that insure they cause no environmental damage. Oil and gas producers come and go. Periodic price shocks, like the one that recently ravaged the sector, drive companies into insolvency. When the owner of an inactive well is no longer around to pay for its abandonment costs, the well becomes orphaned. Alberta’s permissive policies have led to a situation where there are now more than 80,000 inactive wells in the province. Some have been inactive for decades. If the possibility existed that they could eventually become economical, those wells might be considered a blessing. However, the simulations that model scenarios where prices are substantially higher or where production technology is significantly improved, clearly show that the vast majority of these wells will never be reactivated, no matter how dramatically conditions improve. If oil prices rise 200 per cent, the modeling shows that just 12 per cent of oil wells become reactivated, and just seven per cent of gas wells. When the model tests to see what happens when a technological innovation improves so that the remaining oil or gas in a well that cannot be recovered is suddenly made recoverable (i.e., a 514 per cent increase in oil reserves), just 10 per cent of inactive oil wells are reactivated, and just six per cent of gas wells. The most effective way to reduce the number of inactive wells, the model finds, is by reducing the cost of their abandonment. With a 25 per cent reduction in abandonment costs, the pool of inactive wells shrinks by 20 per cent for both oil and gas, while the number of abandoned wells increases by nearly 50 per cent for both oil and gas. In all cases, the amount of oil and gas production that would change one way or the other — either by a minimal level of reactivation or a significant wave of abandonment — is marginal and not of meaningful benefit to Albertans. Creating an industry fund that takes responsibility for a well that has been orphaned has been Alberta’s approach to managing all its orphan wells. The deemed liability of 80,000 inactive wells is so large presently that the fund would be insufficient to cover the costs. The only way to prevent the province’s vast and growing number of inactive wells from remaining an ongoing risk to the public is by limiting the ability of owners to keep wells inactive as long as they like. Policies should recognize that most inactive wells will likely never produce oil or gas again

A historical development of P&A requirements on the NCS and its effects on permanently plugged and abandoned wells

Master thesis in Petroleum engineeringThis master thesis presents the development of the regulation in the field of permanent plug and abandonment in the Norwegian Continental Shelf (NCS). It describes how the regulations have been developed for Permanent Plug and Abandonment (P&A) and focusing on effects of regulations since 1967. The overall aim of the work is to highlight major changes in the regulations and assess the effects on the oil and gas industry in Norway. In addition, I am focusing on the barriers and barrier management in P&A operations and how the operating companies in Norway implemented and complied with the requirements. The first chapter of the thesis is a general introduction to regulations and standards related to the P&A in the NCS. The second chapter describes the development of the regulations and describes the main actors in developing these requirements. While the third chapter describes the historical developments in details from the first issued regulation to the establishment of the NORSOK standard D-010 with specific focus on drilling activities and well activities. The fourth chapter describes the major changes in NORSOK D-010 and describing the major changes in details. The fifth chapter is focusing on the barriers, well barriers and well barrier acceptance criteria, and defines how the Norwegian management regulation section 5 is emphasizing that the barriers shall be established at all times. The sixth chapter of the thesis is highlighting the data selection process and present the scope of P&A activities by fields and major operating companies in NCS. The analysis part in chapter seven is focusing on the effects of the changes in regulation on issues related to; integrity, HSE, costs, effectiveness, resource utilisation and the need for the technology development in the field of P&A. The eighth chapter is the discussion part where I have interpreted and described the significance of the findings and the effects on the operations in the field of P&A: The chapter is explaining the developments in the regulation, challenges and main actors in the field. The primary source of data, information on wells and well status discussed with the currently available knowledge in the field. This thesis provides the overview of the changes in regulations, the need for more in-depth research in the field in the future. As it is presented in chapter nine for conclusions, the presenting findings are based on my experience with gathered data, communications with major oil and gas operating companies and with Norwegian Petroleum Safety Authorities. The finding from the thesis is clearly indicating the possibility for improvements in data quality, feedback from industry to students and researchers as well as evaluating the need for establishing a monitoring system for all permanently plugged wells

Introduction to Permanent Plug and Abandonment of Wells

This open access book offers a timely guide to challenges and current practices to permanently plug and abandon hydrocarbon wells. With a focus on offshore North Sea, it analyzes the process of plug and abandonment of hydrocarbon wells through the establishment of permanent well barriers. It provides the reader with extensive knowledge on the type of barriers, their functioning and verification. It then discusses plug and abandonment methodologies, analyzing different types of permanent plugging materials. Last, it describes some tests for verifying the integrity and functionality of installed permanent barriers. The book offers a comprehensive reference guide to well plugging and abandonment (P&A) and well integrity testing. The book also presents new technologies that have been proposed to be used in plugging and abandoning of wells, which might be game-changing technologies, but they are still in laboratory or testing level. Given its scope, it addresses students and researchers in both academia and industry. It also provides information for engineers who work in petroleum industry and should be familiarized with P&A of hydrocarbon wells to reduce the time of P&A by considering it during well planning and construction

Hierarchical Bayesian model for failure analysis of offshore wells during decommissioning and abandonment processes

Risk analysis of offshore wells decommissioning, and abandonment processes is challenging due to limited life-cycle information of the well, and failure data of safety barriers in place. To this end, it is essential to capture and implement the variability associated with the sparse data for conducting risk analysis with considerable confidence level. The hierarchical Bayesian analysis provides a viable alternative to address the uncertainty of the data through aggregation for each causation. Bayesian network, through its robust computation engine, is used to define dependence of causations and uses Bayes' theorem to update the analysis as new information becomes available. In addition, the Bayesian network helps to represent complex dependencies among causations through appropriate relaxation strategy to minimize uncertainty in the data, link parameter of interest, and overall accident scenario modelling. This paper presents the integration of Hierarchical Bayesian model with a Bayesian network to conduct the risk analysis of well decommissioning and abandonment processes. The proposed methodology is illustrated using a well plugging and abandonment operational failure reported by the Department of Mineral Management Service (MMS). The results demonstrate the potential of the proposed approach as a robust means to study complex well decommissioning activities

Regulatory Fracture Plugging: Managing Risks to Water From Shale Development

Debates about the desirability of widespread shale development have highlighted outstanding uncertainty about its health, safety, and environmental impacts—most prominently, its water-contamination risks—and the ability of current institutions to deal with these impacts. States, the primary regulators of oil and gas extraction, face pressure from the energy industry, local communities, and, in some cases, the federal government to strike the right balance between energy production and the health and safety of individuals and the environment—an elusive balance given the ongoing risk uncertainty. This dynamic is not especially unique to fracking, or even oil and gas extraction; instead, this dynamic, characterized by tradeoffs between environmental protection and economic development under risk uncertainty, is a common theme of environmental risk regulation. Regulators at every level of government weigh and evaluate potential interventions against this background. This Article contributes to a symposium held at Texas A&M School of Law that explores the advantages and disadvantages of various government interventions in the environmental context in an effort to identify ideal risk-management tools under various circumstances. It argues that the most important considerations for identifying risk-management tools in the environmental context are risks, incentives, and cost-benefit analysis. These cornerstone principles provide a useful framework for environmental policy in general, especially in situations that involve heterogeneous and uncertain risks. By paying attention to risk, incentives, and cost-benefit analysis, government regulators are more likely to promote optimal levels of environmental quality and avoid unintended, or even perverse, consequences. To demonstrate the usefulness of these concepts concretely, this Article applies them to the fracking context, focusing on the most prominent risks from widespread shale development, risks to water from shale gas extraction. It identifies risk-management gaps in tort litigation, insurance markets, and regulation schemes and suggests potential solutions

Plug and Abandonment Technologies evaluation and Experimental material testing.

Abstract The conventional method to plug and abandonment (P&A) is characterized by its time-consuming nature, high costs, and associated challenges and risks related to Health, Safety, and Environment (HSE) considerations. In recent years, there has been a growing focus on P&A operations to enhance efficiency and reduce costs. Furthermore, cement plays a critical role in the P&A process, and any failures in its performance can result in various issues such as loss of zonal isolation, loss of wellbore integrity, and potential leakage. This thesis examines the performance and challenges associated with conventional plug and abandonment (P&A) technologies, including cut and pull, section milling, and perforate, wash, and cement (PWC). Case studies are presented to assess the P & A technologies. Moreover, new alternative technologies, solutions, and tools that aim to improve P&A operations are reviewed. This thesis also experimentally investigated the impact of using nano-SiO2 in G-class cement with a 0.44 water-to-cement ratio (WCR). The findings from field trials and laboratory research indicate that alternative technologies, solutions, and tools have demonstrated promising improvements in performance and effectiveness. However, it is necessary to conduct further research and establish performance guidelines before implementing these alternatives. Based on the considered case study, PWC demonstrated significant time savings, with a 65% reduction in operational time compared to section milling and a 70% reduction compared to cut and pull operations. Moreover, the addition of an optimal dosage of 0.242 wt. % SiO2 (by weight of cement) resulted in a significant increase in the uniaxial compressive strength (UCS) of neat cement. After 3 days and 28 days of curing at atmospheric pressure and temperature, the UCS improved by 39.53% and 24.88%, respectively. Additionally, the optimal SiO2 reduced the water absorption of the neat cement, by 15.00% after 3 days and 20.14% after 28 days cured at 105oC and atmospheric pressure

Permanent plug and abandonment on Gyda field, challenges, solutions, and qualification of creeping formation to be used as a well barrier in Gyda

Master's thesis in petroleum EngineeringWell plugging and abandonment (P&A) presents a very substantial challenge to oil and gas operators, and this challenge will increase exponentially in the coming decades. P&A operation cost the operators billions of dollars without any return in investment. Every well needs a unique program to plug it, that depends on the construction design, type of well and depth. Many challenges appear during the operation, as restricted access to the desired depth due to the scale deposits, casing collapse and other obstruction. In Gyda field many wells suffer from scale in the production tubing that required remedial operation to remove the scale and get access in order to set the deepest plug and cut the tubing. P&A is divided into three phases: phase I (wireline phase) where it is conducted from the BOP deck to check well accessibility, cut the tubing and install a double well barrier to remove XMT and install BOP. Phase II is conducted from the drill floor using the rig, where the main and heavy operation is performed as pulling the production tubing and casing, install cement plugs, perform PWC or formation test. Phase III (decommissioning phase) is performed after phase II, which is conducted by cut and remove conductor and wellhead. To permanently plug and abandon a well, a cross sectional barrier must be formed. In some wells, there is no cement behind the casing at the desired depth to install a barrier. In this case annular barrier must be established to get a cross sectional barrier. This means heavy and costly remedial operation is needed to establish the annular barrier as PWC or casing milling. In some wells, logging showed good bonding between formation and casing above the theoretical top of cement, and formation communication pressure test verified it, the only justification behind that is the formation deformation where the formation moved toward the annular space and seal it off. To qualify a formation as an annular barrier, two conditions must be fulfilled, the formation must have an enough strength to withstand the future reservoir pressure and the bonding between casing and formation must provide a hydraulic isolation. In Gyda field, the lower Hordaland formation (Creeping formation) was tested and qualified as an annular barrier

Negative-Value Property

Ownership is commonly regarded as a powerful tool for environmental protection and an essential solution to the tragedy of the commons. But conventional property analysis downplays the possibility of negative-value property, a category which includes contaminated, depleted, or derelict sites. Owners have little incentive to retain or restore negative-value property and much incentive to alienate it. Although the law formally prohibits the abandonment of real property, avenues remain by which owners may functionally abandon negative-value property, as demonstrated recently by busts in certain coal and oil & gas markets. When negative-value property is abandoned, whether formally or functionally, the rehabilitation of such property typically requires public expenditure—an externality which cuts against property’s general and salutary tendency to internalize spillovers at a low social cost. The existence of negative-value property, as well as its increasing abundance, reveals an underdeveloped aspect of property theory and a pressing need to fortify legal mechanisms that prevent abandonment and enforce owners’ financial responsibility for severely degraded property