The decreasing gap between technology and the it’s applicability in the oil industry has led to a rapid development of deepwater resources. Beginning with larger fields where the chances of economic success are high, to marginal fields where project economics becomes a more critical parameter, the petroleum industry has come a long way. However, the ever growing water depths and harsher environments being encountered are presently posing challenges to subsea production. Being able to develop a field and then proceeding to ensure flow for the life of the field comprises many situations where the production equipment can fail and falter or through external factors, be deemed unavailable. Some of the areas where most of the current developments in subsea production are being seen are in subsea processing, flow assurance, long term well monitoring and intervention technologies – areas that pose some of the biggest challenges to smooth operation in the deepwater environment. This research highlights the challenges to overcome in subsea production and well systems and details the advances in technology to mitigate those problems. The emphasis for this part of the research is on multiphase pumping, subsea processing, flow assurance, sustained casing pressure problems and well intervention. Furthermore, most operators realize a reduced ultimate recovery from subsea reservoirs owing to the higher backpressure imposed by longer flowlines and taller risers. This study investigates the reasons for this by developing a global energy balance and detailing measures to improve production rates and ultimate recoveries. The conclusions from this energy balance are validated by simulating a deepwater field under various subsea production scenarios.

Recent discoveries of hydrocarbons within reservoirs deposited within ancient deepwater clastic systems has necessitate further studies into this sedimentary environment. The aim of such studies is to gather information about the internal heterogeneities within submarine fans. This Ph.D. study focuses on such heterogeneities within an exposed, Miocene aged, sand-rich deep-marine system, the Cingöz Formation deposited within the Adana Basin in southern Turkey. A quantitative and qualitative sedimentological study into geometry, spatial and temporal variations in internal architecture and facies distributions has been undertaken. The study area is divided into two regions, the eastern and western areas of the Cingöz Fan, previously interpreted as representing two coeval and separated submarine fans, but interpreted as a single deepwater clastic system within this study. The eastern areas are sourced from at least four feeder channels. Channels display multiple phases of infilling, facies that indicate deposition from fan deltas that pass upward into deep water turbidities. Variations in the internal architecture and channel-floor gradient within a seven km depositional-dip section of one of these channels indicates changes in hydraulic conditions with complex inter-relationship between turbulence, erosion, gradient and confinement of the turbidity currents. The western areas display landward to basinward facies changes from fluvial, alluvial fan, fan delta and deep-marine fan environments. This area of the submarine fan is sourced via a single, 4 km wide and 9 km long, topographically controlled fairway. This conduit displays multiple phases of infilling on a variety of scales, indicating pulses of sediment supply. Sediment is deposited basinwards of the fairway, initially in elongate, 0.3-1 km wide and at least 15 km long, tongue-shaped bodies that are both vertically and offset stacked and separated by packages of siltstone.

The shift of hydrocarbon exploration and production to deepwater has resulted in new opportunities for the petroleum industry(in this project, the deepwater depth greater than 1,000 ft) but also, it has introduced new challenges. In 2001,more than 999 Bcf of associated gas were produced from the Gulf of Mexico, with deepwater associated gas production accounting for 20% of this produced gas. Two important issues are the potential environmental impacts and the economic value of deepwater associated gas. This project was designed to test the viability of storing associated gas in a saline sandstone aquifer above the producing horizon. Saline aquifer storage would have the dual benefits of gas emissions reduction and gas storage for future use. To assess the viability of saline aquifer storage, a simulation study was conducted with a hypothetical sandstone aquifer in an anticlinal trap. Five years of injection were simulated followed by five years of production (stored gas recovery). Particular attention was given to the role of relative permeability hysteresis in determining trapped gas saturation, as it tends to control the efficiency of the storage process. Various cases were run to observe the effect of location of the injection/production well and formation dip angle. This study was made to: (1) conduct a simulation study to investigate the effects of reservoir and well parameters on gas storage performance; (2) assess the drainage and imbibition processes in aquifer gas storage; (3) evaluate methods used to determine relative permeability and gas residual saturation ; and (4) gain experience with, and confidence in, the hysteresis option in IMEX Simulator for determining the trapped gas saturation. The simulation results show that well location and dip angle have important effects on gas storage performance. In the test cases, the case with a higher dip angle favors gas trapping, and the best recovery is the top of the anticlinal structure. More than half of the stored gas is lost due to trapped gas saturations and high water saturation with corresponding low gas relative permeability. During the production (recovery) phase, it can be expected that water-gas production ratios will be high. The economic limit of the stored gas recovery will be greatly affected by producing water-gas ratio, especially for deep aquifers. The result indicates that it is technically feasible to recover gas injected into a saline aquifer, provided the aquifer exhibits the appropriate dip angle, size and permeability, and residual or trapped gas saturation is also important. The technical approach used in this study may be used to assess saline aquifer storage in other deepwater regions, and it may provide a preliminary framework for studies of the economic viability of deepwater saline aquifer gas storage.

Slugging involves pressure and flowrate fluctuations and poses a major threat to optimising oil production from deepwater reserves. Typical production loss could be as high as 50%, affecting the ability to meet growing energy demand. This work is based on numerical simulation using OLGA (OiL and GAs) a one- dimensional and two-fluid equations based commercial tool for the simulation and analysis of a typical field case study in West Africa. Numerical model was adopted for the field case. Based on the field report, Flow Loop X1 consisted of well X1 and well X2, (where X1 is the well at the inlet and X2 is the well connected from the manifold (MF)). Slugging was experienced at Flow Loop X1 at 3000 BoPD; 4MMScf/D and 3%W/C. This study investigated the conditions causing the slugging and the liquid and gas phase behaviour at the period slugging occurred. The simulation work involved modelling the boundary conditions (heat transfer, ambient temperature, mass flowrate e.t.c). Also critical was the modelling of the piping diameter, pipe length, wall thickness and wall type material to reflect the field geometry. Work on flow regime transition chart showed that slugging became more significant from 30% water-cut, especially at the riser base for a downward inclined flow on the pipeline- riser system. Studies on diameter effect showed that increasing diameter from 8” – 32” gave rise to a drop in Usg (superficial velocity gas) and possible accumulation of liquids on the riser- base position and hence a tendency for slugging formation. Depth effect study showed that increasing depth gave rise to increasing pressure fluctuation, especially at the riser- base. Studies on the Self-Lift slug mitigation approach showed that reducing the internal diameter of the Self-lift by-pass pipe was effective in mitigating slug flow. S3 (Slug suppression system) was also investigated for deepwater scenario, with the results indicating a production benefit of 12.5%. In summary, the work done identified water-cut region where pipeline-riser systems become more susceptible to slugging. Also, two key up-coming slug mitigation strategies were studied and their performance evaluated in-view of production enhancement.

Currently the "Pump and Dump" method employed by Exploration and Production (E&P) companies in deepwater is simply not enough to control increasingly dangerous and unpredictable shallow hazards. "Pump and Dump" requires a heavy dependence on accurate seismic data to avoid shallow gas zones; the kick detection methods are slow and unreliable, which results in a need for visual kick detection; and it does not offer dynamic well control methods of managing shallow hazards such as methane hydrates, shallow gas and shallow water flows. These negative aspects of "Pump and Dump" are in addition to the environmental impact, high drilling fluid (mud) costs and limited mud options. Dual gradient technology offers a closed system, which improves drilling simply because the mud within the system is recycled. The amount of required mud is reduced, the variety of acceptable mud types is increased and chemical additives to the mud become an option. This closed system also offers more accurate and faster kick detection methods in addition to those that are already used in the "Pump and Dump" method. This closed system has the potential to prevent the formation of hydrates by adding hydrate inhibitors to the drilling mud. And more significantly, this system successfully controls dissociating methane hydrates, over pressured shallow gas zones and shallow water flows. Dual gradient technology improves deepwater drilling operations by removing fluid constraints and offering proactive well control over dissociating hydrates, shallow water flows and over pressured shallow gas zones. There are several clear advantages for dual gradient technology: economic, technical and significantly improved safety, which is achieved through superior well control.

Deepwater Gulf of Mexico well construction operations are some of the most challenging and expensive operations in the E&P industry; not only does the outer continental shelf of the Gulf of Mexico present the distinct environmental challenges of hurricanes and loop currents, its geologic profiles can include such challenges as salt, tar or pressurized zones. To overcome these challenges technology is being pushed to its operational and mechanical limits but technology advances can only accomplish so much without the presence of capable personnel. In the E&P industry, human resources are becoming more limited due to the “Big Crew Change”; a disproportionate relief of the retiring Baby Boomers by Generation X workforce that now requires Generation Y assistance. Regardless of the aforementioned, operators venture out into deepwater with hopes to capitalize on the recently discovered attractive development and exploratory opportunities, but to do so they must organize and properly develop their internal well construction organization in a manner that all members are capable to address the challenges as they come. Therefore, team organization is an operator’s priority, a challenge that should be addressed through common project management practices. This paper parallels the project management practices to establish the appropriate organizational structure for an operator’s deepwater well construction group, manage the human resources to properly delineate responsibilities and to structure their staff management processes to acquire, develop and manage personnel in a manner scalable with the operator’s expansion agenda. / text

Previous studies have come to contrasting conclusions regarding nutrient limitation of hydrocarbon biodegradation in the Gulf of Mexico, and rate measurements are needed to support oil plume modeling. Thus, this study investigates the rates and controls of biodegradation in seawater and sediments, largely in the deepsea. Sediment and seawater samples were collected on research cruises in the northern Gulf from 2012 to 2014, where the seafloor was impacted by the Deepwater Horizon (DWH) oil spill. Biodegradation was clearly limited by both nitrogen and phosphorus availability in surface waters with significant rates of CO₂ production (100 μmol CO₂ l⁻¹ d⁻¹) only observed in treatments amended with ammonium and phosphate. In deepsea sediments, nutrient amendments resulted in an average of 6 fold higher degradation rates (0.49 μmol CO₂ g sed⁻¹ d⁻¹) compared to unamended controls. Microbial communities responded to oil contamination rapidly in a series of enrichment cultures, and selection was observed for populations of native hydrocarbon-degrading bacteria. Temperature was shown to be a major factor in controlling microbial community composition in the enrichments. At room temperature, community diversity in the enrichments was significantly reduced in the presence of oil, while under 4 °C, the community diversity and evenness remained relatively high upon oil amendment. From the same deepsea sediments, 30 strains of known oil-degrading bacteria (Rhodococcus and Halomonas) were enriched and isolated with hexadecane, phenanthrene, and Macondo oil as the sole carbon and energy source. Detection of these strains in sequence libraries indicates that they may have contributed to the degradation of oil deposited onto the sediments. Rhodococccus strain PC20 degraded approximately one-third of total petroleum hydrocarbons amended into cultures within 7 days. This work elucidates the controls of biodegradation and we provide model pure cultures to further elucidate the ecophysiology of hydrocarbon degradation, focusing on deepsea sediments of the northern Gulf of Mexico.

archives@tulane.edu / During the Deepwater Horizon (DWH) oil spill in 2010, approximately 0.5 billion liters (3.1 million barrels) of oil were released into the northern Gulf of Mexico during the largest marine oil spill in history . A significant portion of the released oil was weathered into residues by physical, photochemical, and biological processes prior to landing on 1773 km of coastline, including 754 km of marsh shoreline in Louisiana. Researchers endeavored to describe effects of oil residues in the soil on salt marsh organisms and communities. Many studies focused on two pillars of salt marsh ecology: the microbial communities through which a large portion of the salt marsh food web is connected and Spartina alterniflora, a foundational species of Gulf Coast salt marshes. In this dissertation I describe how cryptic, or difficult to observe, elements of salt marsh ecology, like microbial communities and plant genetics, respond to oil residues in the environment. Using a suite of field, growth chamber, and greenhouse experiments I show that these microbial communities are difficult to characterize and may respond to other factors more strongly than they do to oil residues. I present evidence that the plant is resilient to oil in the environment, and changes in its microbiome, but exerts a measurable influence on the biodegradation of oil residues and the microbiome in the soil. This dissertation provides a greater understanding of the complexity of the salt marsh response to an oil spill. / 1 / Stephen K. Formel

The Deepwater Horizon (DWH) blowout, in the Gulf of Mexico, heavily contaminated miles of sandy beaches. Previous experience of petroleum contamination has shown that oil residues can persist in the sediments for decades. Biodegradation is the major mechanism of remediation regarding petroleum hydrocarbons. There is an urgent need to evaluate the competent indigenous microbial biomass in contaminated sediments if the risks posed by toxic oil residues, for the coastal ecosystem, are to be minimized. We report a field investigation during December 2010 and January 2011 regarding measurement of microbial activity in a sandy beach at the Bon Secour National Wildlife Refuge in Alabama. One transect of wells for sampling was installed in the beach; starting with multiport one, being most landward and thought to be least exposed to oil residue and ending with multiport four being the most seaward and exposed to the open waters of the Gulf of Mexico. Sediment samples were collected from different depths purposely chosen from above, inside, and below the oil layers for microbial analysis. Dissolved oxygen (DO) measurements were obtained and temperature was recorded while collecting the oxygen measurements. Pore water samples were collected for nutrient content and were monitored using the multiport sampling wells. Moisture content was analyzed from the sediments extracted at various depths at each well. pH and salinity were also analyzed for their contributing affect on the microbial community. Grain size distribution analyses were conducted on samples collected at all wells and at multiple depths to characterize the field study location. Results show that the bacterial biomass, as measured by Adenosine-5-triphosphate (ATP) and numbers of alkane and polycyclic aromatic hydrocarbon (PAH) degraders determined by Most Probable Number (MPN), are consistently higher in the sediment layers where oil had been detected. A very good correlation was observed among the relative abundance of bacteria in the different samples using MPN and ATP measurements. As expected, ATP based estimates of the microbial populations were two orders of magnitude higher than the alkane and PAH numbers determined by MPN, which reflect the non-cultivability of most environmental bacteria. The lower concentrations of PAH degraders than alkane degraders that were observed in this study are consistent with other studies, even though both populations are lower than in studies involving fresh oil trapped in beach or wetland sediments. PAHs (aromatics) are notoriously more resistant to biodegradation than alkanes, therefore allowing a lower number of biomass to grow using them. The overall smaller size of the bacterial numbers could be explained by the naturally occurring low-organic content of beach sand. On the other hand, this may be due to the highly weathered nature of the oil or it could reflect some other limitation. / Civil Engineering

This dissertation explores the discursive production of, and response to, environmental disaster. The project is contextualized through the case of the 2010 Deepwater Horizon disaster in the Gulf of Mexico. By interrupting traditional perceptions of environmental disaster, this project frames socio-environmental disasters as a normal and increasingly experienced part of global hydrocarbon capitalism. The project purports that disaster is embedded within the current global economy and the high-]modernist ideologies that underlie it. As such, the strategies and techniques employed to respond to environmental disaster are intimately bound up within the same systemic processes that have created them in the first place. Moreover, because instrumentalist responses are quickly employed to mitigate disaster, the systemic factors productive of disaster remain concealed. Environmental disaster is thus a process of hydrocarbon capitalism rather than a product of it; as such it can, among other categories, be understood as manageable, profitable, and litigable. This research also highlights the normalization of chronic socio-environmental disaster though sensationalistic perspectives on acute disaster. This project explores the potential for resistance through artistic endeavors, highlighting how the discursive processes that construct traditional power/knowledge formations of environmental disaster might be subverted through non-traditional means. While the framework of eco-governmentality is especially useful in highlighting the problematic social relationships to nature, the project nonetheless acknowledges that counter-discourses for are likely to be appropriated by industry for the purpose of new enterprise and profit. / Ph. D.