• Alaska Arctic coastal plain gravel pad hydrology: impacts to dismantlement removal and restoration operations ; a study on the human - hydrology relationship in Arctic environments

      Miller, Ori; Barnes, David L.; Stuefer, Svetlana L.; Shur, Yuri (2019-08)
      To guard against thawing permafrost and associated thaw subsidence, the oil facilities in the Arctic are constructed on gravel pads placed on top of the existing arctic tundra, however the impacts of this infrastructure to the sensitive hydrology are not fully understood. Production in some of the older fields is on the decline; however oil exploration in the Arctic Coastal Plain is resulting in the discovery and development of new reserves. In the coming years, old sites will need to be decommissioned as production transitions to new sites. New facilities will also need to be designed and constructed. Oil companies in Alaska have historically conducted operations under leases issued through the Alaska Department of Natural Resources. The leases stipulate that once resource extraction operations are completed, the facilities must be decommissioned and the sites restored, however they are often vague in their requirements and are variable in their specifics from lease to lease. As the oil companies transition to the new sites, decisions must be made regarding what should be done with vacated gravel pads. The construction of gravel pads essentially destroys underlying arctic tundra. In undisturbed areas in the Arctic, the tundra itself creates an insulating layer that limits the seasonal thaw depth to around 0.5 m. Removal of this layer causes thaw depths to greatly increase impacting the stability of the ground and the hydrology of the surrounding area. Because of this impact, other possible restoration techniques are being considered, such as vegetating and leaving the pads in place. Water movement is one of the major driving factors in the arctic contributing to permafrost degradation. Groundwater carries with it heat, which is transferred to the soil as the groundwater moves. Therefore, hydrology plays a major role in the stability of the arctic environment. This is especially relevant in areas where gravel pads exist. Gravel pads are anthropogenic structures that have significant water storage potential. Because of the unique conditions in the Arctic, pore-water flow through these gravel pads is not yet well understood. The purpose of this study is to develop a more complete scientific understanding of the driving forces behind pad pore-water movement. This study expands on fieldwork from a prior hydrological field study conducted by others. The prior study is expanded through this work by developing an associated groundwater model to the gravel pad from the field study to examine the flow through it and the controlling factors for this flow. The study site used for this project is located in Prudhoe Bay and is the pad constructed for the very first production well in Prudhoe Bay in 1968. This study demonstrates that it is the topography of the silt layer beneath the gravel pads that is the most significant factor controlling pad pore-water movement. The results from the modeling study will assist engineers and environmental scientists in better understanding the groundwater flow. This understanding will aid in the decommissioning and restoration process and help inform decision making in regards to the future of the existing pads. The results may also be used to inform the development of new infrastructure such that any new pads which are built may be constructed with their relationship to the local hydrology more in mind.
    • Alkali-surfactant-polymer (ASP) flooding - potential and simulation for Alaskan North Slope reservoir

      Ghorpade, Tejas S. (2014-09)
      Enhanced oil recovery (EOR) is essential to recover bypassed oil and improve recovery factor. Alkaline-surfactant-polymer (ASP) flooding is a chemical EOR method that can be used to recover heavy oil containing organic acids from sandstone formations. It involves injection of alkali to generate in situ surfactants, improve sweep efficiency, and reduce interfacial tension (IFT) between displacing and displaced phase, and injection of a polymer to improve mobility ratio; typically, it is followed by extended waterflooding. The concentration of alkali, surfactant, and polymer used in the process depends on oil type, salinity of solution, pressure, temperature of the reservoir, and injection water quality. This project evaluates the effect of waterflooding on recovery, calculates the recovery factor for ASP flooding, and optimum concentration of alkali, surfactant, and polymer for an Alaskan reservoir. Also, the effects of waterflooding and improvement with ASP flooding are evaluated and compared. Studies of these effects on oil recovery were analyzed with a Computer Modeling Group (CMG)-generated model for the Alaskan North Slope (ANS) reservoir. Based on a literature review and screening criteria, the Western North Slope (WNS) 1 reservoir was selected for the ASP process. A CMG - WinProp simulator was used to create a fluid model and regression was carried out with the help of actual field data. The CMG - WinProp model was prepared with a 5 spot well injection pattern using the CMG STARS simulator. Simulation runs conducted for primary and waterflooding processes showed that the recovery factor increased from 3% due to primary recovery to 45% due to waterflooding at 500 psi drawdown for 60 years with a constant producing gas oil ratio (GOR). ASP flooding was conducted to increase recovery further, and optimum ASP parameters were calculated for maximum recovery. Also, effect of alkali, surfactant and polymer on recovery was observed and compared with ASP flood. If proved effective, the use of ASP chemicals for ANS reservoirs to increase the recovery factor could replace current miscible gas injection with chemical EOR. It will help to develop chemical flooding processes for heavier crude oil produced in harsh environments and create new horizons for chemical industries in Alaska.
    • An assessment of suspended sediment transport in Arctic Alaskan rivers

      Lamb, Erica K.; Toniolo, Horacio; Schnabel, William; Kane, Douglas (2013-05)
      Provided here is an initial assessment of suspended sediment transport in several rivers on the North Slope of Alaska. This study was divided into two parts: the Umiat project, which involved the Chandler, Anaktuvuk and Itkillik Rivers, and the NPR-A study, which considered Prince, Seabee and Fish Creeks, as well as a brief look at the lkpikpuk River, Otuk Creek, Judy Creek and the Ublutuoch River. Methods used included depth-integrated suspended sediment samples, grab samples, automatic pump-style samplers, discharge measurements, bed sediment grain size analysis and the inclusion of a variety of meteorological measurements from other projects. With slightly less than two years of data collection from May 2011 to September 2012, an initial analysis was completed. Suspended sediment rating curves developed for the Anaktuvuk and Chandler Rivers over the two-year study period revealed a strong correlation between suspended sediment concentration (SSC) and discharge. The most data was collected for the Anaktuvuk and Chandler Rivers; on these rivers, suspended sediment discharge was also analyzed, showing that over 90% of suspended sediment transport occurred during the spring melt period in 2011. Spring melt was not measured in 2012, so analysis was only completed for 2011.
    • Climatic and physiographic drivers of peak flows in watersheds in the North Slope of Alaska

      Hinzman, Alexa Marion Hassebroek; Stuefer, Svetlana; Arp, Christopher; Barnes, David (2017-08)
      The failure to accurately predict peak discharge can cause large errors in risk analysis that may lead to damage to structures and in some cases, death. Creating linear regression (LR) equations that accurately predict peak discharges without historic data provides a method to estimate flood peaks in ungauged watersheds on the North Slope of Alaska. This thesis looks at the independent variables that drive, or are significant in predicting snowmelt peak discharge in the North Slope watersheds. The LR equations created use independent variables from meteorological data and physiographic data collected from four watersheds, Putuligayuk River, Upper Kuparuk River, Imnavait Creek and Roche Moutonnée Creek. Meteorological data include snow water equivalent (SWE), total precipitation, rainfall, storage, length of melt. Physiographic data summarize watershed area (2.2 km2 to 471 km2) and slope (0.15:100 to 2.7:100). This thesis compared various Flood Frequency Analysis techniques, starting with Bulletin 17B, multiple USGS regional methods and finally created LR equations for each watershed as well as all four watersheds combined. Five LR equations were created, three of the LR equations found SWE to be a significant predictor of peak flows. The first equation to estimate peak flows for all watersheds used only area and had a high R2 value of 0.72. The second equation for all watersheds included area and a meteorological independent variable, SWE. While the evidence presented here is quite promising that meteorological and physiographic data can be useful in estimating peak flows in ungauged Arctic watersheds, the limitations of using only four watersheds to determine the equations call for further testing and verification. More validation studies will be needed to demonstrate that viable equations may be applied to all watersheds on the North Slope of Alaska.
    • A comprehensive analysis of the oil fields of the North Slope of Alaska: their use as analogs, recent exploration, and forecasted royalty and production tax revenue

      Michie, Joshua J.; Patil, Shirish; Dandekar, Abhijit; Khataniar, Santanu; Sonwalker, Vikas (2018)
      Revenues from petroleum production supply most of the revenue for unrestricted general funds for the State of Alaska. As such, variations in the price of oil, decline from existing production and new developments greatly affect the money available for the state to spend on everything from roads to education. This study reviewed all producing oil fields on the North Slope, characterized their reservoir performance and forecasted future production. This was coupled with analysis of recent exploration discoveries and ongoing project developments to forecast future North Slope production and create potential royalty and production tax revenue forecasts. After 40 years of production, Prudhoe Bay remains the dominant field on the North Slope, accounting for 45% of current production. Relatively large changes in the non-anchor field pools are only able to change North Slope production by a couple of percent due to the nature of their size compared to Prudhoe Bay, Kuparuk and Alpine. New developments however, are able to materially contribute to changes in North Slope production if they are large enough. With continued activity in the many fields, creating an accurate forecast is challenging, however, without new developments, the Trans Alaska Pipeline will need to make changes to accommodate low flow rates. Currently identified new developments have the potential to extend current production rates 10-20 years. Some of these announced developments and discoveries have announced productivity rates that are not realistic compared to analog well performance, and will likely require many more wells to achieve the announced rates and volumes.
    • Economic assessment of Alaska North Slope hydrate-bearing reservoir regional production development schemes

      Nollner, Stephanie P.; Dandekar, Abhijit; Patil, Shirish; Ning, Samson; Khataniar, Santanu (2015)
      The objective of this project was to evaluate the economic feasibility of producing the upper C sand of the Prudhoe Bay Unit L Pad gas-hydrate-bearing reservoir. The analysis is based on numerical modelling of production through depressurization completed in CM G STARS by a fellow UAF graduate student, Jennifer Blake, (2015). A staged field development plan was proposed, and the associated capital and operating costs were estimated using Siemens's Oil and Gas Manager planning software and costing database. An economic assessment was completed, incorporating the most common royalties, the current taxes laws applicable to conventional gas development, and most recent tariff estimates. The degree of vertical heterogeneity, initial average hydrate saturation, well spacing and well type had a significant impact on the regional gas production profiles in terms of cumulative volume produced, and more importantly, the expediency of gas production. The volume that is economically recoverable is highly dependent on how the field is developed. A field that has higher vertical heterogeneity and corresponding lower average initial hydrate saturation is most economically produced using horizontal wells at 160 acre spacing; the acceleration of gas production outweighs the increased drilling costs associated with the longer wells and tighter well spacing. The choice of development scenario does not impact the project economics significantly given a field that has lower vertical heterogeneity; however, development using horizontal wells at 320 acre spacing is marginally more economic than the alternatives. Assuming a Minimum Attractive Rate of Return of 20%, the minimum gas price that would allow economic production of ANS gas hydrates was found to be $29.83 per million British thermal units; this value is contingent on the reservoir having high average initial hydrate saturation and being developed with horizontal wells at 320 acre spacing. A slightly higher gas price of $36.18 per million British thermal units would allow economic production of a reservoir having low average initial hydrate saturation that is developed with horizontal wells at 160 acre spacing.
    • Electromagnetic heating of unconventional hydrocarbon resources on the Alaska North Slope

      Peraser, Vivek; Patil, Shirish L.; Khataniar, Santanu; Sonwalkar, Vikas S.; Dandekar, Abhijit Y. (2012-05)
      The heavy oil reserves on the Alaska North Slope (ANS) amount to approximately 24-33 billion barrels and approximately 85 trillion cubic feet of technically recoverable gas from gas hydrate deposits. Various mechanisms have been studied for production of these resources, the major one being the injection of heat into the reservoir in the form of steam or hot water. In the case of heavy oil reservoirs, heat reduces the viscosity of heavy oil and makes it flow more easily. Heating dissociates gas hydrates thereby releasing gas. But injecting steam or hot water as a mechanism of heating has its own limitations on the North Slope due to the presence of continuous permafrost and the footprint of facilities. The optimum way to inject heat would be to generate it in-situ. This work focuses on the use of electrical energy for heating and producing hydrocarbons from these reservoirs. Heating with electrical energy has two variants: high frequency electromagnetic (EM) heating and low frequency resistive heating. Using COMSOL ® multi-physics software and hypothetical reservoir, rock, and fluid properties an axisymmetric 2D model was built to study the effect of high frequency electromagnetic waves on the production of heavy oil. The results were encouraging and showed that with the use of EM heating, oil production rate increases by ~340% by the end of third year of heating for a reservoir initially at a temperature of 120°F. Applied Frequency and input power were important factors that affected EM heating. The optimum combination of power and frequency was found to be 70 KW and 915 MHz for a reservoir initially at a temperature of 120°F. Then using CMG-STARS ® software simulator, the use of low frequency resistive heating was implemented in the gas hydrate model in which gas production was modeled using the depressurization technique. The addition of electrical heating inhibited near-wellbore hydrate reformation preventing choking of the production well which improved gas production substantially.
    • End-to-end well planning strategies for Alaska north slope directional wells

      Mahajan, Neeraj Hemant; Khataniar, Santanu; Patil, Shirish; Dandekar, Abhijit; Fatnani, Ashish (2018-05)
      Directional well planning has gained special attention in the Alaska North Slope (ANS) as operators are being compelled to drill increasing numbers of wells from already congested pads because of low oil prices, Capex restrictions, and environmental regulations. This research focuses on two major components of directional well planning: anti-collision and torque and drag analysis in Schrader Bluff, Milne Point. The drilling pattern at the ANS implies very high wellbore collision risk, especially at the shallower section, which affects the safety of drilling operations. However, satisfying anti-collision norms is not the solitary step towards successful well planning. Integration of anti-collision results with torque and drag analysis is essential in evaluating the safety and feasibility of drilling a particular well path and avoiding drill string failures. In the first part of the study, three well profiles (horizontal, slant, and s-shaped) were planned for each of the two new targets selected in the Schrader Bluff OA sand. Initially, this part of the research compared the performance of the newly developed Operator Wellbore Survey Group (OWSG) error model and the industry-standard Industry Steering Committee for Wellbore Surveying Accuracy (ISCWSA) error model. To provide effective guidelines, the results of error model comparison were used to carry out sensitivity analyses based on four parameters: surface location, well profiles, survey tools, and different target locations in the same sand. The results of this study aid in proposing an improved anti-collision risk management workflow for effective well planning in Arctic areas. The second part of the study investigates the drillability of the well paths planned using the improved anti-collision risk management workflow. Furthermore, this part of the research aims at defining the end point limits for critical well planning parameters, including inclination and dogleg, such that within these limits, the well path satisfies anticollision as well as torque and drag considerations. These limits were generated using a drill string optimized in terms of steerable tool, drill pipe size, mud rheology, trip speed, rotational speed, and weight on bit (WOB) during drilling and tripping out operations. The results of this study would help reduce the cumbersome iterative steps and narrow down the design domain for any well to be drilled on the North Slope of Alaska.
    • Experimental investigation of low salinity water flooding to improve viscous oil recovery from the Schrader Bluff Reservoir on Alaska North Slope

      Cheng, Yaoze; Zhang, Yin; Dandekar, Abhijit; Awoleke, Obadare; Chen, Gang (2018-05)
      Alaska's North Slope (ANS) contains vast resources of viscous oil that have not been developed efficiently using conventional water flooding. Although thermal methods are most commonly applied to recover viscous oil, they are impractical on ANS because of the concern of thawing the permafrost, which could cause disastrous environmental damage. Recently, low salinity water flooding (LSWF) has been considered to enhance oil recovery by reducing residual oil saturation in the Schrader Bluff viscous oil reservoir. In this study, lab experiments have been conducted to investigate the potential of LSWF to improve heavy oil recovery from the Schrader Bluff sand. Fresh-state core plugs cut from preserved core samples with original oil saturations have been flooded sequentially with high salinity water, low salinity water, and softened low salinity water. The cumulative oil production and pressure drops have been recorded, and the oil recovery factors and residual oil saturation after each flooding have been determined based on material balance. In addition, restored-state core plugs saturated with viscous oil have been employed to conduct unsteady-state displacement experiments to measure the oil-water relative permeabilities using high salinity water and low salinity water, respectively. The emulsification of provided viscous oil and low salinity water has also been investigated. Furthermore, the contact angles between the crude oil and reservoir rock have been measured. It has been found that the core plugs are very unconsolidated, with porosity and absolute permeability in the range of 33% to 36% and 155 mD to 330 mD, respectively. A produced crude oil sample having a viscosity of 63 cP at ambient conditions was used in the experiments. The total dissolved solids (TDS) of the high salinity water and the low salinity water are 28,000 mg/L and 2,940 mg/L, respectively. Softening had little effect on the TDS of the low salinity water, but the concentration of Ca²⁺ was reduced significantly. The residual oil saturations were reduced gradually by applying LSWF and softened LSWF successively after high salinity water flooding. On average, LSWF can improve viscous oil recovery by 6.3% OOIP over high salinity water flooding, while the softened LSWF further enhances the oil recovery by 1.3% OOIP. The pressure drops observed in the LSWF and softened LSWF demonstrate more fluctuation than that in the high salinity water flooding, which indicates potential clay migration in LSWF and softened LSWF. Furthermore, it was found that, regardless of the salinities, the calculated water relative permeabilities are much lower than the typical values in conventional systems, implying more complex reactions between the reservoir rock, viscous oil, and injected water. Mixing the provided viscous oil and low salinity water generates stable water-in-oil (W/O) emulsions. The viscosities of the W/O emulsions made from water-oil ratios of 20:80 and 50:50 are higher than that of the provided viscous oil. Moreover, the contact angle between the crude oil and reservoir rock in the presence of low salinity water is larger than that in the presence of high salinity water, which may result from the wettability change of the reservoir rock by contact with the low salinity water.
    • Factors Affecting Water Management on the North Slope of Alaska

      Greenwood, Julian K.; Murphy, R. Sage (University of Alaska, Institute of Water Resources, 1972-02)
      The North Slope of Alaska is undergoing sudden development following the recent discovery of large oil and gas reserves in the area. The water resources of the region should be carefully managed both to ensure adequate supplies of usable water at reasonable cost, and to guard against excessive deterioration of water quality. The likely effects on the environment of man's activities are investigated and found to be poorly understood at the present time. Research priorities are suggested to supply rapid answers to questions of immediate importance. The applicability of a regional management concept to the North Slope waters is considered and the concept is recommended as part of a broad land and water planning philosophy which would emphasize regional control over state and federal control. The use of economic incentives rather than standards for the control of water quality is not recommended at the present time.
    • Long term evaporation pan data to estimate potential evaporation during the warm season on the Alaskan North Slope: Imnavait Creek basin

      Mumm, John Paul; Kane, Douglas L.; Toniolo, Horacio; Schnabel, William (2017-12)
      Evapotranspiration plays a significant role in the hydrologic cycle of all basins, yet is only ccasionally measured in the Arctic. One simple index method to evaluate evapotranspiration is the evaporation pan. The energy environment surrounding the simple evaporation pan varies considerably from that of the natural environment. Yet, an evaporation pan is a sound way to determine and estimate the potential evapotranspiration, and actual evapotranspiration can be estimated from evaporation pan data by determining and employing a pan coefficient. An evaporation pan was initially installed in 1986 in the northern foothills of the Brooks Range on the North Slope of Alaska in Imnavait Creek Basin, collecting data for 22 years. The total summer maximum, average, minimum and standard deviation of pan evaporation were 34.9 cm, 29.9 cm, 19.7 cm and 9.3 cm, respectively from 1986 to 2008 (1989 missing). Both, the seasonal water balance and the Priestley-Taylor method for the 2.2 km² Imnavait Creek catchment were used to produce seasonal estimates of actual evapotranspiration. When used in conjunction with the evaporation pan measurements, an average pan coefficient of 0.58 was found in both cases, which was very similar to what was found in an earlier study on Imnavait Creek Basin. The evaporation pan results can also be correlated effectively with other measured variables (such as thawing degree days, air temperature, net radiation, vapor pressure deficit, precipitation, wind speed, and wind direction); this is a method that allows one to predict potential evapotranspiration in areas where it is not measured at broader spatial scales.
    • Modeling the injection of CO₂-N₂ in gas hydrates to recover methane using CMG STARS

      Oza, Shruti; Patil, Shirish; Dandekar, Abhijit; Khataniar, Santanu; Zhang, Yin (2015-08)
      The objective of this project was to develop a reservoir simulation model using CMG STARS for gas hydrates to simulate the Ignik Sikumi#1 field trial performed by ConocoPhillips at the North Slope, Alaska in 2013. The modeling efforts were focused exclusively on the injection of CO₂-N₂ in gas hydrate deposits to recover methane after an endothermic reaction. The model was history matched with the available production data from the field trial. Sensitivity analysis on hydrate saturation, intrinsic permeability, relative permeability curves, and hydrate zone size was done to determine the impact on the production. This was followed by checking the technical feasibility of the reservoir model for a long-term production of 360 days. This study describes the details of the reservoir simulation modeling concepts for gas hydrate reservoirs using CMG STARS, the impact on the long term production profile, and challenges and development schemes for future work. The results show that appropriate gas mixture can be successfully injected into hydrate bearing reservoir. The reservoir heat exchange was favorable, mitigating concerns for well bore freezing. It can be stated that CO₂-CH₄ exchange can be accomplished in hydrate reservoir although the extent is not yet known since the production declined for long term production period during forecasting study.
    • Processes controlling thermokarst lake expansion rates on the Arctic coastal plain of Northern Alaska

      Bondurant, Allen C.; Arp, Christopher D.; Jones, Benjamin M.; Daanen, Ronald P.; Shur, Yuri L. (2017-08)
      Thermokarst lakes are a dominant factor of landscape scale processes and permafrost dynamics in the otherwise continuous permafrost region of the Arctic Coastal Plain (ACP) of northern Alaska. Lakes cover greater than 20% of the landscape on the ACP and drained lake basins cover an additional 50 to 60% of the landscape. The formation, expansion, drainage, and reformation of thermokarst lakes has been described by some researchers as part of a natural cycle, the thaw lake cycle, that has reworked the ACP landscape during the course of the Holocene. Yet the factors and processes controlling contemporary thermokarst lake expansion remain poorly described. This thesis focuses on the factors controlling variation in extant thermokarst lake expansion rates in three ACP regions that vary with respect to landscape history, ground-ice content, and lake characteristics (i.e. size and depth). Through the use of historical aerial imagery, satellite imagery, and field-based data collection, this study identifies the controlling factors at multiple spatial and temporal scales to better understand the processes relating to thermokarst lake expansion. Comparison of 35 lakes across the ACP shows regional differences in expansion rate related to permafrost ice content ranging from an average expansion rate of 0.62 m/yr on the Younger Outer Coastal Plain where ice content is highest to 0.16 m/yr on the Inner Coastal Plain where ice content is lowest. Within each region, lakes vary in their expansion rates due to factors such as lake size, lake depth, and winter ice regime. On an individual level, lakes vary due to shoreline characteristics such as local bathymetry and bluff height. Predicting how thermokarst lakes will behave locally and on a landscape scale is increasingly important for managing habitat and water resources and informing models of land-climate interactions in the Arctic.
    • Reservoir simulations integrated with geomechanics for West Sak Reservoir

      Chauhan, Nitesh; Khataniar, Santanu; Dandekar, Abhijit; Patil, Shirish (2014-07)
      Geomechanics is the study of the mechanical behavior of geologic formations. Geomechanics plays an important role in the life of a well. Without a proper understanding of the geomechanics of a reservoir, the projects associated with it may run into problems related to drilling, completion, and production. Geomechanics is important for issues such as wellbore integrity, sand production, and recovery in heavy oil reservoirs. While studying geomechanics, proper weight is given to mechanical properties such as effective mean stress, volumetric strain, etc., and the changes that these properties cause in other properties such as porosity, permeability, and yield state. The importance of analyzing geomechanics increases for complex reservoirs or reservoirs with heavy oil. This project is a case study of the West Sak reservoir in the North Slope of Alaska. Waterflooding has been implemented as enhanced oil recovery method in the reservoir. In this study, a reservoir model is built to understand the behavior and importance of geomechanics for the reservoir. First, a fluid model is built. After that, reservoir simulation is carried out by building two cases: one coupled with geomechanics and one without geomechanics. Coupling geomechanics to simulations led to the consideration of many important mechanical properties such as stress, strain, subsidence etc. Once the importance of considering geomechanical properties is established, different injection and production pressure ranges are used to understand how pressure ranges affect the geomechanical properties. The sensitivity analysis defines safer pressure ranges contingent on whether the formation is yielding or not. The yielding criterion is based on Mohr's Coulomb failure criteria. In the case of waterflooding, injection pressure should be maintained at 3800 psi or lower and production at 1600 psi or higher. And if injection rates are used as the operating parameter, it should be maintained below 1000 bbls/day. It is also observed that injection pressure dominates the geomechanics of the reservoir.
    • A review of oil spill history and management on the North Slope of Alaska

      Davila, Amanda (2013-12)
      Alaska has an abundance of natural resources including oil, natural gas and coal. It is critical to minimize the occurrence of oil spills to ensure protection of Alaska's people and the environment. The objective of this project is twofold. One is to provide a quantification of the number of spills on the North Slope (NS) as well as the number of contaminated sites that are generated, describe the regulatory requirements for the Arctic zone, and discuss cleanup methods. Second is to describe the ADEC regulations as they pertain to terrestrial oil spills. The region of study begins north of Alyeska's Pump Station 4 at the Dalton Highway milepost 270, TAPS 144, north to the Beaufort Sea, encompassing all oil related operations. This review excludes spills at villages (not related to oil field operations), and releases to the atmosphere (e.g., halon, propane). Additionally, spills at formally used defense sites (FUDS) and long range radar sites are also excluded from this study. Spills that result in long term monitoring and cleanup are managed as contaminated sites. The data reveals that the majority of contaminated sites have been cleaned up with no institutional controls in place. The number of spills on the North Slope is consistent with activity. The time during the peak oil is when there are a higher number of spills. Over time, as the oil production and activity decline, so do the number of spills with a few exceptions. The decline in oil production has limited activity and growth on the NS.
    • A study of waterflood sweep efficiency in a complex viscous oil reservoir

      Jensen, Marc Daniel; Khataniar, Santanu; Dandekar, Abhijit; Patil, Shirish (2014-12)
      West Sak is a multi-billion barrel viscous oil accumulation on the North Slope of Alaska. The unique geologic complexities and fluid properties of the West Sak reservoir make understanding ultimate sweep efficiency under waterflood a challenge. This project uses uncertainty modeling to evaluate the ultimate sweep efficiency in the West Sak reservoir and honors a rich dataset gathered from 30 years of development history. A sector model encompassing the area of the West Sak commercial pilot was developed and a sensitivity analysis conducted to determine the most important parameters affecting sweep efficiency. As part of this process unique constraints were incorporated into the model including measured saturations at the end of history, and observed completion performance. The workflow for this project was documented and can be adapted for use in larger scale models. The workflow includes the development of static cell properties which accurately represent field behavior, a preliminary history match using conventional methods and a sensitivity analysis employing a multi-run visualization tool to effectively navigate and process large amounts of data. The main contributions of this work include the identification of key parameters affecting sweep efficiency in the West Sak oil field, a documented workflow, and increased insight into observed production behavior.
    • Thermal analysis on permafrost subsidence on the North Slope of Alaska

      Agrawal, Neha Dinesh; Patil, Shirish; Chen, Gang; Dandekar, Abhijit; Bray, Matthew (2015-11)
      One of the major problems associated with the oil fields on the North Slope of Alaska is thawing permafrost around producing oil wells. In these wells, the heat from the producing well fluid gradually thaws the permafrost. This thawing in turn destroys the bond between the permafrost and the casing and causes instability that results in permafrost subsidence which further causes subsidence of the soil surrounding the wellbore and, subjects the casing to high mechanical stresses. The above problem has been addressed by several engineers, and several preventive measures, such as controlling the subsidence by refrigeration or by insulation of the wellbore, have been analyzed. Understanding the thermal behavior of the permafrost is imperative to analyzing permafrost subsidence and providing preventative measures. The current project focuses on building a scaled-down axi-symmetric model in FLAC 7.0 that will help us understand the thermal behavior (i.e., the heat input to the permafrost interval due to hydrocarbon production) and temperature distributions that result in permafrost subsidence. The numerical analysis estimated the thaw influence of steam injection used for heavy oil recovery and its effect on the area around the wellbore for 10 years. The developed model was compared with Smith and Clegg (1971) axi-symmetric model and COMSOL model and correlations of thaw radius and wellbore temperatures were obtained for different types of soils. Heat transfer mitigation techniques were also attempted which are discussed in the report further.
    • Transportation economics of coal resources of northern slope coal fields, Alaska

      Clark, P.R. (University of Alaska Mineral Industry Research Laboratory, 1973)
      This paper describes the Northern coal fields, the environment in which they are situated, and various routes and systems for transporting metallurgical qua1ity coal from these deposits to a potential market in Japan. Each transportation mode is discussed with respect to northern Alaska conditions. Capitol and operating costs were developed for each system. If the coal must support the entire transportation system cost, the transportation of coal from the North Slope of Alaska to Japan appears to be economically feasible only from easily mined areas which are close to an ocean shipping port. In the case of transportation cost sharing by other users, or by government subsidization, the prospects of northern coal exploitation would be enhanced. The final feasibility of developing any of this coal deposit cannot be determined until the mining costs and the factors which influence these costs are known.