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Appendix D Oil-Field Technology and the Environment TECHNOLOGY IN EXPLORATION Advances in exploration-related technology have been directed toward more precisely identifying subsurface drill- ing targets in order to reduce the number and cost of explo- ration wells (DOE 1999) and to reduce the impact on the physical/biological environment. Technologies such as 3-D seismic-data acquisition and 4-D visualization allow for the drilling of fewer wells, and the use of ice roads and ice pads, plus remote sensing, can decrease the direct impact on the tundra, although the long-term effects are not fully known. These newer technologies have largely replaced the older, less-efficient and, in some cases, less environmentally friendly practices and techniques. 3-D Seismic-Data Acquisition and 4-D Visualization Improvements in 3-D seismic-data acquisition and other exploration technologies allow geologists to identify higher quality prospects and to improve success rates by as much as 50% or more. In 1970, the success rate for exploration wells in the U.S. was about 17%. In addition to the advances in data quality and acquisition procedures, there have been im- portant advances in the engineering of the vehicles used to move the camp equipment and to acquire the data. The ma- jor changes have been in the development of new "light- weight" rubber tracked caterpillar-type vehicles and vibra- tors that do less damage to the tundra and willows than the older vintage steel-tired vehicles. With the use of 3-D seis- mic-data acquisition, the success rate had increased to 48% in 1997 (DOE 1999, Revkin 2001~. Phillips Alaska, Inc., and Anadarko Petroleum Corporation's recent exploration success in the National Petroleum Reserve-Alaska was an astonishing five successful wells of six drilled (Petroleum News Alaska 2001~. About 25 years ago, 3-D seismic technology was intro- duced. Data are acquired in a grid-like manner with the indi- 183 vidual lines spaced only a few hundred feet apart, and are computer manipulated to create multidimensional represen- tations of the subsurface. The result is a far better under- standing of the geologic structures and continuity of the po- tential hydrocarbon-bearing formations. As with the older generation 2-D seismic data, onshore 3-D seismic data are acquired during winter, after freeze-up, to a depth of 12 in. (30 cm) and an accumulation of 6 in. (15 cm) or more snow. Vibrators are used, and these energy sources and the crews, camps, and other support facilities are carried on and/or are usually towed by low-impact tundra travel vehicles (Lance 2000~. Seismic grids may cover an area of hundreds of square kilometers. Most offshore 2-D and 3-D seismic data are ac- quired during the open water season using airguns rather than vibrators. Some offshore data, in the area of bottom-fast ice, are acquired during winter using land technology. The 3-D data sets are often used throughout the life of a field to plan infill and injection wells. The older land-based 2-D seismic technology consisted of long, intersecting seismic lines that used either dynamite or vibrators as the energy source. In the early stages of ac- quisition on the North Slope, much less care was taken to protect the tundra from damage during data acquisition. Damage, then as now, can result from inadequate snow cover and inappropriate equipment. Recent seismic data, both 2-D and 3-D, have been acquired in a much more environmen- tally sensitive manner. Offshore seismic data are acquired using patterns and spacing similar to those used in onshore acquisition. These data can be acquired only when the sea is relatively ice-free and boats can maintain long uninterrupted traverses. A high noise level is associated with marine acquisition, and it nega- tively affects marine organisms, especially whales. Four-dimensional (4-D) visualization adds the element of time to 3-D seismic databases. A reservoir's fluid vis- cosity, saturation changes, temperature, and fluid move- ments can be analyzed by time-lapse monitoring in three

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184 APPENDIX D dimensions (DOE 1999~. The time-lapse picture is built out No negative consequences have been identified with the use of data re-recorded, compared, and plotted by computer of this technology. Onto the 3-D model. Additional data, such as well logs, production information, and reservoir pressures, may be integrated into the time-lapse imagery. The resulting infor- mation provides geologists and others with data that are valuable for both exploration for and management of exist- ing resources. The exploration element comes from the greater ability to predict the best locations for exploratory drilling. The 3-D seismic-data acquisition and 4-D visualization technologies provide a number of environmental benefits (DOE 1999~. They include more accurate exploration well- siting that reduces the number of dry holes and the number and length of ice roads and the number of ice pads that have to be built; generation of less drilling waste and decreased volumes of materials that are thereby lessening the possibil- ity of a spill or other accident; better understanding of flow mechanics so that less water is produced relative to oil or gas; and increased ability to tailor operations to protect sen- sitive environments. Overall fewer wells are required in or- der to evaluate and produce the reserves. Nonetheless, considerable concern has existed regard- ing the effects of any seismic activity conducted either on land during winter or at sea during the open water season (Van Tuyn 2000~. Land-based seismic-data acquisition with its large vehicles and numerous traverses across the tundra has left scars of the vehicle paths, some of which have been slow to heal and recover. At sea, migrating bowhead whales have been deflected by noises generated by seismic explora- tion and drilling. The 3-D seismic-data acquisition programs require more closely spaced grids, a few hundred feet between lines as opposed to several kilometers with standard 2-D seismic pro- grams. This closer spacing has the potential to affect a greater amount of the tundra surface. These trails are often highly visible the following summer, in part because the old dead vegetation has been flattened by the vehicles and the green new vegetation can be more readily seen in sharp contrast to the undisturbed surrounding areas. The closer spacing of the seismic traverses may also increase the risk that donning polar bears may be disturbed. This risk could be lessened by studies of bear donning sites and planning the acquisition programs accordingly. Remote Sensing Remote-sensing techniques such as infrared photogra- phy have been used to design and locate roads and facilities, such as development facilities and ice roads and ice pads, to reduce effects on the environment. Satellite infrared photog- raphy has been utilized to facilitate habitat mapping in the Alpine field (Lance 2000~. The environmental benefits come from the avoidance of critical habitat and better design of facilities that must be placed within less than ideal locations. Ice Roacis and Ice Pacis Arctic tundra is easily disturbed and slow to recover from damage. Disruption of tundra may also have a pro- nounced effect on permafrost and result in thawing and ero- sion. Historically, roads to exploration well sites were built of peat, bladed bedrock, or gravel, causing long-term dam- age to tundra that remains evident after 40 or more years. Drilling pads were similarly built of gravel or bulldozed bed- rock in some areas of the National Petroleum Reserve- Alaska during the Navy exploration efforts in the 1940s and 1950s. Because of these factors and potential damage from transporting equipment across the tundra either in the sum- mer or winter, ice roads have replaced gravel roads and have become the means of access to isolated drilling locations. In a similar fashion, ice pads have become the standard for ex- ploration drilling sites, eliminating the need for gravel to build pads and for cleanup after drilling. All onshore explo- ration drilling is done during winter and all materials neces- sary for drilling a well, including the drilling rig, are moved to and from well locations on ice roads. An ice road 6 in. (15 cm) thick and with an average width of 30 to 35 feet (9 to 11 m) would require 1 million to 1.5 million gallons of water per mi (620,000 to 930,000 gal- lons of water per km) of length (Van Tuyn 2000~. BP Explo- ration (Alaska), Inc. reports that the ice roads are generally 12 to 18 in. (30 to 46 cm) thick. Frequently, exploration ac- tivity within a specific area requires more than one drilling season; therefore, more than one ice road may be built from the staging greats) to the same drilling site or prospect. To avoid possible damage from multiyear usage of the same area, any subsequent ice road is offset by at least a road width from previous ones. A 6-acre (2.4 ha) drilling pad, 12 in. (30 cm) thick would require approximately 500,000 gallons of water (Van Tuyn 2000~. The ice pads provide a solid, stable base from which to drill an exploration well. Upon completion and abandon- ment or testing of the well, the rig and all support facilities are moved off-location and the pad is allowed to melt. The result is a very low impact operation, and usually the only indication of the drilling activity is the abandoned wellhead. In special situations, specifically where drilling and evaluation are expected to require either an extended drilling season or two drilling seasons, insulated ice pads have been utilized. BP Exploration used such a system when drilling the Yukon Gold No. 1 and Sourdough No. 2 wells in the 1993-1994 drilling season (DOE 1999~. A 190 by 280 ft (120 by 85 m) ice pad was built in March 1993 and covered with wind-resistant insulating pads. The pads remained in place over the summer and were removed in October. Drill- ing began in mid-November, two months ahead of conven- tional Arctic practice. With this advanced drilling start, the

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APPENDIX D Yukon Gold well was completed, the rig moved to the Sour- dough site, and that well completed the same season. This would not have been possible with a conventional ice pad. There is the potential for some level of short-term dam- age in areas that have either experienced low snow fall or removal of snow by high winds, thus creating substandard snow cover conditions. However, in most instances there is little evidence of either the ice road or ice pad once the snow cover is gone. The use of the ice-road and ice-pad technology reduces the need for gravel during the exploration phase of oil and gas activity. Smaller volumes of gravel are mined during the history of a given field, less area is covered by gravel, and there is little recognizable damage to the tundra. The use of an insulated pad allows the drilling of more wells in a single season, reducing the need to build ice roads in two seasons to serve the same general area. The older technologies had greater potential to seriously disrupt tundra, thaw permafrost, and mar the viewscape. These effects can persist for many years and many damaged sites have not been adequately remediated. Although the use of ice roads and pads has largely eliminated those problems, a different set of potential effects has been identified. Insu- lated ice pads have some degree of influence on the underly- ing tundra, simply because the area loses a growing season, but these effects have not been studied. The construction of ice roads and pads relies on a ready and plentiful supply of water. Water is drawn from rivers or lakes, existing ice is crushed or chipped and spread along the prescribed roadway or pad site. Concern has been expressed that the extraction of such large volumes of water may en- danger fish and drinking water resources. Areas such as the Arctic National Wildlife Refuge have low lake densities and a reliable source for water to build ice roads and pads may not be present. At this time, there are few reliable data that address the controversy over the appropriate use levels for water in the construction of ice pads and roads. Rolligons and the Arctic Drilling Platform Potential problems associated with exploration drilling in areas with limited freshwater supply or shortened ice-road seasons may be alleviated by the use of low ground-pressure vehicles (Rolligons) and the Arctic Drilling Platform. Rolligons can extend the drilling and off-road seasons on the North Slope. Current Rolligons put 4 to 5 psi of footprint pressure on the tundra, but that would be reduced to 1 psi per tire, depending on the load and the tire size (Rolligon Corpo- ration Web site, www.rolligon.com; Petroleum News Alaska 2002b). The vehicles have been used to move drilling rigs to remote locations on the North Slope. Their primary use would probably be to access locations that are far from cur- rent infrastructure and where the economics of the operation favors their use over the costs and the associated delays of building an ice road. 185 The Arctic Drilling Platform is an adaptation to land of offshore technology. The platform is light and mobile. It can eliminate or reduce the need for ice roads or ice pads (Petro- leum News Alaska 2002b; Anadarko, unpublished material, 2002~. The platform is self-contained and elevated. It can serve as a temporary drilling facility or a long-term produc- tion facility. It is supported by steel pilings that contain coils for circulating hot or cold fluids. The elevated platform con- sists of interlocking aluminum components (12.5 ft by 50 ft [3.8 m by 15 m]) with reinforcing elements and rests on a base of shallow containers that capture any deck fluids or other spillage. The components are transported by Rolligons, thus eliminating the need for ice roads, as well as ice pads. A small version of this system is being used by Ana- darko during the 2002-2003 drilling season on a 3,000 to 3,500 ft (914 to 1067 m) gas hydrate core well south of the Kuparuk oil field. DRILLING AND COMPLETION TECHNOLOGIES An oil reservoir is part of a porous and permeable layer of rock in which the oil is trapped. On the North Slope, each production well is designed to produce from a subsurface area of at least 80 acres (32 ha). Wells are located on gravel pads and are drilled vertically through approximately 2,000 ft (600 m) of permafrost. Once through the permafrost, the bit is directed toward the desired bottom hole location. The number of wells per pad generally ranges from 16 to 40 (BP Exploration Alaska, Inc. and ARCO Alaska, Inc.1997~. The size of the pad and associated facilities is largely governed by the spacing between wells, and the number of pads is a function of the size of the area that can be drained by the wells on a pad. Historically, production wells were either straight or deviated holes and the number per pad was lim- ited; hence, the number of pads needed to drain a specific area was high. The lateral reach of deviated holes rarely ex- ceeded the true vertical depth (TVD) of the well. New tech- nologies have done much to improve the lateral reach of a well and to reduce the size and number of well pads. The technologies developed over the last two decades have greatly reduced the size of the "footprint" left by the industry when developing an oil field. Wells may be much more closely spaced, far larger areas can be developed from a single small pad, the mud systems are less toxic, and re- serve pits have been eliminated. Coilecl Tubing The use of coiled tubing is particularly valuable in sen- sitive environments such as the North Slope. Coiled tubing technology is quieter and has far less impact on a drilling site than conventional equipment (DOE 1999~. The technology dates from the 1950s, but only after rapid technological ad- vances in the late 1980s did it come into common use. The tubing is mounted on a large reel and is a continuous flexible

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186 coil that is fed into the hole. The use of coiled tubing does not require the repeated "tripping" out of the hole to add additional pipe segments. One of the byproducts of coiled tubing drilling is a significant reduction in the volumes of drilling fluids compared with conventional drilling. Coiled tubing mud volumes are commonly less than half those re- quired or generated by conventional drilling practices (DOE 1999~. In many wells, conventional methods are used to drill the initial hole and then coiled tubing is utilized to drill hori- zontal segments or multilateral completions. The coiled tub- ing technology is also commonly used for slim-hole drilling (i.e., a rotary borehole of 5 in. [12.7 cm] or less, or a drill hole of the smallest practical size) and reentry projects. The use of coiled tubing technology has substantial envi- ronmental advantages over the conventional drilling technol- ogy, but does have some limitations in its application. The primary benefits include (DOE 1999~: reduced mud volumes and drilling waste; cleaner operations, no connections to leak mud; reduced operations noise; minimized equipment foot- prints and easier site restoration; reduced fuel consumption and emissions; reduced risk of soil contamination due to in- creased well control; and better well-bore control. These advantages clearly support the use of coiled tubing whenever it is technically feasible. Many of the newer fields, such as Alpine, use this technology almost exclusively in con- junction with extended-reach horizontal drilling. No detrimen- tal environmental effects are known to be associated with the introduction of coiled tubing technology to the North Slope. Horizontal Drilling Horizontal drilling became a reality in the 1970s due to advances in computers, steerable down-hole motor assem- blies, and measurement-while-drilling tools. A horizontal well is drilled from an initially vertical well-bore at an angle between 70 and 110. Vertical or near vertical wells drain oil from a single hole and have limited contact with the oil- bearing interval (usually limited to the vertical thickness of the rock unit). Horizontal wells penetrate the formation up to 8 km (5 mi) or more from the vertical well bore allowing more oil to drain into the well. The results are a greater number of wells per pad, closer well spacing on the pad, and fewer well pads than using the old technology. Well spacing has decreased from 120 ft (37 m) or more to as little as 10 to 15 ft (3 to 5 m) between wells (BP Exploration Alaska, Inc. and ARCO Alaska, Inc.1997~. Pad size and radius of reach of the wells on the pad have undergone remarkable changes since the start-up of the Prudhoe Bay field in the 1970s. An example of the reduction in pad size and corresponding area of reach is summarized below (Revkin 2001~: . 1970 Prudhoe Bay Drillsite 1; covers 65 acres (26 ha), has an effective reach radius of 1 mi (1.6 km), and pro- duces from an area of 2,010 acres (814 ha). APPENDIX D 1980 KuparukDrillsite2B;covers24acres(10 ha), has an effective reach radius of 1.5 mi (2.4 km), and pro- duces from an area of 4,522 acres (1,831 ha). 1985 Kuparuk Drillsite 3H; covers 11 acres (4 ha), has an effective reach radius of 2.5 mi (4 km) and produces from an area of 12,500 acres (5,100 ha). 1999 Alpine Pad #2; covers 13 acres (5 ha), has an effective reach radius of 4 mi (6 km), and produces from an area of 32,154 acres (13,022 ha). The marked increase in drillable area per pad, as dem- onstrated at Alpine, is largely due to the extensive use of horizontal drilling technology, although Pad #2 is connected to the rest of the 97-acre (39-ha) Alpine site. The environmental benefits include smaller footprints requiring less gravel and fewer wells to produce the same volume of hydrocarbons. These more effective drilling pro- grams require less water and subsequently generate less drill- ing waste. Horizontal drilling results in smaller and fewer pads than did the older technologies, but gravel is still needed and effects on tundra and permafrost may result from gravel mining and emplacement. The closer spacing of well-bores has the potential to increase the rate at which permafrost thaw bulbs form, reducing surface stability and causing sub- sidence. However, some factors can limit the application of this technology (MMS 2001a, Vol IV, Appendix D). Multilateral Drilling Multilateral drilling, a variant of the horizontal drilling technology, creates an interconnecting network of separate, pressure-isolated and reentry accessible horizontal or high- angle boreholes surrounding a single major borehole (DOE 1999~. Multilateral drilling is most effective in reservoirs that have isolated accumulations in multiple zones, have oil above the highest perforations, have lens-shaped pay zones, are strongly directional, contain distinct sets of natural fractures, and are vertically segregated with low transmissibility. The environmental benefits are similar to those achieved with horizontal drilling and include fewer drilling sites and smaller footprints, less drilling fluids and cuttings, and pro- tection of sensitive habitats and wildlife. Multilateral drill- ing poses no recognized risk to the environment other than those associated with horizontal drilling. Measurement-While-Drilling {MOOD) Conventional down-hole logging practices consist of running a variety of remote sensing tools down a borehole prior to setting the surface casing, before any intermediate casing strings, and prior to completing the well at total depth. These tools are on wire-lines and are lowered into the uncased hole and pulled back to the surface. The tools record specific types of data as they are withdrawn from the hole. These data are then used to evaluate the rock type, reservoir

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APPENDIX D properties, hole integrity, and the other features concerning the physical environment of the well-bore. The procedure is routine, but it can be a risky because irregularities in the hole can result in stuck or even lost tools. Conventional logging can be especially risky in a highly deviated or horizontal hole where there is an increased probability that the tool, while being pulled out of the hole, may become snagged on a resistant rock projection or become buried by loose debris collapsing into the hole. Additionally, these important data are not available to the geologist until some time after the well or interval has been drilled. This delay may vary from hours to days or even weeks. An example would be the desire to correlate the drilled section with that seen in a well some distance away, in order to predict a coring point or anticipate a stray high- pressure sandstone. Measurement-while-drilling (MOOD) technology can pro- vide data virtually as the intervals are drilled. Additionally, sensors provide directional information and other key data that facilitate more effective geosteering and trajectory control (DOE 1999~. The recording sensors and other necessary equip- ment are housed in the drilling assembly at the bottom of the pipe-string, just a few meters above the drill bit. Conventional logging tools are still run in many wells and provide a wide range of critical data that are not currently replicated by the MWD tools. Thus, the current technology is a blend of the older wire-line tools and the real-time MWD instruments. Geologists and drilling engineers can benefit from the best of both worlds in today's drilling environment. Because of its real-time capability, the MWD technol- ogy can be used to avoid formation damage by alerting the rig crew of problems before they become too serious to cor- rect; similarly there is a reduced possibility of blowouts and improved overall rig safety. This technology is also a con- tributing factor in the reduction of drilling waste volumes because it facilitates horizontal and multilateral drilling prac- tices and provides better well-bore directional control. However, the conventional logging package requires long trips to remove pipe from the hole and run a number of wire-line tools down the hole to record data. This process can take several hours to as much as a few days, depending on the number of tools to be run and the depth and condition of the hole to be logged. Repeated flushing of the hole can cause formation or hole damage and result in sloughing of materials into the hole from the walls of the well. The poten- tial for loss of a tool assembly exists. If a tool cannot be extracted or milled up, the hole must be sidetracked and re- drilled, thus creating more waste and extending the duration of the drilling process. The MWD technology significantly reduces this risk and its associated impacts. Light Automatecl Drilling System {LADS) The construction of ice roads and ice pads in remote areas requires an abundant water supply. There is legitimate 187 concern regarding means of access in areas that lack suffi- cient water and/or freshwater ice to build roads or if global warming were to prevent the use of ice roads. A possible solution to this problem, the Light Auto- mated Drilling System (LADS), is in the research phase and is being considered for use on the North Slope. This poten- tial drilling system is expected to be a light-weight drilling rig that can be easily broken down into several components and transported across tundra in winter by light impact ve- hicles that would not require ice roads. This system or others like it could be adapted to work in areas that lack sufficient water for ice roads or during mild winters when it would not be possible to build an ice road, transport a rig to a drilling locations, and return it to the staging area. The principal benefit of LADS would be to reduce the need for water to build ice roads. The primary drawback from the environmental perspective would be the increased risk of damage to the tundra while transporting rigs between locations in the absence of adequate snow cover. The same concerns exist as are presently expressed for seismic activity but on a much reduced scale. PRODUCTION TECHNOLOGIES Production and associated operations are the longest- term activities in an oil field. The life of major oil fields on the North Slope is expected to be on the order of 30 to 40 years, occasionally as much as 50 years. During this time pipelines, production facilities, waste disposal systems, wa- ter treatment plants, injection facilities, road systems, and other specialized units continue to operate. Industry attempts to produce the maximum amount of oil (gas) at the least cost in order to remain competitive and viable in the event of competition for funding or a low oil/gas price environment. The most cost efficient technologies are the obvi- ous choice of the operators. It is not surprising that in the early phases of development and production some of these choices have proven to be less than optimal from an environmental per- spective. The use of reserve pits for the disposal of used drilling muds, cuttings, and other waste is one such example. Today, on the North Slope, as fields continue to be dis- covered, developed, and produced, there continues to be the need for new pipelines, production facilities, waste disposal wells, etc. To reduce the environmental effects of these ac- tivities, new technologies have been developed or adapted for use on the North Slope. New methods do not eliminate the need for gravel, water, and other materials, but they re- duce their use and cause less disturbance, therefore reducing the potential negative effects associated with wastes and road and pipeline construction. Enhancecl Oil Recovery {EOR) This technology, discussed in Chapter 4, involves the injection of formation and source water, natural gas, and

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188 miscible fluids into the producing reservoir to maximize re- covery of hydrocarbons. In this process, not only is more oil recovered per well, but much of the waste water associated with oil production is reintroduced into the reservoirs from which it was produced. Many problems that formerly were handled by surface or reserve pit disposal techniques are solved. The principal environmental benefits are greater recov- ery of oil without a proportionately greater number of wells and their associated waste, environmentally friendly disposal of produced water, and reduction of emissions that would be associated with the flaring of excess produced gas. Few nega- tive environmental effects are associated with FOR. The pri- mary unease is in regard to spills of produced water and the remote possibility that a reservoir may be over-pressured through the injection process, cause fracturing to the sur- face, and allow oil and other fluids to escape to the pad and/ or tundra. Waste Disposal From the 1940s to the 1980s, most well-associated wastes were either stored in reserve pits or handled through other surface disposal means such as incineration. The re- serve pits were prone to seepage and spills, and they con- tained undesirable metals and volatile organic compounds. These did, and still do, present environmental risk, especially at old, unclosed remote exploration sites. The reserve pit closure program was instituted in 1996. To date, 50% of approximately 600 reserve pit sites have been closed. The ADEC required submittal of closure plans for all sites by January 28,2002 (Maham 2001~. These plans, which do not require full restoration of the sites, have been submitted (ADEC 2002~. Down-hole disposal of wastes by injection into subsur- face disposal intervals is utilized in all present-day explora- tion wells and producing fields. This mode of waste disposal is an effective and noncontaminating method of removing many unwanted materials from the surface environment. The grind-and-inject project was undertaken to dispose of drill- ing muds and cuttings stored in reserve pits. Other wastes processed through the grind-and-inject plant include: Class II, RCRA-exempt oily wastes, and drilling muds and cut- tings from ongoing drilling operations. As of May 31,2000, injection at the Surfcote pad included 5.2 million bbl (218.4 million gallons) of water, 16.4 million bbl (688.8 million gallons) of slurry containing 1.1 million tons (1 million met- ric tons) of excavated reserve pit material and drilling solids, and 166 million bbl (7 billion gallons) of fluid from ongoing drilling operations (Bill 2000~. Annular injection is an environmentally safe method of disposing of drilling muds and cuttings, and the injection of Class I and Class II materials into discrete disposal zones has provided a mechanism for the handling of produced for- mation waters and other associated wastes (API 1996~. APPENDIX D However, a large number of unclosed reserve pits re- main at remote exploration well-sites. No adequate plan is in effect to handle the possible pollution and resultant damage from poorly sealed and covered pits. The annular injection process has some potential to create or take advantage of poor casing or cement jobs and result in leakage to the sur- face. This has occurred on several occasions, but with no contamination of permafrost. Worries regarding subsidence and marine contamination have been expressed, but the ex- isting evidence indicates that subsidence is not a concern and disposal units are effectively and naturally isolated from any contact with the ocean or seafloor. Roadless Construction Prudhoe Bay, Kuparuk, Endicott, and other early gen- eration oil fields were developed, facilities and pipelines constructed, and distinct operating areas joined together through a network of gravel roads. This required large vol- umes of gravel that have been extracted from 13 gravel mines. The U.S. Fish and Wildlife Service has estimated that more than 60 million yd3 (46 million m3) of gravel have been mined to supply the construction needs of the North Slope oil fields (Van Tuyn 2000~. Data from the Department of Natural Resources (DNR) place the volume of gravel ex- tracted from 1974 to date at 57,880,481 yd3 (44,252,803 my. Because of a decrease in scale of facilities and well pads, the rate of demand for gravel is decreasing. Also, new roadless construction methods for remote operations have eliminated much of the need for gravel in road construction. As an example, the Alpine construction was done during the winter with equipment, personnel, and modules transported to the site via ice road. Similarly, the pipeline from Alpine back to the existing pipeline infrastructure at Kuparuk was built using ice roads. Gravel was used to build two produc- tion pads, a 3 mi (5 km) road between the two Alpine pads, and an airstrip, totaling about 97 total acres (39 ha). Future oil-field development will be based on refined variants of the Alpine model. Pads will be small and few in number and construction will be largely a winter activity with transportation via ice roads. The use of gravel will be appreciably reduced. However, the scarcity of water in some areas, climate change, and other factors could make use of gravel roads more attractive economically and practically in some areas. The issue of removing and possibly cleaning the exist- ing volumes of gravel, some of it contaminated from spills related to a variety of causes and fluids, is not resolved. In some instances, the operators have removed gravel, cleaned it if necessary, and reused it elsewhere, but the truly massive task of removal or remediation awaits the abandonment of the fields. The primary environmental benefits are use of less gravel and reduced damage to the tundra. This practice may eventually be efficient enough to be implemented

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APPENDIX D through the reuse of gravel from older abandoned roads and pads. The environmental concern is the large volume of gravel on existing roads and pads of the major North Slope oil fields. The effects this material has on caribou movements and deflections, especially at roads in close proximity to el- evated pipelines; the potential for pending waters; destruc- tion of the tundra; and long-term effects on permafrost may be real and significant. There appears to be a genuine poten- tial for large-scale gravel mining and usage to result in envi- ronmental effects that accumulate on the physical and bio- logical components of the region. Pipeline Construction Among the standard practices utilized in the construc- tion of pipelines are gravel maintenance and construction roads, elevated river crossings, and block valves to reduce the likelihood and sizes of leaks and spills. Recent develop- ments have lessened the environmental effects of pipeline construction, the hazards to the pipeline due to flooding, the probability and severity of leaks, and impediments to cari- bou movement. These new approaches were all used in the design and construction of the Alpine oil pipeline (Lance 2000), which was built largely during the winter and con- structed using ice roads. The lack of a gravel maintenance road removes one potential barrier to caribou movement, reduces the volumes of gravel required for the Alpine-like projects, and reduces the amount of tundra impacted by burial. The Colville River pipeline crossing posed a consider- able challenge. During breakup and the associated flooding, the river is almost a kilometer wide and it could destroy an above ground pipeline or erode deeply enough to expose and rupture a line buried in a surface trench. ARCO Alaska, Inc., elected to use horizontal directional drilling (HDD) to posi- tion the pipeline deep beneath the river channel (Lance 2000~. More than 4,000 ft (1,200 m) of pipeline were placed 100 ft (30 m) below the river. There was no need to erect pylons for an overhead crossing or trench within the flood- plain of the Colville during the winter. However, 8.3 million liters (2.3 million gal) of drilling muds were lost under the Colville River in 1998; its fate is not known. After conducting an oil-spill isolation strategy study that reviewed ways of meeting federal leak-containment regulations, ARCO Alaska, Inc., elected to use 12 to 14 m (39 to 46 ft) high vertical loops on the Alpine pipeline in lieu of the more conventional block valves. The study con- cluded that when used in tandem with emergency pressure- letdown valves or divert valves, vertical loops would con- tain drain-down-related spills as well as block valves, while 189 offering operations and maintenance efficiencies (Pavlas et al. 2000~. The loops are better than manual block valves for re- ducing catastrophic failures, and they provide protection lev- els similar to those achieved by remotely actuated valves for leaks of all sizes. They are not themselves potential leak sites, as valves are, but they do not provide any substantial benefit over block valves for pinhole leaks. With approval from the Department of Transportation, the loops were placed at river crossings and high points along the line. These new pipeline construction methods greatly reduce the environmental effects on tundra, provide for a safer line, and lessen the probability of spillage due to river induced pipeline damage. They also more effectively limit the size of catastrophic spills. However, the placement of a pipeline at depth beneath a river could make detection and cleanup of a spill in the buried segment difficult. The preexisting and pre- dominant North Slope pipeline technology presents impedi- ments to caribou movement when in close proximity to roads, and river crossings are sites of potential severe envi- ronmental consequences if a spill occurs. The accumulation of effects of continued construction of pipelines and road systems could increase the magnitude of displacement of the calving caribou away from the coastal strip and prime forage and insect relief areas. Remote Sensing Satellite infrared photography was used in the Alpine planning and construction phases for selecting the locations of pads and other structures to avoid sensitive, critical habi- tat. Remote sensing devices have the potential to serve other needs on the North Slope. One of the more recent applica- lions may prove to benefit several diverse areas. A Forward Looking Infrared sensor system (FLIR) can be used to detect pipeline leaks. An airborne FLIR unit is an effective tool in surveying pipelines for potential corrosion and detecting leaks. The system may also have use as a spill response tool for tracking spill movement under ice and snow. FLIR can image a spill site and supply pertinent information either as video footage or as a video frame registered map. An additional FLIR application is locating large mam- mals. Although its effectiveness is yet to be fully determined, this system might facilitate the location of polar bear dens. Such an application could be used to plan seismic surveys in such a way as to avoid donning bears. The potential environmental benefits include avoidance of critical habitat, leak and spill detection, corrosion detec- tion, and planning of seismic and other winter programs to avoid donning bears. There are no obvious environmental drawbacks to these technologies.