Slope, North

Introduction and commercial application Investment opportunities in the exploration and production (E P) sector of oil and gas business are abundant. Despite areas such as the North Sea, Gulf of Mexico and the North Slope in Alaska being mature areas, there are still many new fields under development in those regions, and new areas of business interest are opening up in South America, Africa and South East Asia. Some fields which have a production history of decades are being redeveloped, such as the Pedernales Field in Venezuela. 

As reservoir pressure is reduced by oil production, additional recovery mechanisms may operate. One such mechanism is natural water drive. Water from an adjacent more highly pressured formation is forced into the oil-bearing formation by the pressure differential between the formations. Another mechanism is gas drive. Expansion of a gas cap above the oil as oil pressure declines can also drive additional oil to the wellbore. Produced gas may be reinjected to maintain gas cap pressure as is done on the Alaskan North Slope. Additional oil may also be produced by compaction of the reservoir rock as oil production reduces reservoir pressure. 

Gas injection into a gas cap overlaying an oil reservoir is considered an EOR method. The resulting repressurization of the reservoir promotes additional oil production. Reinjection of natural gas is responsible for a significant fraction of Alaskan North Slope oil production. 

The other refining centers in the United States are all located near one of the major pipelines that are suppHed either from the Gulf Coast oil fields or from Oklahoma, Texas, or Louisiana fields. The Pacific Northwest refineries were originally suppHed mostly by Canadian production. Currently (ca 1995), these refineries are predominantly suppHed by Alaskan North Slope cmde, which is brought in from Valdez to the refinery ports in tankers. 

Apparently triggered by an earthquake of Richter magnitude 5.0, die endre north slope burst open along the upper edge of die bulge, releasing the... 

Although the pipeline from the North Slope to the port of Valdez was the route chosen and completed in 1977, the scientific community preferred the trans-Alaska-Canada route its use would have prevented the Exxon Valdez ianker accident of 1989. 

Another U.S. policy to attain energy independence was to force all Alaskan North Slope crude oil to he consumed inside the United States and not be allowed to he exported. The problem was that North Slope crude oil is relatively heavy and not suitable for west coast fuel needs. The mismatch of supply and demand caused California refineries to sell heavy distillate fuels abroad and import lighter fuel additives. Furthermore, the forced selling of Alaska crude oil on a very saturated west coast market caused Alaska crude prices to he 1 to 5 per barrel less than the international price, resulting in less oil exploration and development in Alaska. The upshot of all this was lower tax revenue, a loss of jobs in the oil fields, and less oil exploration and development on the North Slope. The United States actually exported heavy bunker fuel oil at a loss, as opposed to the profit that could have been attained by simply exporting crude oil directly. 

Ylolds Typical examples North slope vac. resid Maya crude P.R. Springs bitumen... 

Figure 8 shows the 180/160 ratio for a Bavarian fir, Abies alba, the rings of which were counted by Becker and Siebenlist [36], compared with temperature records made near where the tree grew, both coming from 1000 meters altitude on the north slopes of the Alps. This is mountainous country so that local differences in temperature may be expected. 

Figure 6. Stratigraphic section above economic basement for the central portion of the North Slope of Alaska. The Brookian and Ellesmerian sequences are separated at the major Lower Cretaceous unconformity. Both commercial and noncommercial oil gas fields are shown at right (from Engel and Macko, 1993).

An example is presented from the North Slope of Alaska, where the largest producing oil field was discovered in 1968. The petroliferous sedimentary rocks of the North Slope consist of Mississippian through Tertiary sandstone, conglomerates, shales, and carbonates. Two major rock sequences comprise the sedimentary succession. The... 

Kvenvolden KA, Rapp JB, Bourell JH (1985) In Magoon LB, Claypool GE (eds) Alaska North Slope oil/rock correlation study. American Association of Petroleum Geologists, Tulsa, OK, Study in Geology, No 20, p 593... 

Alaska North Slope crude, North Sea, mean = 1.190 2 SD... 

Variation among Sampling Sites. Dissolved humic substance samples from seven end-member environments were isolated for study. Autochthonous inputs to DOM were expected to dominate in Big Soda Lake and in Island Lake, which is a groundwater-sustained eutrophic lake in the sandhills of western Nebraska. Allochthonous inputs to DOM from a swamp environment predominate in the Suwannee River. They also dominate in the Calcasieu River in western Louisiana, but the proportion of swampland is much lower there. The Temi River is a tropical blackwater tributary of the Orinoco River in Venezuela, where allochthonous inputs dominate. The entire Sagavanirktok River basin is located north of the tree line on the North Slope of Alaska a mixture of allochthonous and autochthonous inputs was expected for the various rivers and lakes in this basin. Lastly, Hidden Lake Creek, which is the outlet of Hidden Lake on the Kenai Peninsula of Alaska, was sampled to determine if nutrient inputs from decaying salmon were contributing to primary production and autochthonous inputs to DOM. 

Kobayashi and coworkers (Sloan et al., 1976 Song and Kobayashi, 1982, 1984) and workers in the CSM laboratory (Sloan et al., 1986, 1987) have measured concentrations of water in hydrate-forming fluid phases in equilibrium with hydrates (when there is no free-water phase present) for application in single phase pipelines in cold regions, such as the North Slope or subsea. The trend in deepwater pipelines appears to be toward multiphase transmission (Shoup and Shoham, 1990) and their inhibition. 

Because free gas (or gas-saturated water) is less dense than either water or sediments, it will percolate upward into the region of hydrate stability. Kvenvolden suggested that a minimum residual methane concentration of 10 mL/L of wet sediment was necessary for hydrate formation. The upward gas motion may be sealed by a relatively impermeable layer of sediment, such as an upper dolomite layer (Finley and Krason, 1986a) or the upper siltstone sequence, as in the North Slope of Alaska (Collett et al., 1988). Alternatively, permafrost or hydrate itself may act as an upper gas seal. These seals can also provide traps for free gas that has exsolved from solution, and the seals can subsequently act to provide sites for hydrate formation from the free gas. 

Collett, T.S., Bird, K.J., Kvenvolden, K.A., Magoon, L.B., Geologic Interrelations Relative to Gas Hydrates Within the North Slope of Alaska, Final Report DE-AI21-83MC20422, U.S. Department of Energy, (1988). 

Collett, T.S., Ehlig-Economides, C., Detection and Evaluation of the In-Situ Natural Gas Hydrates in the North Slope Region, Alaska, SPE 11673, in Proc. 1983 SPE California Regional Meeting, March 23-25 (1983). 

Crude oil origin. . . Residuum type. Arabian light Atmospheric Safaniya Atmospheric Louisiana Vacuum Saudi Arabia Vacuum Alsaka (North Slope) Atmospheric Vacuum Boscan... 

Arabian heavy >760°F Arabian heavy >850°F Maya >650°F Alaska north slope >1000°F... 

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