Permafrost well

Collett (1983) and Collett and Ehlig-Economides (1983) studied the logs of 125 wells in the Prudhoe Bay region, to find 102 hydrate occurrences in 32 wells. The analyses of other permafrost wells were based upon the logs of a known hydrate well, the Northwest Eileen State Well Number Two, in which ARCO/Exxon recovered hydrate cores in 1972. Other studies on the effects of hydrates in wells and logs in the permafrost are by Weaver and Stewart (1982), Collett et al. (1984), Kamath and Godbole (1987), Mathews (1986), Collett (1992), Prensky (1995), with the most recent review of hydrate well logs in by Anderson et al. (2005). 

For permafrost well compositions, the binder content in the slurry is as high as 72.5 wt%, and the rest is wollastonite and boric acid. The high binder content provides sufficient KH2PO4 solution, which lowers the freezing point of the slurry and allows the acid-base aqueous reaction to continue. With low binder content, the water in the slurry freezes before it reacts. At ambient temperamre, however, one may reduce the amount of binder and substitute it with suitable extenders. Wollastonite, because of its temperature of maximum solubility at 109 °F (43°C) is the preferred choice, but a combination of Class C and F ashes has also been used by researchers [9]. 

Majorowicz Osadetz (2001) reported that the Mallik gas hydrate-bearing deposit in permafrost regions tends to occur at depths of 700 m to 1400 m where the permafrost is 100 m to 900 m thick. The Mallik 2002 Gas Hydrate Production Research Well Program conducted scientifically constrained production tests of the natural gas from the Mallik gas hydrate deposit, which is situated in the Mackenzie Delta on the coast of the Beaufort Sea, Northwest Territories, Canada (Dallimore et al. 2005a Satoh et al. 2005). Gas hydrate production tests demonstrated the potential for possible commercial production. Japan intends to establish commercial production from gas hydrates within the time frame of conventional natural gas production from the Mackenzie Delta (Yonezawa 2003). 

The third period, from the mid-1960s until the present, began with the discovery that nature predated man s fabrication of hydrates by millions of years, in situ in both the deep oceans and permafrost regions as well as in extraterrestrial environments. 

Hydrate dissociation is of key importance in gas production from natural hydrate reservoirs and in pipeline plug remediation. Hydrate dissociation is an endothermic process in which heat must be supplied externally to break the hydrogen bonds between water molecules and the van der Waals interaction forces between the guest and water molecules of the hydrate lattice to decompose the hydrate to water and gas (e.g., the methane hydrate heat of dissociation is 500 J/gm-water). The different methods that can be used to dissociate a hydrate plug (in the pipeline) or hydrate core (in oceanic or permafrost deposits) are depressurization, thermal stimulation, thermodynamic inhibitor injection, or a combination of these methods. Thermal stimulation and depressurization have been well quantified using laboratory measurements and state-of-the-art models. Chapter 7 describes the application of hydrate dissociation to gas evolution from a hydrate reservoir, while Chapter 8 describes the industrial application of hydrate dissociation. Therefore in this section, discussion is limited to a brief review of the conceptual picture, correlations, and laboratory-scale phenomena of hydrate dissociation. 

Similarly, if channels are available, biogenic gas may migrate to regions within the hydrate stability envelope. Most of the gas was of biogenic origin in the hydrate core recovered from the Northwest Eileen State Well Number 2, one of the first wells to recover hydrates (Collett, 1983). The biogenic source is likely to predominate for hydrates in permafrost (Kvenvolden, Personal Communication,... 

Figure 7.14 Typical well log responses to hydrates in permafrost. (Reproduced from Collett, T.S., Detection and Evaluation of Natural Gas Hydrates from Well Longs, Prudhoe Bay, U. Alaska, Anchorage (1983). With permission.)...

The Mallik case study (Figures 7.36 and 7.37) provides the best example of well logs in a permafrost hydrate reservoir, followed closely by the Leg 204 (Figures 7.26 and 7.27) example for ocean hydrates. All four of the case studies for field hydrates have associated logs. 

The 2002 Mallik well provided an indisputable proof of the concept—namely, it is possible to in transient testing to recover energy from permafrost hydrates upon dissociation. 

Other permafrost-associated hydrate wells should be drilled in 2007-2008 to move beyond the proof of concept, to a proof of long-term... 

In the Mallik L-38 (ca. 69°27 latitude, 134°40 longitude) well drilled in 1972, Bily and Dick (1974) provided one of the first permafrost hydrate descriptions, from a MacKenzie Delta well site on Richard s Island bordering the Beaufort Sea in Canada. In 1998 the JAPEX/JNOC/GSC 2L-38 well at the same site found core and well-log evidence for hydrates from 900 to 1100 m with in situ porosities of 35% and hydrate concentrations often in excess of 80% of the pore volume. The documentation of the 2L-38 well is provided in a compilation of 31 technical papers in GSC Bulletin 544 (Dallimore et al., 1999). 

Estimates place the world reserves of natural gas hydrates as being in the region of 5 X 1013 m3 on land, mostly in the permafrost regions of Alaska and Siberia, as well as a further 5-25 X 1015 m3 of gas in the oceans, particularly around Central America. This figure is around twice that of the total fossil fuel reserve this is an enormous wealth of energy which will become increasingly important as fossil fuels run out. Indeed, in the Russian Federation the enormous gas hydrate deposit at Messoyakha has been used as a natural gas source since 1971. 

Because MgO has high solubility even at room temperature, Ceramicrete compositions are suitable for permafrost and shallow wells only. Boric acid is used to retard the reaction in these formulations. The amount of water used in these formulations is also higher than normally needed for the acid-base reaction. This excess water and a minimum amount of boric acid (0.125 wt% of the powder blend) are needed to reduce the initial Be (or reduce the yield stress and the initial viscosity) of the slurry. 

Adding cenospheres and Styrofoam up to 10wt%, its thermal conductivity can be lowered to half that of conventional cement. When Ceramicrete-based permafrost sealant was cured in a CO2 environment, it set well, and when stored in CO2 for a week, it did not show any deterioration. Sugama and CarcieUo [8] predict that these sealants are durable up to 20 years in a downhole environment, compared to conventional cements that last for only a year. Unlike conventional cements, because CBS are neutral in pH and are not affected by downhole hydrocarbon gases, they are ideal for use in the gas hydrate regions in arctic climates. 

Mammoth fossils are occasionally discovered in various parts of the world, from South Africa to Siberia. In America fossils of the mastodon, Mammut americanum, a relative of the mammoth, are also found. They died out about ten thousand years ago. Mastodon tusks have sometimes been carved, but the tusks most commonly used today come from the mammoth. Fair quantities are unearthed in Siberia, during the two months of the year when the permafrost softens sufficiently to permit digging. Finds are also made in Alaska. The carcasses are deep frozen, which means that the mammoth tusks are fresh and well preserved - not mineralised - though they are usually stained dark brown on the outside. Much of the material found is too degraded to use, and what is used can have a tendency to crack. For this reason the tusks are nowadays used for small carvings or in mounted slices as jewellery, with cracks disguised by ornamental filler. 

Lowlands. Sites in areas of discontinuous permafrost as well as other areas susceptible to permafrost melting should be part of the network. Static chamber flux measurements are legendary as labor-intensive, and they should be replaced where possible with automated chambers and supplemented with continuous eddy flux measurements (Hargreaves et al., 2001). Development of a held-portable, rapid-response CH4 sensor suitable for continuous eddy covariance measurements should be a high priority. 

The pollen of many plants can be classified by genus, and sometimes by species, on the basis of such characteristics as size, shape, and surface texture, hi contrast, most spores can only be classified by higher taxonomic levels, such as family or order. Both pollen and spores are well preserved in lake sediment, peat bog, and many archaeological sites. Fossil pollen has even been identified from the bodies of extinct animals, such as mammoths discovered frozen in arctic permafrost (permanently frozen subsoil). 

Exploratory drilling in tundra or permafrost areas requires greater care because of the much slower natural recovery capability [68]. Wildcat wells in these areas require more precautions for the handling of warm drilling mud, etc., to avoid terrain collapse from the introduction of a thaw-susceptible area into permafrost [69]. 

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