Gas Hydrate Control

Gas hydrates were first reported at the beginning of the 19th century, and until the 1930s they remained a scientific curiosity. At that time it was realized that hydrates were more likely to be the causative agent in blocking pipelines than ice. Today, gas hydrate control continues to be a problem in the oil and gas industry. In the 1960 s it was realized that natural gas hydrates are present in the geo-sphere with worldwide reserves estimated at 10,000 to 40,000 trillion cubic meters (TCM). Considerable efforts are underway to refine global estimates and to develop technology and exploit this resource. On the other hand these hydrates may... 

A GAS HYDRATE, also known as a gas clathrate, is a gas-bearing, icelike material. It occurs in abundance in marine sediments and stores immense amounts of methane, with major implications for future energy resources and global climate change. Furthermore, gas hydrate controls some of the physical properties of sedimentary deposits and thereby influences seafloor stability. 

In 1934, Hammerschmidt showed that gas hydrates are implicated in a natural gas pipeline blockage and since then hydrate control has been a major activity in the gas and oil industry with a substantial associated cost factor. The recent (2010) Deep Star Horizon oil well problems in the Gulf of Mexico again brought to the fore that gas hydrates often show up where they are not wanted. Gas hydrate control comes under the discipline of flow assurance in petroleum and chemical engineering. A comprehensive text in this area is the book by Sloan and Koh. ... 

Townsend. F. M., 1953, Vapor Liquid Equilibrium Data for Diethylene Glycol Water and Triethylene Glycol Water in Natural Gas Systems. Proc. Gas Hydrate Control Conf., University of Oklahoma. Norman, OK, May 5-6. 

From the condition 21a it immediately follows that if the clathrate is formed in the presence of a number of compounds which are potential solutes, i.e., sufficiently small to have 0 for some i, all these compounds contribute to its stability. As has already been pointed out by Barrer and Stuart4 this at once explains the stabilizing influence of "Hilfsgase" such as air, C02, or H2S on the formation of gas hydrates discussed by Villard49 and von Stackelberg and Meinhold.47 If there is only one solute, Eq. 21a with the = sign determines the minimum vapor pressure fiA necessary to make the clathrate stable relative to Qa. Since all cavities contribute to the stabilization, one cannot say that this minimum pressure is controlled by a specific type of cavity. 

Majorowicz, J.A. Osadetz, K.G. 2001. Basic geological and geophysical controls bearing on gas hydrate distribution and volume in Canada. American Association of Petroleum Geologists Bulletin, 85, 1211-1230. 

Bucklin, R.W., Toy, K.G, Won, K.W., Hydrate Control of Natural Gas Under Arctic Conditions Using TEG in Proc. Gas Conditioning Conference, Norman, OK, (1985). 

There are four requirements for generation of natural gas hydrates (1) low temperature, (2) high pressure, (3) the availability of methane or other small nonpolar molecules, and (4) the availability of water. Without any one of these four criteria, hydrates will not be stable. As indicated in both the previous section and in Section 7.4.3, the third criteria for hydrate stability—namely methane availability—is the most critical issue controlling the occurrence of natural gas hydrates. Water is ubiquitous in nature so it seldom limits hydrate formation. However, the first two criteria are considered here as an initial means of determining the extent of a hydrated reservoir. 

Brewer P. G., Orr F. M., Jr., Friederich G., Kvenvolden K. A., and Orange D. L. (1998) Gas hydrate formation in the deep sea in situ experiments with controlled release of methane, natural gas, and carbon dioxide. Energy and Fuels 12, 183-188. 

Gas hydrate should be considered as a material which directly impacts our planet s population, in many ways as yet to an unknown extent. Although hydrates and their structures have been studied for many years, the understanding of hydrate formation processes is still in its infancy but is of critical importance today for a variety of reasons understanding the nature of natural gas hydrate deposits and how they accumulate", the prevention and control of pipeline hydrates, and the development of hydrate-based processes such as gas storage. ... 

A common feature associated with cold seeps is the presence of gas hydrates, which are naturally occurring solids comprised essentially of natural gas, mainly methane, trapped in frozen, crystalline water (see reviews by Kvenvolden, 1993 and Buffet, 2000). The occurrence of gas hydrates is controlled by an interrelation among temperature, pressure and composition, and they are stable in solid form only in a narrow range of these conditions (Kvenvolden, 1993). Because of these restrictions, gas hydrates are common mainly in polar and deep... 

The presence of gas hydrates is controlled by several factors, among which, temperature, pressure, ionic strength of the water and gas composition and abundance are key parameters (Sloan 1998). The pressure/temperature conditions required for pure methane hydrate stability are illustrated inFig. 14.3. In this case, methane hydrate is stable at temperatures... 

The amount of biogenic methane is essentially controlled by both the availability and reactivity of organic matter in the upper hundreds of meters of the sedimentary sequence. Davie and Buffett (2001, 2003) demonstrated the critical need for quantitative models of biogenic methane production to describe the distribution of gas hydrate in the top few hundred meters of sediment. Key parameters are rates of sedimentation, quality and quantity of the organic matter and biological activity rates. They show that hydrate accumulation from in situ production in sediment with a TOC of 1.5%, will be less than 7% of the pore volume... 

The presence of negative spikes in the chloride distribution suggests that the distribution of gas hydrate in marine sediments is highly heterogeneous. Whereas some observations reveal association of hydrate with coarse, high porosity horizons (Clennell et al. 1999), the factors controlling distribution of gas hydrate are not fully understood. Nevertheless, the question remains as to whether the patchy distribution of these deposits can be adequately mapped with pore water analyses. Limitations on how much pore water can be extracted from a section of the core, how many core sections can be dedicated to these analyses, and the time needed for each measurement, usually only allow for sparse measurements of the pore water composition. 

Optimum parameters for a successful accomplishment of the EOR process are defined in [239]. First, they can be realized in reservoirs consisting of sandstones, sands, carbonates or mixtures of these materials with a layer thickness of under 25 m and permeability of over 20 mD, containing crude oil with a viscosity of <60 mPa s. In this case, a formulation containing, along with alkali, 20 - 30 g/1 salts, ethoxysulphates and alkyl sulfonates, used for injection at a temperature below 80 °C. The authors are optimistic about the wide commercial use of EOR, since oil will remain the main energy source up to the second half of the 21 century. Surfactants can also be used to recover oil containing gas for the purpose of gas hydrate formation control [240]. 

The test equipment of crystal type of gas hydrates consists of a laser Raman spectrometer, gas supply system, jacketed cooling type high-pressure visual cell, temperature control system, data acquisition and other parts. The experiment using a laser Raman spectrometer for the JY Co. in French produced Lab RAM HR-800 type visible confocal Raman microscope spectrometer. Laboratory independently designed a cooled jacket visible in situ high-pressure reactor, reactor with sapphire window to ensure full transparency of laser, and high pressure performance, visual reactor effective volume 3 ml, compression 20 MPa effective volume, to achieve characteristics of gas hydrate non-destructive and accurate measurement. The schematic representation of equipment is shown in Eigure 1. 

Triaxial compression test of SI hydrate bearing coal used gas 1, and the one of SII used gas 2. We adopt heating and cooling of repeated during the course of the experiment, to make distribute hydrate in coal uniformly. We adopt gas consumption calculating and resistance measuring method to controlling gas hydrate saturation at about 70%. 

Qiang Wu, Chenglin Li Chuanli Jiang 2005. Discussion on the control factors of forming gas hydrate. Journal of China Coal Society, 30(3) 283 87. 

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