引用楼主zxflin于2009-03-28 18:51发表的 请问有水合物形成条件的资料吗 :
请问有水合物形成条件的资料吗？谢谢
本人曾经参与国外某气田采气工程方案研究，其中涉及到天然气水合物形成的问题及防治，现摘录于下，供您参考。5.5 Prevention and treatment of gas hydrate
5.5.1 Hazards of gas hydrate
An inherent problem with natural gas production or transmission is formation of gas hydrate. Gas hydrate forms when water molecules crystallize around natural gas guest molecules. The co-crystallization process has been recognized for many years. Gas hydrate is the crystalline compound that occurs when water forms a cage-like structure around smaller hydrocarbon molecules. It is well characterized that it just occurs at a certain combination of temperatures and pressures. Gas hydrate may form anywhere water coexists with natural gas at temperature of 260C. Long gas transmission lines are particularly vulnerable to hydrate blockage during lasting cold weather in winter. During production, if the hydrate forms in annulus or in a pipeline on the ground it will affect normal production, once gas hydrate forms, it can plug up the wellbore and cease gas production, and make the surface equipment frozen and broken.
5.5.2 Prediction of gas hydrate
During Du-103 completion and test production, gas was sampled on regular requirement in order to determine its physical and chemical properties. The analyses showed that methane content is 97.405%, ethane 2.370%. Gas specific gravity is 0.5682. More details were listed in Table 5-12, Table 5-13, and Table 5-14.
According to the analysis on gas composition, the produced gas is composed of methane, ethane and CO2. The compositions are easy to form hydrate. The hydrate formation is predicted by means of thermodynamics model (see Fig. 5-20). With pressure increasing, the temperature of forming hydrate also increases. When the wellhead pressure is 4MPa, the gas produced from well Du 103 will form hydrate at the temperature of 14℃. The ambient temperature is about 0℃ in cold weather, far below 14℃, hydrate will occur on the ground-gathering pipeline.
In the East reservoir, the bottom-hole flowing pressure is 36 MPa at the rate of 200 Mm3/d, and the temperature after choke is about 27℃, but the bottom-hole temperature is about 75℃, so hydrate will not form at the bottom; the wellhead pressure is 26 MPa, the temperature to form hydrate is about 25℃, (see Fig.5-21). So it is very easy to form hydrate on the surface.
5.5.3 Control and removal of gas hydrate
There are a few methods of preventing hydrate formation in the following:
Injecting Hydrate inhibitors
In the oil and gas industry, ethylene glycol is often used to inhibit gas hydrate formation during production. One economic solution to prevent hydrate formation is to inject a large quantity of ethylene glycol.
Gas heating
This is an obvious thermodynamic solution such as heating, to increase temperature of the produced gas and keep its temperature above the critical temperature of hydrate formation.
Kinetic inhibitors
They are usually water-soluble polymers and effective at concentrations typically ten to one hundred times less than ethylene glycol or methanol concentrations to delay the formation of hydrates.
For convenience of easy operation,and economy, it is recommended to inject hydrate inhibitors as a measure to prevent hydrate formation in the Duvanny.
Table5-12 Duv-103 gas composition
Table5-13 Duv-103 gas property
Table5-14 Liquid content in the West reservoir
Table 5-15 Temperature at the wellhead in the East reservoir
Fig.5-20 Du-103 gas hydrate prediction
Fig.5-21 Hydrate prediction for the East Duvanny
