Солнечная электростанция 30кВт - бизнес под ключ за 27000$

15.08.2018 Солнце в сеть




Производство оборудования и технологии
Рубрики

Cement

In a thermal well, casing must be bonded securely to provide sufficient strength to the pipe and to prevent it from buckling. Accordingly, casing cementing has at least two distinct parts: a lead section and a tail section.

The lead section extends from the casing shoe to the top of the producing for­mation and it is characterized by high-strength material that ultimately may be stressed to the limit of safety during thermal stimulation. Pozmix 80 cement with 20 — 40 % silica flour (by weight of cement) is commonly used up to a temperature of 600 °F. Above this temperature part of the silica flour is replaced by pozzolanic material (Rahman, 1990).

In the tail section, cement is subjected to a lower level of stress. Sometimes, as discussed earlier, it is designed to allow the pipe to slide up and down in response to temperature changes. Class G cement with 20 — 40% silica flour is commonly used to cement this section. The requirements for a cement section designed to allow movement of casing are extraordinary. The composition and physical properties of the cement must meet all the design criteria except that the shear bond strength must be as low as possible. To remedy this, casing is often coated with thermoplastic material that prevents the cement from establishing a bond with the casing. The plastic material is an asphaltic material with regulated properties. The softening point is 214°F (according to ASTM Cube Method) and the initial boiling point is 680 °F at atmospheric pressure. This material also helps: to seal the low-strength cement, to provide structural support and to serve as a lubricant above the melting point.

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