M Mostofi - M.Sc. Student in P.U.T
M Salehi - Kasayi, NISOC

Deviated and horizontal wells have great application in petroleum industry all over the world. Therefore cementing of these wells has great importance in field operations. Cementing of prospective wells has some additional criteria that vertical wells are not encountered with them. It is essential to consider these criteria to have good cement operation in deviated and horizontal wells .These criteria are discussed and some remedies are proposed to control or prevent them.Criteria for this purpose are classified in two categories. On one hand cement slurry design must be in a form that prevents some problems that would be involved in deviated and horizontal wells such as cement sheath deposition in side the casings or liners and free water generation which is one of slurry properties. Free water generation of cement could be stand for vertical wells but it is highly harmful in deviated and horizontal wells. Some harmful characteristics of cement slurry for prospective wells are determined and it is estimated that how they could be controlled. On the other hand, drilling fluid and spacer which are used before and while cementing operation must have some characteristics to prevent problem called mud channels. These depositions gathered at the lower side of casing or liner and produce a low strength zone after the end of cementing. Therefore, it is discussed how to control and avoid formation of mud channels in prospective wells.