الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Directional wells present a number of drilling problems as well as those experienced in vertical wells. These additional problems are connected to factors such as the well profile and the minimized axial component of gravity acting along the borehole. As the angle of inclination increases, drilling problems become more strict, also abnormal pore pressure will develop unplanned event which will increase time and cost of the well. Poor hole cleaning will develop a lot of problems such as mechanical sticking so we need to select the correct hydraulic model in order to avoid all this problem during drilling.The most important factor in drilling operation is optimum drilling program. For years it has been recognized that rate of penetration (ROP) might be boosted by drilling with water by rotating the bit quicker, enlarging flow speed through jets within the bit. Lack of enough mechanical and hydraulic horsepower (Challamel, 2000). The problem is the high cost due to unexpected events which lead to NPT (non-productive time). The cost of nonproductive time in the approximated budget for 2006 is 13% of the cost of a well (Fig.