عنوان مقاله [English]
نویسندگان [English]چکیده [English]
The drilling fluid weight is determined according to the pressure and depth of drilling end stage fractures. The control of underground pressure of drilling fluid, as well as, transferring the solids and Cuttings of oil and gas wells are governed by drilling fluid weight. The drilling fluid weight causes to produce a pressure Equal to that of the formation and preventing the overflow of well and loss of drilling fluid. The accumulation of drilling solids and Cuttings in the fluid increase its weight resulting in slower drilling rate and decreasing the drilling bit life and undesirable fluid properties yielding mechanical and operational problems and hence more money and time consuming well driving process, while proper drilling fluid weight adjustment eliminate these problems. The combined physical and mass transfer methods results in better drilling fluid weight adjustment. In the present study the separation and improvement of drilling fluid weight in a 12 1/4" hole of a gas well in three stages was studied. First and second stage is related to change in mechanical separation and third step has been to using separators of mass transfer. In this formation, with enhancement of the fluid weight, the change in the screen (First stage) of the fluid weight at upper dolomite layer has been reduced and is kept at an optimal level. With the further enhancement of the fluid weight in the cherty zone layer, the change in screen rubber protector (second stage) caused the weight loss in this layer. Finally, the weight of the fluid is kept by centrifuge (third stage) in the mand member on 9.4 PPG proportional to the formation pressure. By continue drilling to neyriz and dashtak formations and require to higher drilling fluid weight (up to 11.5 PPG), adding weighting material is recommended.