| Popis: |
Cutting transportation is one of the most crucial drilling problems during penetrating shale formations juxtapose well stability events. It is equally important the drilling team should consider real time monitoring to the flow rate based on hole problem in the shale formation being drilled. Several authors have conducted extensive analysis to optimize the optimum flow rate in real time bases but the problem has not been fully understood especially when it comes for hole enlargement. Due to its simplicity, drilling engineers usually use deterministic method to control cutting transportation. The method adjusts drilling parameters such as pump flow rate (FR), plastic viscosity (PV), yield point (YP), Rate of penetration (ROP), revolution per minute (RPM), and mud weight (MW). The past practices of this method did not show significant improvements in well stability's events. This paper will introduce a numerical model to quantify the most sensitive hole cleaning parameters. For that purpose, the research will examine the real time modification of the drilling parameters based on rock fragments for sufficient hole cleaning. A tornado chart has been constructed based on hole enlargement considering hole cleaning, mud weight, elastic viscosity, yield point, ROP, RPM, and well angle. A Monte Carlo simulator has been utilized to reduce the uncertainty in hole enlargement during calculating the optimum parameters. 1000 trials have been fitted to the model based on the range of 0.5 to three times of hole enlargement. This method can articulate a huge impact on selecting drilling parameter based on the probabilistic evaluation. Drilling data from sixty wells in Southern Iraq have been investigated and they revealed a significant augment in none productive time because of the inappropriate selection of drilling parameters deteriorates well stability. This paper develops an engineering method to ensure sufficient lifting capacity to the rock cuttings while drilling an instable formations and it offer acceptable range of flow rate, yield point and elastic viscosity based on the severity of wellbore instability. The traditional wellbore stability is not panacea to wellbore problems without considering wellbore condition. Thus, a combination of all the interstice and extrinsic factors can be crucial in order to drill a well safely and cost effectively. |
