The Impact of Drilling Operation Parameters on the Lost Circulation Problems for Oil and Gas Wells Based on Field Data

Lost circulation, the loss of drilling fluid into holes or fractures throughout the geological formations being drilled, is the most expensive problem encountered in drilling operations for oil and gas wells. It is known that when there is a loss of circulation during the drilling process, the operation activities are delayed or stopped for curing or treatment, resulting in extra time known as non-productive time (NPT). The NPT issues during the drilling operations are the most important priorities for planning any drilling program. Therefore, the lost circulation is one of the main problems which can control the NPT. To mitigate the lost circulation problems, an integrated investigation is necessarily needed for the main parameters which enhance/downgrade the rate of lost circulation.
Drilling through the Dammam and Hartha formation is typically accompanied with substantial nonproductive time due to severe and often entire drilling fluid losses. The majority of the curing this problem require time for preparation, placement or setting. In this research, a field study was carried out to investigate the effect of 6 drilling parameters on the rate of the lost circulation. The investigated parameters are the rate of penetration, weight on bit, stand pipe pressure, mud weight, flow rate, and the equivalent circulation density. Furthermore, the effect of lithology type on the lost circulation rate was clearly determined and correlated. In addition, a graphical representation of bit depth vs the real drilling time/date was constructed to compare the lossy wells vs non-lossy wells named frithogram. This study was based on field data for 350 wells drilled in Rumaila Oilfield, southern Iraq. The results of this study showed that if these six operating parameters are standard and controlled, the significance of lost circulation problems could be reduced. However, the main factors which are responsible for the lost circulation problems are lithology types, facies and/or diagenesis process, which mainly distinguish the carbonate formations.