Analysis of Transmission Mud Losses and Coherence in North Rumaila Oilfield, Southern Iraq, Mishrif Formation as a Case Study

Abstract

One of the biggest oilfields in the world is the Rumaila field in southern Iraq. Drilling through the Mishrif Formation puts wells drilled in this field at risk of lost circulation issues. Lost circulation occurrences are a major problem in field development and can range from seepage losses to the total loss of the borehole. Drilling mud losses have been reported in seven wells; however, this issue affects numerous wells. In order to ascertain the most effective cures for each sort of loss, the lost circulation method to the Mishrif Formation has been presented based on 3D geological models (3D seismic section) and frithogram analysis. The results of the coherency data showed that the coherent zones are located in the western and southwestern regions of the Rumaila oilfield, while these zones diminish as one moves towards the east and southeast. Oil wells that were coded as A to G are situated within the incohesive zones, whereas the other wells are located at cohesive zones. Firhograms can be plotted alongside other real-time drilling data to analyze how conditions evolved over time. These graphs illustrate the events leading up to mud losses, providing valuable insights into the underlying causes. After a careful study of seven wells that had a mud loss and comparing them with one of the wells that had no loss, the results showed that the mud losses were primarily due to the nature of the lithology; microfacies study of the affected depths revealed that the losses were also associated with extensive dissolution processes. Large channels and significant porosity were observed at these depths, further contributing to the losses.