Managing lost circulation during drilling is a great challenge issue in naturally fractured or vugy formations.This situation becomes further complicated if there are gas or oil returns at the same formation or at a formation above it.The lost circulation problem happens in some of the northern Iraqi oil fields such as Khabaz oil field.Particulate lost circulation materials(LCM)have been used for many years to control lost circulation.However,these traditional LCMs are not efficiently applicable to cure sever to total losses,such as highly fractured formations and formation with large vugs.In this work,an experimental attempt was done to solve such problem in Khabaz oil field.The experiments were carried out using a closed loop circulation system that simulates the drilling fluid loss into formations.Five core plugs from Azkand formation of Khabaz oil field from different depths were used.The experiments were grouped into three,the first was done with the fresh-water-based drilling fluid to measure the severity of losses.The second,fresh-water-based drilling fluid was treated with traditional LCM(cotton seeds)to investigate how the severity of losses is affected by these materials.Adding polymer lost circulation material were the last sets to modify the drilling fluid rheological properties which prepare a medium within the lost circulation zone that increases the friction inside the losses paths to increase the LCMs(the polymer itself)sealing efficiency.
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