Cause analysis of lost circulation and plugging method in Paleogene of Kuqa Piedmont structure

Geology of piedmont structure is extremely complicated in kuqa depression. During the drilling, lost circulation in various degrees often occurs in Paleogene formation. Therefore to find a suitable method for plugging the leakage caused by different reasons is essential for the solution of lost circulation. In this paper we first made a statistical analysis of absorption wells in Paleogene about working condition, lithology and leakage path. And it is revealed that the main reasons leading to permeable and fissured loss in Paleogene are seriously broken stratum and over high drilling fluid density. The plugging methods for the stratum are selected in accordance with various causes, and the advantages and disadvantages of different plugging methods are analyzed as well. Application of the optimized method has obtained good result, laying a reference for lost circulation control in Kuqa Piedmont structural belt.