PROCEDURE FOR DRILLING BOREHOLES INCLUDING HORIZONTAL ONES UNDER CONDITIONS OF LOST CIRCULATION HORIZONS Russian patent published in 2011 - IPC E21B21/00 C09K8/00 

FIELD: oil and gas production.

SUBSTANCE: borehole is drilled with bottomhole flushing including normal and abnormal with lost circulation horizons. Flushing is performed with drilling agent on water base wherein there is added gelling complex containing polymer and binding agent. Also, as a polymer, gelling complex contains guar gum, and, as a binding agent, it contains titanate. Normal horizons are drilled with a drilling agent wherein there is added a gelling complex at amount of 0.15-0.25 wt % at weight ratio of guar gum and titanate in it as 20÷50:1 correspondingly. Abnormal with lost circulation horizons are drilled with a drilling agent wherein there is added thesaid gelling complex at amount of over 0.25 wt % at weight ratio of guar gum and titanate in it as 7÷30:1 correspondingly.

EFFECT: raised efficiency of borehole drilling process under conditions of lost circulation horizons due to non-stop drilling under operative control over rheological characteristics of drill agent.

3 cl, 2 tbl