DRILLING TECHNOLOGY IN THE ORDOVICIAN SYSTEM OF NORTH TARIM, DRILLING WHILE LOST CIRCULATION

wells drilled in the Ordovician Carbonate formations in Tahe Oilfield of North Tarim are commonly deeper than 5500 meters, and caves and fractures are well developed.It is easy to cause severe lost circulation when drilling in this area, and sometimes as worse as no return drilling fluid can be found, or well kick and lost circulation take place at the same time, it is very difficult to achieve a balanced drilling.With the help of surface equipment (such as rotary BOP) to control the wellhead back-pressure, and by applying modified reverse killing technology, drilling can be continued while lost circulation or blowout, thus effectively minimizes formation damage.The engineering design, operation requirements and field operations of this technology are focused on in this paper.As a non-conventional drilling technology, this technology has been widely used in well drilling for improving oil recovery, minimizing formation damage and eliminating drilling troubles.