Field test of special rotary control head in CBM well under-balanced drilling in Well ZHP4

In order to prefect domestic corollary equipment of under-balanced drilling in CBM development, reduce drilling cycle and the transportation cost, we designed and manufactured a special rotary control head with low pressure and fine type for CBM reservoir drilling and conducted the field test in well ZHP4H Block Zhengzhuang Qinshui basin. Matching performance of rotary control head and under-balanced drilling technology has been examined. The rotary control head’s overall performance has been tested in field test to prove the rationality of its structural design. This device can seal the pressure of annular space effectively at the wellhead. Bearing group, dynamic seal elements, and lubrication and cooling system were still in perfect performance after 479 hours continuous operation which provide guarantees for implementing under-balanced drilling safely and lead the drilling fluid into the mud tanks smoothly. The theoretical and field experiment results show that the structural design of rotary head is reasonable, and the cooling and lubricating system could protect the dynamic seal elements and bearing group effectively. Meanwhile, the life of rubber core can satisfy the needs of field operation, so the rotary control head worth popularizing in the future.