OMV-Benchmark for 8-1/2' Hole Section with One Bit in Sawan Field of Pakistan

摘要

OMV Pakistan applied an original design of Genesis XT fixed cutter bit with improved features for bit stability to drill the 8.5" section of Sawan-11 development gas well in southern Pakistan. Multiple vertical wells were drilled in this field with similar parameters and operating conditions. Latest proven technology was applied successfully to drill the 1760m of 8.5" section with record ROP of 25 m/hr which is more than twice as fast compared to previous wells records. Instantaneous rates in excess of 70 m/hr were also recorded while drilling this section. This section was previously drilled with multiple bit runs using multiple roller cone and PDC bits. Later, this was reduced to 2-3 PDC bits and now the complete section has been drilled with one PDC bit (HC 606Z). Dull grading comparison with bits used in the offset wells will also be discussed. The lithology of the drilled section consists of Ranikot formation (dominating claystone with inter bedded sandstone and siltstone). Throughout this zone bit stability and optimized drilling parameters of the bit were key factors affecting its performance. Below this zone Upper Goru (UG) and Lower Goru (LG) formations are found. UG Member mainly consists of marl with streaks of limestone having an UCS of > 35 kpsi in its contact with the Ranikot formation. This type of formation is generally the most difficult to drill. LG Member comprises of claystone and siltstone with occasional traces of pyrite having UCS of 20-25 kpsi. Towards the end of section, last 400m witness increased percentage of abrasive siltstone which affects cutter's sharpness and reduces the ROP. Offset data conforms that around this point bits quit drilling. However, at Sawan-11 bit maintained its sharpness and good ROP till the end of this section.