Abstract

The Operator is developing a large onshore field in the Sultanate of Oman. Its full field development requires the construction of over 300 wells. Critical to the success of the project is the sustained reduction in drilling time per well. This paper outlines the strategy and performance improvements achieved through the 12-1/4" intermediate hole section in the pursuit of this goal.

The vertical 12-1/4″ section measures 2,650 m and consists primarily of hard carbonate sequences. There is a 350 m clastic base, of which the final 170m comprises very hard and abrasive sandstone. Multiple bit runs with sub-optimal ROP characterize drilling performance through this section. The ideal section TD is 20 m below the hard basal section.

Several drilling optimization initiatives were developed into a Continuous Improvement strategy to address performance opportunities. Work streams included, offset well analysis, KPI delineation, standardized drilling practices and procedures, BHA and drill bit design, parameter optimization, real-time monitoring, and rig site bit run supervision. The removal of unnecessary downhole tools and the transition from matrix to steel body PDC bits has also helped reduce costs. The Operator fostered collaborative working relationships with its bit vendors to develop applicable bit technology whilst encouraging competition to drive incremental performance.

A novel initiative specifically developed for this application has been real-time monitoring using an ROP console. The advisor console is located both in the office and on the drill floor. The key functionalities of the system include, engineered optimum parameter fairways, real-time performance benchmarking, look-ahead lithology/rock strength/stringer identification, drilling related risk alerts, and current/upcoming formation information. The system is tailored to each rig type, BHA and bit type, and ensures latest performance expectations and parameter advice can be disseminated across rig lines.

The strategy has meant the section can now be drilled twice as fast, using half the number of bits. Section Total Depth (TD) is also frequently reached to the optimized depth (in one bit run) enabling continued optimization for the start of the next section (8-3/8").

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