ABSTRACT
This paper outlines how a drilling team is meeting the challenge of drilling deep horizontal drain sections in a tight sandstone reservoir. It is intended to show how the application of existing technologies and processes is leading to performance gains and improvements in wellbore quality.
The full field development plan for the Khazzan project in Sultanate of Oman is based on drilling around 300 wells targeting gas producing horizons at measured depths of around 6,000m MD with 1000m horizontal sections. Target reservoirs are the Barik and Amin sandstones. The first attempt to drill these wells had to overcome many drilling challenges before finally achieving the well objectives. These challenges include wellbore instability and drilling dysfunctions, and it was clear that a more efficient solution was required.
The hard abrasive sandstone is considered towards the upper boundary of the industry operating window for Polycrystalline Diamond Compact (PDC) drill bits. A strategy had to be developed to maximize bit performance and penetration rates. Bottom Hole Assembly (BHA) design and drilling tool selections were adapted to improve performance, which included the use of high performance motors and rotary steerable systems. The drilling fluid design was optimized to improve the wellbore stability and quality.
Torque and drag had to be carefully managed in order to deliver the deep kick off well profile. The rig team implemented procedures for monitoring hole conditions and this enabled them to take remedial action before any major drilling challenges developed. A web based real time data transfer system was put in place for the second well, which, in conjunction with a wider range of downhole sensors, allowed the drilling team to engage with global support functions and identify where performance improvements could be applied.
This paper will present how BP addressed a variety of drilling challenges for subsequent wells. The on-going improvement in performance will be presented and areas for future focus will be discussed.
