Continuous core acquisition across formations of interest to perform quantitative and qualitative analysis is extremely important for exploration geologists and reservoir engineers. Measurements performed on cores are typically calibrated against well logging data for accurate and better reservoir interpretations. However, the coring cost is directly proportional to coring technique, core length and a significant part of coring cost is associated with rig time. In deep formations, the coring cost becomes extensively high due to multiple trip times required after each conventional coring run (90 ft). The best way to minimize the coring cost is to reduce the rig time efficiently achieved by reducing the number of trips required to acquire core.

Abu Dhabi Oil Company for Offshore Oil Operations (ADCO) has recently investigated different coring scenarios and technologies to optimize the coring operation time. An innovative and cost effective solution was developed and applied as a result of this investigation by Extended Coring (Long Barrel) which meets ADCO's objective of continuous coring across formations of interest. This procedure reduced number of trips, rig time and eventually drilling cost. The extended coring (Long Barrel) can be run in lengths from 120 ft to 810 ft with proper timing and planning for the jobs.

This paper describes ADCO's new strategy of extended coring (long barrel) acquisition based on formation's geological description. The case histories of extended coring in different formations in 8 ½" and 6" hole size sections, the core handling procedures applied and lessons learned in a continuous iterative process to optimize drilling cost in future operations are presented and analyzed.

You can access this article if you purchase or spend a download.