CHALLENGE

Drilling and setting casing in two big hole sections at an inclination of 55° in an ultra-deepwater “S” well with poor hole cleaning parameters due to rig limitations.

SOLUTION

K&M carried a quick review of two similar offset wells and documented a hole cleaning strategy considering the rig limitations. The strategy including:

• Drilling and tripping/backreaming parameters for each section
• Specific hole cleaning monitoringactions and responsibilities
• Connections and cleanup cycleconsiderations to not affect directional control

K&M Wellsite Advisors supported hole cleaning monitoring, adjusting the drilling and tripping practices and parameters based on real time observations.

RESULTS

Despite the rig was not able to deliver the required parameters for a good hole cleaning, no problems were observed drilling or tripping, and the liner runs were successful without difficulties to reach the target setting depths.

Critical Casing Runs In High Angle, Big Holes In Ultra-Deepwater Wells

The Client planned to drill an ultra-deepwater “S” well. The intermediate tangent reached an inclination of ~55° and was drilled in two sections in 18⅛”x21” and 16½”x19” boreholes. A 18” and a 14” Liner were run in each of the sections. The Client had recently drilled two other similar wells with the perception that no hole cleaning problems occurred.

Given that a larger liner size was going to be used in the new well (18” vs 16” in the previous wells) and the criticality of setting the 18” liner on bottom, The Client contacted K&M to review both high angle sections, assess the hole cleaning risk, and make recommendations to drill the hole sections successfully and get the critical casing strings to the prognosed depths.

The High-Dogleg Trajectory Is The Clear Winner

K&M reviewed the two offset wells with similar trajectory to understand the previous experiences and their applicability to the new well. Both wells drilled with sub-optimal hole cleaning parameters due to rig limitations, especially in the flow rate. Despite the perception of having drilled without problems, the analysis showed that:

• High ECD, tight hole and overpulls events, typical of a poor hole cleaning environment occurred in one of the wells. 
• The 16” casing in the second well had to be set 300’ above the planned depth due to an obstruction likely caused by cuttings beds.

Given the experience observed in the offset wells, it was determined that even if no problems may not be observed drilling and tripping, using the same practices as the offset wells, it was going to be very likely that the casings will not reach the planned setting depth, especially in the 18” section where the annular clearance will be narrower and Autofill systems are planned to be used.

A hole cleaning strategy for drilling and tripping in the new well was elaborated, considering the rig limitations. Specific actions were recommended to address the related risks focused in:

• Drilling and tripping/backreaming parameters for each section
• Specific hole cleaning monitoring actions and responsibilities
• Connections and cleanup cycle considerations to not affect directional control

The High-Dogleg Trajectory is the Clear Winner