DrillScan France +33 4 82 90 01 50 // DrillScan Europe +33 5 59 98 75 90 // DrillScan US Inc. +1 281 679 6370
Case Study // Directional Drilling
Rotary Steerable System in Loose Sands Field Case
BHA directional responsiveness depending on hole overgauge
A 9 ½” point-the-bit RSS BHA was planned to build a full section showed an inability to build in loose sands.
The full activation of the RSS would not help resulting in the drain misplacement and a consequent decrease in the expected HC reserves access. As an important development was planned for the field with multiple similar wells, the Operator specially required DrillScan to run a BHA Directional Post-Analysis to understand the BHA directional counter-performance, and to provide recommendations for next wells.
The RSS BHA was used to drill both shaly and sandy formations. It was found that when going from the shales to the loose sands, the BHA would not produce the predicted build rate.
The Caliper log showed a significant hole overgauge and a post-analysis enabled the fitting of formation hardness. Our calculations clearly showed that the system was losing its steerability with hole overgauge.
Using measured hole overgauges and a fitting profile for the formation hardness, the BHA and bit designprocess showed that increasing the second stabilizers diameter and decreasing the bit steerability (optimizing the passive gauge length) had a major influence on the coupled Bit & RSS response.
Bit & BHA design managed to achieve the planned directional objectives.