Drilling a slim lateral in chalk

Drilling of slim diameter laterals in the Southern North Sea carbonates can be troublesome due to friction. In this case a new lateral was drilled in an old field using AST technology.

Objectives

In the process of improving drilling efficiency in the Murdoch field, ConocoPhillips and Sperry Drilling Services decided to add Anti Stick-slip Tool (AST) technology to the rotary steerable system for the 6” horizontal section.

Results

Drilling commenced with fast penetration 30-60% over reference values from the start of the section. Torsional oscillations from pipe friction however placed limitations on the drilling parameters and the operator consequently decided to change the mud to improve the situation. Now the 4 ¾” XD-AST tool could be exploited to its full capacity and the well was drilled to TD with steady penetration > 100% faster than reference values with no vibrations.

Value

Improvement in penetration for the section amounted to 2 days at USD 0.5 million daily or USD 1 million for the job.