Schlumberger

Performance Report: DEEPCLEAN Delivers New Solution for Displacements in Malaysia

Challenge: The operator completed drilling a gas producer and required a displacement program to remove contaminated seawater left behind after the liner lap negative test. Due to problems encountered while cementing the 4 ½-in liner, the operator had decided earlier to displace synthetic-based drilling fluid with seawater, without using any chemical spacers. As a result the wellbore was left with highly contaminated seawater and emulsion.

Solution: M-I SWACO was requested to design a displacement to remove the contaminated seawater and clean the casing. Lab testing revealed the DEEPCLEAN single-stage spacer at concentrations of 5 and 15% was the most viable option. The Virtual Completion Fluids (VCF) displacement simulation software was used to design the displacement.

Result: All pills were pumped at the VCF- recommended pump rate of 1,000 gpm (24 bpm). Spacer returns reached surface within 48 min of starting the pumps, which is right at one full circulation for 1522 bbl. In addition, shortly after 141% of the well volume had been displaced, the well returns were within specification with NTU’s of 50.9 and a solids content of 0.1%. All interfaces were kept to less than 15% of the spacer volume.

The seawater was tested against the M-I SWACO line of displacement chemicals to determine the most effective candidate. The company’s X-clean test method, which contains a 14-point data matrix that takes in to account; chemical concentration, annular velocities, contact time and pill contamination, was used for the evaluation. The Virtual Completion Fluids (VCF) displacement simulation software was used to design the displacement by determining the bottom hole and stand pipe pressures, the cleaning efficiency, ECD, interface volumes and the pump rate expected during the clean-up.

During planning, the VCF simulation indicated a successful displacement could be achieved using the following pills:

  • 100 bbl 1.4 s.g. (11.8 lb/gal) hi-vis transition spacer 5% v/v DEEPCLEAN
  • 325 bbl 1.0 s.g. (8.6 lb/gal) wash spacer 15% v/v DEEPCLEAN
  • 75 bbl 1.0 (8.6 lb/gal) tail spacer 5% v/v DEEPCLEAN

That displacement formulation was pumped through the work string, which contained a 9 ⅝ in. RAZORBACK scraper with an integral landing sub.

The displacement of the contaminated seawater began with the work string at total. The interface volumes for each pill were also recorded and consisted of:

  • 11.8 lb/gal hi-vis transition spacer – 12 bbl interface
  • 15% DEEPCLEAN wash spacer – 48 bbl interface
  • Hi-vis tail spacer – 12 bbl interface

Download: DEEPCLEAN Delivers New Solution for Displacements in Malaysia (0.26 MB PDF)

Related services and products

 
Contact Us