Remedial Well Treatment

BACKGROUND

A GoM operator witnessed uneconomical well performance due to significant, early production decline. However, there were substantial reserves remaining in place. Previously recovered downhole solids had been analyzed that showed a layered mixture of calcium carbonate scale and paraffinic wax.

The typical industry treatment design would be to include a solvent preflush, followed by various aqueous acid systems. This treatment design would simply remove one layer of wax and a layer of carbonate scale and bypass the remaining deposit mass. This usually results in minimal removal of the deposit and allowing the bulk of the treatment to spend on the nondamaged portion of the zone or the area of highest water saturation. Even more critical is that 50% to 80% of the deposits remain in place which normally results in increased water production and ultimately much less oil.

Solution

  • Deposits were recovered from below the bottom gaslift valve and sent to the Bluefin Science and Technology Center for analysis.
  • The deposit contained 71% paraffin, 26% calcium carbonate, 2% silica and <1% salt.
  • Traditional designs would only yield a 15-20% effective treatment.
  • BlueFin's objective was to develop a solvent system that would dissolve the wax at the low BHT conditions. In addition, BlueFin needed an oil soluble organic acid to mix into the solvent system to remove the calcite scale layering

Technical Achievements

  • This treatment produced a 5 fold production increase at 1/5 the cost of the next viable treatment.
  • Before the treatment the well had a 70% water cut and 30% oil cut. After the treatment the water cut dropped to 22% and the oil cut was 78%.
  • The treatment payout took less than one day to payout and production has been largely maintained for 15 months.