FIRST DOWNHOLE JETTING TOOL JOB COLLECTS SAMPLES AND CLEANS SCREENS TO RESTORE PRODUCTION

Welltec Milling Solutions

Background

A client in Norway had a well that unexpectedly died after a re-completion. It was suspected that the screens had been plugged by particles from mud solids or completion fluid and  plugged from both inside and outside the screens, due to lack of injectivity and production. The client’s objective was to first get a sample of fill and fluid blocking the screens and from that, choose suitable chemicals to flush the screens in order to re-open the flow path from the reservoir.

Welltec proposed an approach that would fulfill the client’s objectives in two runs.  The first run would sample both solids and liquids at the target depth (TD) using the Well Cleaner® Downhole Jetting Tool (DJT) and its bailer system with a new valve setup custom designed for this application.  Following a lab analysis of the clogging material, the subsequent run would convey the chosen chemicals down to TD, again with the Welltec® DJT bailer system and flush the screens through the tool’s powered jetting nozzle.

OPERATION

DJT Sampling
A full test to find the best DJT setup with pumps, valves and flappers was conducted in Bergen which demonstrated that samples of both solids and liquids will be preserved in the bailers from TD to surface.  The first run into the well would not pass the downhole safety valve (DHSV) and the tool-string needed to be reconfigured with standoffs, centralizers and modified nozzle which then passed the DHSV and successfully sampled the 6 liters of solids in one chamber and 1 liter of fluid in a second separate chamber during the same run in hole.  The samples were then delivered to the client for lab analysis.

DJT Injecting
On the following day the chosen chemical surfactant was loaded into the DJT bailer and run in hole.  The DJT nozzle was positioned at the bottom of the screens and performed two passes through the screens as per program.  Each pass consisted of stations every third meter, with 2 minute intervals.

ACHIEVEMENTS

After completing the treatment, the well was put back on production and began to flow, which it had not done previously.  The treatment proved the effectiveness of the DJT nozzle and flow rate to jet flush and clean plugged sand screens.  By modifying the DJT with a new valve, it has proven to also be effective in sampling both solids and fluids in separated chambers and returning them to surface.

WELL DATA

PLUGGED BACK TOTAL DEPTH: 3097m
LINER AND SCREEN SIZE: 4 ½” (3.96” ID)
SCREEN LENGTH: 2 X 12m screens = 24m total