Intelligent-Thinking Restored Well Productivity in Horizontal Completions Plugged-off by Sand-Deposits: Huge Reward

This paper presents improved CTU foam cleanout operation for horizontal producers completed with pre-drilled liners and provides insight into the technicalities of optimized removal of sand-deposits in horizontal wells. Excessive sand production (800-lbs/MSTBO) characterized JKJ reservoir in Niger-Delta, with sand-deposits in the doglegs, drastically plugging the wellbore to abandonment and subsequent shut-in on LTP. Wireline runs and previous unsuccessful attempts to gas/nitrogen-lift the wells confirmed existence of sand-plugs along the wellbore. Rigless CTU sand-cleanout operation was performed on five wells using key design and placement techniques. Limiting sand-cleanout to optimized depths at first point where hole-inclination is 90° within the heel gives valuable results. Further cleanout beyond this depth to the toe breaks apart already-formed cohesive sand-configuration (acting as filters) outside the pre-drilled liners into the wellbore, generating massive sand returns of about 30 bbls to the surface thereby increasing treatment costs and adds negligible value to productivity. Each well was treated within six days at an average total cost of $130,000.00. Incremental 1200 bopd was achieved on average per well, given rise to 4 ½ days Pay Out with respect to oil price of $24 per barrel.

Summarily;

1. Good eccentricity, under-balanced cleanout, stable foam quality and incremental oil were achieved with valued engineering thinking and decision.

2. Because much of the production comes from the heel of horizontal wells, cleanout of sand-deposits to the toe adds little value to productivity with excessive / high additional job costs.

3. Treatment duration is reduced and production time accelerated by limiting cleanout of sand-deposits to optimized depths.

4. Severe production fall-off in horizontal pre-drilled liner completions is caused by sand-plugs in the doglegs, which act as mechanical bridge-plugs.

5. Observation not to cleanout horizontal wellbore completed with pre-drilled liners beyond the depth at first point where hole-inclination is 90° within the heel has been established, and reveals that cleanout beyond this optimal depth creates excessive sands to be handled on surface and adds negligible value to productivity.

6. There is threat of possible formation deconsolidation and early production decline when low bed sands are washed out in horizontal section.