The Situation

Drilling was being performed with a 12¼-in bit at 5853 ft (1784 m) with 1.30 SG (10.8 lb/gal) VERSADRIL invert-emulsion fluid and partial lost circulation at a rate of 11 m3/hr (69.2 bbl/hr) was observed. Pills containing 100 kg/m3 (35 lb/bbl) of lost circulation materials (LCM), M-I-X II Medium and CaCO3 M-70 and M-200 were pumped.

Drilling was continued with a partial loss of 5 to 11 m3/hr (31.4-69.2 bbl/hr) to a depth of 5,938 ft (1810 m) while pumping LCM pills, accumulating 110 m3 (692 bbl) of lost mud, resulting in suspension of the operation.

Client operating personnel met with M-I SWACO engineers in search of a technical alternative to properly seal the loss zone and to continue with normal operations.

The Solution

M-I SWACO recommended the use of a FORM-A-SQUEEZE pill to seal the zone where the partial lost circulation occurred. A 50-bbl, 1.31 SG (10.9 lb/gal) FORM-A-SQUEEZE pill consisting of diesel, FORM-A-SQUEEZE additive, and calcium carbonate was prepared and blended.

• Having the bit at 5905 ft (1800 m), 40 bbl of FORM-A-SQUEEZE pill was pumped. Pressure: 600 psi, displaced at 800 strokes per min
• Lifted bit to 5459 ft (1664 m), circulated at a low flow rate of 10 strokes for 5 min; then pumping was suspended, annular preventor was closed, satisfactorily repressurizing with 200 psi for 10 min
• Pressure was discharged to zero; annular preventor was opened and initially circulated at a low flow rate. The flow rate was gradually increased until initial drilling conditions were attained: 120 strokes, 540 gal/min, 2200 psi. No mud losses to the formation were observed
• The 12¼-in section was taken to bottom, circulated at a low flow rate, increasing little by little until reaching and maintaining 540 gal/min, and continued drilling with normal circulation

The Results

After pumping the FORM-A-SQUEEZE pill:

• A complete cycle was circulated at 540 gal/min, keeping normal levels
• Drilled to bottom without experiencing lost circulation, keeping normal levels at surface
• No waiting-on-cement times were required
• Continued drilling at the scheduled depth with normal circulation
• Waiting times were eliminated
• Operational costs were reduced
• Continued drilling the stage below scheduled times