Schlumberger

Performance Report: C-Seal Additive Reduces Non-Productive Time and Drilling Costs in Algeria

A steerable bottomhole assembly was used to drill the 8 ⅜-in. section. The Trias Argileux G 35 till zone d’alternance formations were drilled with 1.40 SG without any LPM in the mud system. Prior reaching Cambrian Ri formation by 131.2 ft (40 m), the circulating system was treated by dilution with the C SEAL/SAFE CARB loss prevention material pill.

To allow for depletion of the C-SEAL/SAFE CARB pill consumed downhole and lost over the shakers, the active system was continuously treated at a rate of 4 sx/hr. Any pre-mix that was used to maintain the volume in active system was treated with the LPM. LPM concentration is reported in Table 1. The configuration of the shaker screens had to be modified to retain a good part of the LPM in the mud. The two derrick shakers were dressed with 110-mesh screens.

The 8 ⅜-in. interval was drilled in rotary and sliding mode. Mud properties and hole cleaning remained good while drilling the entire interval. The HTHP fluid loss of the system was also controlled below 5 cc at 200°F (93°C)/500 psi.

The 8 ⅜-in. interval was drilled from 10,869 ft (3,313 m) MD to TD at 11,499 ft (3,504 m) MD 11,037 ft (3,364 m) TVD, at the top of Cambrian R2 formation, in a total of 88.75 drilling hours without any problems. A total of 627 ft (191 m) were drilled at 79° inclination.

Prior to pulling out of hole to run the 7-in. liner, a 07 m3 wellbore strengthening pill was spotted in the 8 ⅜-in. open hole. The objective was to decrease the possibility of mud losses due to surge pressure induced fractures.

While running and cementing the 7-in. liner, no downhole losses were recorded. The job was considered successful and recommended as the proposed procedure for the incoming wells.


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“A blend of C-SEAL additives and sized calcium carbonate allowed us to drill depleted reservoir with high overbalance till the planned liner point without any NPT”.
Bencheikh/Benbrika
Algeria Technical Services
M‐I SWACO