Fracturing of multiple zones using CT
The operator determined that the zones in the southeastern Alberta wells should be fractured individually at reduced pump rates for adequate stimulation and optimum production from each of the reservoirs perforated. The objective was to find a more cost-effective method for shallow gas fracturing on the wells: more fracturing in less time with better economic results.
The reduced injection rates, coupled with the short time frame considerations, have facilitated the use of CT-conveyed fracturing treatments for segregated multizone stimulations. Now, the entire well is preperforated with select fire perforating guns, which results in significantly fewer runs into the well. Next, the coiled tubing and fracturing equipment is mobilized. A straddle tool is then deployed on CT to straddle each zone separately. When the zone is straddled, the fracture stimulation treatment is pumped down the CT and into the zone of interest. Once all the zones are completed, the entire well is flowed back and put on production. No composite plugs are left in the well to mill, and no bridge plugs are left to retrieve. The operation has become so efficient that a single CT/fracturing crew often completes 2 wells in 1 day.
The same technique can be used to recomplete wells by fracture stimulating bypassed zones. The bypassed interval is perforated, straddled with the CT, and fracture stimulated down the CT. The bypassed zone is now effectively fracture stimulated without affecting the other zones of interest that were already completed.
Operational and economical advantages
The following operational and economical advantages were realized using CoilFRAC stimulation through CT
- reduction in operational logistics, set-up costs, travel time, and equipment
- reduction in the total cumulative flowback time per well by a factor of 2 or greater, resulting in payout in less time
- reduction in average total completion time (4 days versus 16 days)
- individual fracture stimulation of each zone, maximizing reservoir contact
- elimination of retrievable and millable plugs left in the wellbore