Published: 04/14/2014
Published: 04/14/2014
Operating in the Eagle Ford Shale, an operator has been working with Schlumberger to improve production from horizontal shale wells. New wells are completed in high-pressure, high-temperature (HPHT) areas with fracturing gradients of 0.85−0.95 psi/ft, TVDs of 12,000−13,500 ft, and bottomhole temperatures ranging from 300 to 345 degF. Typical completions are based on the plug-and-perf technique, with four to eight perforation clusters per interval isolated by bridge plugs.
An area of recent interest for the operator is the restimulation of old wells. The operator sought to accelerate and increase the estimated ultimate recovery (EUR) of oil and gas by reestablishing conductivity in old hydraulic fractures and stimulating new reservoir volume. This endeavor is gaining significant traction across the industry because the number of candidates for refracturing is increasing rapidly as the shale plays continue to age.
A key challenge for refracturing operations is effective stimulation along the length of the wells (4,000−6,000 ft). Since all perforations are open, mechanical aids such as bridge plugs cannot be used.
The operator decided to address these challenges with the BroadBand Sequence fracturing service. The BroadBand Sequence service is a key enabler for refracturing operations since it delivers temporary isolation of clusters through engineered application of a proprietary, fully degradable composite fluid comprising a blend of degradable particles and fibers.
The candidate well, originally one of the field’s best oil producers, had been stimulated two years earlier with multiple fracturing stages. The refracturing operation included 13 fracturing stages, which were completed using an identical amount of proppant from the first stimulation campaign as well as the HiWAY flow-channel hydraulic fracturing technique. Composite pills were pumped between fracturing stages to enable temporary isolation of previously stimulated clusters. A shut-in was applied after placing each composite pill to monitor changes in fracturing gradient.
All 13 refracturing stages were pumped sequentially in 36 hours and without use of mechanical aids such as bridge plugs or inflatable packers.
Initial shut-in pressure (ISIP) measurements captured at the end of each stage showed progressive increase toward
After refracturing, the well was put in production using a smaller choke (8⁄64 in) than the one used prior to
Calculations for the well’s productivity index (PI), which take into account both rates and pressures to normalize production, indicate an increase in PI of more than 600% after the restimulation operation. These outstanding results demonstrate the effectiveness of the BroadBand Sequence fracturing service to boost oil and gas production from depleted horizontal shale wells.
Challenge: Increase production from depleted, previously fractured shale well.
Solution: Apply the BroadBand Sequence fracturing service to enable effective refracturing through engineered application of a proprietary, fully degradable composite fluid comprising a blend of particles and fibers.
Results: Improved production based on average results over the first 45 days after refracturing:
