_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 227989, “Hydraulic Fracturing the Nanushuk: Review of the Pikka Fracturing Campaign, North Slope, Alaska, ” by Elizabeth Spiteri Schulpen, SPE, Andy Bond, SPE, and Scott Leahy, SPE, Santos, et al. The paper has not been peer-reviewed. _ The Nanushuk reservoir is the primary target for the new Pikka development on the North Slope of Alaska. Because of the challenging and environmentally sensitive terrain, Pikka Phase 1 wells are drilled from a single surface gravel pad. Hydraulic fracturing is the primary technology used to connect hundreds of feet of laminated reservoir to horizontal wells. The data collected from each fracture is analyzed for effect on well productivity, and key learnings from challenges encountered in the field are presented in the complete paper, with an emphasis on improved conductivity, diversion, fracture height, and screenout prevention. Treatment Designs The hydraulic fracturing design integrates a comprehensive set of parameters aimed at optimizing reservoir stimulation, selected to balance effective fracture geometry and conductivity with operational efficiency. The available completion technology used to provide mechanical diversion and behind-pipe isolation is diverse, and the final design was selected to meet criteria of pressure, temperature, hole size, and screenout recovery. Completion Design. The Pikka completion system uses a collet and dissolvable ball mechanism for mechanical diversion. This assembly travels through the production tubing into the 4. 5-in. P110 liner and seats in a matching profile, triggering the opening of a reclosable sliding sleeve. Mechanical packers are installed between each fracturing stage, with additional packers at the heel to protect the liner top packer that separates the production annulus from the intermediate casing. Once the balls dissolve, the system allows full wellbore access through a 3. 264-in. inner diameter (ID). Clean fluid around the collet is essential for proper function. The sleeve closes under 23, 500 lbs of tension, while the collet releases between 9, 000 and 13, 500 lbs. A selective closure tool enables individual sleeve closure without disturbing other collets, though coiled tubing (CT) is required to place collets during refracturing operations. Sleeves can be opened individually during run-in-hole procedures, but the ability to retrieve collets post-fracturing is limited. The system is cementable and must navigate significant internal diameter transitions. The ball was selected to dissolve in broken fluid at 100°, where dissolution testing showed that the 3. 5-in. Category 3 ball took 5. 2 hours to reach the upper rated pass-through diameter (3. 38 in. ) and 6 hours to reach the lower pass-through diameter (3. 34 in. ). Full dissolution was calculated by extrapolation and is predicted to occur after 48. 9 hours. The current 8-in. outer-diameter hydraulically set openhole packer is designed to expand up to a 9-in. openhole ID, suitable for most Tier 1 and 2 wellbore configurations. The collet and ball-launch assembly is mounted on top of a 10, 000-psi rated fracturing tree and uses dual 3- or 4-in. lines on a goat head.
Chris Carpenter (Mon,) studied this question.