A well which was drilled in the Pronghorn formation of the Williston Basin had significant trouble during the cementing process. While the lateral length was 11,103 feet, only the 9,296 feet of the lateral closest to the toe had adequate cement to provide the isolation needed for hydraulic fracture stimulation. An integrated solution with evaluation of well integrity and novel diversion material used over the remaining 1,807 feet of the lateral to generate multiple hydraulic fractures was proposed and results were confirmed with production log evaluation.
After using an ultrasonic imaging logging tool conveyed via tractor to determine the point at which the cement isolation became unreliable, the appropriate completion was designed. The first 33 stages of the stimulation were done using a standard plug and perf technique. The last 1,807 feet of the lateral were completed in two intervals with only one additional bridge plug. The two intervals were each stimulated with seven hydraulic fracturing stages and six diversion pills consisting of a proprietary blend of degradable materials. While more stages were pumped in the heel section, the same amount of proppant per foot of lateral was used as in the larger conventionally completed toe section.
The 14 stages pumped in the heel portion of the lateral showed that in both intervals, the instantaneous shut-in pressures at the end of each one of them increased by 2,300 psi and 340 psi respectively. This increase is consistent with fractures initiating at lower pressure intervals, and then being diverted to higher pressure, unstimulated areas. Well production was evaluated with a production log capable of identifying multiphase holdup along the lateral. This evaluation showed that 42% of the total oil production was coming from the 18% of the lateral which was stimulated using the degradable diversion material.
The application of this degradable diversion material in poorly cemented or un-cemented lateral sections in order to create a more uniform distribution of hydraulic fractures can significantly improve both completion efficiency and hydrocarbon production.