A unique sequenced fracturing technique using formation notching and degradable diversion pills was applied for the first time in a vertical open hole completion to stimulate multiple pay intervals in a well in the "Q" sandstone formation of Saudi Arabia.
The challenge to divert fractures in a vertical open hole is made more difficult by the large fracture surface area in contact with the wellbore. A robust, efficient and repeatable two-step technique was implemented to provide the diversion and controlled breakdown of higher-stressed sections of the interval. The first step used a specialized jetting nozzle to create circular notches and weaken the formation at target depths. The second step involved the pumping of a small volume of a composite fluid of degradable non-damaging fiber and particles that bridge at the fracture face, to divert the remainder of the treatment to under-stimulated sections of the interval.
The target for this well was a shallower formation due to completion pressure limitations while fracturing. This left six pay intervals spread across the tight, heterogeneous sandstone layers of the Q formation, which was completed as a single 552-ft. vertical open hole section. Previous experience showed large stress variations in the layers with contained fractures, and fracturing all pay intervals required separate treatments for each interval. After notching the pay intervals to reduce breakdown pressures, the interval was fractured with three proppant ramps separated by two diversion pills in the span of 8 hours, improving efficiency by more than three times. Diversion was confirmed by: (1) pressure increases of 380 psi and 500 psi, respectively, when the pills landed on formation; (2) increasing trend of the instantaneous shut-in pressures (ISIP's) throughout the treatment, resulting in 1,270 psi of net pressure gain; and (3) comparison of post-diagnostic injection test temperature log data with post-fracturing neutron log data, showing where nonradioactive traceable proppant was placed, including into at least three pay intervals not broken down during the injection test. Post-treatment production expectations were met and confirmed with a well test.
This paper will present the design, execution, and evaluation methodology and challenges overcome to divert hydraulic fractures in long vertical open hole intervals using this two-step diversion process for sequenced fracturing. The ability to do this consistently and predictably can provide a practical, efficient, and cost-effective preferred solution that does not exist today for completing and fracturing similar zones that are traditionally bypassed, resulting in increased production and reserves.