Original fracs were ineffectively stimulated with limited entry designs. Infill wells treated and tested each zone individually, with enhanced rates. One refrac candidate was initially frac’ed with 510,000 lb 20/40 sand. One of 6 intervals was isolated with inflatable packers and refrac’ed with 142,900 lbs 20/40 sand. Post-refrac production from single “G” interval alone peaked at 1070 mcfd and stabilized at 650 mcfd. Of the 120 mcfd initial (six zones) assumed only 20 mcfd from “G” interval. GRI later estimated over 1 BCF incremental reserves added with this restimulation treatment.
The Mendota, NW (Granite Wash, SW) field in east central Roberts, County, Texas produces gas and gas condensate from the Cherokee Granite Wash section. Due to multiple producing intervals spread over a long vertical section, many of the wells in this field were fracture stimulated using the "limited entry" diversion technique. Later comparison of actual gas recovery versus volumetrically calculated gas-in-place indicated very low gas recovery for wells originally stimulated by limited entry. It was concluded that some of the zones in these wells did not receive adequate treatment and would benefit from restimulation.
In order to fracture stimulate individual zones in wells with multiple open producing intervals, it is necessary to isolate the individual zone to be treated from the other open intervals. For the first well in the study area to be restimulated, a frac liner was configured utilizing two inflatable packers straddling a segment of tubing covering the upper producing intervals. This enabled fracture stimulation of the deepest zone with the treatment pumped down the casing and through the short liner interval, allowing an adequate injection rate with a reasonable injection pressure.
Author(s): R.G. Hailey, Seagull Midcon Inc.; C.A. McKaughan, Baker Oil Tools
Paper Number: SPE 28610