A Cost-Effective Technique for Squeezing Perforations
- Robert M. Beirute (Amoco Argentina) | Roberto Bugli (Amoco Argentina) | Horacio Rossignoli (Amoco Argentina)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- February 1994
- Document Type
- Journal Paper
- 100 - 100
- 1994. Society of Petroleum Engineers
- 2 Well Completion, 1.14 Casing and Cementing, 1.6 Drilling Operations, 3 Production and Well Operations, 4.1.3 Dehydration, 3.1.2 Electric Submersible Pumps, 3.1.1 Beam and related pumping techniques, 2.2.2 Perforating, 2.4.3 Sand/Solids Control
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Amoco Argentina developed a cost-effective squeeze technique to seal offfreshly opened perforations across water and/or gas zones. The method uses verylittle cement, a retrievable packer, and a retrievable bridge plug. Thetechnique has been optimized to where the success ratio is extremely high (morethan 95% in 1991-92).
Amoco Argentina has been operating in the Comodoro-Rivadavia area since1958. The Cerro Dragon contract area consists of about 25 fields. Since 1958,1,723 wells have been drilled with depths ranging from 3,000 to 11,500 ft. Allwells are either beam pumped or on electric submersible pumps. On average,about 22 zones are perforated per well, and about 3.4 zones per well requiresqueezing.
Before developing the current squeeze cementing technique, the company usedabout 30 sacks (7.5 bbl) of cement per zone to be squeezed. The zones wereisolated between retrievable packers and drillable bridge plugs. Frequently,the cement slurry was pumped at pressures above fracture gradient from thebeginning of the squeeze operation. Time was allowed for the cement to fullyset [waiting-on-cement (WOC) time] before drilling out. Because the nonproductive zones to be squeezed were very close to the oil zones, relatively littleroom usually was available between the packer and the bridge plug. This meantthat final squeeze pressures often were obtained before a substantial portionof the cement slurry volume was pumped. When large volumes of cement slurry hadto be reversed out, often the packer could not be unset and/or it could not beremoved from the hole easily.
Amoco Argentina developed the current squeeze cementing technique byadjusting procedures to minimize or eliminate the potential causes of failuresand to capitalize on the practices that produced successes. Working with theservice companies as a team has contributed to the success. The zone to besqueezed is now isolated between a retrievable packer and a retrievable bridgeplug. Squeezing is almost always done with exposed open perforations above thezone to be squeezed. The present procedure uses about 0.5 sack cement/3 ft ofperforated interval, plus the volume of the casing (from the deepestperforation to the estimated top of cement), plus 1 bbl extra of slurry toaccount for contamination. The average is 12 sacks of cement per zone to besqueezed. Because of the low volumes of slurry used, all the slurry can beeasily mixed in the recirculating mixer tub before the start of the squeezeoperation.
Before the squeeze (Fig. 1), sand is placed above the bridge plug to preventit from cementing up. Next, injectivity is established. At the beginning,pumping is conducted below fracture pressure. Cement slurry is pumped to theperforations at a low rate, and squeezing is started using the hesitationsqueeze technique from the on set. After achieving an initial squeeze (seal) ofthe perforations, pressures are gradually increased to levels that exceed thezone's fracture pressure to promote complete dehydration of the slurry in theperforation tun nels (pressure holding steady). This step ensures that thecement will remain in the perforation tunnels. Often, the wash-throughtechnique to clean excess cement slurry from across the perforations is usedright after the squeeze and before the cement has had time to set completely(no allowance made for WOC time). The wash-through technique is used only whenoil-productive zones are not open above the zone being squeezed.
In the Cerro Dragon area, the use of minimum volumes of cement slurry haseliminated the need to reverse-circulate excess cement, reducing operationalrisk and saving rig time. The use of retrievable bridge plugs instead ofdrillable bridge plugs has resulted in rig time savings of about 6 hours perzone, plus the cost of the permanent bridge plug. When the wash-throughtechnique is used, it has resulted in a savings of about 14 hours of rig timeper zone. Be cause of the high success achieved with the new technique, AmocoArgentina does not test a squeezed zone after the job unless the zone exhibitshigh gas/water rates or operational problems were encountered during thesqueeze. This practice has resulted in savings of about 3 rig hours per zone.Overall, the new technique has reduced the cost of a typical squeeze job in theCerro Dragon area by about 30%.
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