Unique Solution for Fracture Isolation Resolves Breakthrough Challenges in Horizontal Slim Hole Well

Abstract

A mature well in a carbonate reservoir in Saudi Arabia was no longer producing and was sidetracked in a workover operation to regain production. This paper describes the usage of swellable packers to isolate a detrimentally water producing fracture encountered during drilling of a 3–7/8" slim hole horizontal in a naturally fractured carbonate reservoir. No means of open hole/slim hole isolation were available prior to the introduction of swellable packers. The packers were successfully run and the well was brought into production at good rates and low water cut. Introduction Natural fracturing is believed to pervade most of the carbonate reservoir due to the brittle nature of these rocks. Today most production wells are drilled as 6–1/8" horizontals and completed with 4–1/2" inflow control devices and open hole packers to delay and manage water production. A number of workover wells are drilled with smaller bit sizes. Consequently, this requires slimmer completion equipment to complete the wells in an optimum manner. Well history Well A was drilled in 1999 as a 6–1/8" open hole high slanted (83°) producer and completed with 7" packer and 4–1/2" tubing. In 2005 the first workover operation was carried out to revive the well that was dead as a result of excessive water production. A window in the 7" liner was cut after decompleting the well and setting a whipstock. A 2,200ft 6–1/8" horizontal sidetrack was drilled in the formation and the well was completed with 7" packer and 4–1/2" tubing. The well was found dead after only one month of production. An acid job was subsequently carried out in an attempt to restart the productive life of the well; however it did not prove successful. Surface and downhole bailer samples were collected and lab tests suggested that an adjacent reservoir was dumping water into the formation. Another workover operation was planned and carried out in 2007. A balanced cement plug was set to abandon the existing lateral. A window in the 7" liner above the reservoir was cut, new 6–1/8" curve section to the top of the formation was drilled, an expandable liner run and set and a 5–1/2" horizontal hole was drilled. If needed, the well would be completed with inflow control devices and open hole packers. After the 5–1/2" shoe was milled out and a negative test was performed after displacing the well to water the well flowed water from the reservoir. A 4–1/2" scab liner was run to isolate the leak in the 5–1/2" liner from 6,598 to 6,720ft. A 3–7/8" open hole was drilled to TD at 8,800ft. A fracture was encountered at 7,586ft with total losses. The remainder of the lateral was drilled with water with no returns. The well was not logged since no caliper was available at that time for this hole size. Slim hole well design Saudi Aramco typically complete the 6–1/8" horizontal open holes in the carbonate reservoirs with inflow control devices to even out the inflow profile along the wellbore and to delay water break-through. Open hole packers are used to compartmentalize the open hole, to isolate fractures and hence manage water production in combination with the inflow control devices. No open hole packer technology was available or approved by Saudi Aramco for such slim holes prior to the introduction of swellable packers; i.e., there was no mechanical means of isolation of fractures or of compartmentalization. The potential consequence was excessive water production and loss of the lateral, resulting in a costly workover operation.

First Coiled Tubing Swellable-Packer Deployment in the Middle East

“…Swellable-packer technology has been described in numerous technical articles (Al-Mumen et al 2008;Antonia et al 2007;Fryer 2005;Hembling et al 2006;Kleverlaan et al 2005;Triolo et al 2006), and its functionality and reliability as a means for openhole-isolation has been proven since its introduction to the industry in 2001. The technology has also been tested and proven to form a reliable seal inside casing, even if it is severely corroded (Pradie et al 2008).…”