Expandable Tubular Successfully Scab off Severe Casing Leaks

Abstract

Abstract The number of old wells completed with uphole packers showed a dramatic increase in casing leaks. The leaks were dumping aquifer fluid directly to the reservoir and vice versa. Many wells experienced this kind of problem. The conventional practice to isolate these kinds of leaks was to run and cement a scab off liner. This resulted in running smaller production strings andconsequently resulted in a dramatically reduction in the production rate and choking wells with high pressure it also limits future remedial workovers of developed future leaks. Saudi Aramco launched a campaign to recover and salvage wells that had been affected by severe casing leaks and hot spot corroded sections. The solid expandable liner was introduced in two sizes of casing. Introduction and usage of this new technical application will have a maximum ID after setting the solid expandable to run the maximum tubing size, to achieve the highest production rate. This paper will describe the successful application of this technology and its comparative advantages, including reduced cost and salvaging wells without the need to sidetrack as had been done before. The paper also includes some review of recently applied casing repair results in several wells. Introduction The number of old wells completed with uphole 7" packers showed a dramatic increase in casing leaks over the years. The leaks were dumping aquifer water directly to the reservoir. The cause of casing leaks is well known to be a combination of very poor to nonexistent primary cement bond around 9–5/8" casing due to severe lost circulation in aquifer during drilling and cementing phase, and very corrosive aquifer water that entered the well bore and corroded through both 9–5/8" and 7" casing, which resulted in an increased water production and a drop in pressure and temperature as demonstrated by SBHP/T surveys (refer to Figure 1 for an illustration of the well selected for the case history). The conventional practice to isolate these kinds of casing leaks was to run and cement a scab off 4–1/2" liner inside 7" production casing or liner. This resulted in running smaller production strings and consequently resulted in a dramatical reduction in the production rate and choking wells with high pressure it also limits future remedial workovers of developed future leaks. Previous case histories In early July 2003 well A with 4–1/2" scab off liner were selected to workover due to severe corrosive aquifer water that again corroded the scab off liner. A 3–1/2" x 4–1/2" expandable casing patch was deployed to seal off the leak and allowed the well put back on production. The expandable casing patch contained solid expandable launcher and hanger joint each with 10 elastomer seals, and spaced out with regular un-expanded 3–1/2" 9.3# N-80 tubing. In early August 2003 well B with 4–1/2" scab off liner were selected for workover due to severe corrosive aquifer water that again corroded the scrab off liner. Another expandable casing patch was utilized to isolate the leak. The top and bottom seal element of the casing patch were designed to be expanded by hydraulically forcing a swedge into the casing overlap to achieve a metal-to-metal seal with pin element that has a slip-like setting mechanism. Because of the very tight clearance between the casing patch and existing 4–1/2" liner, first two attempts to run the patch into the well failed. Two 3–7/8" milling & clean-out runs and a dummy run were performed before finally getting the patch into the well and set across the planned interval.