Successful Application of through Tubing Mechanical Shut Off Technique in a Deviation More than 70°

Abstract

Through Tubing Mechanical Shut off Process using electric line has been an economical and successful way to isolate undesired perforated intervals in cased whole completions. During the late 1980s & early 1990s the technology became more reliable so the oil & gas industry began to put more trust in eline capabilities for the through tubing shut-offs. Many of offshore operating companies including Gulf Of Suez Petroleum Company "GUPCO" adopted the technique in order to minimize the number of rig work overs and accelerate add rate activities using rigless units. TTBP has proved very reliable in most of the cases however; the success rate has been debatable for highly deviated wells with high-pressure differential across the plug. Eline applications normally struggle at deviations > 60°, because of losing the gravity force driving the tools downward, limitations of tool string length due to dogleg in the angle build up sections. Several through tubing options are now available to overcome these challenges, for example coiled tubing, which requires rig assist for offshore sattelites application, & eline tractoring, which adds more cost to eline job and depends on local availability in the area of operation. TT mechanical shut offs face some challenges more than ability to deploy tools to required depth. Several types of through tubing cement dump bailers are available in the market; however not many jobs were performed in deviations > 70°, there is always a debate about capability of bailer to dump all cement on depth at such deviation where gravity force is minimal. In addition, the effect of cement slumping in higher deviations is another challenge for building a good cement sheeth that guarantees good sheer bond strength and able to withstand required pressure differential. A Challenging example was an offshore horizontal well where the primary target is required to be isolated and the objective is to test a new reservoir in the field which was not tested before in the area. Due to uncertainity in productivity, saturation & fluid type "Oil or gas" of the new characterized reservoir. The operations was intended to be at the minimum possible cost in order to keep the business risk at the lowest level. The target perforation interval was located in the build section of the horizontal well where deviation angle is 74-76 degrees. The existing perforations were flooded out and it was necessary to isolate prior to test of the target reservoir. Isolation using through tubing bridge plug on eline was assessed and different operation risks were evaluated, conveyence to the target depth without an eline tractor was assessed in the planning phase using a tension model. Slickline operation was modified to confirm the validity of the model and we successfully reached the target depth using slickline. During the planning phase, we considered many precautions to guarantee job success. A successful mechanical shut off job in a deviation of 74-76 degree was confirmed by positive test to the plug and the successful production from the well that produced more than 10 MMSCFD & 300 Barrels of condensate per day.