Inflatable-Packer Well-Intervention Techniques Cut Rig Time, Costs

The oil and gas industry’s efforts to develop tools that meet and exceed operational objectives with less cost have led to advancements in downhole tools that enhance slickline technology, making it a more versatile means of providing accurate depth measurement. The development of slickline-deployed inflatable packers also exemplifies ongoing efforts to simplify costs, operations, and logistics.

Fig. 1—A rigless thru-tubing gravel pack recompletion,
left. The tubing changeout using an offline approach
reduces rig time, right.

Setting inflatable packers on electric line began in the early 1990s. The next logical step was to set an inflatable packer on slickline, which had several advantages over the use of electric wireline. Lower frictional values at the stuffing box were possible, and surface grease-injection pressure control equipment was not needed. That made it more versatile in highly deviated wellbores.

The introduction of battery-operated slickline tools increased productivity and decreased costs, making slickline a frequent choice for complex mechanical workovers. This led to the development of SlikPak, a slickline-conveyed inflatable-packer setting system. The initial development was a joint effort between TAM Intl. Inc. and Halliburton. The system used existing technology, coupling a TAM inflatable bridge plug and electric-wireline motor/pump module with the Halliburton Advanced Slickline Downhole Power Unit and Collar Locator. TAM subsequently developed a complete system for inflating packers using slickline (Fig 1). Many remedial operations can be performed with slickline systems available from a variety of service companies. Memory logging capabilities include a wide variety of logging options, running packers (both inflatable and hydraulically set versions), and perforating.

The following case studies show how the technology has been deployed in different regions and environments.

Case Study 1: Cabinda

Small platforms and well jackets in shallow offshore water in Cabinda required the use of a jackup or lift boat to perform coiled-tubing or electric-wireline intervention operations. Because of a shortage of contracted lift boats, the feasibility of performing various remedial operations using only a slickline unit operating from the helideck was economically attractive and allowed a higher quantity of remedial operations to be performed.

The Slickline unit and the associated downhole tools were lifted by helicopter to the satellite well jacket and rigged up on the helideck. Remedial operations were performed by setting an inflatable bridge plug above existing perforations, dumping a cement plug, and perforating a higher interval. Per-well savings in the remedial operations here were estimated to be more than U.S. $150,000 compared to previous coiled-tubing-type programs on similar well configurations. In addition, the well program was completed 8 months in advance of the scheduled coiled-tubing intervention and lift-boat plan.

An additional well used a two-packer, scab-liner configuration to block production from a joint of failed wire-wrapped screen and reduce sand production. The scab liner was configured and run in three separate runs to minimize lubricator height. The lower inflatable packer was run with a polished-bore receptacle (PBR) and latch profile left up, while blank spacer pipe was run with another PBR with the latch left up, followed by the upper inflatable packer.

Case Study 2: Vietnam

A remedial program to change out production tubing and install or modify the gas lift design was required for multiple wells in a project offshore Vietnam. Because of partially depleted pressure in a Miocene sandstone reservoir and a well-control requirement to maintain the well full, a typical operation would result in loss of several thousand barrels of seawater or produced brine during a workover operation. Not only did this slow down rig operations, but it often resulted in formation damage requiring acid stimulation after the new completion string was installed.

Most of the wells here did not have a nipple in the tail pipe below the production packer that would allow use of a slickline plug, so the project required a retrievable, inflatable packer as the bridge plug. The method for setting and retrieving the inflatable plug was evaluated using coiled tubing, electric wireline, and slickline. In both the coiled-tubing and electric-line methods, rig time was required to accommodate the lubricator rig-up. However, the small footprint of the slickline system could be accommodated while the rig was operating on an adjacent well.

The inflatable plug was run in the first well, and it filled with seawater. The rig skidded over the well and changed out the production tubing while a plug was run in the second well. The rig was then skidded to the second well, and the plug was retrieved using slickline from the first well.

During this four-well program, three wells did not have nipples in the tail pipe, thus requiring an inflatable plug. In one well, fill (rust and scale) above the retrievable bridge plug required rigging up a coiled-tubing unit to perform cleanout before retrieval. The estimated reduction in rig time for the four-well program exceeded 22 days, with net cost savings estimated at more than U.S. $2 million.

Case Study 3: North Sea

A well producing approximately 400 BOPD at 95% water cut was evaluated using production logs on electric line. The analysis indicated that the water production was coming from the lower set of perforations. An inflatable bridge plug was run using the slickline conveyance system and set above the lower perforations. The strategy was to test the well for 24 hours to determine that no flow was occurring outside the casing and then dump a cement plug on top for longevity. As the initial test resulted in 1,500 BOPD with a 5% water cut, the well was not shut in for the 24–30 hours required to dump a plug and allow the cement to cure.

After 12 days of a high rate of oil production, the water cut again reached close to 100%, and a slickline run determined that the inflatable bridge plug had failed and fallen downhole. On the second run, a cement plug was placed before production testing. In conjunction with artificial-lift optimization, the well is producing at 3,000 BOPD after 9 months.

Case Study 4: Gulf of Mexico

A slickline-conveyed gravel-pack completion was achieved using an inflatable bridge plug set above the original completion as a bottom for the proposed new completion. After perforating a new interval, a wire-wrapped screen was run and set on the bottom. A wireline-retrievable plug was left in the top of the screen to prevent sand from entering, and a gravel pack was completed using a fracture/packing technique.

Because of an excess volume of sand left above the screen, coiled tubing was required to clean the well down to the screen. With the coiled-tubing unit rigged up, a decision was made to pull the plug from the screen inside diameter and run an inflatable packer onto the top of the screen to prevent the flow of gravel from the screen to the casing annulus. The result was production income in excess of U.S. $100,000 per day and reduced intervention cost in excess of U.S. $1 million.

Information provided by TAM Intl. Inc.