Options grow for cementless isolation

Historically, operators had only three choices with regard to long-term horizontal openhole wellbore isolation: no isolation at all, cementing and perforating, or cement-inflated external casing packers. A barefoot completion does not allow for zone isolation and cannot mitigate water or gas production along the well bore. Cementing and perforating, sometimes referred to as “the hard way,” is time-consuming; costly; and requires specialized personnel and logistics to handle health, safety and environmental issues. Cement potentially impairs near-wellbore permeability. A poor cement job allows uncontrolled flow in the annulus through void spaces. Uncontrolled flow in the annulus of a long, horizontal well can lead to hot spots, water coning or gas breakthrough, all of which can reduce production, reserves, profitability and well life and thus defeat the original purpose of the horizontal well.

New technologies including swelling elastomers or reactive polymers have applications in wells that previously would have been completed without zonal isolation. This technology is applicable for gauge holes or where barriers are sufficient to prevent migration of fines. In other applications where hole geometry is unknown, gas is present or an immediate seal is required, an inflatable packer with a core that reacts with wellbore inflation fluid can provide an immediate, long seal for the life of the well without the need for cement inflation. New developments in non-inflatable mechanical packers that can conform to irregular wellbore geometries are further expanding the options for wellbore isolation.

MPas openhole packer is run in well. (All graphics courtesy of Baker Oil Tools)

The MPas packer is a new technology designed to achieve reliable selective wellbore isolation in horizontal openhole completions without the risk and cost associated with cementing and perforating. Run as an integral part of the casing or liner string, it uses an elastomeric element with composite structure, which is hydraulically set. Shifting a balance sleeve allows wellbore hydrostatic pressure to act against an atmospheric chamber, which applies setting force to the non-inflatable element for the life of the well. The packer can be set by two methods. An inner workstring with setting collet can be used to shift a sleeve in the MPas packer to activate the setting mechanism as the string is pulled out of the hole. Or, differential pressure can be applied, which will activate and set the packer. A lock mechanism maintains the setting force even if hydrostatic pressure is removed. Additional setting force can be applied at any time by increasing the hydrostatic or applied pressure at the packer.

One-trip deployment and instant sealing allow for immediate testing following activation. The seal element is effective in both water-based and oil-based fluids.

The packers can be run on blank casing to isolate unwanted zones, in slotted casing or standalone screens to separate producing zones, or between screens in a gravel pack for zone isolation. In horizontal gravel packs, the packers can be run and set in a single trip when used with BetaBreaker valves. The valves prevent sand from being deposited around the packer outside diameter before it is set. When pulling out of the hole after pumping the gravel pack, a shifting tool on the end of the washpipe sets all isolation packers in the casing string. In uniform flow completions MPas packers provide compartmentalization between inflow control devices to mitigate coning along the horizontal well.

MPas packers have performed successfully on more than 1,000 runs in many applications. They have isolated gas caps in wells where the exact positions of the top and base of the gas zone were unknown. They have isolated lost circulation and water in high-angle wells that would be difficult to plug back with cement. And they have been used in many uniform flow wells to enhance the positive effects of uniform inflow control systems by creating a seal between reservoir sections of varying permeability.

MPas and the Equalizer Screen form a one-trip uniform flow completion system.

Aiding uniform flow
Uniform reservoir flow systems create uniform flow profiles along lateral well sections to optimize reservoir production with fewer wells and to significantly reduce field development costs. They also delay water and gas coning and increase the amount of oil recovered. In Baker Oil Tool’s uniform flow system, the one-trip mechanical isolation packers enhance the positive effects of the inflow control by creating an annular seal between sections of varying permeability. The combination, spacing and geometry of packers and inflow control devices are determined through detailed engineering analysis. Uniform reservoir flow has been used successfully in sandstone formations and naturally fractured carbonates in horizontal and highly deviated wells with lateral lengths from 400 to 13,000 ft (122 to 3,963 m). Uniform inflow control completions substantially reduce gas cusping, water coning and costs of cementing and perforating. They prolong well life, improve depletion, maximize sweep, provide effective sand control and reduce the need for future well intervention.

Slimhole expandable liner application
Recently, the first slimhole-size (31?2 in.) MPas packers were successfully run and set with four slim inflow control devices (ICDs) through an expandable liner in Saudi Arabia. This was the latest in an ongoing extension of applications in the country that also include scab liners to consolidate fractures; gas cap isolation to eliminate gas coning; carbonate uniform flow completions, including a 5,000-ft (1,524-m) horizontal section and dogleg severity of 30°/100 ft (30.5 m); uniform flow completions in sandstone; shoe applications; and plug and abandonment with up to 58°/100 ft dogleg severity, including one job where circulation was regained from total losses at the toe of the horizontal section. Among the most notable completions in Saudi Arabia was a long horizontal across the reservoir sand in the Zuluf field that enabled the toe of the lateral to contribute 43% of the well’s total production versus 10% from a conventional openhole completion.

MPas technology improves production, injection profits.

Time savings in gas recycling project
Using one-trip mechanical isolation packers with slotted liners in a long horizontal section enabled the well team on a gas recycling project in the Timor Sea to cut 8 days of rig time, increase production and injection rates to more than 350MMcf/d, and shut off water, with no perforation damage or debris.

Water management offshore India
The advantages of a one-trip mechanical zone isolation packer are proving valuable in India’s Mumbai field, where ever-increasing water production rates pose a significant challenge. In one well, running the packer system in open hole below the water zone significantly reduced water content from the previous 93%, saved several days’ rig time, and eliminated the need to perform a complicated and difficult cementing and perforating operation in a highly deviated well.

In another well, completed in March of this year, the operator was able to arrest water production and increase oil production in a rigless intervention that reduced completion costs. In addition to using one-trip mechanical isolation packers to help lower water production from 2,088 bw/d to 954 bwpd while increasing oil production from 340 bopd to 390 bo/d, the well team installed sliding sleeve assemblies to segment the horizontal open hole into three sections (heel, middle, toe) to study the behavior of the different heterogenic sections and shut off the undesirable portion to reduce water production.

Like swelling packers, one-trip mechanical zone isolation packers are not a panacea. Knowing the right wellbore isolation solution requires knowing the well and the desired productivity, in both volume and duration. For situations where sand management and maximized well productivity vie for importance with the need for simple, cost-effective, non-cemented wellbore isolation, solutions like the MPas packer are enjoying rapid field acceptance.