A new expandable screen system maintains screen integrity despite high expansion ratios.

A total of nine wells have been completed using PoroFlex expandable sand screen technology from Halliburton for a variety of customers in West Africa, South America, the Gulf of Mexico and Asia Pacific. The PoroFlex system contains four key features that make it unique in its ability to provide flow assurance, longevity and reliability.

Flow assurance

To address the issue of flow assurance, the system uses both expandable solid and near-solid base pipe. This provides higher burst and collapse resistance in all loading scenarios over slotted base pipe. The completion will thus experience less deformation over time, which not only assures production integrity, but also ensures that any remedial operations can be conducted in a production conduit with a known internal diameter. Since solid base pipe can be installed as needed, the installation of flow controls such as packers or plugs can be performed reliably. This base pipe configuration thus lends itself to selective multi-zone completions, including intelligent well architecture.

Filter

One feature that addresses the reliability issue is the construction of the filter media. Manufactured by Purolator Facet, the screen is based on its patented Poroplate design. The result is the only one-piece, diffusion bonded, laminated expandable screen available. The warp and weave wires, the upper and lower drainage layers, and protective outer shroud are diffusion-bonded together. This locks in the dimensions of the openings in the screen. Doing so prevents any change in the micron rating of the screen under a variety of load conditions, thus ensuring the integrity of the screen over time.

A unique feature of this design is that the micron rating does not change during expansion. Expansion increases the distance between the warp wires. However, while the diameter of the weave wires decreases slightly, the diameter of the larger warp wires remains unchanged. The resulting increase in area is not sufficient to change the rating of the screen.

To reduce rig time and improve run-in efficiency and expansion integrity, the PoroFlex system incorporates integral joint threaded connections. The premium thread makes up like standard casing on the rig floor and allows rotation of the screen, if required. Full envelope testing, including bend radius testing with the toe of the screen constrained, (which sets the maximum allowable surface pressure during expansion to reduce greatly the possibility of exceeding the tensile limit of the system), has confirmed the operational limits of the connection.

Expansion

Fixed cone hydraulic expansion was selected to achieve greater expansion reliability and enable expansion in highly deviated and/or extended reach well bores. The use of fixed cone expansion provides a uniform outside and inside diameter of the screen and base pipe, which contributes to the load capacity of the system as a whole. In addition, fixed cone expansion, when combined with the stronger base pipe, can reduce the amount of solids free to flow in the formation by reducing the depth of plastic failure of the rock in the near-wellbore region. This, in turn, reduces the potential for the screen to plug, which diminishes the probability of erosional failure and the consequential loss of sand control downhole.
These features thus combine to provide long term reliability, flow assurance, reduced risk when performing remedial operations, and provide a longer-lived completion when run in the appropriate environment.

It should be noted that expandable screen technology is not a one-for-one replacement for gravel packing. Poorly sorted sands with high uniformity coefficients should still be completed using gravel pack techniques. While it is true that many wells today completed with either stand alone screen or gravel packs should be completed with expandable screens instead, to say that this technology is the magic cure-all where sand control is required would be an overstatement.

Nevertheless, the use of expandable screen technology is gaining acceptance around the world. Two recent installations are noteworthy; one completed in Brazil, the other in Brunei.

Case study: Brazil

In March, 2002, Petróleo Brasileiro S.A. (Petrobras) elected to complete a dual-zone openhole horizontal well with an expandable sand screen. At the time it was to be the longest expanded interval for the system and the first installation of the system utilizing the new VersaFlex liner system's expandable liner hanger as a screen suspension tool.

The completion, out of 7-in., 26-lb casing, called for the 61/8-in. 250 micron alloy expandable screen system. The expandable portion of the completion consisted of a 125 ft (38 m) upper interval, 183 ft (56 m) of solid expandable blank pipe with openhole annular barrier tools placed across the shale interval, and a 164 ft (50 m) lower producing interval, for a total expansion length of 472 ft (144 m).

Upon reaching the planned setting depth of 4,922 ft (1,500 m) for the screen suspension tool, the service supervisor was unable to build pressure to initiate expansion. In an effort to reduce rig time the string had been run in with the phenolic ball on seat, which degraded during running the screen to depth. Upon retrieval at the surface, a brass ball was installed, the string again run to depth, and the screen suspension tool set per plan.

The hydraulic expansion tool was then run to depth. Three intervals were expanded in one expansion run with an average surface pressure of 3,000 psi with no reported job incidents. The well bore was subsequently placed on production with rates approximately 25% above those expected. It should be noted that the production achieved when expandable screen technology is utilized typically exceeds expectations, particularly early in the life of the well.

In May of the same year, Brunei Shell Petroleum (BSP) selected the system to be run in a cased and perforated well. Another VersaFlex screen suspension tool was to be used. This well was being converted from a producer to an injector and the placement of screen to prevent sand production during shut-in was needed.

This completion was to inject into a single zone inside 7-in., 26-lb casing using the 61/8-in. 125-micron alloy system. With a total expansion length of 775 ft (236 m), the Brunei job would set a new record for expanded interval length.

The second deployment put all the planning into effect downhole. The screen suspension tool was run to a depth of 3,169 ft (966 m) and set without incident after dropping the setting ball to initiate the expansion process. The screen expansion tool was run to depth where it was discovered that the expected operating pressure for the pump rate was low. It was determined that the Full Flow Circulating Valve, which is run to allow the string to fill during running and provide a method of controlling the well if needed, was open. Setting down additional weight closed the valve and the expansion process was begun. The entire interval was expanded without incident in one expansion trip at twice the expansion rate of the previous well. This increase in rate has been attributed to rig capabilities and increased familiarity with expansion operations. In the post-job debriefing conducted at the base, everyone involved agreed that it was a virtually flawless job. Future candidates for the system are currently being identified by the Halliburton/BSP team in Brunei.

These and previous installations of the system have identified several critical factors for safe, reliable and productive expandable screen completions, namely:

• Candidate selection requires review and discussion of all wellbore and formation data. This will ensure that expandable screen technology is correctly applied in the environments for which is it best suited.
• Pre-job planning is essential. Job results are directly proportional to the amount of information exchanged and reviewed prior to the job.
• Borehole quality is critical to completion performance. No screen can be expected to conform to the wellbore under all circumstances until plastic failure of the rock has occurred. Therefore, every effort to drill a gauge and drift wellbore should be made.
• A proper fluids program must be developed. Attention must be paid to the cleanliness of the entire fluids handling system. Doing so will ensure the filter cake will either flow back through the screen or be readily treatable by remedial means.
• Computational methods for estimating the load placed on the screen should be used. Only through accurate prediction of these loads can one determine the long term viability of an expandable screen completion from a flow assurance and remediation perspective. Unacceptable reductions in completion ID over time will significantly decrease the value of the technology.
• Training programs for operational personnel result in superior rig site performance. This training should include expandable theory as well as on site job conduct.

Since the completion of these two jobs, Halliburton has finished development of the 81/2-in. alloy system and will be introducing the CRA version of both systems early in the third quarter of 2003. With inventory in place, a growing number of installations, and no reported failures of base pipe, screen, or connection in any installation to date, this expansion of the product line gives Halliburton a full range of technologies to meet the needs of operators in sand control environments around the world.