Oil Country Tubular Goods

Field tests of the next phase of monobore construction further validate its practicality

A live well, drilled in late 2004, provided key data to evaluate single-trip technology for economically constructing single-diameter wells.

Perry A. Fischer, Editor; and Robert E. Snyder, Executive Engineering Editor

After five years, with several hundred commercial installations in place, solid expandable tubular technology has proven to be a viable and economically feasible alternative to conventional drilling technology. This installation record, the evolving technology and applications spectrum, and the ever present need to lower lifting costs and maximize recovery have provided the impetus for the latest step-change toward the one-trip section, single-diameter wellbore.

This article is a follow-up of last year’s status report on progress made on the single-diameter well in World Oil’s July 2004 issue. That introduction discussed: 1) key drivers, emphasizing potential major cost savings for well developments, particularly in deepwater wells; 2) challenges, including tubular size limits, with 9-5/8-in. being the smallest usable size, with present tubular materials; 3) the necessary creation of a “bell,” or expanded section on the bottom of the existing string, into which the smaller, landing string is expanded and sealed to extend the single-diameter string; and 4) the need to underream and maintain an annulus sufficient for cementing around the bell.

In addition, the 2004 article detailed the testing of two short expansion sections in a South Texas well in 2002, creating a true single-diameter section. This monobore test required two expansions: one upward, from a pre-installed cone to expand the pipe up to the receiving pipe’s ID, and the other downward, to further expand the pipe to its final, single-diameter state and, in doing so, “over-” expand the outer pipe in the overlap section, creating a bell in the upper pipe. This second expansion for the bell is the reason for the current limitation of 9-5/8-in. expandable pipe. Smaller diameter pipe, if expanded that much, would exceed expansion (percentage) limits.

That early test was studied thoroughly to see what could be improved. The newest developments described here are: 1) an all-in-one tool was built and tested to see if the two expansion trips, and more, could be done in a single trip; and 2) whether expansion against, and into, a formation would be feasible and offer sufficient zonal isolation.

The tool was created by Enventure Global Technology and was tested in a live well in late 2004. This article describes these tests. It is based on discussions with Enventure personnel and from a presentation at OTC 2005.¹

THE OBJECTIVE

The single-diameter well has always been envisioned as the final evolutionary extension of solid expandable tubular technology. The resulting benefits from this ultra-slimmed wellbore configuration have been well documented² and include:³ 1) cost reduction – smaller riser, wellhead and BOP, smaller drilling vessel/ rig, smaller diameter casing, less drill fluids and cement; 2) reduced environmental impact: smaller environmental footprint, less cuttings/ fluids disposal; 3) operations efficiency – single drillstring, adaptable to automated drilling, optimal borehole for ROP, no drillstring changes; and 4) reservoir optimization.

In recently modeled worldwide offshore and subsea developments, the system greatly reduced observed and/or forecast drilling risks and trouble time. The prudent application of successive single-diameter expanded liners has proven to increase lateral reach potential by 20% to 50% and, in select applications, these results exceed the current industry lateral reach record by over 35%.¹

LIVE WELL TESTS

These tests were planned and executed in late 2004 with the following primary goals: full compliance with Health, Safety and Environmental (HSE) policies; and deploy/ expand 9-5/8-in. single-diameter liners. One test was for single-diameter well construction, the others tested the merits of expansion against, and into, the formation to achieve hydraulic isolation without cement and/or mechanical isolation.

All of the objectives were satisfied in these tests, which were planned and executed in a live well with a full Class III BOP stack, HSE systems, closed-loop mud system and zero-discharge tolerance.

A tool string, as illustrated in the figure, comprises seven major components and three minor components, from top to bottom:

• Sizing mill – hydraulically activated tool to cut/ pull excess casing/ ballast casing clad in the bell
• Anchor – hydraulically activated tool to anchor tension actuator to casing during expansion
• Safety sub – specially threaded connection with low breakout torque; used for contingency release
• Tension actuator – multiple-piston hydraulic actuator used to expand casing until packer is set
• Cup sub – provides surface area for hydraulic expansion
• Casing lock – carries casing weight as tool string moves downhole
• Extender – hydraulically activated tool to deploy cones and packer outside use to initiate expansion
• Expandable cones – hydraulically activated to expand the bell section for subsequent casing clad and liner body, sizes: 10.95 and 10.4 in.
• Packer setting tool – available as mechanical or hydraulic setting
• Packer – primarily used to seal off end of casing to provide pressure integrity during hydraulic expansion, and as a retainer during cementing operations; contains a sliding valve to provide cementing sequence flexibility.

Single-trip test procedure. The following series of steps were performed to test the new toolstring – a single trip, all-in-one, tool that can form both the bell and expand the casing run, as well as provide for contingencies.

For the surface strings, a 20-in. surface conductor was set at 101 ft, followed by 16-in structural casing, set at 450 ft. A special 11-3/4-in. surface casing was set at 2,098 ft. This string comprised 65 lb, L80 casing and three joints of proprietary, expandable 47-lb, LSX-80 casing and connections. These three joints were chosen so that their ID would match the expanded OD of the final single-diameter string. In other words, it served as the shoe track and bell, without actually being bell-shaped. An actual pre-formed bell would serve the same purpose, namely, allowing for cladding back the subsequent single-diameter liner with a metal-to-metal expansion and 100% hydraulic seal.

A pendulum assembly with a 10.25-in. rock bit and near-bit reamer, pinned for a 12-1/2-in. hole, drilled over 500-ft of hole for subsequent deployment of 9-5/8-in., 36-lb, LSX-80 expandable liner. After cementing the surface casing, the shoe track was drilled out with a 10.25-in. bit, short collar and 1° bent sub. This cleaned out cement without damaging the surface casing, which was subsequently used to expand against with the expanded liner. Ideally, this cleanout step should be part of a single-trip expansion deployment, perhaps achieved with a near-bit reamer.

Using specialized casing-handling equipment, which is required for expandable tubulars, the first two casing joints were run into the hole, with the bottom part of the monobore tool-string assembly pre-installed and locked against the inside of the casing. This section of the tool, from the safety sub down, comprised the extender, setting tool, both expansion cones, and the packer (see figure).

Fig. 1. Steps required for single trip bell formation and subsequent casing expansion. Click for enlarged view

Using a false rotary table, several more joints of casing were then run into the hole, followed by the rest of the toolstring, which is threaded onto the bottom portion of the tool. Both casing and toolstring are simultaneously run into the hole to bottom on drillstring/ toolstring, with the casing lock supporting the vertical casing load. The packer is also pinned to the casing, which holds the extender pipe and cones in the up (retracted) position.

Referring to the figure:

1. When on bottom, the casing and toolstring are picked up about 50 ft, Step a. Then a dart is pumped from surface.
2. The dart lands, pressure is applied, which shears the pins on the packer, which allows the extender, packer and expansion cones to drop out of the casing, Step b. Hydraulic pressure opens both cones to an OD of 10.95 in. (green) and 10.4 in. (blue). Once the extender has stroked out, the casing lock is disengaged and the casing is released.
3. The anchor is set, and then the tension actuator hydraulically multiplies force to begin lifting the expansion cones into the pipe. In inchworm-like fashion, and against the anchor, 10 to 12 pressure cycles are repeated to mechanically expand 20 to 36 ft of pipe to 10.95 in. (Steps c and d) to form the bell section. The 10.4-in. cone adds nothing at this point.
4. When the bell section is finished, the expansion cones are dropped into the bell and the pressure is released, retracting the 10.95-in. cone, which will not be used again, Step e.
5. Expansion of the remaining liner joints begins using the 10.4-in. cone. This can be done mechanically, as a contingency, but is designed primarily to be expanded hydraulically, by applying pressure through the toolstring to push up on the 10.4-in. cone. If done hydraulically, a small portion of the liner is first expanded to 10.4-in, Step f. 
       The anchor is released, and the packer is set by rotation in the 10.4-in. section, just above the bell, Step g. At this point, cementing, to any (annular) extent desired, can proceed through the packer. Regardless of cementing, the remaining expansion of the 10.4-in. section can now proceed, shown mechanically in Step h.
6. Once the 47-lb, surface casing shoe track is reached (Step i) a metal-to-metal seal can be established purely through expansion of the 10.4-in. ID (11.0 in. OD) pipe inside the 47-lb, 11-3/4-in. surface casing, as was done in the test well.
7. In the test well, the toolstring was then pulled, laid down, and a sizing mill assembly was run to cut off the unexpanded liner within and above the bell. However, in future tool generations, it is planned to be an integral part of the toolstring, since it would be ideal to have this as a self-contained contingency capability. This is shown in Step j.

Casing evaluation logs were then run, indicating uniform expansion IDs, with minimal-to-no ovality and minimal distortion of the cutting face.

Second test. This test was performed to evaluate expansion against, and expansion into, shallow Gulf Coast gumbo-laden formations. This test required drilling at least three separate hole diameters. A 9-5/8-in., LSX-80 expandable casing was expanded to a 10.4-in. ID and an 11.0-in. OD. The 10.25 x 12.5-in. drilling assembly was used to drill the first 120 ft of large hole as a fail-safe. Based on previous drilling results, a 9-7/8-in. bit with a straight hole motor was employed at low pump rates to control drill the next 200-ft section to limit washouts and obtain a continuous interval of 10.3 to 10.6-in. hole diameter for the expansion into the formation test.

The next 50 ft section was drilled with a 10.25-in. bit and 10.4-in. near-bit reamer to achieve a 10.77 to 11.0-in. hole diameter for the expansion against formation test. It was necessary to perform several isolated near-bit reamer runs to achieve the desired continuous hole diameters for the test, as confirmed by openhole mechanical/ acoustical caliper logs. Once the formation strength was obtained, sidewall cores were taken every 2 ft throughout the planned expansion interval for later analysis.

The expandable liner was run as in the initial test, but with a modified expansion string and a single, solid, expansion-cone assembly. Once on bottom, the liner was mechanically expanded to just above the planned expansion interval, and the tools were pulled. Prior to removing the non-expanded casing, the expanded liner was logged with an acoustic caliper and bond log suite that indicated highly uniform expansion diameter with limited to no ovality, and a 100% bond index throughout the expansion into the formation interval. This test confirmed a 100% hydraulic seal without cement or mechanical isolation.¹

SUMMARY

For the single-trip bell formation, casing expansion test, significant engineering and operational lessons were learned, furthering the tool development and testing efforts of the last several years. Although a single-diameter well was not attempted, the test successfully demonstrated positive results on several objectives, including: drilling operations; emergency release; a bell section formed, and a full, successful, single-diameter liner expansion using the mechanical jacking method. These raised the team’s confidence in the single- trip concept.

For the expansion against and into the formation, the tests confirmed the feasibility of doing this, and logging data indicated that isolation had been achieved. 

Click here for a complete list of World Oil’s annual expandable technology reports.

LITERATURE CITED

   ¹   Flippov, et al., “Continued evolution of the one-trip expansion, single-diameter wellbore,” Paper OTC 17437, presented at the 2005 Offshore Technology Conference, Houston, May 2 – 5, 2005.

   ²   Dean, et al., “Monodiameter drilling liner – from concept to reality.” SPE/IADC 79790, SPE/IADC Drilling Conference, Amsterdam, Netherlands, February 19 – 21, 2003.

   ³   Waddell, K., “Advances in single-diameter well technology: The next step to cost-effective optimization,” Paper SPE 90818, presented at the SPE Annual Technical Conference and Exhibition, Houston, September 26 – 29, 2004.