In 2003, the industry began a journey towards the next target for expandable reservoir completions — multizone systems for 8 1/2-in. open hole. Operators were beginning to recognize that drilling this hole size could facilitate zonal isolation and intelligent completions so that the last drops of hydrocarbons could be squeezed from mature fields as well as increase overall efficiency for new ones. At the time, expandable technology centered on sand screens (ESS) of 4 in. to 51¼2 in., ideal for long horizontal wells in a single formation, but was not significantly applied to situations requiring zonal isolation or multizone completions especially where high differential pressure ratings are required.

At that time Weatherford and BP began a multiyear collaboration to develop a new approach to expandable completions in 8 1/2-in. holes. BP made available a number of wells in several locations where different variants of the developing Expandable Reservoir Completion (ERC) system could provide further proving ground for the technology.

Technology overview
ERCs depend on two capabilities: expandable zonal isolation and expandable sand screens.

Figure 1. Expandable zonal isolation (EZI) system is being made up in rotary during the Azerbaijan job. (Image courtesy of Weatherford)
Expandable zonal isolation (EZI) must achieve results equal to well-cemented casing in order to be usable. The technology developed adds an elastomer to the outside of the tubing to seal tightly against the formation. In theory, a zonal isolation system could provide a more reliable seal than conventional cemented casing, because it could reduce the risks associated with cement-job quality. Eliminating the necessity to set casing also helps maintain a larger hole diameter for the eventual completion. The challenge with the zonal isolation portion of the system was wear in the rotary expansion tool, which relies on pressured rollers to force the tubing compliantly against the well bore. Because this is solid tubing rather than the slotted tubing used for ESS, higher wear rates were expected. The 7-in. ESS is a variant of standard, smaller systems, and is designed to be fully compliant in an 8 1/2-in. hole, using a weave tailored specifically to the particular sand formation of each zone to be completed.

The third component is blank pipe, which is run between expandable zones. For example, isolating a thick formation requires only two EZI joints, one at the top and the other at the bottom, with blank unexpanded pipe in between. Using blank pipe speeds installation and saves the cost of additional expandables. Blank pipe is also used between the EZI and the ESS and between sections of ESS. This unexpanded blank pipe provides the setting point for conventional sized packers and other intelligent completion equipment.

The first wells for BP
As prototype tools were developed through the collaboration program, they were put through the paces in a number of BP’s wells:
Onshore US (multizone gas production well). The world’s first 7-in. ERC was run and fully expanded in a single trip in a well in South Texas in the United States. Five EZI units were used to isolate the six zones encountered in the well and two sections of ESS were run across the upper and lower gas zones. The operation was performed without any downtime, equipment failure, or major issues, and a post-expansion caliper log confirmed that full and compliant expansion was achieved. All indications are that the gas zones are isolated from the water zone below.

Caspian Sea 1 (single-zone water injector). The Caspian installation represented the first commercial installation of the 7-in. ESS into a known sand-producing reservoir. The field provides a challenging sand-control environment, with high reservoir stresses and complex wellbore trajectories. A post-expansion caliper log confirmed that full and compliant expansion was achieved. Following a short flow-back period for wellbore clean-up, the well has very good injectivity.

Alaska well 1 (triple-zone water injector). The completion was successfully installed, and the full and controlled expansion of the range of commercially available 7-in. expandable components was performed in two trips. A second expansion trip was required because of tool-life limitations of the first generation EZI expander. A post-expansion caliper log confirmed full and compliant expansion of all components.

Alaska well 2 (triple-zone, four sand, water source well). This application was planned to allow low salinity water production with future high water salinity breakthrough shut-off options. Two expansion trips were required because the length of screens exceeded the capability of the first-generation ESS expansion tool. A post-expansion caliper log confirmed expansion, and the well was brought online.

Unfortunately, one of the sand zones had a particle size distribution smaller than could be retained by the 150 micron weave, and sand production was observed. This was later confirmed during production logging tool and downhole camera runs.

Azerbaijan well
This was the first application of ERC in an oil production well. EZI and blank pipe would be used to isolate the upper formation (which was already being drained by a nearby well), while ESS would be used to selectively produce the lower oil-producing formation underneath. The conventional approach would have been to drill the upper sand in 81¼2-in. hole and run a 7 5/8-in. cemented liner to isolate this productive zone. The reservoir is then drilled with a 6 1/4-in. hole, completing it with a slim, openhole gravel pack (OHGP) or 4 1/2-in. ESS.

In this application, an ERC system was used in an attempt to reach total depth (TD) with an 8 1/2-in. hole. This saves the cost, risk and time of the liner and has a slight productivity benefit from the larger diameter screens.

The expansion bottomhole assembly was run into the well, and the EZI and ESS were expanded without incident. When the expansion tools reached the surface, they were still in excellent condition, with negligible wear of the enhanced, Generation X expansion tool roller bearings. Subsequent image logging confirmed that both the ESS and EZI were in contact with the well bore and that the EZI would affect a seal.

Once the upper completion was installed, the well was brought online with outstanding results.

The pressure build up analysis of the well infers that the EZI device provides an effective seal from the upper sand. Having reached an operating flow rate in excess of 25,000 b/d of oil, this well is now one of the highest production rate ESS wells of any size globally. Sand control is also very good with minimal solids production at a level that places the well among the best sand control wells in the area.

Benefits and futures
There have been a total of six installations performed during the qualification of the 7-in. ERC system. These installations are providing business units across BP with the confidence to select the 7-in. ERC system as a viable alternative to currently available sand control completions such as open-hole gravel packs or stand-alone screens in a range of environments. The 7-in. ERC system is becoming the completion of choice and the completion basis of design in a number of BP developments for both producers and injectors. The drivers for using ERCs include:
• Reduced exposure to logistics and health, safety and environmental risks during installation;
• Reduced costs during installation;
• Reduced well count required to develop more marginal areas by allowing the use of multizone completions;
• Cased-hole functionality, multizone production/injection;
• An alternative to OHGP; and
• Improved sand control integrity compared to stand-alone screens.

This system is expected to play a crucial role in future field developments. In effect, ERC offers all the benefits of openhole multizone completions without cased-hole costs and compromise in terms of productivity. And by maintaining an 81¼2-in. hole size to TD while offering zonal isolation and targeting multiple producing/injecting zones, ERC also expands the potential for intelligent well completions.

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