Currently, production from sand-prone environments accounts for approximately one-third of BP’s current total production, and this will grow significantly as many of BP’s new growth areas ramp up production over the next few years. In addition many of BP’s water injectors will require sand control.


Well completions in sand-prone environments raise several major risks not normally faced in more competent formations. In many cases these risks, and the costs of remedial activities, are magnified by the wells being operated subsea. The nature of these risks can be summarized as:


· Infant mortality associated with equipment failure in a demanding environment;


· Loss of integrity or productivity on production due to the selection of a non-optimum sand-face completion technique;


· Loss of integrity down hole or on surface due to sand production on water breakthrough;


· Production and/or reserves losses due to watering-out of wells due to the inability to shut-off unwanted water from discrete zones;


· The build up of scale impacting productivity; and


· Injector performance impairment due to loss of injectivity and conformance owing to sand fill.


The potential consequence of these risks is degradation of the capital efficiency of many projects through the inability to deliver either planned production profile and/or reserves or through a substantial increase in capital or operating expenditure.


Over the past decade BP’s primary sand control techniques have been principally frac packs, openhole gravel packs (OHGP) and standalone screens (SAS).


Service hands get ready to lower an expandable sand screen into a well bore. (Photo courtesy of Weatherford International)

In the Gulf of Mexico frac packs have been widely employed, and the region has built up a high level of knowledge and expertise in installing and operating this sand control completion type. Frac packs are highly suited to reservoir sections with multiple laminated sands or stacked pay where the combination of stimulation and sand control has been highly productive.


In other parts on the world such as Azerbaijan, Angola and Trinidad, BP has installed OHGP in high angle wells, delivering very high production rates. Over recent years, BP has completed a large number of OHGP and is now setting industry standards with regards to productivity and is building a good track record with reliable longer-term performance.


A large proportion of BP’s future water injector portfolio will require sand control completions. Many of these wells will need to be multizone injectors. A key requirement is for a completion type that offers the sand control and injectivity capability of an openhole completion coupled with the selectivity of a cased-hole completion. Expandable sand control technology will provide the operator with the ability to selectively produce from or inject into multiple zones to maximize reserves recovery.


Additional benefits of running expandable completions include the increased installation efficiency due to the reduced logistical concerns of pumping and gravel handling issues associated with typical OHGP.


BP has been gaining a considerable amount of expandables experience since the first expandable completion was run in 2001 in Egypt. Since then BP has installed more than 20 expandable completions around the world with the majority in oil producers and the remainder in water injectors and gas producers.


The drivers for using expandable sand completions in these areas include:


• Reduced exposure to logistics and health, safety and environment risks during installation phase;


• Reduced costs during the installation phase;


• Reduced well count;


• Cased-hole functionality, in particular compatibility with downhole flow control (DHFC),


• Eliminating the need for multistage cased hole gravel pack completions;


• An alternative to OHGP completions; and


• Improved sand control integrity when compared to stand alone screens.


The 20-plus installations have included the world’s first one-trip expandable sand control systems installed in a horizontal oil producer in the Schiehallion field, West of Shetland. This completion was chosen to provide improved sand control integrity compared to a standalone screen which has been the completion type typically run in this field. The completion included Weatherford’s 5½-in. MKII expandable sand screens (ESS) — 1,220 ft (372 m) of which were run — a swell packer to prevent migration of gas into the oil producing section of the well and a fluid loss valve (FLV) to provide loss control after the ESS deployment.


The screens were expanded in two passes (from top to bottom). The first pass was with a 6 5/8-in. fixed cone bottomhole assembly, and the second pass achieved compliant expansion using the axial compliant expansion (ACE) tool. The installation and expansion of the screens was carried out successfully, and the well was completed 6 days ahead of the plan.


BP has also recently installed and expanded in one trip, the longest Weatherford 4½-in. ESS string in the Schiehallion field, West of Shetland, 1,865 ft (569 m), and operates a well on the Chirag field in Azerbaijan which has produced over 20,000 b/d through a 4½-in. ESS completion.


In early 2002, BP prepared a set of minimum specifications for the development of an 8½-in. expandable completion system and formed collaboration agreements with several oilfield completion equipment suppliers. The aim was to develop a cost-competitive high-performance sand control system which would provide openhole productivity with cased-hole functionality in an 8½-in. open hole. The system would be run and expanded in a single trip to ensure efficient installation, an essential requirement in making the new system competitive with more established sand control technologies in high-cost environments. Once the lower completion was run, a smart or intelligent upper completion would then be run and set across the screens in order to manage fluid flow across the reservoir section.


A strategy was adopted that involved the initial testing of the equipment in test wells and jigs, then progressing to installations in relatively simple low-cost environments, e.g. onshore. Once enough confidence was achieved, the system was installed in higher cost offshore environments.


As part of this program the world’s first Weatherford one-trip 7-in. expandable reservoir completion (ERC) was run in an onshore well in south Texas in 2004 as part of BP’s Field Trial Qualification Test Program. The planning of the job was managed by the business unit in partnership with BP’s Exploration and Production Technology Group.


The completion installed included two joints of 7-in. ESS across two gas zones and five 7-in. expandable zonal isolation (EZI) joints run in between them and other water-bearing zones in the open hole to isolate the reservoirs from each other. Once the completion was run to depth, the hanger was set and the completion compliantly, selectively expanded in one trip. The openhole zonal isolation capability of the EZI joints run in this well was successfully tested to a differential pressure of up to 1,500 psi.


Since this installation, three more 7-in. ERC completions have been run in more and more challenging environments, including a single-zone water injector installed offshore in Azerbaijan.


One of the major lessons learned throughout the qualification testing of the 7 in. ERC system is just how critical stack-up trials and then field trials have been in developing this technology. Ongoing work is aimed at broadening the operating envelope of the expansion tools and ERC components in more challenging environments (such as subsea applications). We will then assess the long-term performance of the completions in a number of environments, such as producing wells with high water cuts and multizone water injectors operating above fracture pressure.


BP, along with its key partners, is at the forefront of developing and applying expandable completion technology. Rigorous planning and detailed engineering are at the core of making this technology applicable in a wide range of applications. With an ever increasing number of applications, the next few years will see expandable completions playing a bigger role within BP’s and other operators’ sand control portfolio.