The drilling industry has always relied on cement as a primary barrier. Although the cement represents about 5% of the well cost, when squeezes are required, cementing averages 17% of the well cost. Only 50% of the squeezes achieve the objective of establishing a barrier for well integrity. A little bit more than half of the failures can be attributed to operational challenges (pump failure, cement contamination), or design oversights (cement recipe, centralizers). However there are still cement failures with perfect design and field execution. These failures typically exhibit some of the following characteristics: high deviation, high pressure, washouts, natural fractures, long casing section, heterogeneous sands. For these specific conditions, it is beneficial to add an assurance that would maintain the integrity of the well even in case of bad cement. Some of the assurances used include port collars, external casing packers (ECP) and swell packers. Port collars allow a squeeze above the first stage cement, while ECP serves as a base for a second stage cement, and swell packers provides a baffle for sustained casing pressure. A more recent technology is the well annular barrier that can form a combined barrier with cement, and can also be used as a stand-alone primary barrier. The well annular barrier is a metal-expandable barrier that is expanded with hydraulic pressure. It is full bore, highly customizable, and qualified to ISO 14310. The metallurgy allows the packer to shape fit into either an open hole with irregular geometry or inside a casing to preclude annular pressure build up by giving a life-of-well reliable seal. The well annular barrier has been deployed in a variety of wells to achieve well integrity with and without cement, protect the B-annulus from sustained casing pressure, or serve as a barrier between reservoirs that cannot be commingled. This paper performs a review of the technologies used for cement assurance, their advantages and disadvantages. Case histories of well annular barrier deployments are presented, including a case where the well annular barrier was used as a stand-alone well barrier element without the need for dispensation. This paper also discusses how the well annular barrier fits into the regulatory requirements for well construction providing to the drilling industry an alternative to cement for the purpose of well integrity.

In December 2014 a metal annular packer equipped with sealing elastomers, was installed and verified in an offshore platform well in Norway. The annular packer was installed to function as a barrier element against pressure buildup from shallow formations in the overburden with limited flow potential, containing liquid only (no gas). The packer was installed between the intermediate casing and the production casing. Upfront the installation the packer was tested and qualified according to ISO 14310 V3. This paper describes the operation, which was a world’s first, as well as the implications this achievement has for the industry in terms of preventing the plague of sustained casing pressure (SCP). SCP can be defined as pressure in any annulus that is measurable at the wellhead and rebuilds when bled down, not caused solely by temperature fluctuations or imposed by the operator. The wells were facing B-annulus pressure build-up. Studies revealed that it originated from shallow formations in the overburden. A project team was challenged to investigate find and verify a barrier for the 9 5/8’’ x 13 3/8’’ annulus. The initial, two main methods attempted were second stage cementing and long primary cement jobs. Second stage cementing had operational limitations while long primary cement jobs were subject to narrow ECD margins. Alternative methods were evaluated because of these challenges and the concept of the metal packer was considered being the most suitable option. This new type of packer had already been qualified for use in this operator’s wells; however, further testing was required before installing the packer as a barrier element. These tests extended the qualification from 345 bar ISO 14310 V3 rating within the load envelope and needs defined for the well. In addition, an ISO 14310 V6 test was performed (V0 gas test without axial load). One of the potential limitations of the packer was that it was an anchor-less design lacking a dedicated axial load- bearing element. Simulations had shown significant axial movement during casing pressure tests in green cement. The concern was that this might result in damaging the packer seal area during expansion. This risk was in the end mitigated by testing the annular barrier in fully set cement. The packer was mounted on a 9 5/8’’ casing joint and installed as a part of the casing string. The casing was successfully run to total depth (TD) and cemented around the shoe as planned without any losses. After cement had fully set, the casing was tested to 345 bar, simultaneously setting the packer. The packer was successfully verified by pressure testing the B-annulus to 100 bar for 10 minutes. The packer’s sealing capability will continue to be monitored during production (B-annulus monitoring) for ongoing verification of integrity. SCP is a concern throughout the industry, where it is of vital importance to evaluate the flow potential and associated risk. In wells where it can be concluded that both the flow potential and the associated risk is limited, the operator may operate the wells with SCP. In all other cases the SCP should be eliminated. With the introduction of this new type of annular barrier element, operators will not only save money on costly slot recovery - but it will construct safer wells without SCP.

A novel, Well Annular Barrier (WAB) was introduced back in 2011 as an open-hole, zonal isolation packer. Its strength, ruggedness and pressure capacity over the past four years has proven it a valuable solution. Especially for ensuring the successful cementing of casing strings which were required to be run through challenging environments such as overburden, depleted zones, water bearing sands or unconsolidated zones. Work is in progress to develop a verification system for WAB expansion and integrity, further growing its capabilities and the operating envelope in which it can be deployed. This will in turn increase the WABs potential applications, and use as a stand-alone, open-hole barrier. The newly developed system consists of pressure and temperature sensors either mounted independently from, or integrated with, the WAB. Annular sealing integrity will be confirmed by direct pressure measurement down-hole. For SCP applications, this will replace indirect confirmation of integrity via cement bond logs, which is the current practice. A verification table in line with requirements outlined in Norsok D-010 has been prepared to comply with industry standards for barrier verification. The current climate in the oil & gas industry calls for novel solutions to known challenges. Well integrity in the overburden is one such challenge the industry has a high focus on, and solutions must meet a challenging set of requirements. New solutions need to be equal to or better than existing ones, hence qualification requirements and documentation are paramount in delivering innovative solutions. Some operators do not accept sustained annulus pressure in producing wells, especially in HPHT applications. The WAB combined with this new Well Data Monitor (WDM) for verification of pressure seal is an evolutionary step that could eliminate this challenge. It offers a new ‘tool in the box,’ expanding the operating envelope and enabling advanced well construction with no compromises. This evolution of the WAB can aid to further prevent surface casing pressure (SCP), a huge concern throughout the industry. With the introduction of the WAB with sealing verification, operators can more easily construct robust and safe wells while at the same time, reducing construction time and cost.

International standards for well barrier integrity traditionally prescribe cement as annular sealing material. Despite a more than 100-year long history using cementing techniques, a high number of wells have poor annular integrity and are facing sustained casing pressure (SCP). A quality assessment of the cement seal is obtained by return volume and surface pressure trend calculations together with bond logs. All of these measurements are indirect and open for interpretation. Commonly, excess cement volumes are pumped to account for uncertainties but cement failure rate remains high. This paper describes an extensive testing and qualification program performed on a wireless downhole measurement system. Testing has been done on a component and system level basis on the permanently deployed equipment together with the hardware, software and telemetry on the equipment designed to retrieve the data. Focus has been given to robustness and simplicity to accurately capture the data of interest and ensure a fast and reliable download. A direct measurement of annular integrity is now available. A continuous pressure and temperature measurement, named the Well Data Monitor (WDM), can be mounted on the exterior of the casing or liner. The system is non-intrusive to the tubulars and communicates by acoustics through the pipe-wall. No control lines to surface are needed. Interrogation of the sensor pack will provide a full history of events from deployment to the time of download. Hence, historical pressure and temperature data are available from the time of deployment, through the process of establishment of annular barriers to the final verification test. The verification test will provide a direct and non-negotiable measurement of integrity. The development of the WDM was initiated following a need to provide verification for the Well Annular Barrier (WAB) to confirm to Norsok D-010 barrier requirements and to use the WAB as a barrier in open-hole.

The annulus between the 9⅝″ and the 13⅜″ casing strings within a Norwegian field development had historically exhibited pressure build-up at surface on many wells. It had been determined that the source of the pressure was a gas-charged formation just below the 13⅜″ shoe. Eliminating surface annular pressure (SAP) was a priority along with easy barrier verification for the lifetime of the well. To eliminate the SAP several methods had been trialled over the years, including single-stage cementing, ECPs, and liner tie-back solutions—all of which had failed to resolve the problem. Meanwhile, a hydraulically expanded steel annular barrier had been successfully deployed by the operator for zonal isolation in a number of wells across various reservoir sections. It was proposed that the same technology be used as an alternative solution to eliminate the SAP. To be utilised as a primary well barrier, the solution had to pass a number of significant criteria. It was carefully reviewed by the operator’s well integrity team to ensure that the system complied with their own company standards and the Norsok D10 guidelines. Verification of the annular barrier as the primary barrier was achieved by the application of surface pressure down the 13⅜″ by 9⅝″ annulus; pressure equivalent to the fracture gradient of the formation below the 13⅜″ shoe plus a 1,030 psi surplus. This installation marks the first time that something other than cement has been installed in a well completion as a primary barrier.