Fernando C. Hernandez, of SECC Oil & Gas, and Efrain Rodriguez, of IMP, discuss efforts to research rigless production solutions for Mexican deepwater operations.
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Figure 1: SECC’s connector installed on a manifold.Images from SECC. |
Mexico’s December 2016 Round 1.4 ushered in a new era for Mexico’s deepwater industry, with unprecedented commitments from international oil companies (IOCs).
The infusion of international technology will be key to Mexico’s success in unlocking deepwater developments. Mexico’s proximity to the US will support this quantum leap into deepwater, due to the supply chain, intellectual capital, and the workforce experienced in managing and delivering deepwater projects for many of the IOCs, who will now be expanding into Mexico.
Instituto Mexicano del Petroleo (IMP), a public research organization, has carried out extensive preparatory work to develop Mexico’s deepwater fields, years before the blocks were awarded to the IOCs, leveraging over 50 years of experience. In the last 30 years, IMP has provided state oil firm Pemex with technological support for the planning and development of offshore fields. Moreover, IMP’s researchers, complemented with SECC Oil & Gas’ global subsea experience, set out with the following objectives: (1) Increasing the feasibility of having future deepwater fields in Mexico produce optimally at first oil; (2) to enhance fields by incorporating and centralizing global lessons learned and best industry practices; (3) to reduce the reactionary and unplanned interventions that are common with deepwater fields
Rigless production
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Figure 2: A view of the connector’s inner workings. |
A key emphasis, from IMP’s researchers and SECC’s engineering and technical group, has been on introducing rigless production systems. This method was borne out of a step-change maneuver of pre-installing SECC’s female connectors on subsea manifolds in the North Sea. This, in turn, allows all wells linked to a manifold to be stimulated and intervened on, via single access point, by way of a DP (dynamically positioned) vessel. Rigless production differs from rigless interventions, as intervention equipment is bypassed altogether, and operations focus on an entire subsea production scheme, instead of just Xmas trees.
Operationally, once a manifold is installed subsea, a rigless male connector is deployed from a DP2+ vessel—via an open water downline, and mated with the corresponding female on a manifold, allowing for well stimulations to be carried out to the tune of 16-56 bbl/min, at 15,000psi. This methodology highly benefits deepwater developments, as it allows for the following:
Furthermore, should an operator opt to not install a connector at the build stage, a spare hub can be used to land seabed-based equipment. This is accomplished by mating a modified jumper—to a hub on a manifold—which ties in into a female SECC connector—reference Figure 3. Safety wise, SECC’s connectors allow for a vessel to connect and disconnect, with zero spills during normal operations. Should a DP2 vessel have a drift off, requiring an emergency disconnect, the connector solely requires tension or pull from the downline to disconnect. Upon this occurring, the connector instantaneously seals at both the male and female end, ensuring that the downline, and the well, are secured.
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Figure 3: The retrofit approach, which allows a connector to enhance a field. |
Intelligent access points and hydrates
Because deepwater temperatures are inseparably linked with hydrate formation, the international venture analyzed fields where production was disrupted due to blockages, or where hydrates indefinitely blocked an export line. IMP and SECC realized that key access points were not always accounted for – to inject chemicals to disassociate/remediate hydrates – instead an improvisation philosophy was used to find/create entry points.
The aforementioned improvisation demonstrated the effectiveness of the rigless production method in proactively creating intelligent access points at the build stage, or via the retrofit option, on manifolds. Furthermore, such points can also be created on pipeline end manifolds (PLEMs), to further target hydrates throughout a field lifetime.
There are, however, limitations to improvisation. In a scenario where a API 17H hot stab is the only means of injecting chemicals into a field, the stab severely restricts injection flow rates. Furthermore, if the access point is located on a PLEM that is kilometers away from the blockage near a manifold, the chemicals success is limited, as it comingles with a pipeline’s content, diluting a chemical’s effectiveness.
Reactive access points
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Figure 4: SECC’s seabed based equipment, with gimbaling and swiveling capabilities, for retrofit operations |
Alternatively, dedicated injection points can become blocked, requiring alterations to the subsea architecture. This is highlighted by pulling a jumper from a manifold, to create an access point, to enable a bespoke intervention panel with a hot stab entry point—for chemical injections—to be installed. This is common when an export line is completely blocked. Moreover, the bespoke panel must be designed, built, and tested, before it is deployed subsea: all of which delays hydrate remediation efforts.
Alternatively, when an export line isn’t blocked, but half of the flowlines that connect to a manifold are blocked, a jumper is also pulled, to create an entry point (jumpers with blockages cannot be pulled, as the hydrocarbons cannot be flushed). The drawback is that a producing well is now offline as the jumper linked to it has been pulled.
Importance of depressurization
IMP and SECC equally concluded that access points need to equally enable remotely operated vehicles (ROVs), and subsea depressurization/remediation equipment, to remove blockages via a vacuum. Depressurization is paramount, as chemical injections doesn’t guarantee the removal of obstructions. Furthermore, SECC’s male connectors are designed to accept a male intervention panel, enabling ROVs to swiftly mate the male connector, without a downline, onto a manifold to depressurize a subsea production scheme (See Figure 3).
Additionally, removing hydrates from a singular hot stab entry point on a subsea asset is to be avoided, as hydrates tend to reform in hydrate remediation equipment when removed. Thus, it is vital to outfit an intervention panel with ROV paddle valves and a hot stab, with a large bore, to remove hydrates at an efficient rate. A secondary hot stab is used to methodically inject chemicals—via the paddle valves—at the large bore stab. This allays hydrates from reforming as they exit, as they are dosed with chemicals, increasing the success rate of a remediation project. Failing to dose inevitably leads to additional downtime, as the subsea equipment must itself be cleared of hydrates before it can resume operations, which can occur multiple times.
Conclusion
IMP and SECC’s collaborative work concluded that the following be accounted for in Mexico’s imminent deepwater fields: (1) A minimum of one spare hub be available for two manifolds that connect to each other, or one spare hub if only one manifold is brought online; (2) that a manifold have access to all the flowlines and export lines (via intelligent valve arrangements) for flow assurance operations; (3) that said valve arrangement allows for well interventions to be carried out on all the wells linked to it. Furthermore, the creation of intelligent access points is not limited to manifolds, but it is to be equally applied to trees, as well as PLEM’s, to increase the productivity of future fields.
Fernando C. Hernandez is the subsea technical advisor at SECC. Hernandez speaks three languages and has extensive international experience in the ROV tooling, automated controls, subsea and well intervention sectors.
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Efrain Rodriguez is an offshore field development project manager at IMP. He holds a PhD in mechanical engineering from University College London and has 30 years’ experience in the offshore oil industry.
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