编者注：本封面故事首次出现在《Offshore》杂志 2023 年 9 月/10 月号上。单击此处查看完整问题。

随着全球减排的要求，运营商正在迫切寻找“绿化”其生产平台的方法。特别关注计划部署在巴西近海的新型和即将推出的 FPSO。

实现这一结果的一些最有希望的途径包括重新审视发电技术，运营商正在寻求通过使用联合循环电力系统来“电气化”他们的系统，以及用所有的技术取代燃气轮机。 -电力驱动器和电机。在某些情况下，他们实际上正在扩大燃气轮机的规模以实现更高的效率，从而降低排放。

传统上，海上勘探与生产行业一直使用开式循环燃气轮机，因为它们操作简单、重量轻/占地面积小，并且成功使用的历史悠久。但其中许多涡轮机，尤其是较旧的涡轮机，是大量碳排放的来源。FPSO 消耗的大部分能量通常由伴生气提供，伴生气要么由燃气轮机消耗用于发电，要么用于机械驱动；或压缩用于加工、出口或再注入目的。所有这些系统都提供了减排的机会。但仅发电一项通常就代表了新一代 FPSO 60% 以上碳排放的来源，因此提供了最大的减排机会。

总体而言，新的和即将推出的 FPSO 减排策略可分为三种策略。一是采用更大、更高效的燃气轮机，从而提高上部功率密度并减少占地面积。这种选择可以提供经济和环境效益。第二种选择是部署电动电机压缩机作为（旧式）燃气轮机驱动压缩机的替代品，这也有助于减少排放，同时提高功率密度。这两种选择可以与联合循环燃气轮机结合使用，在某些条件下可以进一步提高效率并有助于降低生命周期成本。FPSO 的全面电气化可能会重点关注联合循环发电技术的使用。

为了研究这些选择，贝克休斯的一个团队最近开发了一个生命周期成本分析模型，以比较典型大型 FPSO（220 kbbl/d，87 MW 电力需求）的发电和压缩要求的替代配置。该模型既考虑了碳足迹/碳价格，也考虑了经济因素，即燃气成本。正如论文 OTC-32513 中所述，结果表明，从开式循环发电系统转向联合循环发电系统时，碳排放量可减少约 20%。研究还发现，更大、更高效的燃气轮机（>40 MW ISO）带来更多好处，即总体成本节省 10% 以上，特别是与开式循环效率相比。

贝克休斯将有机会在巴西近海实施其中一些设计举措。它最近赢得了 MODEC 的一份合同，为 Equinor 位于盐下坎波斯盆地的 BM-C-33 项目的 FPSO 提供联合循环技术。新技术预计将减少该项目的碳足迹。

该订单包括涡轮机械设备，包括 LM2500 燃气轮机发电机和蒸汽轮机发电机技术，用于安装在 BM-C-33 FPSO 上的联合循环发电解决方案。今年 5 月，Equinor 向 MODEC 授予了一份工程、采购、施工和安装活动的一次性交钥匙合同。预计交付日期为 2027 年。

贝克休斯预计，在电力需求相同的情况下，与采用开式循环燃气轮机系统的类似 FPSO 相比，该 FPSO 的碳排放量可减少 20% 以上。这是继2020年Bacalhau FPSO获奖后，贝克休斯为MODEC和Equinor在巴西深水区开发的第二个联合循环发电FPSO项目。

对于BM-C-33项目，Equinor及其合作伙伴预计FPSO能够在油田生命周期内实现低于6公斤/桶油当量的碳强度目标，而全球行业平均水平为每桶油桶16公斤 CO ₂桶。

巴西国家石油公司还计划为其至少两艘即将推出的 FPSO 提供电气化服务。在最近于休斯顿举行的场外交易会上，公司官员提出了他们转向全电动 FPSO 概念的计划，首先是即将推出的 P-84 和 P-85 FPSO。这些 FPSO 将部署在桑托斯盆地的 Atapu 2 (P-84) 和 Sépia 2 (P-85) 油田。两个平台均采用标准化设计，产能为22.5万桶/天，油气处理能力为10MMcm/天。

最值得注意的是，FPSO 的标准化设计将包括巴西国家石油公司的全电动概念，该概念在很大程度上依赖于用电动机驱动所有旋转设备，这对于巴西近海的大型 FPSO 来说是首次。这一概念背后的想法是在每个即将推出的 FPSO 中配备一个单一能源中心，该能源中心将比现有浮船中安装的能源中心大 60% 左右。公司官员表示，FPSO的设计融合了更高效的发电系统和全面优化的工艺工厂设备，因此代表着平台减排技术向前迈出了关键一步。重要的是，巴西国家石油公司官员表示，这些设计不仅可以减少排放，还可以增加盐下地区的产量，从而提高这些储量的价值。

两艘FPSO还将基于MACC（边际减排成本曲线）方法和巴西国家石油公司自己的低碳战略，纳入其他减排系统和技术。除了减少发电排放外，该战略还重点关注其他典型的 FPSO 排放源，例如火炬、排放和逸散气体。通过回收货舱和加工厂排放的气体，可以实现零常规排放。通过封闭火炬系统回收气体，将实现零常规火炬燃烧。其他减少排放的措施包括对泵和压缩机使用变速驱动器；专为低无组织排放而设计的阀门； 从产生的气体中捕获、使用和地下储存CO _{2 。}

巴西国家石油公司表示，其中许多减排设计对于这种规模的大容量 FPSO 来说将是首创。这不仅包括全电力工厂概念，还包括更深的海水取水系统；货舱气体覆盖；以及注水泵的变速控制。Petrobras 表示，由于这些设计变更，温室气体排放强度将比以前的 FPSO 设计减少约 30%。

据报道，两家主要的建筑造船厂——中国海洋石油工程公司和 Seatrium（胜科海事/吉宝海洋与海事合并后的 实体）—— 正在研究建造 P-84 和 P-85 FPSO 的商业提案。这些提案原定于七月底提交。这两艘 FPSO 预计将于 2028 年就位并投入运营。

而且，新的 FPSO 设计即将问世，有望进一步减少排放。在 OTC 上，马来西亚工程集团 MISC 首次展示了其新建的 MMEGA FPSO 设计，据称该设计有可能将典型的 CO ₂ 排放量减少近 40%。

该公司声称，MMEGA设计基于适用于深水和超深水油田的第五代FPSO，据称可提供高生产能力和更长的油田寿命（长达35年）。排放量的减少将来自于封闭式火炬系统与联合循环发电的结合；用于压缩的全电动驱动系统；和气体回注。

分散系泊MMEGA设计包括双面单底船体，可容纳8个上部巨型模块，在左舷设有一个立管阳台，可支持多达51个立管插槽。 其上部工艺和公用设施系统将设计为处理 225,000 桶/天的石油、424 MMcf/天的天然气、250,000 桶/天的注水以及处理井流中高达 60 mol% CO 2 的能力_。石油储存容量为2 MMbbl，24小时内可卸载1 MMbbl。据说“超级模块”上部设计可以最大限度地减少接口，同时还提供了改进的系统集成。其他声称的好处包括减少总体工程、采购、施工、安装和调试时间表以及优化资本支出。MMEGA 表示，该设计已获得 ABS 的原则批准 (AiP) 和 SUSTAIN -1 符号。

Editor's note: This cover story first appeared in the September/October 2023 issue of Offshore magazine. Click here to view the full issue.

With the worldwide mandate for emissions reduction, operators are urgently looking for ways to ‘green’ their production platforms. A particular focus is being placed on new and upcoming FPSOs scheduled for deployment offshore Brazil.

Some of the most promising paths toward that result include a re-examination of power generation technologies, and here operators are looking to “electrify” their systems through the use of combined-cycle power systems, and the replacement of gas turbines with all-electric drives and motors. And in some cases, they are actually upsizing their gas turbines to achieve greater efficiencies, thereby lowering emissions.

Traditionally, the offshore E&P industry has used open cycle gas turbines due to their simplicity of operation, low weight/compact footprint, and long history of successful use. But many of these turbines, especially the older ones, are a source of significant carbon emissions. A large portion of the energy consumed on an FPSO is typically supplied by associated gas, which is either consumed by the gas turbines for power generation or for mechanical drives; or compressed for processing, export, or re-injection purposes. All these systems present opportunities for emissions reductions. But power generation alone typically represents the source of more than 60% of the carbon emissions on recent-generation FPSOs, and thus provides the largest opportunities for emissions reduction.

Broadly, the strategy to reduce emissions on new and upcoming FPSOs can be divided into three strategies. One is to adopt larger and more efficient gas turbines, thus increasing topside power density and reducing footprint. This option can provide both economic as well as environmental benefits. The second option is to deploy electrically driven motor compressors as an alternative to (older) gas turbine-driven compressors, which also helps to reduce emissions while also improving power density. These two options can be combined with combined cycle gas turbines, which can bring further efficiencies and help reduce lifecycle costs under certain conditions. Full electrification of FPSOs will likely focus heavily on the use of combined cycle power generation technologies.

To study these options, a team at Baker Hughes recently developed a lifecycle cost analysis model to compare alternative configurations for both power generation and compression requirements on a typical large size FPSO (220 kbbl/d, 87 MW power demand). The model took into account both the carbon footprint/carbon prices, as well as economic considerations, namely fuel gas costs. The results, as described in the paper OTC-32513, showed that carbon emissions can be reduced by ~20% when moving from an open cycle to a combined cycle power generation system. The study also found that larger and more efficient gas turbines (>40 MW ISO) bring further benefits, namely a greater than 10% savings in overall cost, especially when compared to open cycle efficiencies.

Baker Hughes will have the opportunity to put some of these design initiatives into effect offshore Brazil. It recently won a contract from MODEC to provide combined cycle technology for the FPSO on Equinor’s BM-C-33 project, located in the presalt Campos basin. The new technology is expected to reduce the project’s carbon footprint.

The order comprises turbomachinery equipment, including LM2500 gas turbine generators and steam turbine generator technology, for a combined cycle power generation solution to be installed on the BM-C-33 FPSO. Equinor awarded a lump sum turnkey contract to MODEC for engineering, procurement, construction and installation activities this past May. It has an expected delivery date of 2027.

For this FPSO, Baker Hughes expects a more than 20% carbon emissions reduction versus similar FPSOs with open cycle gas turbine systems, with the same power demand. This is the second combined cycle power generation FPSO project developed by Baker Hughes for MODEC and Equinor in Brazilian deep waters, following the award for the Bacalhau FPSO in 2020.

For the BM-C-33 project, Equinor and its partners expect the FPSO to be able to achieve a carbon intensity target of less than 6 kg/boe over the field’s lifetime, while the global industry average is 16 kg CO₂ per barrel.

Petrobras also has plans to electrify at least two of its upcoming FPSOs. At the recent OTC in Houston, company officials presented their plans to move towards an all-electric FPSO concept, starting with its upcoming P-84 and P-85 FPSOs. These FPSOs will be deployed at its Atapu 2 (P-84) and Sépia 2 (P-85) fields in the Santos basin. The two platforms will have a standardized design, with each having a production capacity of 225,000 bbl/d of oil and gas processing capacity of 10 MMcm/d.

Most notably, the FPSOs’ standardized design will include Petrobras’ all-electric concept, which relies heavily on driving all rotating equipment with electric motors—a first for FPSOs of this large size, offshore Brazil. The idea behind this concept is to have a single energy center in each forthcoming FPSO that will be about 60% larger than those installed in existing floaters. Company officials say that the FPSOs’ design incorporates more efficient power generation systems and fully optimized process plant equipment, and thus represents a key step forward in platform emissions reduction technology. Importantly, Petrobras officials said that these designs will not only reduce emissions but also increase production from the presalt regions, and thereby boost the value of these reserves.

The two FPSOs will also incorporate other emissions reduction systems and technologies, based on MACC (marginal abatement cost curve) methodology and Petrobras’ own low-carbon strategy. Besides reducing emissions from power generation, that strategy is focusing on other typical FPSO emission sources such as flaring, venting and fugitive gases. Zero routine venting will be achieved by recovering vented gases from the cargo tanks and the processing plant. Zero routine flaring will be achieved through recovery of gases through a closed flare system. Other measures that will reduce emissions include the use of variable speed drives for the pumps and compressors; valves designed for low fugitive emissions; and capture, use and subsurface storage of CO₂ from the produced gas.

Petrobras says that many of these emissions-reducing designs will be firsts for large-capacity FPSOs of this size. That includes not only the all-electric plant concept, but also deeper seawater intake systems; gas blanketing for cargo tanks; and variable speed control on water injection pumps. As a result of these design changes, Petrobras says that the GHG emission intensity will be about 30% less than previous FPSO designs.

Two major construction shipyards – China Offshore Oil Engineering Corporation and Seatrium (the merged Sembcorp Marine/Keppel Offshore & Marine entity) – are reportedly working on commercial proposals for the construction of the P-84 and P-85 FPSOs. The proposals were due to be delivered at the end of July. Both FPSOs are expected to be in place and in operation by 2028.

And, new FPSO designs are coming that promise even greater emissions reduction. At OTC, Malaysian engineering group MISC premiered its newbuild MMEGA FPSO design, which it says has the potential to cut typical CO₂ emissions by almost 40%.

The MMEGA design is based on fifth-generation FPSOs for deepwater and ultradeepwater fields, and is said to provide a high-production capacity and longer field life—up to 35 years, the company claims. The emissions reductions will come from the inclusion of a closed flare system teamed with combined cycle power generation; an all-electric drive system for compression; and gas reinjection.

The spread-moored MMEGA design comprises a double-sided single-bottom hull and can accommodate eight topsides mega-modules, with a riser balcony at the port side that can support up to 51 riser slots. Its topsides process and utility systems will be designed to handle 225,000 bbl/d of oil, 424 MMcf/d of gas, 250,000 bbl/d of water injection and treatment of up to 60 mol% CO₂ in the wellstream. Oil storage capacity is 2 MMbbl, with offloading of 1 MMbbl feasible within 24 hours. The “Mega-Module” topsides design is said to minimize interfaces, also providing improved system integration. Other claimed benefits are a reduced overall engineering, procurement, construction, installation and commissioning schedule and optimized capex. MMEGA says that it has secured approval in principle (AiP) and the SUSTAIN -1 notation from ABS for this design.