作者：Simon Leiper，Viking 完井技术公司

平衡能源需求以及碳排放对全球可持续性和净零排放努力的影响是能源供应链中每个人都必须认真考虑的挑战。尽可能清洁高效地生产碳氢化合物是共同的责任。 

随着对天然气的需求不断增长，最大限度地提高最终采收率并尽量减少实现该目标所需的资源对于实现更好的平衡至关重要。因此，运营公司越来越需要一种解决方案来应对影响或在许多情况下停止生产的气井积液问题。当行业考虑最佳前进方向时，速度管柱在延长油井寿命方面的进步和集成为运营商提供了另一种途径。 

不断发展的完工要求

速度管柱是现有油井的补救措施 — 可能在需要速度管柱解决方案的数年前就已完工。它适用于各种油井要求，因为不同油井面临的挑战可能各不相同，具体取决于油井最初的开发和完工方式、油井的地面基础设施以及当地服务（如钻机、提升机、盘管、电缆和专业知识）的可用性。 

速度管柱理论非常简单。通过减小生产管柱直径，产气速度会增加，同时流体承载能力也会随之提高，从而恢复稳定的生产条件。图 1 展示了这一点，该图比较了载液大口径生产油管与速度管柱 VLP 的垂直提升性能 (VLP) 曲线。     

生产管柱直径是通过在现有生产管柱内安装和悬挂较小直径的管柱来实现的。尽管速度管柱理论的基础相对简单，但成功应用却并非如此。 

速度管柱是现有井的补救措施。因此，目前还没有可供参考的标准速度管柱设计。 

对于集成速度管柱的项目，要想成功，需要详细审查现有井设计和与井相关的任何操作信息，以选择正确的解决方案来重新完井并延长井的使用寿命。除此之外，其他考虑因素（如服务、钻机、盘管、液压修井机、提升机、电缆和流量控制设备的本地可用性）也同样重要。

速度弦设计

最简单的速度管柱形式之一是将内管柱从安装在地面的传统油管四通上下入并悬挂。这些管柱通常基于连续油管或涉及简单的接头管柱。 

常规速度管柱安装在悬挂器上，安装在地面的四通管段上，需要永久锁定油管可回收地下安全阀 (TRSSSV)。这些常规方法存在井控问题，可能会妨碍速度管柱的安装。

通过集成完井设计，解决与常规速度管柱安装相关的具体问题，其中所有速度管柱设备都安装在 TRSSSV 下方的井中。常规钻机、提升机、液压修井机或盘管都是部署选项之一。 

所需的核心设备是液压设定速度管柱悬挂封隔器，它需要穿过 TRSSSV 中的限制，然后设置在下方内径更大的油管柱中。未来的退役将需要通过相同的限制进行回收。

TRSSSV 轮廓、油管柱尺寸、重量、材料和压力等级的不同组合需要各种专门设计的封隔器，而由于当今专注于行业验证，因此需要按照 API 11D1 V0-R 进行测试。 

如图 2 和图 3 所示，在封隔器下方，油管悬挂长度可达 5,000 米，以提供提升油井所需的生产管道。可能需要滑动门 (SSD)、接头型材和陶瓷盘等临时封堵装置等附加设备来促进从安装到废弃的作业。 

在某些情况下，在安装速度管柱之前，必须暂停井。这可以通过运行电缆封隔器来实现，该封隔器是短 BHA 的一部分，它充当塞子，直到通过速度管柱将其打开。

对于通过 TRSSSV 和回收，存在相同的设计要求。因此，两种封隔器类型的设计、开发和测试通常同时进行，以提供最佳的设计灵活性。当试图修复最初设计时没有考虑未来安装的井时，这一点至关重要。 

图 4 和图 5 显示了两个使用悬挂管柱完井的示例。图 4 显示的是速度管柱位于悬挂管柱上方，图 5 显示了速度管柱和悬挂管柱之间的机械连接。

第三个选择是密封连接，从而隔离井的特定部分。在这个隔离区域内安装 SSD 可以有效管理不同的储层或修复完整性问题，例如衬管顶部损坏。

案例研究：速度管柱箱井设计和注意事项

十多年来，Viking Completion Technology 一直是阿曼地区基于完井的速度管柱解决方案的先驱。这些解决方案对数百口当地天然气井的最终恢复起到了关键作用。自 Viking 首次为阿曼的运营商应用其速度管柱解决方案以来的 10 多年里，其团队已对设备进行了调整，以满足不断变化的客户需求 — 目前提供的解决方案压力高达 7,500 psi，评级为 V0。 

对于特定的阿曼运营商而言，Viking 设备的改进对于支持其长期运营和技术进步至关重要。在合同的早期阶段（始于 2013 年），规格不涉及任何特殊验证要求，而压差较低，约为 3,000 psi。在 10 多年合同的最初几年，这演变为对 API 11D1 V2 验证和 5,000 psi 压力的要求。 

由于最终用户的政策变化，最新的井设计于 2023 年问世，采用 API 11D1 V0-R 封隔器和 7,500 psi 压力等级。在能源行业，在相对较短的时间内进行如此多的调整和高度的设计变化，使这种类型的解决方案成为新技术或不断发展的技术。 

在过去的十年中，油井设计不断发展，并不断进行新的迭代，以满足操作员的不同要求并同时解决经验教训。 

有些井在完井阶段没有引入流体就完成了完井，这就需要特别考虑悬挂管柱下方的压差，因为这可能会影响干预操作，例如破坏陶瓷盘（塞子）以打开井。 

如果处理不当，电缆工具串可能会被推入井中，造成鸟巢和打捞作业。通过加入均衡阀等设备或通过电缆工具串设计和操作顺序可以避免这种情况。

在某些情况下，为了增加井控，会引入流体作为额外的屏障。这会产生相反的情况，即流体速度会在工具串流向储层时发生，而气体则会通过工具串向上迁移到井中。针对这种情况，Viking 设计了特定的电缆工具串，其中包括一个止动装置、流体旁路和报警装置，以便在将井拉出井眼之前使井稳定下来。

预测未来需求

随着时间推移，随着更多气井完井和现有气井老化，对补救解决方案的需求将越来越普遍，以扩大产量并最大程度地提高最终采收率。完井速度管柱提供了维护 TRSSSV 的重要功能，并且不会对地面基础设施产生影响，地面基础设施可能难以修改，尤其是在空间有限而无法增加井口或采油树高度的情况下。

由于没有标准的完井方法，世界上存在的完井设计变化数量巨大。因此，必须掌握各种现有的和经过验证的规范，才能设计出适合用途的速度管柱。

除此之外，供应商还应有此类系统的设计、制造和安装记录，以降低工作执行过程中的风险。如果需要修改规范，那么拥有设计和验证新完井设备经验的供应商（如 API 11D1 和 API 19AC）至关重要。

在具有地理优势的地方，设备供应商需要与当地服务公司密切合作，向最终用户提供完井设备，并在油井的整个生命周期内提供长期支持。  

By Simon Leiper, Viking Completion Technology

Balancing energy demand alongside the impact of carbon emissions on global sustainability and net zero efforts is a challenge that everyone within the energy supply chain must consider carefully. There is a shared responsibility to produce hydrocarbons as cleanly and efficiently as possible. 

With an increasing demand for natural gas, maximizing ultimate recovery and minimizing the resources required to achieve that goal is critical to achieving a better equilibrium. Thus, operating companies increasingly require a solution for liquid loading of gas wells that impacts or, in many cases, ceases production. As the industry considers the best way forward, the advancement and integration of velocity strings in extending the life of a well provides an alternative route for operators. 

Evolving completion requirements

A velocity string is a remedial solution to an existing well – one that may have been completed several years prior to the requirement of a velocity string solution. It is suitable for diverse well requirements, as such varying challenges may often exist from well to well depending on how the well was originally developed and completed; the well’s surface infrastructure; and the availability of local services such as rigs, hoists, coil tubing, wirelines and expertise. 

The velocity string theory is quite simple. By reducing the production string diameter, the velocity of the produced gas increases, and along with it, the fluid-carrying capacity allows stable production conditions to resume. This is demonstrated in Figure 1, which compares the vertical lift performance (VLP) curves of the liquid-loaded larger bore production tubing versus the velocity string VLP.     

The production string diameter is achieved by installing and suspending a smaller-diameter string inside the existing production string. Despite the fundamentals of the velocity string theory being relatively simple, the successful application is not. 

Velocity strings are a remedial solution for existing wells. Therefore, there is not a standard design of velocity string ready to be picked from a catalog. 

With projects that integrate velocity strings, success requires a detailed review of the existing well design and any operational information related to the well to select the right solution for recompleting and extending the life of the well. Beyond this, other considerations like the local availability of services, rigs, coil tubing, hydraulic workover units, hoists, wirelines and flow control equipment are just as critical.

Velocity string designs

One of the simplest forms of velocity string is to run and suspend an inner string from a traditional tubing spool installed at the surface. These are typically coiled tubing-based or involve a simple jointed pipe string. 

Conventional velocity strings installed in a hanger from a spool piece at the surface will require the tubing retrievable subsurface safety valve (TRSSSV) to be permanently locked out. These conventional approaches present a well control issue that may preclude the installation of a velocity string.

Specific issues relating to conventional velocity string installation are addressed and solved by integrating a completion-based design where all the velocity string equipment is installed into the well below the TRSSSV. Conventional rigs, hoists, hydraulic workover units, or coil tubing are among the deployment options. 

The core piece of equipment required is the hydraulically set velocity string hanger packer that needs to run through the restriction in the TRSSSV, and then set in the tubing string below that will be a larger ID. Future decommissioning will require retrieval through the same restriction.

The varying combination of TRSSSV profiles, tubing string sizes, weights, material and pressure ratings require a wide range of specially designed packers that, with today’s focus on industry validation, will require testing to API 11D1 V0-R. 

As illustrated in Figures 2 and 3, below the packer, tubing is suspended up to 5,000 m in length to provide the required production conduit to lift the well. Additional equipment such as sliding slide doors (SSD), nipple profiles and temporary plugging devices like ceramic disks may be required to facilitate operations – ranging from time of installation to abandonment. 

In some cases, it’s necessary to suspend the well before installing the velocity string. This can be achieved by running a wireline set packer as part of a short BHA that acts as a plug until such time as it’s opened by accessing it through the velocity string.

For passing and retrieving through the TRSSSV, the same design requirements exist. Therefore, the design, development and testing of both packer types are typically performed in parallel to provide optimal design flexibility. This is critical when trying to remedy wells not originally designed with a future installation in mind. 

Two examples of completions with suspension strings are shown in Figures 4 and 5. Figure 4 features the velocity string spaced above the suspension string, and Figure 5 features a mechanical connection between the velocity string and suspension string.

A third option exists – sealing the connection and resulting in the isolation of a specific section of the well. The inclusion of an SSD in this isolated area allows for the effective management of different reservoirs or remedying integrity issues such as a failed liner top.

Case study: velocity string case well designs and considerations

For over a decade, Viking Completion Technology has pioneered completion-based velocity string solutions within the Oman region. These solutions have been pivotal in the ultimate recovery of hundreds of local gas wells. In the 10+ years since Viking first applied its velocity string solutions for operators in Oman, its team has adapted the equipment to suit evolving customer needs – with solutions now available in up to 7,500 psi and a V0 rating. 

For a specific Oman-based operator, the evolution of Viking’s equipment was crucial in supporting the operational and technical progression over time. In the early stages of the contract, commencing in 2013, the specifications didn’t involve any particular validation requirement whilst the pressure differentials were low at approximately 3,000 psi. During the initial years of the 10+ year contract, this evolved into requirements for API 11D1 V2 validation and pressures of 5,000 psi. 

Arriving in 2023 due to policy changes from the end user, the latest iterations of well designs featured API 11D1 V0-R packers and a 7,500-psi pressure rating. Within the energy industry, this amount of adaption and a high level of design variation, over a relatively short period, put this type of solution in the bracket of new or evolving technology.  

Over the past decade, well designs have consistently evolved, resulting in new iterations to facilitate different requirements from the operator and simultaneously addressing lessons learned. 

Some wells have been completed without introducing fluid during the completion phase, which required specific consideration of pressure differentials below the suspension string that may impact intervention operations, such as breaking the ceramic disk (plug) to open the well. 

Wireline tool strings could be forced up the well, causing a bird’s nest and fishing operation if the situation was not properly managed. This was avoided either by the inclusion of equipment such as equalization valves or through wireline tool string design and operational sequences.

In some cases, for additional well control, fluid is introduced as an additional barrier. This creates the opposite scenario whereby a fluid velocity will occur over the tool string heading to the reservoir whilst gas migrates up the well over the tool string. For this scenario, Viking designed specific wireline tool strings that included a no-go, fluid bypass and tell tales to allow for the well to stabilize before pulling out of the hole.

Anticipating future requirements

Over time, as more gas wells are completed and existing wells age, the need for remedial solutions to extend production and maximize ultimate recovery will be increasingly common. Completion-based velocity strings provide the vital feature of maintaining the TRSSSV and have no impact on the surface infrastructure that can be challenging to modify, especially in situations where space is limited to increase the height of the wellhead or Christmas tree.

The number of variations of completion design that exist in the world are vast since there is no standard way to complete a well. It is, therefore, imperative to have access to a wide range of existing and proven specifications to make the process of designing a fit-for-purpose velocity string manageable.

Beyond that, the provider should have a track record of design, manufacture and installation of such systems to mitigate risks during execution of the work. Where a modified specification is required, suppliers with the experience of designing and validating new completion equipment to industry standards, such as API 11D1 and API 19AC, are critical.

Where geographically beneficial, equipment suppliers need to work closely with local service companies to deliver, to the end users, the completion equipment and longer-term support through life of well.  DC