NOV提供eVolve优化服务助力盐下油藏钻探

随着钻井难度的加剧，已经为钻井行业带来了大量新型挑战，特别是在海上市场。运营商们在积极寻求新方法来应对油价持续下跌的同时，也逐渐意识到技术创新必将是行业变革的催化剂。为了在复杂的海上油井环境中进行性能改造方面的创新，此项工作必须在曾经的“常规”范围外进行。

盐下油藏钻探

为了保证海上油井的信息完整性，需讨论如何钻取盐下油藏。目前，盐下油藏已经成为巴西和安哥拉近海作业公司关注的重要领域，过去十年的重要发现表明：石油和天然气储量丰富，有可能改变海上钻井市场的现状。然而，盐下油藏钻探却有异常的挑战。典型的盐下油藏层的深水或超深水位置通常存在经济可行性的问题。此外，现场和非现场的钻探技术都需要大量投资，寻找好的方法和技术来钻探这些难以开发的地层。尽管面临诸多挑战，但新技术的兴起和储备的获取将为行业向前发展提供机遇。

国民油井华高(NOV)开发了eVolve优化服务软件，可用范围包括从表面数据优化到完全闭环井下钻井自动化，以应对石油和天然气行业不断变化的经济和技术状况。eVolve服务汇集了几款NOV产品系列的技术和经过验证的钻井专业知识，以提高运营效率和增强决策。BlackBox记忆模式测井工具布置在钻头，井底组件(BHA)和/或捕获压力、扭矩、重量传递和振动数据的钻柱中，并进一步观察钻井实践如何影响性能和可靠性。值得注意的是，需警告钻井者潜在的功能障碍，例如粘滞/滑移和扭转/横向振动，并且评估井下的动态行为增进对钻井环境的更深入了解。此外，可结合地面和井下数据来分析钻井动力创造的优化基础，使后续井中的BHA能实现更好的设计和部件选择。

案例分析

NOV与南美客户合作，使用eVolve服务软件为一个独特的盐下油藏应用开发了全面的解决方案。客户在项目中遇到了许多钻井障碍，包括使得电机和有原始钻头的顶驱停转的高扭矩问题，以及由于钻头重量轻而影响了ROP的偏差问题。除此之外，还需要减小并保持倾斜度以优化ROP。以前的偏移井使用的是正位移电动机，并且通常在具有牙轮钻头的两轮运行孔或有多晶金刚石压块(PDC)钻头的单轮运行孔中钻孔。另外，具有挑战性的地层的复杂岩性也是一个难题。

该项目的第一步是使用BlackBox工具来获得高频井下数据。然后分析这些数据以确定下一个佳钻井实践和参数，客户设定保持低倾斜度和改善ROP的目标，并且在单次运行中通过表面孔底层钻探整个部分，并在盐中油藏中停止。从分析来看，顶部驱动的井孔垂直度和弯曲度以及极限扭矩，钻孔硬石膏时的高反作用扭矩和潜在粘滞/滑移，以及潜在的设备损坏是主要挑战。此外，在钻孔时需要保持高的周向接触以改善侧向稳定性，并且需要采取谨慎措施使钻探盐层时刀具不会断裂。

在重新设计BHA和实施NOV的建议参数变化之后，客户看到优化井中钻头和钻柱的横向振动显著减少。振动减轻是导致该应用中性能提高和设备损坏减少的因素之一。(来源：NOV)

NOV与客户合作设计了一个全新的创新版BHA，使用17½英寸的 PDC钻头匹配26英寸的同心铰刀和抗冲击的Helios刀具。这个重新设计使一个成熟的17½英寸旋转导向系统可钻探具有挑战性的26英寸截面，并且减少了为下一个井孔部分更换BHA所需的时间，允许钻头和BHA重复使用。振动在无水石膏运行结束时减轻，使客户既达到了总深度(TD)又不会损坏设备，并且铰刀和中间叶片的偏移和螺旋提供360度圆周接触以横向稳定性。通过使用计算流体动力学，扭矩和阻力分析以及有限元分析来优化钻井实践和参数，确保佳性能。

偏移井中的ROP使用原来的26英寸PDC钻头，约为17.6米/小时(57.74英尺/小时)，本项目的ROP场平均值约为14.4米/小时(47.24英尺/小时)。客户在钻探盐下油藏时使用重新设计和优化的BHA，改进钻头选择和eVolve团队推荐的钻井参数，能够获得28米/小时(91.9英尺/小时)的ROP现场记录。这次改进使得偏移井的ROP增加超过57%，几乎是现场平均值的两倍。客户还实现了在单次运行中达到总深度而无任何事故发生的目标，并且按照油井计划保持低倾斜度。ROP的显着增加以及各种其他性能改进使得与偏移井相比，总钻井时间减少超过1.5天，从而为该项目节省了超过70万美元。

ROP的改进，包括从偏移井的17.6米/小时增加到NOV建议的28米/小时的实地记录，是这个项目的几大益处之一。偏移井之后倾斜继续减小，低至35度，并且客户能够一次运行每个油井的所有段，而不再是偏移井需进行四次运行。优化使得相比偏移井，钻井时间节省1.5天。 (来源：NOV)

BlackBox工具收集的大量数据的分析以及据此分析结果所采取的行动不仅对该项目的客户有利，而且，实际上附加井的改善也可以从本项目的经验教训中学到。在随后的钻井活动中，例如，还设计了另一个定制BHA，并且客户能够根据NOV的参数推荐而在BHA中避免具有高频核振动的区域。这些建议的实施要结合钻探时客户运营中心的连续实时的反馈，提高整体效率，并获得了等于或大于前一口井实现的ROP收益。扭转和横向振动也相应减少，并且在系统中优化机械比能量使用。

注：该文章由鼎恒石油编译，转发须注明出处。

附英文原文：

Presalt Drilling Benefits From Real-time Data

Increasingly difficult wells have led to a significant number of new drilling challenges, particularly in the offshore market. Operators that are actively searching for new ways to combat the persistent decline in oil prices are becoming more aware that technical innovation must be the catalyst for industry change. To deliver innovation that drives impactful performance increases in complex offshore well environments, work must be done outside the confines of what has historically been considered “ordinary.”

Drilling the presalt

A conversation on difficult offshore wells would not be complete without discussing how the presalt is drilled. The presalt has become a major area of interest for operators working offshore Brazil and Angola, with important discoveries in the past decade revealing vast reserves of oil and natural gas and a potential to change the landscape of the offshore drilling market. Drilling the presalt, however, presents distinct challenges. The deepwater or ultradeepwater location of typical presalt layers and the large areas over which such layers are spread often present issues of economic feasibility. In addition, the expertise necessary for extraction necessitates significant investment in researching, both onsite and offsite, looking for the best methods and technologies to drill such difficult formations. Despite these challenges, the rise of these new technologies and access to such reserves will provide powerful opportunities for the industry to move forward.

National Oilwell Varco (NOV) has developed the eVolve Optimization Service, a tiered approach ranging from surface data-based optimization to full closed-loop downhole drilling automation, to address the changing economic and technological landscape of the oil and gas industry. The eVolve service brings together technologies from several NOV product families and proven drilling expertise to enable improved operational efficiency and enhanced decision-making. BlackBox memory-mode logging tools placed in the drillbit, bottomhole assembly (BHA) and/ or drillstring capture data on pressure, torque, weight transfer and vibration and provide insight into how drilling practices affect performance and reliability. The driller is alerted to potential dysfunctions such as stick/slip and torsional/lateral vibration, and dynamic behaviors downhole are assessed to provide a deeper understanding of the drilling environment. In addition, combining surface and downhole data to analyze drilling dynamics creates an optimization foundation, enabling better design and component selection for the BHA in subsequent wells.

Case study

NOV worked with a South American client to develop a comprehensive solution in a unique presalt application using the eVolve service. The client was experiencing a number of drilling dysfunctions in the project, including high torque, which was stalling the motor and topdrive with the original bit, and deviation issues, which were compromising ROP due to low weight on bit. It was also necessary to reduce and then maintain inclination to optimize ROP. Previous offset wells had used a positive displacement motor and were usually drilled in either two runs with roller-cone bits or a single run with a polycrystalline diamond compact (PDC) bit. The complex lithology of the challenging formations was also a concern.

The first step in this project was to use the BlackBox tools to obtain high-frequency downhole data. These data were then analyzed to determine optimal drilling practices and parameters moving forward, with the client setting the objectives of maintaining low inclination, improving ROP and drilling the entire section in one run through the surface hole formation, stopping in the salt. Hole verticality and tortuosity, limited torque at the topdrive, high reactive torque and potential stick/slip when drilling the anhydrite, and potential equipment damage were the main challenges determined from the analysis. In addition, high circumferential contact needed to be maintained while drilling to achieve improved lateral stability, and caution needed to be taken so that the cutters did not break when drilling the salt.

After redesigning the BHA and implementing NOV’s suggested parameter changes, the client saw a significant reduction in lateral vibration in the optimized well both at the bit and in the drillstring. Mitigating vibration was one of the factors leading to increased performance and reduced equipment damage in this application. (Source: NOV)

NOV worked with the client to design a completely new and innovative BHA, using a 17½-in. PDC bit matched with a 26-in. concentric reamer and impact-resistant Helios cutters. This redesign enabled a proven 17½-in. rotary steerable system to be used to aggressively drill the challenging 26-in. section and reduced the time required to change the BHA for the next hole section, allowing both the bit and the BHA to be reused. Vibration was mitigated at the end of the run in the anhydrite, allowing the client to reach total depth (TD) without damage to the equipment, and the offset and spiral of reamer and midreamer blades provided 360-degree circumferential contact to maximize lateral stability. Drilling practices and parameters were optimized through use of computational fluid dynamics, torque and drag analysis, and finite element analysis, ensuring optimal performance.

ROP in the offset well, using the original 26-in. PDC bit, was about 17.6 m/hr (57.74 ft/hr), and the field average of ROP for the project was about 14.4 m/hr (47.24 ft/hr). Using the redesigned, optimized BHA, improved bit selection and the drilling parameters recommended by the eVolve team, the client was able to achieve a field record ROP of 28 m/hr (91.9 ft/hr) when drilling the presalt. This improvement represented an ROP increase of more than 57% over the best offset well and almost double that of the field average. The client also achieved the objective of reaching TD in a single run without incident, and low inclination was maintained as per the well plan. The significant increase in ROP combined with the various other performance improvements enabled a reduction in total drilling time of more than 1.5 days in comparison to the offset wells, yielding savings in excess of $700,000 for the project.

Improvements in ROP, including an increase from 17.6 m/hr in the offset well to a field record of 28 m/hr with NOV’s recommendations, were one of several benefits on this project. Inclination continued to decrease after the offset well, reaching as low as .35 degrees, and the client was able to drill the entire section in one run on each well vs. four runs on the offset well. Optimization yielded drilling time savings of 1.5 days vs. the offset well. (Source: NOV)

The analysis of the large amounts of data collected by the BlackBox tools and the actions taken as a result of this analysis were not only beneficial to the client on this project, improvements on additional wells, in fact, were enabled through implementation of this project’s lessons learned. On the subsequent well of this drilling campaign, for example, another customized BHA was designed, and the client was able to avoid areas with high-resonance vibration potential in the BHA due to NOV’s parameter recommendations. Implementation of these recommendations combined with continuous, real-time feedback while drilling from the client’s operations center enhanced overall efficiency and yielded ROP gains that were equal to or greater than those achieved on the previous well. Torsional and lateral vibration also were reduced, and mechanical-specific energy use was optimized in the system.