隨著鉆井難度的加劇，已經為鉆井行業帶來了大量新型挑戰，特別是在海上市場。運營商們在積極尋求新方法來應對油價持續下跌的同時，也逐漸意識到技術創新必將是行業變革的催化劑。為了在復雜的海上油井環境中進行性能改造方面的創新，此項工作必須在曾經的“常規”范圍外進行。

鹽下油藏鉆探

為了保證海上油井的信息完整性，需討論如何鉆取鹽下油藏。目前，鹽下油藏已經成為巴西和安哥拉近海作業公司關注的重要領域，過去十年的重要發現表明：石油和天然氣儲量豐富，有可能改變海上鉆井市場的現狀。然而，鹽下油藏鉆探卻有異常的挑戰。典型的鹽下油藏層的深水或超深水位置通常存在經濟可行性的問題。此外，現場和非現場的鉆探技術都需要大量投資，尋找好的方法和技術來鉆探這些難以開發的地層。盡管面臨諸多挑戰，但新技術的興起和儲備的獲取將為行業向前發展提供機遇。

國民油井華高(NOV)開發了eVolve優化服務軟件，可用范圍包括從表面數據優化到完全閉環井下鉆井自動化，以應對石油和天然氣行業不斷變化的經濟和技術狀況。eVolve服務匯集了幾款NOV產品系列的技術和經過驗證的鉆井專業知識，以提高運營效率和增強決策。BlackBox記憶模式測井工具布置在鉆頭，井底組件(BHA)和/或捕獲壓力、扭矩、重量傳遞和振動數據的鉆柱中，并進一步觀察鉆井實踐如何影響性能和可靠性。值得注意的是，需警告鉆井者潛在的功能障礙，例如粘滯/滑移和扭轉/橫向振動，并且評估井下的動態行為增進對鉆井環境的更深入了解。此外，可結合地面和井下數據來分析鉆井動力創造的優化基礎，使后續井中的BHA能實現更好的設計和部件選擇。

案例分析

NOV與南美客戶合作，使用eVolve服務軟件為一個獨特的鹽下油藏應用開發了全面的解決方案。客戶在項目中遇到了許多鉆井障礙，包括使得電機和有原始鉆頭的頂驅停轉的高扭矩問題，以及由于鉆頭重量輕而影響了ROP的偏差問題。除此之外，還需要減小并保持傾斜度以優化ROP。以前的偏移井使用的是正位移電動機，并且通常在具有牙輪鉆頭的兩輪運行孔或有多晶金剛石壓塊(PDC)鉆頭的單輪運行孔中鉆孔。另外，具有挑戰性的地層的復雜巖性也是一個難題。

該項目的第一步是使用BlackBox工具來獲得高頻井下數據。然后分析這些數據以確定下一個佳鉆井實踐和參數，客戶設定保持低傾斜度和改善ROP的目標，并且在單次運行中通過表面孔底層鉆探整個部分，并在鹽中油藏中停止。從分析來看，頂部驅動的井孔垂直度和彎曲度以及極限扭矩，鉆孔硬石膏時的高反作用扭矩和潛在粘滯/滑移，以及潛在的設備損壞是主要挑戰。此外，在鉆孔時需要保持高的周向接觸以改善側向穩定性，并且需要采取謹慎措施使鉆探鹽層時刀具不會斷裂。

在重新設計BHA和實施NOV的建議參數變化之后，客戶看到優化井中鉆頭和鉆柱的橫向振動顯著減少。振動減輕是導致該應用中性能提高和設備損壞減少的因素之一。(來源：NOV)

NOV與客戶合作設計了一個全新的創新版BHA，使用17½英寸的 PDC鉆頭匹配26英寸的同心鉸刀和抗沖擊的Helios刀具。這個重新設計使一個成熟的17½英寸旋轉導向系統可鉆探具有挑戰性的26英寸截面，并且減少了為下一個井孔部分更換BHA所需的時間，允許鉆頭和BHA重復使用。振動在無水石膏運行結束時減輕，使客戶既達到了總深度(TD)又不會損壞設備，并且鉸刀和中間葉片的偏移和螺旋提供360度圓周接觸以橫向穩定性。通過使用計算流體動力學，扭矩和阻力分析以及有限元分析來優化鉆井實踐和參數，確保佳性能。

偏移井中的ROP使用原來的26英寸PDC鉆頭，約為17.6米/小時(57.74英尺/小時)，本項目的ROP場平均值約為14.4米/小時(47.24英尺/小時)。客戶在鉆探鹽下油藏時使用重新設計和優化的BHA，改進鉆頭選擇和eVolve團隊推薦的鉆井參數，能夠獲得28米/小時(91.9英尺/小時)的ROP現場記錄。這次改進使得偏移井的ROP增加超過57%，幾乎是現場平均值的兩倍。客戶還實現了在單次運行中達到總深度而無任何事故發生的目標，并且按照油井計劃保持低傾斜度。ROP的顯著增加以及各種其他性能改進使得與偏移井相比，總鉆井時間減少超過1.5天，從而為該項目節省了超過70萬美元。

ROP的改進，包括從偏移井的17.6米/小時增加到NOV建議的28米/小時的實地記錄，是這個項目的幾大益處之一。偏移井之后傾斜繼續減小，低至35度，并且客戶能夠一次運行每個油井的所有段，而不再是偏移井需進行四次運行。優化使得相比偏移井，鉆井時間節省1.5天。 (來源：NOV)

BlackBox工具收集的大量數據的分析以及據此分析結果所采取的行動不僅對該項目的客戶有利，而且，實際上附加井的改善也可以從本項目的經驗教訓中學到。在隨后的鉆井活動中，例如，還設計了另一個定制BHA，并且客戶能夠根據NOV的參數推薦而在BHA中避免具有高頻核振動的區域。這些建議的實施要結合鉆探時客戶運營中心的連續實時的反饋，提高整體效率，并獲得了等于或大于前一口井實現的ROP收益。扭轉和橫向振動也相應減少，并且在系統中優化機械比能量使用。

注：該文章由鼎恒石油編譯，轉發須注明出處。

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.