隨著鉆井難度的加劇，已經(jīng)為鉆井行業(yè)帶來了大量新型挑戰(zhàn)，特別是在海上市場。運(yùn)營商們在積極尋求新方法來應(yīng)對油價持續(xù)下跌的同時，也逐漸意識到技術(shù)創(chuàng)新必將是行業(yè)變革的催化劑。為了在復(fù)雜的海上油井環(huán)境中進(jìn)行性能改造方面的創(chuàng)新，此項工作必須在曾經(jīng)的“常規(guī)”范圍外進(jìn)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(jīng)成為巴西和安哥拉近海作業(yè)公司關(guān)注的重要領(lǐng)域，過去十年的重要發(fā)現(xiàn)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(xiàn)狀。然而，鹽下油藏鉆探卻有異常的挑戰(zhàn)。典型的鹽下油藏層的深水或超深水位置通常存在經(jīng)濟(jì)可行性的問題。此外，現(xiàn)場和非現(xiàn)場的鉆探技術(shù)都需要大量投資，尋找好的方法和技術(shù)來鉆探這些難以開發(fā)的地層。盡管面臨諸多挑戰(zhàn)，但新技術(shù)的興起和儲備的獲取將為行業(yè)向前發(fā)展提供機(jī)遇。

國民油井華高(NOV)開發(fā)了eVolve優(yōu)化服務(wù)軟件，可用范圍包括從表面數(shù)據(jù)優(yōu)化到完全閉環(huán)井下鉆井自動化，以應(yīng)對石油和天然氣行業(yè)不斷變化的經(jīng)濟(jì)和技術(shù)狀況。eVolve服務(wù)匯集了幾款NOV產(chǎn)品系列的技術(shù)和經(jīng)過驗(yàn)證的鉆井專業(yè)知識，以提高運(yùn)營效率和增強(qiáng)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(shù)據(jù)的鉆柱中，并進(jìn)一步觀察鉆井實(shí)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(zhuǎn)/橫向振動，并且評估井下的動態(tài)行為增進(jìn)對鉆井環(huán)境的更深入了解。此外，可結(jié)合地面和井下數(shù)據(jù)來分析鉆井動力創(chuàng)造的優(yōu)化基礎(chǔ)，使后續(xù)井中的BHA能實(shí)現(xiàn)更好的設(shè)計和部件選擇。

案例分析

NOV與南美客戶合作，使用eVolve服務(wù)軟件為一個獨(dú)特的鹽下油藏應(yīng)用開發(fā)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(jī)和有原始鉆頭的頂驅(qū)停轉(zhuǎn)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(yōu)化ROP。以前的偏移井使用的是正位移電動機(jī)，并且通常在具有牙輪鉆頭的兩輪運(yùn)行孔或有多晶金剛石壓塊(PDC)鉆頭的單輪運(yùn)行孔中鉆孔。另外，具有挑戰(zhàn)性的地層的復(fù)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(shù)據(jù)。然后分析這些數(shù)據(jù)以確定下一個佳鉆井實(shí)踐和參數(shù)，客戶設(shè)定保持低傾斜度和改善ROP的目標(biāo)，并且在單次運(yùn)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(qū)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(shè)備損壞是主要挑戰(zhàn)。此外，在鉆孔時需要保持高的周向接觸以改善側(cè)向穩(wěn)定性，并且需要采取謹(jǐn)慎措施使鉆探鹽層時刀具不會斷裂。

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

NOV與客戶合作設(shè)計了一個全新的創(chuàng)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(shè)計使一個成熟的17½英寸旋轉(zhuǎn)導(dǎo)向系統(tǒng)可鉆探具有挑戰(zhàn)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(fù)使用。振動在無水石膏運(yùn)行結(jié)束時減輕，使客戶既達(dá)到了總深度(TD)又不會損壞設(shè)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(wěn)定性。通過使用計算流體動力學(xué)，扭矩和阻力分析以及有限元分析來優(yōu)化鉆井實(shí)踐和參數(shù)，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)�？蛻粼阢@探鹽下油藏時使用重新設(shè)計和優(yōu)化的BHA，改進(jìn)鉆頭選擇和eVolve團(tuán)隊推薦的鉆井參數(shù)，能夠獲得28米/小時(91.9英尺/小時)的ROP現(xiàn)場記錄。這次改進(jìn)使得偏移井的ROP增加超過57%，幾乎是現(xiàn)場平均值的兩倍�？蛻暨�實(shí)現(xiàn)了在單次運(yùn)行中達(dá)到總深度而無任何事故發(fā)生的目標(biāo)，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(jìn)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(jié)省了超過70萬美元。

ROP的改進(jìn)，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(shí)地記錄，是這個項目的幾大益處之一。偏移井之后傾斜繼續(xù)減小，低至35度，并且客戶能夠一次運(yùn)行每個油井的所有段，而不再是偏移井需進(jìn)行四次運(yùn)行。優(yōu)化使得相比偏移井，鉆井時間節(jié)省1.5天。 (來源：NOV)

BlackBox工具收集的大量數(shù)據(jù)的分析以及據(jù)此分析結(jié)果所采取的行動不僅對該項目的客戶有利，而且，實(shí)際上附加井的改善也可以從本項目的經(jīng)驗(yàn)教訓(xùn)中學(xué)到。在隨后的鉆井活動中，例如，還設(shè)計了另一個定制BHA，并且客戶能夠根據(jù)NOV的參數(shù)推薦而在BHA中避免具有高頻核振動的區(qū)域。這些建議的實(shí)施要結(jié)合鉆探時客戶運(yùn)營中心的連續(xù)實(shí)時的反饋，提高整體效率，并獲得了等于或大于前一口井實(shí)現(xiàn)的ROP收益。扭轉(zhuǎn)和橫向振動也相應(yīng)減少，并且在系統(tǒng)中優(yōu)化機(jī)械比能量使用。

注：該文章由鼎恒石油編譯，轉(zhuǎn)發(fā)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.