回顾压裂

几十年来,经过大量的试验和错误,水力压裂才一夜成功。

20 世纪 40 年代,哈里伯顿 (Halliburton) 工人开始进行水力压裂开发。(来源:哈里伯顿)

水力压裂似乎是伴随 2008 年页岩革命而来的一种相对较新的现象,但它自 20 世纪 40 年代以来就已存在。第一个压裂作业于 1947 年夏季完成,哈里伯顿于 1949 年完成了第一个商业压裂。从那时起,该行业已过渡到大规模水力压裂,注入了超过 300,000 磅的支撑剂。

尽管大规模压裂在该行业占据主导地位,但用于钻探这些井的许多方法“不利于完成页岩油藏”,Frac Diagnostics 创始人、在石油行业拥有 50 年经验的莱尔·雷曼 (Lyle Lehman) 告诉 Hart Energy。

“页岩储层被认为是其上方地层的源岩。在地质时期,人们认为页岩中的碳氢化合物会迁移到页岩上方的沙子或石灰岩中,并交换沙子或石灰岩中的一些水,”雷曼说。雷曼表示,米切尔能源公司在沃斯堡的巴尼特页岩中测试了这一理论,但他们得到了“不确定”的结果。

“不确定的结果”是由于米切尔能源公司将传统的、较稠的流体泵入井中以刺激它。虽然该井得到了增产,但清理起来却困难得多,这使得完井更加困难,而且在经济上也不可行。直到 2002 年被德文能源公司 (Devon Energy)收购的米切尔 (Mitchell ) 带着更稀的液体回来时,巴尼特 (Barnett) 的油井才变得经济。

水平钻井

最终,由于水平井的引入,页岩油藏的生产变得更加普遍。

“北海第一口水平井压裂是在 80 年代末和 90 年代初。因此,滑动套筒、压裂套筒技术是最重要的技术,但真正打开北美市场的是……插塞和射孔操作,”哈里伯顿公司技术研究员 Ron Dusterhoft说道。 40 年石油行业资深人士告诉 Hart Energy。

“堵塞和射孔”等分层隔离技术通过增加每口井的裂缝数量并减少裂缝之间的距离来导致更高的裂缝密度。

索利曼马克杯
Mohamed Soliman,SPE 传奇人物、休斯顿大学石油工程系系主任(来源:Mohamed Soliman)

“你有封隔器或桥塞。“你把它放进去,对一口井进行压裂,然后你就可以移动,”休斯顿大学系主任、威廉·C·米勒捐赠主席穆罕默德·索利曼 ( Mohamed Soliman ) 说道,他被石油工程师学会命名为 2023 年水力压裂传奇。

“当我们开始压裂水平井时,我们一次产生一个裂缝,”他说。“你从脚趾到脚后跟;你在脚趾附近进行,然后移动,放置另一座桥,堵塞,在油井中穿孔。然后你穿孔,你创造一个裂缝,另一个桥梁,你堵塞并穿孔,等等。”

新技术一次产生多个裂缝,使过程更加高效,并允许大量裂缝与水平井相交。

滑动套筒比塞子和射孔器更新,可以加速多级压裂作业,因为它允许在一次泵送过程中实现多级压裂。在穿孔发生之前,滑动套筒工具通过机械驱动套筒永久放置在裸眼中。恒定的井下压力可以消除堵塞、射孔和重复过程,从而缩短完井时间。

塞钻完井和滑套完井对于页岩等非常规资源的开发至关重要,因为它们在开井方面比以前的许多方法更有效。它们在水平钻井方面尤其有效,进一步推动了石油工业的发展。

事实证明,在从致密地层开采石油方面,水平井比直井更有效。这些地层通常接近水平,因此水平井与目标地层有更大的接触面积。

“如果你知道这些天然裂缝的方向,那么钻水平井将使你更有可能穿过这些裂缝,”索利曼说。

页岩革命

最终,水平井的广泛采用引发了2008年的页岩革命。在此之前,美国经济高度依赖委内瑞拉和沙特阿拉伯等国家的石油进口。现在美国是原油净出口国。

“巴尼特页岩的米切尔能源公司获得了早期页岩井的全部功劳,因为我们早期发现……致密气技术、致密气压裂似乎在页岩中不起作用,而我们也没有” “不太明白为什么,”达斯特霍夫特说。“如果你看看米切尔所做的,他们转变为水力压裂,摆脱了聚合物……结果,这确实打开了页岩市场的闸门。”

20111129_MG_8863.jpg:
2011 年,马拉松石油工人在德克萨斯州卡恩斯县 Helmerich & Payne Rig #430 钻井的 Salge Kinkler #1H 井场从地面起下管道。(来源:Tom Fox/Hart Energy)

页岩开发腾飞的另一个原因是钻井数据分析技术的实施。将计算机技术添加到钻井过程中,操作员可以预测新形成的裂缝可能采取的路径。它还可以确定井的应力对比,并使操作员能够识别最佳的储层。

“井数据的结合[帮助操作员]了解沿水平方向放置裂缝的位置,以便它们均等张开,”雷曼说。“仅仅因为我在这里、这里和这里打了一个穿孔,并不意味着它们都会打开相同的孔并吸收相同量的液体。我们必须了解沿井眼的应力是多少,以便我们移动这些射孔并将它们放置在应力较低的区域,从而使应力差最小。”

油井数据还通过使用“代理”数据使油井增产过程变得更加容易,“代理”数据是一种人工智能形式,它获取钻井数据并将其转换为地层特性(特别是岩石强度),以便可以进行油井处理最佳地。

但即使收集油井数据具有诸多好处,对其进行管理也可能很困难。

“数据是一件美妙的事情,但它也是我们必须应对的一个巨大的怪物,”达斯特霍夫特说。“我们今天面临的挑战是非常规压裂。我们收到的数据可能比过去多一个数量级——也许两个数量级。因此,管理这些数据并将其转换为有用的格式是一项挑战,我们正在这方面采取措施。”

运营商希望通过自动化、机器学习和人工智能来使用数据。Dusterhoft 表示,Halliburton 自 20 世纪 90 年代以来一直致力于这项技术的研究。哈里伯顿的自动远程控制设备使操作员无需将人员放在卡车上或红色区域即可进行作业。

水力压裂领域当前的使命是实现可持续性。即使进行了能源转型,石油和天然气的生产对能源行业仍然非常重要,因此运营商专注于更安全的生产方式。

“我们在化学密封、液体密封方面取得了巨大进步,同时也在减排方面取得了巨大进展,以及为我们的卡车提供动力的双燃料等方面,”达斯特霍夫特说。

原文链接/hartenergy

Looking Back at the Frac

It took a lot of trial and error over the decades to make hydraulic fracturing an overnight success.

Halliburton workers setting up a fracking development in the 1940s. (Source: Halliburton)

Hydraulic fracturing may seem like a relatively new phenomenon that came along with the shale revolution in 2008, but it’s been around since the 1940s. The first frac jobs were done in summer 1947, and Halliburton completed the first commercial frac in 1949. Since then, the industry has transitioned to massive hydraulic fracturing, with injections of over 300,000 pounds of proppant.

While massive fracturing dominated the industry, a lot of the methods used for drilling those wells were “not conducive to completing shale reservoirs,” Lyle Lehman, founder of Frac Diagnostics and 50-year veteran in the oil industry, told Hart Energy.

“Shale reservoirs were considered to be the source rock for the formation above them. Over geological time, the thought was that the hydrocarbons in the shale would migrate up into the sand or limestone sitting above the shale and swap out some of the water that’s in the sand or limestone,” Lehman said. Mitchell Energy tested this theory in the Barnett Shale in Fort Worth, said Lehman, but they received “iffy” results.

The “iffy results” were due to Mitchell Energy pumping traditional, thicker fluids into the well to stimulate it. While the well was stimulated, it was much harder to clean up, making the well much harder to complete and not economically viable. It wasn’t until Mitchell, which was acquired by Devon Energy in 2002, returned with a thinner fluid that the wells in the Barnett could be economical.

Horizontal drilling

Eventually, production from shale reservoirs became more common due to the introduction of horizontal wells.

“The first horizontal wells that were fractured in the North Sea were in the late ’80s and early ’90s. So, the sliding sleeve, the frac sleeve technologies were some of the first things, but really what’s blown the North America market open has been the … plug and perf operations,” Ron Dusterhoft, Technology Fellow at Halliburton and 40-year oil industry veteran, told Hart Energy.

Zonal isolation techniques like “plug and perf” cause a higher density of fractures by increasing the number of fractures per well and reducing the distance between those fractures.

Soliman mug
Mohamed Soliman, SPE Legend and Department Chair of the Petroleum Engineering Department at the University of Houston (Source: Mohamed Soliman)

“You have packers or a bridge plug. You put it in, you fracture a well, then you move,” said Mohamed Soliman, department chair and The William C. Miller endowed chair at the University of Houston and named a 2023 Legend of Hydraulic Fracturing by the Society of Petroleum Engineers.

“When we started fracturing horizontal wells, we created fractures one at a time,” he said. “You go from toe to heel; you do it near the toe, then you move, you put another bridge, you plug, you perforate the oil cased wells. Then you perforate, you create one fracture, another bridge, you plug and perforate, and so on and so forth.”

The new techniques create multiple fractures at a time, making the process more efficient and allowing for numerous fractures to intersect a horizontal well.

Sliding sleeve is newer than plug and perf and speeds up multi-stage frac jobs because it allows multiple stages to be fractured with a single pumping session. Sliding sleeve tools are permanently placed in open holes with mechanically actuated sleeves before perforation occurs. The constant downhole pressure cuts out the plug, perf and repeat process, reducing completion time.

Plug and perf, and sliding sleeve completions were pivotal in the development of unconventional resources such as shale because they were more effective at opening wells than many of the previous methods. They were especially effective in horizontal drilling, which further advanced the oil industry.

Horizontal wells proved much more effective than vertical wells in producing oil from tight formations beds. Those beds are usually nearly horizontal, so horizontal wells have much larger contact areas with the target formation.

“If you know the orientation of those natural fractures, drilling horizontal wells will give you a lot higher probability that you intersect those fractures,” Soliman said.

Shale revolution

Eventually, the wider adoption of horizontal wells led to the shale revolution in 2008. Prior to that, the U.S. economy was highly dependent on oil imports from countries like Venezuela and Saudi Arabia. Now the U.S. is a net exporter of crude oil.

“Mitchell Energy in the Barnett Shale gets all the credit for the early shale wells because what we found early on … is that the tight gas technology, the fracturing for tight gas, did not seem to work in shale, and we didn’t really understand why,” Dusterhoft said. “And if you look at what Mitchell did, they transitioned into a water frack, got rid of the polymer … and as a result, that really was what opened the floodgates on the shale market.”

20111129_MG_8863.jpg:
Marathon Oil workers trip pipe from the ground on the Salge Kinkler #1H wellsite being drilled by Helmerich & Payne Rig #430 in Karnes County, Texas, in 2011. (Source: Tom Fox/Hart Energy)

Another reason shale development took off was the implementation of drilling data analysis technology. Adding computer technology to the drilling process the operator to predict the path a newly formed fracture might take. It could also determine the stress contrast of the well and enable operators to identify the best reservoirs.

“The incorporation of well data [helped the operator] understand where to place fractures along the horizontal so that they would all open equally,” Lehman said. “Just because I put a perforation here, here and here, it doesn’t mean they will all open up the same and take the same amount of fluid. We have to understand what the stress is along the wellbore so that we move those perforations around and place them in a lower stress area so that the stress differential is minimal.”

Well data also makes the well stimulation process easier through the use of “proxy” data, a form of AI that takes drilling data and converts it to formation properties—particularly rock strength—so that the treatment of the well can be performed optimally.

But even with all the benefits that collecting well data provides, managing it can be difficult.

“Data is a wonderful thing, but it’s also a huge monster that we have to deal with,” Dusterhoft said. “The challenge we have today is with the unconventional fracturing. We probably have an order of magnitude—maybe two orders of magnitude—more data coming in than we ever did in the past. So, managing that data and putting it in a useful format is a challenge and we’re making steps there.”

Operators are looking to use data through automation, machine learning and AI. Halliburton has been working on this technology since the 1990s, Dusterhoft said. Halliburton’s automatic remote-control equipment allowed operators to run jobs without having to put people on the trucks or in the red zones.

The current mission in the fracking space is achieving sustainability. Even with the energy transition, production from oil and natural gas is still incredibly important to the energy industry, so operators are focused on safer ways to produce.

“Chemical containment, fluid containment are things that we’ve advanced tremendously on, but also emissions reduction, and things like dual fuel to power our trucks,” Dusterhoft said.