聚能射孔弹设计师改进了他们的思维过程，以支持操作员和非常规油井增产。传统上，用于有限进入增产市场的射孔系统是通过简单地制作行业一直使用的较长射孔系统的短版本来实现的。发生了很多变化。

那些进行射孔和那些进行压裂的人正在沟通。2014 年底美国经济活动低迷，伴随着裁员和公司倒闭，每个人都得到了改善。在直接采购（砂和塞）方面取得成功的运营商开始谈论其他类别的应用，包括射孔。运营商、制造商/服务公司和投资界现在可以轻松访问和分析数据，包括合并到其中的公共数据和私有数据库。

人们正在分析他们的油井结果，并被迫考虑在补偿面积表现更好时进行更改。造成穿孔变化的其他因素包括集群数量增加、设备短缺、高温炸药短缺以及与中国和钢铁关税不断变化的贸易关系。

孔板流量方程
在当今的大多数设计中，人们普遍接受（也许比应有的程度更多）流体的注入速率遵循孔板流量方程，并且支撑剂和流体一起均匀移动。孔板流量方程如下：

螖P perf = 总射孔摩擦力（psi）；
Q = 通过每个穿孔的流量（bbl/min）；
D = 穿孔直径（英寸）；
C _v = 射孔系数；ρ = 流体
密度（磅/加仑）。

套管上的压差是处理一个阶段中所有簇的方法。注射速率主要受穿孔孔径的4次方影响。操作员正在更好地了解“正确”C _v因素、初始射孔尺寸和泵送过程中的射孔侵蚀率，并认识到低处理压力并不是成功的衡量标准。

工程师们最终放弃了“每性能每分钟两桶”的旧经验法则，转而采用更强大的技术方法。以 2 桶/分钟的注入速度，0.30 英寸。直径穿孔的压差约为 1,540 psi，而 0.40 英寸的穿孔的压差约为 1,540 psi。孔的压差约为 480 psi。射孔侵蚀降低了压差，导致簇的刺激不足。操作员希望了解其特定重量和套管等级的实际射孔尺寸。美国石油学会发布的数据表价值有限，因为火炮系统是在直径较小、等级较低的套管中进行测试的。业界正在加强对 P-110 外壳的测试，并公布这些结果。旧式深穿透装药的孔尺寸变化范围为 0.50 英寸（零间隙）到 3.125 英寸的 0.28 英寸（最大间隙）。5.5 英寸内的枪 P-110 外壳。由此产生的每个射孔注入量的数倍变化导致运营商提出了同等入口孔收费的要求，这一要求得到了市场的认可。

最近的趋势、变化以及为什么
没有载流子集中的等进入/等浅穿透装药效果非常好，设计变化也如此，其中装药以与外壳成一定角度而不是垂直射出。使用这些样式的装药已经成功实现了压裂井，这些装药渗透到地层中几英寸。产品供应商现在在成本、最低孔径变化百分比、针对特定重量和等级套管提供的不同尺寸数量以及在重复压裂应用中通过两串套管实现结果的能力等方面进行竞争。操作员可以获得其要求的特定孔尺寸（约 0.02 英寸）。这增强了工程射孔设计的能力。

等入口孔装料促使操作员进行更多的步进速率测试并确定射孔效率/近井眼弯曲度。已知且尺寸一致的孔可提高分析置信度。焦点已经转移到套管上更高的压差上。石油工程师协会关于“极端限制进入”的技术论文由经常设计 2,500 psi 压差增产的操作员撰写，得到了广泛阅读并在整个行业引发了讨论。

聚能装药设计以更轻的炸药重量和更小的装药实现了所需的孔尺寸结果。这开辟了设计的可能性，包括在同一平面上彼此相邻放置小装药，而不是枪中单独的顺序装药。这些火炮系统于 2017 年开始实地引进，通常采用三发/集束配置。步进速率分析证明，这些较短的枪组件长度系统在单个平面上具有所有射孔，从而减少了近井眼的弯曲度。图 1 显示了这些系统的信息。

新的喷枪系统、安全和法规
在上述竣工活动减少之后，“慢速端口插头”造成的喷枪卡住问题以及相关的补救成本不断升级。由此产生的技术改进是行业向一次性系统的迁移，而不是管理接近其使用寿命的可重复使用的设备。人们将继续看到枪串系统的改进：断电、数据采集、枪引爆/硬件组件，尤其是插头设置工具和“全部就位”方法。区域隔离的趋势正在增加，操作员在射孔之前对球塞进行压力测试。在没有塞子固定的情况下，不要抽走整个级，这在操作和经济上都是有意义的。

需要注意的是：操作员的完井团队不是电子专家。他们严重依赖服务公司来了解电缆卡车/井下电子元件（尤其是雷管）的功能。发生的爆炸事故和未遂事故比人们听说的还要多，而发生事故的公司通常不愿意讨论这一问题。射孔系统具有巨大的能量，不能出现任何错误。几年前，行业专家估计超过 90% 的事故都发生在误操作之后。当今的电子产品开发人员必须确保系统高度可靠、与其他组件正确连接并且不会发生误运行。

其他趋势
在大多数盆地中，每级射孔簇数量持续增加。长期生产历史已达到数据分析可以确定经济效益是否与高集群计数所表明的早期生产结果一样好的程度。美国东北部天然气产量普遍较少，且地质情况不同。分流器正在寻找应用。

操作员利用较高的压差（初始腐蚀后为 1,500 psi 或更高）通常可以获得约 90% 的性能效率。高粘土含量地层，特别是在俄克拉荷马州的一些地区，观察到较低的性能效率。

过去 18 个月中，射孔尺寸不断减小。运营商在每个集群中使用单个更大的孔取得了成功。

“房间里的小猩猩”与颗粒传输和性能侵蚀研究有关。一些大学、运营商和一些服务公司正在试图更好地了解支撑剂随压裂液移动的均匀程度，并正在进行数值模拟。这将导致一个非常不同的思维过程，并对压裂命中和支撑剂回流产生影响。图 2 显示了一组操作员和其他人正在该领域进行的一项更有趣的测试。

编者注：Phil Snider 是 GEODynamics 的完井顾问。

Shaped charge designers have improved their thought processes in support of operators and unconventional well stimulations. Perforating systems for the limited-entry stimulation market were traditionally approached by simply making short versions of longer gun systems the industry had always used. A lot has changed.

Those conducting the perforations and those conducting the fracs are communicating. The U.S. activity downturn at the end of 2014, with associated layoffs and company failures, made everybody improve. Operators that had success with direct sourcing (sand and plugs) began talking about other category applications, including perforating. Operators, manufacturers/service companies and the investment community can now easily access and analyze data, both public data and private databases merged to them.

People are analyzing their well results and are forced to consider changes when offsetting acreage performs better. Other contributing factors to perforating change include increasing cluster counts, equipment shortages, higher temperature explosives shortages and the ever-changing trade relations with China and steel tariffs.

Orifice flow equation
In most of today’s designs, it is accepted (perhaps more than it should be) that injectivity rate of fluid follows the orifice flow equation and proppants and fluids move uniformly together. The orifice flow equation is as follows:

ΔP perf = total perforation friction (psi);
Q = flow rate through each perforation (bbl/min);
D = diameter of perforation (in.);
C_v = perforation coefficient; and
ρ = fluid density (lb/gal).

The differential pressure across the casing is the method to treat all the clusters in a stage. Injection rate is primarily influenced by perforation hole diameter to the 4th power. Operators are developing a better understanding of “correct” C_v factors, initial perforation hole sizes and perforation erosion rates during pumping and realizing low treating pressures are not a measure of success.

Engineers are finally abandoning the old rule of thumb of “two barrels per minute per perf” for more robust technical approaches. At a 2-bbl/min injection rate, a .30-in. diameter perforation has an about 1,540-psi differential pressure, whereas a .40-in. hole has about a 480-psi differential. Perforation erosion reduces differential pressure, leading to understimulated clusters. Operators want to know actual perforation hole sizes in their specific weight and grade of casing. The datasheets published by the American Petroleum Institute are of limited value as gun systems are tested in a smaller diameter, lower-grade casing. Industry is increasing testing in P-110 casing in particular and publishing those results. Older style deep-penetrating charges had hole size variation ranging from .50 in. (zero clearance) to .28 in. (maximum clearance) for a 3.125-in. gun inside 5.5-in. P-110 casing. The resulting several-fold variation in injection rate per perforation led operators’ requests for equal-entry hole charges, which gained market acceptance.

Recent trends, changes and why
Equal-entry/equal-shallow penetration charges without carrier centralization have worked extremely well, as have design variations where the charges shoot at an angle to the casing rather than perpendicular. Success has been realized fracturing wells using these style charges, which penetrate very few inches into the formation. Product suppliers now compete on cost, lowest percent hole size variation, number of different sizes they can provide for specific weights and grades of casing, and ability to achieve results through two strings of casing in refracturing applications. Operators can obtain the specific hole size of their request, within about .02 in. This enhances the ability for engineered perforating designs.

Equal-entry hole charges led operators to conduct more step-rate testing and determine perf efficiency/ near wellbore tortuosity. Analysis confidence level increased with known, consistent size holes. Focus has moved to higher differential pressures across the casing. The Society of Petroleum Engineers’ technical papers on “extreme limited-entry,” written by operators routinely designing stimulations with 2,500-psi differential pressures, were well-read and created conversations across industry.

Shaped-charge design accomplished desired hole size results with less explosive weight and smaller charges. This opened up design possibilities including small charges placed beside each other on the same plane, rather than individual, sequential charges in the gun. Field introduction of these gun systems began in 2017, usually in three shot/cluster configurations. These shorter gun assembly length systems having all the perforations in a single plane reduced near-wellbore tortuosity—as step-rate analysis proved. Figure 1 shows information on these systems.

New gun systems, safety and regulations
After the aforementioned turndown in completion activity, stuck gun issues with “blown port plugs” and associated remedial costs escalated. The resulting technology improvement is industry’s migration to disposable systems rather than managing reusable equipment nearing the end of its life. One will continue to see improvement in gun string systems: electric disconnects, data acquisition, gun detonating/hardware components, and especially plug setting tools and “ball-in-place” methodologies. The trend in zonal isolation is increasing where operators pressure test the plug with the ball in place before perforating. It makes operational and economic sense not to pump a whole stage away without a plug holding.

A word of caution: operators’ completion teams are not electronics experts. They rely heavily on service companies for how wireline trucks/downhole electronics components, and especially detonators, function. More explosives accidents and near misses occur than one hears about, and companies with incidents typically do not want to discuss it. Perforating systems have tremendous energy, and one cannot afford a mistake. A few years ago, industry experts estimated greater than 90% of accidents occurred after a misrun. People developing electronics today must ensure systems are highly reliable, properly interface with other components and no misruns occur.

Other trends
Perforating cluster count per stage continues to increase in most basins. The long-term production history is reaching the point where data analytics can determine if economics look as good as early production results indicated with high cluster counts. The northeast U.S., with its gas production, generally has fewer clusters and different geology. Diverters are finding applications.

Operators utilizing higher (1,500 psi or greater after initial erosion) differential pressures generally obtain about 90% perf efficiency. High clay content formations, notably in some areas of Oklahoma, observe lower perf efficiencies.

Perforating hole size is decreasing in the last 18 months. Operators are having success with single, larger holes per cluster.

The “gorilla in the room” is associated with particle transport and perf erosion studies. Several universities, operators and a few service companies are trying to better understand how uniformly the proppants move with the fracturing fluids and are progressing numerical simulation. This will lead to a very different thought process and has implications to frac hits and proppant flowback. Figure 2 shows one of the more interesting tests in this arena that a group of operators and others are conducting.

Editor’s note: Phil Snider is a completions consultant to GEODynamics.