For Permanent Plug and Abandon Operations, There is No Acceptable Level of Leakage. Can a Noise Tool be Used to Define No Leakage?

D. Troup
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Abstract

A plug and abandon (P&A) operation aims to isolate the subsurface from the surface and success is traditionally gauged by fulfilling arbitrary criteria such as a physical length of an annular barrier. Multiple examples exist where a perfectly legal barrier has leaked. This paper intends to demonstrate that a sufficiently sensitive noise tool can provide the closest measure possible to verification of "no leakage". The principle that fluid moving in a turbulent fashion will emit acoustic energy is very well established and is used in many successful noise logging tools. When the fluid movement is very small, the level of noise is correspondingly small, and conventional tools may miss them. A tool optimised for low energy sensitivity was evaluated in a series of text fixtures and cemented casing sections recovered from real wells to quantify the lower levels of noise detectability. Following this, logs were recorded in previously abandoned wells, detecting minute leakage despite full compliance with guidelines. An industry leading acoustic tool was redesigned from the sensor through to the electronics to enhance its detection range to as low as possible. The sensor to electronics design was optimised to lift the low energy response by a factor of 10, while the intrinsic baseline noise was lowered to significantly increase the dynamic range available. A field test confirmed the low energy response to be 25 decibel (dB) better than pre-modification. Controlled testing under a range of conditions for both liquid and gas leakage resulted in the detection threshold being delineated for a variety of conditions. In addition to this the examination of statistical sampling parameter revealed meaningful acoustic signatures associated with varying flow regimes at very low rates. Field validation of the tool in a previously abandoned well confirmed the low threshold of the optimised tool and an intermittent leak of extremely low rate successfully mapped. This paper demonstrates through controlled testing and field deployment that compliance with P&A barrier condition regulations absolutely does not guarantee zero leakage, but that an optimised acoustic tool is able to detect even very tiny leaks. The judicious use of such technology during the abandonment procedure to verify a barrier is actually sealing will prevent costly returns to remediate faulty procedures.
对于永久性堵塞和废弃操作,没有可接受的泄漏水平。是否可以使用噪音工具来确定没有泄漏?
插头和放弃(堵井)操作旨在孤立的地下表面和成功是传统来衡量满足任意标准如环形屏障的实际长度。有很多例子表明,完美的法律障碍已经泄露。本文旨在证明一个足够灵敏的噪声工具可以提供最接近验证“无泄漏”的措施。紊流运动的流体会发出声能,这一原理已经得到了很好的证实,并被应用于许多成功的噪声测井工具中。当流体运动非常小时,噪声水平相应较小,传统工具可能会忽略它们。在一系列从实际井中回收的文本固定装置和胶结套管段中,对一种针对低能量灵敏度进行优化的工具进行了评估,以量化较低水平的噪声可探测性。在此之后,在之前废弃的井中记录了测井曲线,尽管完全符合指导方针,但仍检测到微小的泄漏。业界领先的声学工具从传感器到电子设备都进行了重新设计,以提高其探测范围尽可能低。对传感器的电子设计进行了优化,将低能量响应提升了10倍,同时降低了固有基线噪声,显著增加了可用的动态范围。现场测试证实,低能量响应比改造前提高了25分贝(dB)。在一系列条件下对液体和气体泄漏进行控制测试,从而确定了各种条件下的检测阈值。除了这个统计抽样参数的检查显示有意义的声学特征与不同流以非常低的利率体制有关。在之前废弃的一口井中对该工具进行了现场验证,证实了优化工具的低阈值,并成功地定位了极低速率的间歇性泄漏。本文通过控制测试和现场部署证明,遵守封堵弃井条件规定绝对不能保证零泄漏,但优化的声学工具能够检测到非常微小的泄漏。明智地使用这种技术在放弃过程来验证一个障碍是密封可以防止昂贵的补救返回错误的程序。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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