As the oil and gas industry is moving towards digital oil field, the selection of leak detection system (LDS) has become more crucial. Early detection of leaks not only saves environment from Hazardous hydrocarbons but considerable loss in production is also saved. This paper discusses about both internal and external LDS and its applicability for onshore and offshore fields. This paper will ease the selection process of LDS for green and brown fields of both offshore and onshore installation.
Wellbore integrity is very critical in oil and gas industry and needs to be maintained through the entire cycle of well's life. The most important item for well integrity is to set cement between two casings or between casing and formation. A good cement job provides isolation and protection for the well and a poor cement job can have cracks and allows corrosive fluids to migrate through micro channels.
Downhole casing repair is a common workover operations worldwide, especially in wells that have been producing over number of years. It is very challenging to control corrosive fluid migration which slowly corrodes casing and tubing over time. An innovative epoxy resin formulations has been developed and tested in the field to repair casing leaks which is extremely easy to handle and very economical. A cost-effective workover program can be developed and implemented depending on the severity of the leak.
The improved approach of using innovative resin can be used by mixing with cement blends to repair major casing damage and can also be used as standalone application to fix minor leaks. The system maintains extremely good rheological properties even when mixed with cement. The system has ability to withstand high differential pressure and is also resistant to acid, salts, hydrocarbons and most importantly various corrosive liquids. The precise application is determined by measuring the injectivity of the well. In the low injectivity wells, only epoxy resin solution will be spotted and repair the damaged casing. In the high injectivity wells, the chemical will be mixed with cement and completely seal the damaged zone. The chemical will enhance the mechanical properties of the cement and will be more resilient to extreme down-hole condition.
The paper will emphasize the added value and potential of the method in restoring the casing integrity. The paper will also discuss the laboratory test reports and application which will highlight effective and economical outcome.
Imrie, Andrew (Halliburton Energy Services) | Negenman, Brendon (Halliburton Energy Services) | Lee, Chung Yee (Halliburton Energy Services) | Iyer, Mahadevan S. (Halliburton Energy Services) | Parashar, Sarvagya (Halliburton Energy Services) | Shata, Mohamed Raouf (Halliburton Energy Services) | Helton, Sean (ConocoPhillips)
The identification of low-rate leaks along with low annular-pressure buildup rates in any type of completion presents challenges in the well-integrity domain. This paper emphasizes the importance of understanding the well-diagnostic problem to determine feasibility, isolate interest zones, enhance stimulation strategies, and ultimately optimize the acquisition of high-resolution acoustical data from the wellbore with a latest-generation advanced leak-detection tool.
This case study discusses the methodology that underlies the successful determination of the depths and the radial locations in the outer casing strings of multiple leaks in an offshore well. In the study presented, emphasis had been placed on the job planning to provide adequate or substantial leak stimulation for the accurate determination of the leak points in terms of radial distance away from the tool axis within the wellbore. Rather than a shut-in and flowing or venting acquisition, it was proposed that the optimal method for the successful determination of an outer casing string leak involved invoking a range of flow rates and, therefore, acoustic levels, across an extended period. The study also demonstrates the advantages of integrating acoustic-based tools with conventional production logging tools.
Two outer string casing leaks with annulus to formation communication areas were identified from high-resolution leak-detection logging coupled with conventional pressure and temperature measurements. The interpretation process included the computation of a 2D radial map of the flow activity across each zone of interest. This process resulted in less ambiguity and clearer results obtained in real time during the acquisition. The location of each leak point was triangulated using an error-minimization algorithm from the received acoustic waveforms at the tool receiver array. Further, the optimized stimulation strategy enabled leak-stimulation responses to be tracked in the computed power spectral density (PSD) at each leak. This process enabled the operator to promptly move on with the well abandonment strategy without waiting for further data analysis.
Attention to detail from the outset and a complete understanding of the well and its annular pressure and fluid behavior enabled an optimized and focused electric line diagnostic strategy to be used. The use of high-resolution acoustic data from an advanced leak-detection tool with an array of hydrophones ensured that the multiple leak locations were identified and characterized.
This paper will introduce a new generation wireline Array Noise Tool (ANT). This tool is used to detect downhole acoustic / vibration activities originating from fluid-structure friction flow. One of main applications in Well Integrity (WI) and Plug & Abandonment (P&A) for ANT is to locate leak sources in well completions and tubulars. The innovative sensor matrix and system configuration together with three novel data processing methods are studied and developed to address the following primary challenges; Tiny acoustic leakage signals (-30dB to -60dB), for example, the minor leaks behind pipes or even inside the formation matrix, Strong road-noise acoustic signal contamination from tool motion while dynamic logging, Nonstationary and/or nonlinear signal distortions because of tool flexural vibrations, and Downhole seismic noise.
Tiny acoustic leakage signals (-30dB to -60dB), for example, the minor leaks behind pipes or even inside the formation matrix,
Strong road-noise acoustic signal contamination from tool motion while dynamic logging,
Nonstationary and/or nonlinear signal distortions because of tool flexural vibrations, and
Downhole seismic noise.
The tool can be operated both in stationary logging and in dynamic logging.
The wide-band sensor matrix is designed with a unique configurable technique to form different measurement arrays. As a result, the tool can simultaneously acquire absolute and differential acoustic signals. By using this sensor matrix we are able to improve Signal-to-Noise Ratio (SNR) by up to 20 to 30dB. From the acquired data, we employ a multi-dimensional machine learning (ML) classification module, cascaded with cluster iteration to separate real leak signatures from other unwanted noise signals. After a data conditioning process, the wave velocity-domain decomposition method is utilized to further distinguish the leak signal propagation characteristics against other noise propagations to enhance overall SNR for leak detectability. Lastly we use a Bayesian likelihood analysis to identify the leak depth locations with a confidence index based on the information contained in both signal energy and signal velocity. We are able to achieve 15dB to 20dB SNR improvement from this data processing methodology. The system design goal is to eliminate unwanted acoustic noise that is not associated with leaks, while maintaining sufficient sensitivity to pick up minor leaks.
The tool has been logged commercially in the US, Middle East, East Asia, and Latin America. The tool performance has been validated through simulation, lab tests, and field logs. Field logging examples are demonstrating a leak detection success rate above 95%. Field cases include multi-annulus, low flow rate, and gas well field examples. Field results will be presented in this paper.
ANT instrument technology and the associated advanced processing methods are a new solution for detecting the leak source locations and monitor leak paths, especially, in Well Integrity (WI), Plug and Abandonment (P&A), and many other well applications.
During drilling or production operations, poisonous, highly flammable hazardous gases can be released into the environment. A next-generation gas emission monitoring system monitors gas leaks and can help the oil and gas industry improve workplace safety. The initial design, architecture, and development of a real-time monitoring and surveillance system consisting of drones capable of performing autonomous aerial inspections is discussed. This system monitors and reports the spatiotemporal evolution of hazardous gas clouds, such as H2S, CH4, and CO2, in the oil and gas facilities in real time and provides necessary actions for a safe operation. The proposed monitoring system is compared to the traditional monitoring approach where sensors are placed near the ground. This work is a significant improvement from the authors’ previous work leveraging state-of-the-art machine learning technologies to create smart drones capable of making intelligent decisions involving gas leak monitoring.
Methane monitoring using improved methods is detecting more gas in the atmosphere, increasing the need for better ways to eliminate releases. With the API and a multi-operator group passing separate programs aimed at reducing methane emissions, the discussions on what defines an acceptable level of regulation continues within the industry. The amount of natural gas flared has plunged in North Dakota, a region that has been the leader by far in gas wasted because gathering systems could not hook up the wells fast enough. Optical gas-imaging is effective for visual identification of volatile organic compound (VOC) leaks. But it doesn't currently quantify the leak rate as required by regulations.
A simple, practical, and reliable method to detect a gas leak under the conditions of unknown inlet or outlet gas rate, or unknown inlet or outlet pressure, is highly desirable. Tube leaks present in a water-cooled sulfur recovery unit (SRU) condenser can lead to a variety of process issues, including corrosion and the oxidative formation of acidic species. This work devised a novel method to verify such leaks within a SRU condenser.
The existing API equation for internal leak predicts the internal pressure to overcome the pin-box contact pressure generated from the makeup interference plus the energizing effect of internal pressure which enhances the seal. For threaded connections, internal and external pressures close the connection and increase the leak resistance, whereas axial loads open the connection and decrease the leak resistance. These competing effects must be included to accurately assess the connection leak resistance under any combination of loads at any point in any string. Following the same approach used by API for internal leak, this paper obtains similar results for external leak. For API connections, the effects of combined axial force and backup pressure are then incorporated into the internal/external leak equations using results from the Mitchell and Goodman (2018) paper presented at the 2018 SPE-IADC Drilling Conference. Sensitivities of leak ratings to combined loads for API connections are presented for both tubing and casing sizes. An example design case shows the importance of considering combined loads.
Cement holds the most critical role for providing long-term zonal isolation for permanent abandonment phase. The loss of cement integrity is undesirable as it may threaten the surrounding environment and safety on the surface. The quality of cured cement is commonly associated with the properties of cement material and cement placement in the wellbore. However, there are still limited investigations that link these factors specifically to the sealing ability of cement plug, especially with the lack of proper equipment in the past.
In the present work, a small-scale laboratory setup has been constructed to test the sealing performance of a cement plug. The cement plug is contained inside a test cell, connected to a pressurizing system and placed inside a heating cabinet. Consequently, the test can be simulated at downhole conditions in a controlled manner. By using this setup, it is possible to monitor the minimum pressure required for the plug to fail and the gas leak rate.
Two different cement systems, neat- and silica-cement, were prepared as plugging materials. Both cement systems are placed inside pipes with three different levels of surface roughness and then tested. Results show that the inner surface roughness of the pipes affects cement plug sealing significantly, and the effect is independent of the type of cement systems. Plugs placed inside a very-rough pipe significantly reduce the gas leak rate. Our results also show that an immediate gas leak occurs in all samples from leak paths formed at the cement/steel interface.
Exxon Mobil sent a letter to the US Environmental Protection Agency in support of methane gas emission rules put in place under the Obama administration, according to a copy of the letter seen by Reuters. The administration of President Donald Trump in September proposed weakening requirements for repairing leaks of the greenhouse gas in drilling operations in a step toward rolling back an Obama-era policy that was intended to combat climate change. The company believes “reasonable regulations help reduce emissions” and supports the use of cleaner-burning natural gas, the letter said.