Servicing oil and gas wells requires their integrity assessment both during operation and before abandonment. One of the main objectives in well integrity analysis is the location of metal losses in tubing and/or casing caused by corrosion, erosion or other types of pipe damage. The first three metal barriers (normally tubing, production casing and intermediate casing) are of the most interest to the industry. Dual string completions is an additional complication to through-tubing assessment of the second and third barriers.Magnetic Imaging Defectoscope (MID) is an electromagnetic scanning tool that recor ds magnetisation decays induced by high-power electromagnetic pulses. Metal pipe barriers contribute to magnetisation decays at different times depending on their diameters, which makes it possible to differentiate each of them and determine their individual thicknesses. Thickness determination requires the numerical finite-element modelling of each recorded magnetisation decay and iterative fitting of the properties and thickness of every metal barrier to the actual tool readings. A data array can store hundreds of thousands decays, and the data processing optimisation loop therefore requires parallel computing with multi-core processors to process data within a reasonable time frame. The MID hardware and interpretation algorithm have been tested on multiple laboratory stands simulating various downhole multi-barrier completions from 2-7/8Љ up to 13 3/8Љ pipes with artificial defects of various shapes and sizes ranging from 7 mm to 140 mm. This paper presents laboratory results and three selected field cases demonstrating the application of Magnetic Imaging Defectoscopy (MID) in single-string and dual-string completions for thickness evaluation of three barriers independently by a memory through-tubing survey.• Well W-01 with metal losses found at the same depth in the second and third barriers, i.e. 9 5/8Љ and 13 3/8Љ casings • Well W-02 with metal loss found in the second barrier, i.e. 9 5/8Љ casing, in an interval containing two strings. This corrosion has been confirmed by a repeated MID survey after pulling out the completion • Well W-03 with through-hole metal loss found in the second and third barriers, i.e. large-diameter 9 5/8Љ and 13 3/8Љ casings, through a 7Љ liner. This through-hole corrosion has been confirmed independently by High-Precision Temperature Logging and Spectral Noise LoggingThe above metal losses have been located by through-tubing memory surveys in offshore wells that were to be abandoned. The results of the MID surveys were then used to design environmentally safe abandonment procedures.

With the onset of offshore decommissioning resulting in an increasing number of permanent plug and abandonment (P&A) campaigns it is critical to manage these in a safe and cost-effective way. A robust methodology is important to manage the magnitude of wells in Norway to be P&A’d including the need to comply with Norsok Standard D-010 (Norsok, 2013). Many technologies have come to the forefront to aid with safe permanent well abandonment, with different criteria to be met, principally by verifying the integrity of the casing and cement barriers across the zones that are plugged. To inspect the cement barrier interval, spectral noise logging was utilized to investigate noise generated by flow in fluid and gas phases. A practical test in a controlled environment was required to document the sensitivity of the spectral noise logging techniques ability to detect liquid and gas flow for different annular cement quality scenarios. Full-scale barrier reference test cells were constructed to represent a range of cement defects such as gas channels, mud channels and de-bonded cement. These test cells have been utilized to evaluate the performance of well barrier verification technologies. The measurement resolution of spectral noise logs to detect flow behind casing was investigated by flowing water and gas through the different leakage paths. The flowrate range used for this experiment was between 1 and 1300 mL/min for water and between 1 and 24 L/min for gas (N2). The experiment was performed in a low noise environment to avoid ambient noise sources that might compromise the experiment. P&A regulations and recommended practices were considered when developing the test procedure. Controlled annular leakage rates of water and gas were established using barrier reference cells representing good cement, no cement, gas channels and micro-annuli. Spectral noise logging measurements were recorded using a memory based, commercially available logging tool and the results were analyzed. The data showed the spectral noise logging tool was able to detect the noise generated by low flowrates of water and gas through different leakage paths. The yard test results provide a basis for considering noise logging and its spectrum analysis as an alternative means or an addition to currently used cement bond logging technologies for cement barrier verification. The applicability of utilizing spectral noise logging as an additional proof of annular barrier integrity was demonstrated.

No abstract

Sharjah National Oil Company (SNOC) operates 3 fields Onshore Sharjah with 30+ years’ production history from over 50 gas condensate wells. The fields were produced historically under a blow down scheme resulting in significant condensate volumes being dropped. While these existing resources could be recovered through drilling additional wells apart from optimization opportunities in the current production regime, the most economical solution would be to verify if the existing well stock could be confirmed as having sufficient well integrity to safely allow the continued use of these wells thereby extending the field life through careful well and risk management. The Sajaa and Moyeveid gas fields feature a series of challenging production issues. These include varying hydrogen sulphide levels upto 500 ppm, surface cemented annuli, sustained casing pressures, carbon steel tubulars, known corrosion issues greater than 0.5 mm per year, carbon dioxide and water production, all from multi-lateral wells at extremely low reservoir pressures. SNOC developed a comprehensive risk ranking process that categorized the wells into low, medium and high risk using a wide range of available production data, well age and corrosion inhibition data. Further investigation included corrosion logging data acquired from 2 wells in 2015 providing indicative well status and validation of electromagnetic corrosion measurement technology. Although, it did not provide a comprehensive and in depth review for a representative wider range of wells. In order to provide a more deterministic status of the well stock, and optimizing the risk ranking process, 10 wells were selected to be investigated with a campaign of corrosion logging in 2016. However, it was important that the intervention program would have minimal production impact with a small footprint slick-line intervention unit that would utilize state of the art magnetic imaging technology to record and measure the status of the well tubulars. Additionally, HSE impact was reduced by restricting the operations to daylight working hours and minimizing the numbers of personnel exposed to the well-site. This paper summarizes the logging operations, analysis of the data collected, well tubular status & issues such as shallow surface corrosion and well correlation on a field basis. It also focuses on how this was integrated into the SNOC risk ranking model to allow continued production from the wells, while still maintaining the well integrity status that supported the company’s philosophy of managing risks ‘as low as reasonably practical’ (ALARP) maximizing recovery from a mature reservoir

Shallow casing corrosion in onshore wells is a well-known phenomenon throughout the Arabian Peninsula. It happens when the carbon steel is exposed to corrosive environment (including moisture and oxygen) due to insufficient barrier protection and isolation. The issue requires periodical casing excavation and inspection which are time-consuming operations with different teams involved. This document describes successful field validation of the alternative cost-efficient method of casing inspection using corrosion logging technology. The method of individual electromagnetic metal loss logging for 3 barriers became recently available. It is electromagnetic-based technology which was modified to be able to provide multiple barrier evaluation. 3 wells were selected for trial logging and later were excavated to compare the logging results with actual findings (physical check). Results of the trial test confirmed applicability of this costefficient technology for Company Surface Casing Inspection. The new method allows extending casing inspection to unlimited depth with less time required and less risks associated. The opportunity to evaluate conditions of all three barriers without retrieving the tubing gives a lot of benefits for the entire Well Integrity Management process; it may include actual corrosion rate measurements of all effective barriers, SAP (Sustained Annulus Pressure) investigations, and risk assessments. Field validation of this technology had a positive impact on Operator's Well Integrity process, giving more options for proactive Well Integrity Management and resulting in total cost reduction and improved HSE (Health, Safety and Environment) performance. Additionally, it helped to identify a serious gap in the existing conventional process of Surface Casing Inspection. This document presents the results of technology validation performed in the third barrier of a producing well in real field conditions. Additionally, it contains specific recommendations for other areas of application of this technology for maximum benefits, like three-barrier evaluation prior to workover and multiple barrier time lapse corrosion monitoring.