Identification of Leakage in Couplings of Tubing, Casing and Intermediate Casing for Wells of Underground Gas Storage in Salt Caverns by means of Spectral Noise Logging (original) (raw)
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Concept of Leak Tightness Monitoring at Underground Gas Storage
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The most important part of the operation of each underground gas storage facility is the implementation of a regular monitoring system for leak tightness monitoring. This article deals with the design of a proposal leak tightness monitoring concept in underground gas storage in porous reservoirs (depleted gas/oil reservoirs, aquifer reservoirs). This concept interconnects all commonly used and established leak tightness monitoring methodologies and evaluates them in time with comparison with historical results with reference to possible solutions or implementation of remedial measures.
Noise Logging Application for Well Integrity Evaluation: A Case Study in Peninsular Malaysia
Field-X was first discovered in 1979, comprising of saturated oil reservoirs with several shallower non-associated gas reservoirs. Field-X is currently producing from several oil producers. X8 well was recently drilled, completed, and produce from A and B reservoirs. However, 5 months later, the oil rate has been reduced by half with gas oil ratio (GOR) increased up to 5 times. Consequently, the well had to be shut-in due to reservoir management plan (RMP) violation. X9 well was drilled and completed, but 5 years later the well started experiencing the sustained production casing pressure (PCP) and was forced to shut-in in the following year with the locked-in potential of both A and B reservoirs. To diagnose the root cause of high GOR (HGOR) in X8 well and sustained PCP in X9 well, the Spectral Noise Log (SNL) was deployed. The main advantage of utilizing SNL is its capability of detecting fluid movement behind tubing and casing. High differential pressure creates lots of fluid movement, which generates higher noise amplitude. Meanwhile, smaller pores or leaks generate higher frequency noise that can be easily picked up by SNL. SNL tool was run in flowing condition for X8 well and the results indicated the HGOR zones were mainly contributed by the shallower B05 sand which was flowing through the leaked 4-1/2″ liner packer. Temperature deflections also indicated that the liner packer seal was leaking and B05 reservoir was contributing to the production. The liner packer leak and B05 reservoir flow would not have been detected by conventional production logging tools as the flow was happening beyond the tubing and casing. For X9well, SNL was run in the wellbore whilst pumping water via annulus, through the leaks and flowing back up the tubing. Three tubing leaks were successfully detected from the SNL run, whereas previous conventional noise log only managed to detect 2 leaks. It is possible that the third small leak was very small, hence the conventional tool was unable to detect it. X8 well successfully back online with 8.4% rate increase than last production with GOR reduced back to initial GOR and X9 well successfully back online as per last production rate. The liner packers which are nonpermanent barriers for reservoir isolation and allocation can be validated, moreover, verifying that tubing leakage is mainly contributed by tubing joints, which can be used as the main input in tubing materials selection in the future. Well integrity issues can cause significant loss of production, oil spill or worst case, even loss of lives. Proper selection in data acquisition tools helps to accurately diagnose well integrity issues that can be swiftly addressed. In the low oil price environment, skimming down on data acquisition costs may not uncover the true underlying well issues or reservoir issues, but might jeopardize future projects to be under taken in years to come. Keywords: Noise Logging, well integrity, high GOR, tubing leak
Leakage simulation and acoustic characteristics based on acoustic logging by ultrasonic detection
Advances in Geo-Energy Research
The detection of casing leakage in oil and gas wells or water injection wells is an important element of wellbore integrity management. Ultrasonic technology is suitable to detect and identify the position of leakage in oil and gas well shafts, providing engineering guidance for subsequent treatment. In this paper, the finite element calculation model of casing leakage in oil and gas wells is established by using the computational fluid dynamics method, and the large eddy simulation model and Ffowcs Williams-Hawkings acoustic model are utilized to simulate the casing leakage condition. The acoustic pressure signals of each monitoring point on the inner axis of the pipeline are obtained, and the influences of the pipeline pressure difference, the leakage hole diameter and the pipeline fluid on the leakage acoustic field are analyzed. The simulation results indicate that the acoustic pressure level measured on the pipeline axis rises with the increase of pipeline pressure difference and leakage hole diameter. The size and variation rule of acoustic pressure level also vary with the type of pipeline fluid. Overall, the results obtained show that ultrasonic logging can accurately locate and detect tubing leakage, and they provide theoretical guidance for practical casing leakage detection, assisting with wellbore integrity management.
Engineering Geology, 2014
A semi-quantitative risk assessment is presented for the storage of gas oil in depleted salt caverns in the Twente region, the Netherlands. It is based on a bow-tie model, in which an incident, leakage of gas oil from the storage system (cavern and wells), is evaluated by assessing its possible causes and effects. The causes are all the events that may lead to leakage from the storage system. The effects are the consequences of the leakage. It is considered that the most serious of the subsurface risks is contamination of the groundwater due to upward migration of the gas oil to the surface. A unique aspect of our risk assessment is the combination of causes and effects. The effects of containment/failure are quantified at multiple time scales using a numerical flow model for multiphase flow through porous medium, based on the geohydrological properties of the subsurface of the Twente area. The probability of occurrence of loss of containment/failure (causes) is quantified semi-quantitatively, using the causal relationships between the causes and effects. Modelling of the leakage shows that, as expected, leakage from the well above the hydrogeological base in the phreatic aquifer produces an immediate risk of contamination of the upper groundwater. However, leakage at a deeper level does not pose a risk of contamination of groundwater, because the low porosity and permeability of the geological layers prevent the upward migration of leaking gas oil. The semi-quantitative approach to the probability of failure finds that for multiple scenarios (e.g. well failure, unstable cavern, high pressure) and in the absence of human intervention, the probabilities of failure are medium to high. If human intervention is assumed, these probabilities of failure diminish considerably, especially those associated with the well. These findings are consistent with those from other hazard studies on storage in salt caverns. The causes (probabilities of failure) and effects (modelling of leakage) together indicate that for most scenarios the risk is low when human intervention (e.g. monitoring of the well) is assumed. Notwithstanding our conclusion that the risk of leakage associated with gas oil injection and storage in salt caverns is low, an extensive monitoring plan should be formulated to monitor the containment of the gas oil in the storage system and its long-term stability, to ensure timely human intervention that reduces the risk considerably.
Downhole Leak Detection: Introducing A New Wireline Array Noise Tool
SPE/ICoTA Well Intervention Conference and Exhibition, 2019
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