Maximum Leakage Rate Research Articles

Analytical solutions for brine invasion across caprock and leakage through an abandoned well in CO2 storage sites

Success in subsurface CO2 storage requires a trapping mechanism that inhibits the flow of storage layer fluid. Due to the wide prevalence of abandoned wells across geological formations, unwanted leakage events of brine and CO2 may occur if old wells near storage sites are not evaluated accurately. The abandoned wells, with time, may become conducive to flow if a sufficient pressure gradient is realized. Classical analytical models theorized abandoned well problems based on Theis’s solution and proposed strategies to find radial coordinates of the abandoned wells. However, in those formulations, brine invasion from storage to the surrounding formation is either disregarded or assumed as a vertical-only flow. In this study, we report a novel mathematical model that accounts for both brine invasion and abandoned well flow. The leakage rate across the abandoned well segment is evaluated from three contributing pressure terms: injection- and the associated brine invasion-induced pressure build-up, leakage-induced pressure drawdown in the storage layer, and leakage-induced pressure build-up in the overlying aquifer. We evaluate the average radial pressure from a two-dimensional coupled flow problem by applying Laplace and Hankel transforms. The obtained solutions in the Hankel-Laplace space were inverted back to the radial-time domain by employing the integration-summation-extrapolation and Stehfest method, respectively. We verified the developed solution against the classical solution analytically and graphically. We observe that Theis’s solution always overestimates the radial pressure as the pressure is diffusing in the lateral direction only. We identified that the abandoned well leakage rate decreases with the increase of permeability ratio, and the degree of reduction is higher in late times. We measured the degree of overestimation in leakage rates compared to classical solutions. A maximum leakage rate is observed for open flow conditions. The abandoned well leakage rate reaches its maximum early when the permeability ratios are higher. The proposed work can be employed as a base solution in old-well leakage modeling to determine the radial coordinate of the abandoned wells with a higher degree of certainty.

Experimental study on lubrication characteristics and leakage inhibition of oil-lubricated seal with herringbone grooves

Experimental research was conducted on mechanical seals with pressurized lubricated-oil, focusing on lubrication and leakage inhibition of herringbone-grooved face seals. Through the visualization experiments and axial displacement tests, this study evaluated the performance of the inner-diameter-side (IDS) and middle-diameter-side (MDS) herringbone grooved seals based on the measured cavitation region, leakage rate, friction torque, surface temperature of stator, and axial displacement of the primary ring. The experiment results show that, increasing the width of the seal dam can reduce the hydrodynamic effect and cavitation development of the liquid film but enhance the hydrostatic effect, maintain a small leakage range, the maximum leakage rate is less than 19 mL∙min−1. Zero-leakage can be achieved in MDS due to cavitation suction. The axial displacement curves indicate that the runout amplitude of IDS is smaller than that of MDS, the maximum axial displacement difference is about 25 µm, the stability of IDS is better than MDS. Comparisons of surface temperature and friction torque demonstrates that the lubrication of MDS is better than that of IDS.

Risk Assessment of Annular Pressure Caused by Tubing Leakage in Offshore Gas Wells with High CO2

CO2 sequestration is a kind of technology that can effectively mitigate the greenhouse effect, and the wellbore integrity of the storage system is the key issue to ensure successful CCUS. Failure to timely diagnose tubing leakage in offshore gas wells with high CO2 will lead to annular pressure risk and wellbore corrosion problems. The annular pressure caused by tubing leakage is characterized by high pressure and rapid rise rate, resulting in wellhead jacking, gas leakage, and wellbore structure corrosion, which has become the main cause of wellbore integrity failure in offshore gas wells. Therefore, a model of heat and mass transfer and distribution in offshore gas wells was established firstly, and the physical process of gas leakage and accumulation was described based on the pinhole model and the principle of gas PVT characteristics and volume compatibility. The results show that the depth and equivalent size of the leakage point are two important factors affecting the pressure rise process and leakage rate. Taking case well parameters as an example, after inversion calculation, the annulus pressure in case well was 23.0 MPa, the leakage point equivalent diameter was 2.3 mm, the maximum leakage rate was 0.30 m3/min, and the wellbore safety risk is relatively high. Mechanical repair and chemical plugging agent are recommended to seal the tubing leakage. These risk assessment technologies provide reference for wellbore integrity design and management to reduce CO2 leakage risk caused by wellbore integrity failure.

Deep water leakage from semi-mobile dunes in semi-arid regions and its response to rainfall patterns

As the main source of soil moisture supply in desertified areas, rainfall has a profound impact on soil moisture changes and plays an important role in deep soil moisture replenishment. Based on the Hydrus-1D model with optimized parameters, we analyzed the dynamic change process of the leakage in the 200 cm deep layer of the semi-mobile dunes in Horqin Sandy Land and its response to the rainfall patterns. The results showed that the averaged leakage replenishment of semi-mobile dunes was 254.31 mm from April to October each year during 2016 to 2019, accoun-ting for 61.8% of the rainfall in the same period. Deep leakage mainly occurred from June to August, accounting for 72.8% of the total. The leakage rate was distributed between 0.03-2.70 mm·h-1, with the maximum leakage rate occurring under heavy rainfall and frequent rainfall events. The deep soil water supplied by rainfall infiltration was affected by the amount of rainfall, rainfall intensity, duration of precipitation and soil moisture content in the earlier period. Precipitation events with long duration and small rainfall intensity were more conducive to deep water lea-kage, with a significant positive correlation between the leakage and rainfall (R2=0.85). 16-18 mm rainfall was the threshold for the leakage of 200 cm soil depth. The high-frequency rainfall event usually reached peak after 17-38 hours, with the entire leakage process being more than 164 hours. Accurate estimation of deep leakage has theoretical and practical significance for water resource assessment and ecological construction in desertified areas.

Improving the Leakage Rate of Ciphertext-Policy Attribute-Based Encryption for Cloud Computing

A Leakage-Resilient Ciphertext-Policy Attribute-based Encryption (LR-CP-ABE) not only supports the fine-grained access control to encrypted data but also guarantees the security of the data under the side-channel attacks. However, the leakage rate in the existing schemes is low or related to the number of attributes. It will make these schemes suffer from continual attacks. In addition, all of them almost not consider the leakage of the users' privacy and rely on the composite order groups which will threaten the privacy security of the users and depress the users in practice. In this paper, we aim at solving the above problems and propose a scheme with the improving leakage rate in the prime order group. In the proposed scheme, an extension of the lattice-based trapdoor is used to make it achieve the maximum leakage rate $1-o(1)$ . Moreover, it achieves the anonymity which can protect the privacy of the receivers. The proposed scheme can be reduced to the standard assumption-Decision Linear (DLIN) assumption in the selective security model and resist the Chosen Plaintext Attacks (CPA security). At last, the performance comparisons are given to confirm the efficiency and security of the proposed scheme.

Environmental Stress Testing of Wafer-Level Al-Al Thermocompression Bonds: Strength and Hermeticity

Hermeticity, reliability and strength of Al-Al thermocompression bonds realized by applying different bonding parameters have been investigated. Laminates of diameter 150 mm were realized by bonding wafers containing membrane structures to wafers with patterned bonding frames. The laminates were bonded applying a bond force of 36 or 60 kN at temperatures ranging from 300 to 400°C for 15, 30 or 60 minutes. The hermetic properties were estimated by membrane deflection measurements with white-light interferometry after bonding. Reliability was tested by exposing the laminates to a steady-state life test, a thermal shock test, and a moisture resistance test. Bond strength was measured by shear test and pull tests. Laminates bonded applying a bond force of 60 kN at temperatures of 350 or 400°C resulted in hermetic bonds. No significant change in membrane deflection was observed after the steady-state life test or the thermal shock test. However, a gross leakage was observed in 1–11% of the dies after exposure to the moisture resistance test. The maximum leakage rate (MLR) estimated from membrane deflection measurements was below 10−11 mbar·l·s−1 for all laminates. The measured average bond strength of dies from selected laminates ranged from 28 to 190 MPa.

Environmental Stress Testing of Wafer-Level Au-Au Thermocompression Bonds Realized at Low Temperature: Strength and Hermeticity

Hermeticity, reliability and strength of four laminates bonded at different temperatures by Au-Au thermocompression bonding have been investigated. Laminates with a diameter of 150 mm were realized by bonding a wafer containing membrane structures to a Si wafer with patterned bond frames. A bond tool pressure of 2266 mbar was applied for 15 minutes at temperatures ranging from 150–300°C. The hermetic properties were estimated by membrane deflection measurements applying white-light interferometry after bonding. Reliability was tested by exposing the laminates to a steady-state life test, a thermal shock test, and a moisture resistance test. Bond strength was estimated by pull test measurements. A dicing yield above 90% was obtained for all laminates. Laminates bonded at 200°C and above had significantly higher hermetic yield than the laminate bonded at 150°C. No degradation in hermeticity was observed after the reliability tests. The maximum leakage rate (MLR) was estimated from two measurements of membrane deflection executed at two different times and was below 10−11 mbar ⋅ l ⋅ s−1. The average bond strength ranged from 44 to 175 MPa.

Uncertainty analyses of CO2 plume expansion subsequent to wellbore CO2 leakage into aquifers

This study focused on CO2 plume expansion subsequent to wellbore CO2 leakage into a shallow unconfined aquifer post-CO2 injection. The target response variables included CO2 plume size, as well as flux to the atmosphere. Many processes contribute to CO2 plume expansion in the aquifer; here we considered process and model parameters including those affecting the abandoned well leak rate, aquifer hydraulic properties, and aquifer geochemistry. In order to identify the significant factors affecting leakage, we adopted an uncertainty quantification framework to quantify input uncertainty, generate exploratory samples effectively, perform scalable numerical simulations, visualize output uncertainty, and evaluate input–output relationships. We combined quasi-Monte Carlo and adaptive sampling approaches to reduce the number of forward calculations while fully exploring the input parameter space and quantifying the output uncertainty. The CO2 migration was simulated with STOMP-CO2 (water–salt–CO2 module). Response surfaces of model outputs were built with respect to input parameters to determine the individual and combined effects. Four most significant parameters were identified to be dominating the CO2 plume expansion process subsequent to wellbore CO2 leakage: distance between the leaky and injection wells, maximum leakage rate, porosity, and hydraulic conductivity.

Safety Analysis of Dual Purpose Metal Cask Subjected to Impulsive Loads due to Aircraft Engine Crash

In Japan, the first Interim Storage Facility of spent nuclear fuel away from reactor site is being planned to start its commercial operation around 2010, in use of dual-purpose metal cask in the northern part of Main Japan Island. Business License Examination for safety design approval has started since March, 2007. To demonstrate the more scientific and rational performance of safety regulation activities on each phase for the first license procedure, CREPEI has executed demonstration tests with full scale casks, such as drop tests onto real targets without impact limiters(1) and seismic tests subjected to strong earthquake motions(2). Moreover, it is important to develop the knowledge for the inherent security of metal casks under extreme mechanical-impact conditions, especially for increasing interest since the terrorist attacks from 11th September 2001(3)-(6). This paper presents dynamic mechanical behavior of the metal cask lid closure system caused by direct aircraft engine crash and describes calculated results (especially, leak tightness based on relative dynamic displacements between metallic seals). Firstly, the local penetration damage of the interim storage facility building by a big passenger aircraft engine crash (diameter 2.7m, length 4.3m, weight 4.4ton, impact velocity 90m/s) has been examined. The reduced velocity is calculated by the local damage formula for concrete structure with its thickness of 70cm. The load vs. time function for this reduced velocity (60m/s) is estimated by the impact analysis using Finite Element code LS-DYNA with the full scale engine model onto a hypothetically rigid target. Secondly, as the most critical scenarios for the metal cask, two impact scenarios (horizontal impact hitting the cask and vertical impact onto the lid metallic seal system) are chosen. To consider the geometry of all bolts for two lids, the gasket reaction forces and the inner pressure of the cask cavity, the detailed three dimensional FEM models are developed and calculated. Main criteria for estimating the maximum leakage rate for the lid metallic seal system are no loss of the pre-stress of the lid bolts, no appearance of the plastic region between the metal seal flanges, and no large relative deformation of the lid seals. Finally, in both cases, the low leakage rate for the metal cask lid closure system under the impulsive loads due to aircraft engine crash will be proved thoroughly.

Efficiency of Carbon storage with leakage: Physical and economical approaches

In this paper, two methods are proposed to assess the efficiency of carbon capture and storage (CCS) involving back-leakage of CO 2 from geological storage reservoirs to the atmosphere. The first method is a physical approach based on radiative forcing. It leads to a criterion that assesses whether a given technology of CCS is physically beneficial compared to a reference technology without CCS. The second method is an economic approach based on the classical framework of net present value (NPV). It leads to an economic feasibility condition that assesses whether a given CCS technology is economically beneficial compared to a reference technology. The two models are compared with respect to their parametric dependence. In particular, a maximum leakage rate may be defined, above which neither of the feasibility criteria is satisfied. The two approaches are also discussed with respect to the type of decision they may generate. Under general assumptions, the economic criterion is stricter than the physical criterion when the leakage coefficient is small, and the opposite is true when the leakage coefficient is large.

Design, construction, performance, and repair of the soil–bentonite liners of two lagoons

A sand–bentonite mix was used to form the liner of four lagoons for the La Tuque and Haute-Mauricie sewage water treatment project. This paper describes the site conditions, design, and construction of the lagoons. Since the results of the control tests on the sand–bentonite were satisfactory, it was expected that the liner would be as impervious as it was designed to be. Such control tests, however, provide local values that can give only an indirect prediction of the waterproofing of each lagoon. The global performance was evaluated in 1988, after filling the lagoons, by comparing their leakage rates with the design theoretical values. The performance of two of the lagoons was satisfactory, whereas the two other lagoons lost 10 times more water than the maximum leakage rate allowed in the specifications. An analysis of the various factors influencing the global performance is developed to explain these contradictory performances, which cannot be explained by the usual deterministic method used in design. The paper demonstrates how to analyze the graph of the total leakage rate of a lagoon to determine where the main hydraulic defects are located and whether or not they are deteriorating. Several techniques for repairing the lagoons were considered and are described. The technique selected was the underwater injection of a bentonite slurry of adequate viscosity. Repairs were successfully completed during the summer of 1989. Key words : impervious liner, soil, bentonite, permeability, case history.

Radiation protection aspects of a new high-energy linear accelerator

The Therac-25 is a new 25-MeV linear accelerator manufactured by Atomic Energy of Canada, Ltd. The first two units have recently been installed in Toronto, Ontario and Halifax, Nova Scotia. Calculations and measurements of primary and secondary radiation levels were made. Neutron dose-equivalent rates were measured inside and outside the room. The maximum leakage rate at 1 m from the accelerator target was 0.4% Sv per peak photon Gy. The tenth value layer for neutrons from the Therac-25, at the entrance to a one-legged maze was found to be 5.5 cm of polyethylene. Measurements were done to estimate daily technologist exposure due to induced activity in the treatment room.