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It is beneficial for both economy and safety to use as little passive fire protection on process equipment as possible and instead prevent unacceptable ruptures in a fire situation by other means like emergency depressurization. To do this, reliable methods and tools for predicting time to rupture is needed. This paper will present results from extensive testing and model development to improve prediction of rupture of process equipment exposed to severe process fires. The experimental work includes high temperature material testing of the most relevant steel types, rupturing of pressurized pipes by heating to flame temperatures and high heat flux jet fire testing of flanges. Based on this, simulation models have been developed which includes a strain-based method for calculating time to rupture of pipes and vessels and the adaption of a finite element program for calculating time to leak and rupture of flanges in a fire situation. Both these models have proved to give better results than older models and have now been implemented for practical use in Equinor.
Gyration tensors, originally devised to quantify shapes of static populations of points distributed in 3D space, are extended to dynamically varying populations, providing the theoretical foundation for analyzing their spatiotemporal evolution. Computation of gyration tensors for hypocenters of microseismic events triggered during hydraulic stimulation allows us to examine the behavior of populations of ruptures associated with the events rather than the behavior of individual ruptures, as conventionally implemented in microseismic monitoring. Synchronization of microseismic and completion data yields further advantages, making it possible to directly observe how changes in stimulation parameters, primarily the slurry rate and proppant concentration, govern the locations of groups of ruptures, either spreading them laterally in a stimulated formation or pushing them out of zone.
Following a brief description of the theory of gyration tensors and ellipsoids, we present two case studies from the Permian Basin in Texas, USA, to illustrate potential uses of spatiotemporal gyration for completion optimization.
Second-rank gyration tensors were introduced in chemical physics (Šolc and Stockmayer, 1971; Šolc, 1971) for quantitative analysis of structures of complex polymer molecules (Teraoka, 2002) through idealization of a monomer in a polymer chain as a point in 3D space. Shapiro et al. (1999) extended the use of gyration tensors to microseismic monitoring by treating hypocenters of microseismic events as points and applying the mathematical tools developed in chemical physics.
The principal contribution of our work is an insight that gyration tensor
In addition to the more immediate operating safety hazards, such as plugging blowout preventers, blocking drillstrings, and collapsing casing and drilling annuli, there are less obvious but very important safety hazards for removing hydrate plugs from flow channels. Hydrates cause safety problems for two reasons (both of which are shown schematically in Figs. The most common way to remove a hydrate plug from a flow channel is by depressurization. Flow is stopped, and the line is slowly depressurized from both ends of the plug. At atmospheric pressure, the hydrate stability temperature is invariably less than that of the surroundings, so heat flows from the environment into the hydrate plug.
Stress corrosion cracking was the cause of a pipeline rupture and fire near Prince George, British Columbia, in 2018, according to investigation results released by the Transportation Safety Board of Canada (TSB). The incident occurred on 9 October 2018, when a 36-in. Following the rupture, natural gas being transported was released and ignited, resulting in a fire and 125 people evacuated. TSB’s investigation into the incident showed deficiencies in predicting the extent of cracking and a deferred inspection led to a hazard being undetected prior to the pipeline rupture. The investigation also found that the pipeline ruptured due to stress corrosion cracks on the outside surface of the pipe; and that the polyethylene tape coating applied to the exterior surface of the pipe as a measure to protect it from corrosion deteriorated over time.
One of the important tasks in the on-site fault assessment of nuclear power plants is the estimation of fault displacements and their impact on the safety functions of facilities. Numerical prediction is one of the preferable methods for estimating fault displacements. The author proposes a numerical prediction method for estimating surface fault displacement using the dynamic fault rupture analysis. The proposed method is applied to the 2016 Kumamoto earthquake with surface faulting.
In this study, both primary and secondary faults are considered. For the primary faults, the fault rupture is initiated at a predefined hypocenter, and programmed to propagate outward along the fault plane with specified rupture velocities and stress drops until it is arrested at the edge of the fault plane. The calculation of the surface slip distribution on primary faults was consistent with the measured slip value. In the simulation, surface slip also appeared on the secondary faults. However, the calculated values of the surface slips on the secondary faults were not as consistent with the measured slip values. Therefore, the proposed numerical method is applicable to evaluating the possibility of surface slip on secondary faults. In the simulation, the appearance of the surface slip almost coincided with the occurrence of strong vibrations along the secondary faults.
One of the aftermaths of the 1999 massive earthquakes in Taiwan and Turkey is the growing concerns regarding the potential damage to various infrastructures and buildings caused by surface fault ruptures. Therefore, for the on-site fault assessment of nuclear power plants (NPPs), it is important to estimate the fault displacement and their impact on facility safety functions. Detailed geological surveys showed that important facilities in the NPPs were separated from the primary faults that are a direct extension from the earthquake fault source. Nevertheless, there are several cases of secondary faults beneath or close to these important facilities. Research has explored the activities of such faults. Estimating fault displacement is a crucial issue in on-site fault assessment. Numerical simulation has the potential to provide a reliable estimation of fault displacement.
Zhu, Jianjun (University of Tulsa) | Cao, Guangqiang (PetroChina Company Ltd.) | Tian, Wei (PetroChina Company Ltd.) | Zhao, Qingqi (University of Tulsa) | Zhu, Haiwen (University of Tulsa) | Song, Jie (PetroChina Company Ltd.) | Peng, Jianlin (University of Tulsa) | Lin, Zimo (University of Tulsa) | Zhang, Hong-Quan (University of Tulsa)
Plunger lift has been widely used in unconventional gas wells to remove liquid accumulation from the well.. Production surveillance provides large amount of data of production process and normal and abnormal operations, which can be used in machine learning (ML) and Artificial Intelligence (AI) to develop algorithms for anomaly diagnosis and operation optimization. However, in the surveillance data the majority is related to daily operation and the data of failure cases are rare. Also the failure cases may not be repeatable and many failure case signatures are not available until they happen. Large data size of anomaly cases are needed to improve the ML model accuracy. Dynamic simulation of the plunger lift process offers an alternative way to generate synthetic data on the specified anomalies to be used to train the ML model. It also helps better understand the trends reflected in the surveillance data and their root causes.
From the available surveillance data of gas wells equipped with plunger lift, the simultaneous measurements of different parameters at different points in a production system with normal and abnormal occurrences can be analyzed and the correspondent trends/signatures can be identified. The typical signatures that conform to pre-determined anomalous patterns can be obtained. Using a commercial transient multiphase flow simulator, the actual field data of tubing/casing pressures can be matched through a tuning process. Trial-and-error is needed to improve the dynamic plunger lift model so that a good agreement with the production data can be achieved by adjusting the reservoir performance, plunger parameters or surface pipeline boundary conditions. Following the validation under different flow conditions, synthetic datasets for various operational and flow conditions can be generated by performing parametric studies. Unlike the field data, the synthetic data from the dynamic simulations mainly comprise anomaly signatures (e.g. tubing rupture, missed arrival of plunger, etc.), which can be added to the ML data pool to reduce the data covariance and increase independency.
ABSTRACT: Fault surface geometries and their natural textures impose dominant control on the slip potential and characteristics of induced seismicity when triggered by reservoir depletion. In this study, we perform refined re-interpretation of subsurface faults on reflection seismic which hosted clusters of recorded production induced seismic events. The interpreted fault geometries are further analyzed utilizing spectral analysis and fractal theory. We identify roughness anisotropy from the slip-parallel and slip-normal power spectra, which indicate less degree of anisotropy in Hurst exponents at seismic scales compared with those at outcrop and specimen scales. By reconstructing artificial self-affine fault planes using parameters derived from seismic-scale faults and extrapolating below the seismic resolution, we develop finite-element based geodynamic fault models to investigate depletion induced dynamic fault rupture. The numerical results demonstrate significant control of fault asperity height on rupture styles and fault slip induced seismogenesis. The generated rupture size and tremor magnitude may be useful in understanding the nature of induced seismicity in an onshore gas field in Northern Europe.
Natural faults exhibit scale-dependent geometric features commonly observed at outcrops (at scales of ∼1-10m) and in the laboratories (at scales of ∼0.01-0.1m), which are associated with their geological history. Commonly recognized are the preferably oriented fabrics on fault plane surfaces due to slip, also known as slicken-sides or slip surfaces that show distinctive slip induced striations along the slip direction compared with the undulations normal to slip. Examples of these fault surface fabrics are shown in Fig. 1.
Despite continuing efforts and recent advances (e.g. [1-2]), the relevance between outcrop fault characterization and the physical conditions of buried faults has constantly posed questions to the validity of projecting ground surface-based observations and measurements to the subsurface. In industry practice, it is widely recognized that faults characterized by reflection seismic has notable limitations which is deleterious to modeling efforts, particularly in terms of dynamic fault rupture models for evaluating production- and injection-induced seismicity. The utilization of realistic structural geometry into geodynamic fault rupture modeling has introduced new challenges which cannot be simply resolved by conventional treatment of importing interpreted subsurface faults:
(i) Reflection seismic has well-known inherent limitations, so do the seismic interpreters’ eyes and fingers on fault picking, and advanced seismic processing and interpretation techniques.
(ii) The relationship between fault rupture size and the magnitude of induced seismicity requires understanding of more detailed fault geometry than those at the resolution of passive seismic survey.
(iii) Most of the pre-processors of current geomechanical simulation packages, for the convenience of geometry handling, over-approximate(up-scale) the input fault geometry in a user-uncontrollable way.
With over 7 decades of wide scale use of concrete reinforced pipe within infrastructure and water utilities in the United States, the overall experience has generally been good. However, problems can occur intermittently and drastically affect its performance. One such high profile and never the less recurring problem associated with concrete reinforced pipe has been discussed in this paper.
In 2012 a rupture occurred on a 30-inch concrete reinforced water main pipe in the Northeastern United States. The 30-inch water main is a prestressed concrete cylinder pipe (PCCP). PCCP is a composite pipe material mainly composed of concrete (concrete core), steel cylinder (or steel liner), mortar/concrete coating and prestressed/high-tension wires wrapped around the steel cylinder which is outside of concrete core.
Penspen Corporation, Houston were contracted by the water main operator to carry out an independent diagnostic root cause analysis (RCA) to determine the probable physical root cause(s) of the concrete reinforced pipe rupture and subsequent functional failure of the water pipe, at the failure location, and to identify the contributing failure factors.
A detailed laboratory program for concrete and steel (wire and sleeve) specimens from both the immediate location of the rupture and locations away from the rupture for testing and comparison was recommended. The tests recommended included: visual inspection, comprehensive metallurgical analysis of the material, steel properties testing and concrete petrographic analysis.
Laboratory test results revealed an anomalous corrosion pattern that occurred near the sleeve. The results indicated that the corrosion to the sleeve and wires at the rupture location occurred primarily to the outside surface of the sleeve/wire construct. That is, only minor corrosion was noted on the inside surface of the sleeve even near the rupture location. This suggests that the thick outer mortar layer of the pressure pipe had been structurally compromised at some time during its life, and ground water had permeated onto the steel sleeve and wire. The test results also showed that the chlorine level was as high as 4.1 weight percent on the corroded wires and 3.0 weight percent on the corroded sleeve. These levels are alarmingly high and far above the levels normally found in soils, and therefore they support the fact that crevice corrosion attack occurred over a long time upon the outer surfaces of the sleeve and high strength wires.
A rupture of buckled steel pipes on the tensile side of a cross-section is studied in this paper as the most plausible case of ultimate failure for the pressurized buried pipelines under monotonically increasing curvature. Finite element simulation of full-scale bending tests on two pressurized X80 pipes with different yield-to-tensile strength (Y/T) ratios were conducted. The Y/T ratio and internal pressure were identified as the crucial factors that have a coupled effect on the ultimate failure mode of buckled pipes. That is, the high values of Y/T ratio and internal pressure mutually trigger the rupture of buckled pipes on the opposite side of the wrinkling.
Steel pipelines are so ductile and can accommodate a large amount of post-buckling deformations while preserving their operational safety and structural integrity. To benefit from this outstanding quality and prevent the buckled (wrinkled) pipelines from premature rupture, the postbuckling behavior of the steel pipes should be well understood.
Rupture is one of the major failure limits to the integrity of pipelines that endangers the environment as well as the public safety and property. Comprehensive experimental and numerical studies on the fracture of buckled steel pipes (Das, 2003; Sen, 2006; Mohajer Rahbari, 2017) show that under increased monotonic curvature, successive buckles (wrinkling) are formed on the compressive side of the wall, and the occurrence of rupture at the wrinkling location is unlikely because of the ductile nature of steel material. Rupture of wrinkling can occur once buried pipelines are subject to a very rare and changing boundary conditions accompanied by extremely large plastic deformations toward tearing the wrinkled wall (Ahmed, 2011). However, experiments have shown that the increasing curvature can easily trigger the postbuckling rupture of the tensile wall on the opposite side of the wrinkling (Sen, 2006; Mitsuya et al., 2008; Tajika and Suzuki, 2009; Igi et al., 2011; Tajika et al., 2011; Mitsuya and Motohashi, 2013; Mitsuya and Sakanoue, 2015). This mode of failure seems very likely to be the rupture limit of the wrinkled pipes, as it occurs following the same regime of monotonic bending deformations that have previously made the pipe buckle.
Norouzi, Hamidreza (Institute of Petroleum Engineering, School of Chemical Engineering) | Rostami, Behzad (Institute of Petroleum Engineering) | Khosravi, Maryam (IOR Research Institute) | Shokri Afra, Mohammad Javad (Institute of Petroleum Engineering, School of Chemical Engineering)
In the current survey, the time required to rupture the water film shielding the oil as a result of oil swelling caused by the diffusion of dissolved gas in the water phase and trapped oil behind it has been investigated in porous medium at high pressure and temperature. To study the active mechanisms, the experiments have been conducted with two different types of injectants: carbon dioxide (CO2) and methane (with different solubility in water), under different miscibility conditions at equal reduced pressures. Experimental observations have been interpreted using theoretical studies. Furthermore, the time of water-film rupture has been identified in production data and matched by an analytical model. This time and its monitoring during various gas-injectant types and regimes under reservoir conditions have not been previously addressed.
The results show that water film reduces the performance of oil recovery by limiting the interface of oil and gas phases. Under such a condition, the best scenario is miscible gas injection because the gas can effectively swell the oil and rupture the water shield. At miscible and near-miscible conditions, the time required to eliminate the water film increases as the injectant solubility in water decreases; however, there is a negligible difference at the immiscible regime. The trend of oil-recovery curves after rupture of the water film shows that oil swelling is one of the main mechanisms involved in water-trapped oil recovery. These results suggest practical guidelines to better understand the effect of the water-shielding phenomenon in the field of tertiary gas injection. The outcome of this integrated study could effectively increase the knowledge of shielded oil recovery using different gas-injectant types under various miscibility conditions and could prepare the required basis for compositional simulation of waterflooded oil production during tertiary gas injection.