Internal Plug Research Articles

CFD-DEM study on the blocking conformation of pre-filled sand control screen by layering method

Preventing screen blockage due to sand poses a significant challenge. The article combines computational fluid dynamics (CFD) and discrete element method (DEM) to establish a fully coupled four-way interaction model. A sophisticated size particle injection model was established, taking into account the particle size distribution (PSD) characteristics of the formation. A layering method was used to study the sand control behavior of a high-performance pre-filled screen. The study also quantitatively investigated the impact of factors such as median sand size (D50), screen structure, and fluid velocity on both wellbore-screen annulus and internal screen plugging patterns. The findings reveal that the sand retention rate within the wellbore-screen annulus exceeds 93.8 %. The risk of pre-filled screen blockage is minimized when the ratio of gravel diameter to sand diameter falls within the range of 3.3–5. At a gravel filling rate of 97 %, fine sand predominantly moves radially, resulting in a low risk of blockage at the screen's entrance layer, thereby favoring oil and gas production. In cases with elevated fine sand content, it is advisable to maintain a production flow rate below 3 m/s to mitigate localized erosion damage caused by increased pressure resulting from screen blockage. This model holds significant importance in optimizing completion tools and production parameters.

Numerical simulation study of fracture propagation by internal plugging hydraulic fracturing

Internal temporary plugging fracturing technology improves the stimulated volume by forming a more complex fracture network, significantly enhancing the reservoir stimulation effect and effectively developing unconventional oil and gas resources. However, the current understanding of the fracture propagation mechanism on internal temporary plugging fracturing is still unclear, making it difficult to determine the main controlling factors that affect the shape of the fractures. In addition, the lack of practical numerical simulation methods for temporary plugging fracturing makes it challenging to provide guidance for field scheme design. Utilizing the finite element cohesive zone method, which incorporates globally embedded cohesive elements, this study constructs a comprehensive numerical model to investigate the propagation behavior of temporarily plugging fracturing fractures. The model delves into the impact of various geological and construction parameters on the opening conditions of branch fractures during the temporary plugging fracturing process, as well as the propagation patterns of fractures within naturally fractured reservoirs. The research findings indicate that the construction factors have the following impacts: When the pumping rate and viscosity of the fracturing fluid are comparatively high, the resulting fluid pressure within the fracture escalates, resulting in the creation of numerous branch fractures within the naturally fractured reservoir. This, in turn, augments the fracture’s complexity. However, these two factors have little influence on the maximum deflection distance of the deflected fracture. As for the geological factors, an increase in the horizontal stress difference will decrease the maximum deflection distance of the deflected fracture, reducing the number of natural fractures intersected and shortening the length of the deflected fracture. Conversely, an increase in the approach angle will increase the maximum deflection distance of the deflected fracture, thereby expanding the affected area. Additionally, the influence of Young’s modulus and Poisson’s ratio on fracture propagation is very slight. A decrease in the tensile strength of natural fractures leads to more natural fractures being intersected during the process, resulting in increasing the length of the fracture and an improvement in the complexity of the fracture grid.

Expansion deformation mechanism and cracking behaviours of chromium-coated zirconium alloy cladding at room temperature

The deformation of the cladding tube triggered by the expansion of the internal plug is used to investigate the hoop deformation behaviour of the Cr-coated zirconium alloy cladding tube at room temperature. A thin-walled pressurized cylinder model is used to transform the axial load-displacement curve working on the expansion plug into the hoop stress-strain curve working on the cladding tube, and it is found that the Cr coating can be able to restrain the cladding tube from hoop deformation. Observation of the Cr-coated cladding tube after different amounts of hoop deformation revealed that the strain corresponding to the generation of the first crack was a ranged from 0.48 % to 0.59 %, the density of cracks started to grow very fast and then entered a saturation stage. The fracture strength of the Cr coating and maximum interfacial shear strength when the Cr coating crack density reaches saturation were calculated by the shear-lag model. Twins and a large number of dislocations were generated in the Zr matrix and a small number of dislocations in the Cr coating after the hoop deformation. The behaviour of crack initiation and propagation occurring in Cr coating is revealed.

Finite element modelling of pipe piles driven in low-to-medium density chalk under monotonic axial loading

Percussive driving in low-to-medium density chalk creates a thin annulus of fully de-structured ‘putty’ chalk around pile shafts and an outer annular zone where fracturing is more intense than in the natural chalk. This damage and the related generation, and subsequent equalisation, of excess pore pressures impacts the piles’ time-dependent axial loading behaviour, as do other ageing processes. This paper presents finite element analyses of open steel tubular piles driven for the recent ALPACA and ALPACA Plus research projects under monotonic axial loading to failure after extended ageing periods. A nonlinear elastic stiffness model with a nonlocal deviatoric strain-based Mohr-Coulomb failure criterion was employed, with different sets of properties to represent the de-structured, fractured chalk and intact chalk. It is shown that the piles’ axial responses are mainly controlled by the puttified chalk annuli. A simplified but efficient means is adopted to impose pre-loading chalk effective stress conditions that explicitly capture the effects of installation damage and subsequent ageing. The potential for strain-softening in the brittle chalk is examined and the effective stress paths developed in representative chalk elements throughout the loading are considered in conjunction with the mobilisation of accumulated deviatoric strains. The simulations indicate 264% higher shaft capacity in compression than in tension, which is mainly attributed to the internal chalk plug.

Jet noise of a low bypass turbofan with internal mixing and external plug

Jet noise generated by turbofan engines which are designed for supersonic aircraft operation is expected to remain a challenge for the aerospace industry. For civil supersonic transport, low bypass ratio engines with internal mixing and external plugs are currently seen as promising exhaust architecture to meet aircraft mission and certification requirements. Measurements of the noise from a representative low-bypass ratio long duct mixed flow with external plug exhaust configuration were made, along with corresponding steady-RANS and LES analyses. The measured data showed excess high frequency noise across a wide range of operating conditions as compared to an equivalent single stream jet, or an equivalent uniform jet with internal plug. The absolute levels of the excess noise were relatively insensitive to forward flight, and the excess noise was most dominant when the primary and secondary streams had large velocity and temperature mismatch just upstream of the internal mixer. Preliminary indications from the LES analysis also indicated that significant pressure fluctuations, at the same frequencies which are insensitive to forward flight, develop inside the nozzle as the internal shear layer from the mixer grows and gets accelerated by the external plug. Parametric study test measurements on the fan and core operating conditions were performed, providing support for the hypothesis that the excess noise is generated as the internal shear layer, starting inside the nozzle, gets accelerated by the plug and passes through the weak shock at the nozzle exit where the flow accelerates more and turns over the external plug.

Design and Evaluation of Aerospike Nozzles for an Upper-Stage Application

Aerospike nozzles are often studied because of their intrinsic self-adaptation behavior to the atmospheric pressure. Another unique feature of aerospike nozzles is their mass- and volume-efficient integration with the underlying vehicle. This latter aspect, if fully exploited, could be of interest for both lower stages operating in the atmosphere and for upper stages operating in vacuum. In this paper, a numerical analysis is carried out of the possible advantages of using an aerospike engine under specific volume constraints of a reference upper-stage configuration, discussing basic aspects of aerospike and internal expansion design, clustering, and plug truncation length. The results of the present preliminary analysis show the extent of possible performance advantages of aerospikes in terms of the specific impulse delivered for a given available volume for the nozzle with respect to a conventional bell configuration.

Innovations for Bolted RHS Column Splices

AbstractTwo novel concepts, recently developed in North America, are presented for bolted splices between Rectangular Hollow Section (RHS) column members. Single‐sided bolting through the RHS wall is performed, but using regular high‐strength bolts rather than “blind bolts”. The first concept employs nut‐holding devices, called “Shurikens”, that are pre‐installed on four splice plates fitted to the inside of the two RHS columns. The second innovation is a custom‐designed, hollow, cast steel insert – made of nut‐quality steel – that extends into both the upper and lower columns and has threaded holes to receive the inserted bolts, in lieu of nuts. This “internal plug” is a pre‐engineered solution, tailored to a particular RHS size, and requires no connection design. For both concepts, a bolted shear connection with little protruding steelwork is the result.

Design Impacts on Ram Air Vane Cooling in an Ultra-Compact Combustor

Abstract The ultra-compact combustor (UCC) aims to decrease the length of gas turbine combustors using a unique design geometry which wraps a combustion chamber around the central axial flow. This distinctive design enables an out of the box type of cooling scheme to be investigated for the turbine inlet vanes, termed the hybrid guide vane (HGV) in the UCC. The leading edge of the HGV experiences only compressor exit air as combustion products do not interact with the vane upstream of the 14% axial chord location. Previous studies were conducted which computationally evaluated the viability of taking in freestream flow through the HGV stagnation region for use as coolant. Based on these studies, a six vane HGV was manufactured which incorporated a solid vane and five hollow vanes. Each of these vanes incorporated different features to vary the size of the internal plug, trailing edge exit, and film cooling holes. In the present study, the cooled HGV was experimentally analyzed using pressure, thermocouple, and infrared (IR) thermography measurements to evaluate internal coolant flowrates and pressure loss along with cooling performance. Furthermore, the vanes were compared to isolate the impact of design differences on vane cooling. It was found that the location of the internal plug and incorporation of film cooling holes had a minor impact on coolant flow and cooling. Additionally, results showed exit area had the largest impact on surface temperature and coolant mass flow where the largest exit area allowed less restricted coolant flow resulting in the lowest average surface temperature. However, completely blocking the exit slot forced coolant to exit only through film cooling holes, stagnating the majority of the internal flow, resulting in surface temperatures higher than the uncooled, solid vane.

Facultative male investment in prolonged mate-guarding in a butterfly

Abstract Sexual conflict over mating may induce male mate-guarding prolonged in time in the absence of males, via devices such as mating plugs, widespread in insects. In most Lepidoptera, internal plugs are common, while in some butterfly families large external devices, called sphragides, evolved independently. Lack of, or incomplete sphragis in a few individuals were reported in sphragis-bearing species. Previous studies focused on typifying species-specific devices in a few specimens of many species. In contrast, we investigated alternative mate-guarding devices in detail of a sphragis-bearing butterfly. We conducted a six-year observational field study in a Clouded Apollo Parnassius mnemosyne population. Inspecting 492 females, we identified 3 different devices, filament, stopple and shield (i.e., sphragis) increasing in size and structure complexity, implying differential male investment and effectiveness in securing paternity. Shield dimensions, colour and all devices’ shapes varied considerably. Shields were far more frequent than other devices. Some devices were lost, and a few were video-recorded when removed by males, showing the role of different parts of male external genitalia. We discuss potential causes of device variation and the role of removal attempts, and assess potential costs and benefits for both sexes.

Carbon-based nanocomposites: Distinguishing between deep-bed filtration and external filter cake by coupling core-scale mud-flow tests with computed tomography imaging

Although Multi-Walled Carbon NanoTubes (MWCNTs) are found to influence the rheological behavior of drilling fluids, there are yet some controversies regarding their performance towards reducing formation damage induced by the invasion of water-based drilling fluids (WBFs). To address this important question, we synthesized novel nanocomposite materials via modifying the MWCNT via varying the proportion of carboxylated MWCNTs to PolyVinyl Alcohol (PVA). These nanocomposites were then used to make nano-based drilling-fluids (NDFs). The performance of the NDFs was evaluated by a set of rheological behavior tests, filtration experiments, and core-scale mud flow tests. To distinguish between the internal and external damages made by the drilling fluid, computed tomography (CT) scanning was performed during the mud flow tests. The best yield stress (YP) and plastic viscosity (PV) were achieved at a 1:36 proportion of carboxylated MWCNTs to PVA (named as PVCNT-3). While the bulk rheological measurements (by varying the concentration of the nanocomposites between 0 and 0.6 wt%) showed a sharp increase in both YP and PV, the filtration tests showed contrary results. Independent of the nanocomposite content, the filtrates were also completely clear, demonstrating that PVCNT-3 acts as an efficient water-clay separation filter. NDFs containing a lower amount of PVCNT-3 (0.1–0.3 wt %) showed a noticeably lower degree of formation damage and a thicker external (impermeable) filter cake as confirmed by the CT scan images taken during the mud flow tests. However, high concentration of nanocomposites was found to cause significant internal pore plugging and formation damage. The results highlight the advantage of coupling core-scale tests with in-situ imaging to unravel the types of damages induced by the mud: build-up of an impermeable mud cakes (external damage) or deep-bed filtration (internal damage). This information is very essential for building proper models which capture different types of damages induced by drilling fluids.

Juvenile Experience with Male Cues Triggers Cryptic Choice Mechanisms in Adult Female Redback Spiders.

Simple SummaryFemales of many species vary in their receptivity to male mating attempts. When many males are present in the habitat, the theory predicts that females should be choosy and discriminate among potential mates. When few males are available, females should mate readily with the first male who courts, and thus avoid the risk of remaining unmated. We predicted that cues perceived as juveniles that indicate male availability would affect the mating behaviour of adult females. In our first experiment, juvenile females were exposed to airborne chemicals produced by males at high or low densities. In our second experiment, we mimicked a natural situation where males or other juveniles live on the webs of females shortly before they become sexually mature, and compared this to females developing in isolation. As was consistent with our predictions, we found that the adult females changed their behaviour after exposure to cues of high male availability during development. When the females perceived many males nearby (high density airborne cues or living with males) they more often interrupted copulation, or cannibalized the males before the mating was complete as adults. In comparison, when the cues indicated low male availability, the adult females were more likely to allow the males to complete mating, and cannibalism was less common.Female choice may be linked to population density if the expected encounter rates with potential mates affects choosiness (the energy and risk engaged to express mate preferences). Choosiness should covary with male availability, which could be assessed using the social cues available during development. We tested whether the exposure of juvenile females to cues of male density affected the mechanisms of choosiness of adult Latrodectus hasselti spiders in two experiments simulating natural contexts. The juvenile females were exposed to (1) volatile chemicals from two densities of adult males (airborne cues), and (2) tactile, vibrational and chemical cues from adult males or other females (cohabitation cues). As adults, the females mated readily, regardless of the treatment, but there was strong evidence for post-copulatory mechanisms of choosiness in females exposed to cues of high male availability. These included abbreviated matings (in both experiments), cannibalism of the males before the mating was complete (cohabitation), and, remarkably, a reduction in the successful placement of internal sperm plugs (cohabitation). These shifts decrease the likelihood that the first mate would monopolize paternity if the female chose to mate again. We conclude that female choosiness may impose a strong selection on males despite the high mating rates, and these effects can hinge on the cues of male availability detected by juveniles.

A review of key tools for oil pipe blockage operation in gas wells under pressure

Blockage in tubing is an important guarantee for gas wells under pressure. The internal blockage is to close the channel inside the tubing through a sealing device, the pipe string can be lifted and lowered under pressure. In order to prevent natural gas from leaking through the tubing channel during well completion and string lifting operations, a plugging tool in the tubing is required to block the tubing channel, and the blockage is removed after the operation is completed to effectively control the pressure in the well. This article starts with the key tools related to internal plugging operations in Snubbing operation, introduces the basic principles of setting the internal plugging barriers when running the tubing string in completion operations, and introduces the key tools for internal plugging when the tubing runs in completion operations. The internal plugging method of the pipe string under pressure is introduced. The key tools (bridge plugs) and setting methods that have been matured or formed at home and abroad when the pipe string is lifted in workover are introduced. Well technology and key tool selection provide reference. Finally, we analyze and think about the domestically developed self-developed internal plugging tools for pressurized operations in my country. It is believed that internal clogging is not an isolated process of oil, gas, and water plugging, but is usually a process of multi-system construction processes working together. The key domestic tools and equipment also need to further improve their autonomous capabilities in terms of overall performance and stability, as well as intelligence.

The influence of the drainage regime on the installation and the response to vertical cyclic loading of suction caissons in dense sand

Offshore wind turbines are considered as an integral part of renewable energy. Dense sand often characterises the sea bed and suction caisson foundations are increasingly used to support offshore wind turbines at North Sea sites. Significant experience with this technology exists in the oil and gas industry, although these platforms are typically located in deeper water with predominantly clay soils. Therefore, research is required to transfer the existing knowledge. This paper discusses a series of centrifuge tests that investigate the installation and the load transfer mechanisms governing the response of suction caissons embedded in dense sand subjected to vertical cyclic loading. The effect of potential loosening of the internal soil plug during suction installation on the in-service foundation performance is evaluated through cone penetration tests inside the caisson following suction installation at different pumping flow rates. In accompanying tests, the load displacement behaviour in response to vertical cyclic loading is investigated, including significant excursions into tension. The results identify the pore fluid behaviour as the key factor affecting the response, with the pumping flow rate applied during installation being less influential. Based on the findings from the experiments a simplified approach for the prediction of suction caisson behaviour under vertical cyclic loading is presented.

Comparison of experimental methods to evaluate seam welds quality in extruded profiles

Abstract The wedge and bulge expansion tests were compared in the assessment of the seam welds strength in a tubular profile extruded at two ram speeds. In the wedge test, the expansion was determined by moving a conical punch into the tube until the specimen fracture. In the bulge test, a hydrostatic tensile stress state was applied by expanding the specimen with an internal rubber plug. The two methodologies were compared in terms of load and hoop strain at fracture and by detecting the fracture morphology and location. Then, the effect of a number of design parameters was investigated in order to evaluate the robustness of the standard testing conditions. For both tests, ductile fractures appeared in the seam welds location, but the bulge test was more robust and conservative with respect to the wedge test, showing less scattered data. Thus, the performances of a second die for the tube profile, designed to optimize the seam welds quality, have been successfully assessed by the bulge test and results compared to those achieved by a novel numerical quality index, coming to a final good matching.

Integrative depiction of the male reproductive system of the commercial purple crab Homalaspis plana (Platyxanthidae): Structure and function.

The information available on structures and function of reproductive systems are female-biased in many animal groups and crabs are not an exception. However, knowledge about the male reproductive system can help us to understand evolutionary and ecological processes such as the mating system and mating behavior. This study focuses on an integrative description of the principal regions of the male reproductive system of the purple crab, Homalaspis plana, a commercially exploited crab from the southeastern Pacific. For this description a combination of morphological observation, gravimetric records, histological and histochemical techniques and biochemical analysis were used. Also, a gross description of the seminal receptacle of the female was performed. The male reproductive system of H. plana was highly extended and complex, with a great capacity to produce and store spermatophores and secrete, at least, two kinds of seminal fluids. Sperm production, sperm packaging in spermatophores, storage of spermatophores and seminal liquid secretion were functions localized in specific regions. The vasosomatic index was the highest recorded to date in crabs, symptomatic of a high investment in reproduction. All these traits allow identification of H. plana as an internal sperm plug producer, which matches well with the highly extensible seminal receptacle of females. The great quantity of seminal material transferred to females during mating indicates that males may be able to mate only one time in the reproductive season and thus this species could be vulnerable to sperm depletion in males and sperm limitation in females if the fishery substantively reduced the abundance of males in the populations.

Penetration Model for Installation of Skirted Foundations in Layered Soils

During installation of a skirted foundation, resistance to penetration is a combination of side and tip resistances. When penetrating a permeable soil unit, tip resistance in particular can be high but if seepage water flow from the outside to the inside of the skirted foundation exists, the pore water gradient will reduce the effective stresses and therefore also penetration resistance. Recent installation data from the field and laboratory suggest that this effect can also occur during installation in layered profiles. This paper presents a model that accounts for seepage flow in unlimited permeable layers that are overlain by one or several impermeable layers. The model assumes that seepage flow in the underlying sand layer is induced by an incremental lift of the internal soil plug, which enables the transfer of some of the differential pressure applied under the foundation lid to the bottom of the lifted soil plug. A single equation is proposed to calculate the critical suction number for layered soil conditions that can be used with an empirical model to calculate the reduction in penetration resistance. A calibration of the proposed equation for the critical suction number is carried out using an axis symmetrical finite-element model that uses a linear elastic soil model and assumes steady-state flow conditions. The calibration of the proposed equation for calculating the critical suction number was first carried out for a homogenous permeable soil. This was done to benchmark the model against previously published data. In a second step, the calibration was done for a layered profile and different flow boundary conditions. The proposed penetration model is demonstrated by back-calculating full-scale installations. The paper closes with a discussion of the main assumption of plug lift, and a simple model to evaluate the degree of plug lift is proposed.

Simulation of Metal Pipe Driving in Soil with Batchwise Removal of Plug

The interaction of an open pipe with an internal soil plug according to the Coulomb’s law of dry friction is investigated. Different soil and pipe models are considered. For all models, finite-difference solutions are obtained, for some—analytical solutions describing the process of elastic interaction of a pipe and a plug. Good agreement between numerical and analytical solutions is shown. The results of numerical calculations for different models are compared and the applicability limits of the models are determined. The effect of Coulomb dry friction on the process of pipe and plug movement is studied.

Influence of energy characteristics of vibropercussion source on efficiency of soil plug removal from casing pipes

This article describes the method of virbopercussion ramming of an open-ended steel pipe in soil. The study focuses on interaction between the pipe and internal soil plug by the law of dry friction. The test bench for the effect exerted by impact impulses on displacement of soil plug is presented. The reduction in the friction force under the simultaneous static influence on the soil plug and vibropercussion load on the pipe is evaluated. The influence of energy characteristics of vibropercussion source on the efficiency of soil plug removal from the pipe is determined.

Single-cell biofuel element of simple construction from sanitary parts and testing of its work

A model of single-chamber biofuel cell from easily accessible sanitary components (sanitary tees for Sinikon internal sewage pipes and plugs to them) was developed and tested. It is characterized by low cost and easy assembly. As the bioagents the authors used, in particular, the individual strain Micrococcus luteus 1-I, isolated from the active sludge of the petrochemical plant. The proposed single-chamber biofuel cells, based on this strain for 96 hours of the experiment generated an open circuit voltage of up to 480 mV, the current strength was up to 1 mA. Promising bioagents for the developed design were commercial microbiological preparations for cesspools and septic tanks and for composting: biofertilizer “EM-Bio” (LLC “Primorsky EM-Center”, Vladivostok); means for cesspools and septic tanks “Doctor Robik” (LLC VIPEKO, Moscow); microbiological fertilizer “Baikal-EM” (OOO “EM-Kooperatsiya”, Moscow); microbiological preparation for eliminating odors and recycling “Won!” (IP Dugarova, D.C., Ulan-Ude). The voltage of the open circuit, which was generated in single-chamber biofuel cells’ commercial microbiological preparations, increased to 357 - 546 mV for 96 hours of the experiment. The short-circuit current was increased to 597 - 843 μΑ. The specific power of the single-chamber biofuel cells on the basis of all the bioagents, tested in the paper, was quite close and varied in the range 10.2 - 12.7 μW / cm2.

05.31: Experiments and fem‐simulations of local buckling of sand‐filled tubular piles

ABSTRACTThin‐walled large‐diameter tubular piles loaded in bending are susceptible to local buckling. Depending on the bending moment distribution over the length of the pile, this local buckling failure may occur in the part of the pile that is embedded in the soil. In large‐diameter piles, soil is also present at the inside of the pile. The soil mass inside and outside of the pile may influence the bending behaviour and local buckling behaviour of the piles.In case the internal soil plug consists of granular material and is sufficiently stiff and resistant, the soil influences the buckling shape and the critical stress and strain at which local buckling occurs.Experiments that were performed in 2012 on empty and fully sand‐filled tubes loaded in pure bending showed a significant effect of the sand‐fill. The experiments were verified with finite element analyses to better understand the occurring failure mechanisms in tube and soil and the effects of parameter variations.In 2014, new experiments were carried out in the port of Rotterdam on 914 mm diameter piles installed in the harbour bed. After installation, the embedded part the piles remained predominantly filled with soil, whereas the upper part was empty. Eight piles were installed and were loaded with a lateral force up to excessive yielding and local buckling failure. These experiments were analysed with FEM calculations. These analyses included effects of the soil plug and the soil around the pile.The outcomes of the FEM model calculations confirm the experimental findings of a change in buckling shape as a result of the presence of sand inside the pile. The experiments and finite element analyses show that there is an evident contribution of the inside sand with certain properties to the resistance to local buckling. For the piles that are not completely filled with sand but have a plug at a certain level, design rules for the effect of the sand plug were derived.