Blind Pipe Research Articles

A new tunnel drainage system using double-adhesive spray-applied membrane: key parameters and applicable scope

To address water leakage in tunnels with high water pressure, a new waterproof drainage system was proposed. The system uses a spray-applied material with double-adhesive properties as a waterproof layer, significantly reducing leakages, and incorporates a unique bottom drainage system to reduce water pressure. In order to check the effectiveness of the new drainage system and to analyze the effects of various structural measures on pressure reduction, a numerical seepage analysis was carried out under the conditions of a water head of 160 m and a surrounding rock permeability of 1 × 10−6 m/s. The results show that the maximum water pressure on the secondary lining is 0.6 MPa, which is about 60% reduction compared to a fully enclosed waterproof system and shows a significant pressure reduction. The spacing of the circumferential drainage pipe and the width of the drainage sheet significantly affect the drainage performance, while the arrangement of the drainage system and the size of the bottom drainage pipe have minimal impact. With full consideration of pressure reduction, cost efficiency and construction feasibility, it is recommended to use the following drainage scheme for iterative calculations during the design stage: “1” shaped arrangement, blind pipe diameter of 10 cm, width of drainage sheets of 0.8 m, and drainage spacing of 6 m. By combining the experimentally determined hydrostatic peel-off strength of 1.4 MPa for spray-applied membrane, the applicable scope of the new drainage system was acquired. The research results can provide valuable insights into the application of spray-applied waterproofing membrane in drainage tunnels with high water pressure.

Skin Factor Test Experiment of the Combined Structure of Blind and Screen Pipes

During the drilling process of horizontal wells in offshore oil fields, when encountering highly clayey shale or sandy shale sections, a common practice is to use a combination of blank pipes and screen pipes in the completion column to isolate high clay content layers. This helps prevent significant clay blockage in the screen pipes or wellbore, thereby reducing production loss. However, when blank pipes cannot effectively isolate clayey or sandy shale sections, the migration of clay content can lead to screen pipe blockage, adversely affecting production capacity. Given the current lack of evaluation methods for the impact of combined blank and screen pipe completion columns on production capacity, an experiment was designed to evaluate the skin factor of the completion column with a combination of blank and screen pipes. Through the calculation of the skin factor, the variation patterns of the skin factor for completion columns with blank and screen pipes under different conditions were obtained. These findings were then applied to a production evaluation. The research results revealed the following: (1) As the proportion of blind pipes increases, the skin factor of the combination of blind pipes and screen pipes in the completion tubing also increases. Excessive blind pipe ratios reduce production capacity. (2) In cases where the annular space is not completely filled, the influence of the blind pipe proportion on production capacity can be negligible. However, when the annular space is 100% filled, a higher proportion of blind pipes and silt content results in a larger skin factor, which leads to reduced production. In the application of the XH horizontal well case study, using the calculated model for the skin factor of the combination of blind pipes and screen pipes in the completion tubing established in this paper, it was determined that when the annular space was not completely blocked and 20 m of blind pipes were not placed in the designated position, the impact on the production index was 0.73%. However, when the blind pipes were not placed in the designated position for 100 m, the impact on the production index reached 1.47%. The method developed in this paper provides theoretical guidance for the optimization of completion tubing in mudstone and sandy mudstone sections and for production evaluation.

APPLICATION OF LINER SYSTEMS WELLABLE ELASTOMERIC PACKERS FOR WELL CONSTRUCTION

The application of liner systems featuring swellable elastomeric packers in well construction has emerged as a groundbreaking development within the oil and gas industry. This technology, which will be discussed in detail in this paper, addresses critical wellbore challenges, providing an in-depth exploration of its advantages and the transformative effects it has on well construction. Swellable elastomeric packers, a key component of these liner systems, play a pivotal role in overcoming various wellbore obstacles. Their unique design allows them to expand when in contact with wellbore fluids, establishing a robust and reliable seal. This characteristic renders them adaptable to a diverse array of applications, showcasing their versatility. These packers are particularly instrumental in creating a barrier between different geological formations or production zones within a well. By expanding and isolating specific zones, they effectively prevent undesirable fluid flow between them. This not only optimizes reservoir management but also enhances overall production efficiency. In addition to their zonal isolation capabilities, swellable elastomeric packers contribute significantly to the integrity of well casings. Acting as an additional protective layer, they guard against corrosion, high-pressure zones, and other challenges encountered in harsh downhole conditions. This protective function becomes especially crucial in ensuring the longevity and reliability of wells subjected to demanding environments. For wells prone to sand production, the deployment of swellable packers proves invaluable. These packers isolate and stabilize sand-prone zones, mitigating the ingress of sand and preserving productivity. Often overlooked in well completion design is the preparation for abandonment. The incorporation of blind pipe sections with swellable packers along the horizontal section of the liner in the new completion procedure has become an effective tool for safely and efficiently shutting down horizontal wells. A noteworthy advantage of liner systems with swellable packers is their cost-effectiveness in providing zonal isolation and ensuring casing integrity. By reducing reliance on traditional cementing methods, these systems offer economic solutions without compromising performance. Their adaptability allows for customization to specific wellbore needs, making them compatible with various completion techniques and wellbore configurations. In conclusion, the incorporation of liner systems featuring swellable elastomeric packers marks a significant leap forward in well construction technology. The versatility and effectiveness of these packers address critical wellbore challenges, providing solutions that optimize reservoir management, enhance production efficiency, and contribute to the overall integrity of oil and gas wells. The purpose of this article was to examine samples and establish the conditions for their application. Keywords: liner systems, swellable elastomeric packers, well construction, zonal isolation, swelling rate, liner hanger.

The Optimization of Waterproof and Drainage Design and an Evaluation of the Structural Safety of Tunnels in Weak Watery Strata

The surrounding rock and high water pressure in weak watery strata have adverse effects on the mechanical properties of tunnel support structures. In order to optimize the anti-drainage design of tunnels in weak watery strata and evaluate their structural safety, this paper relies on the Taidacun Tunnel of the China–Laos Railway to carry out field monitoring research. A dual-field fluid–solid coupling calculation model is established to optimize the tunnel’s waterproof and drainage design, combined with a bending moment curvature model to evaluate structural safety. The main conclusions are as follows: Under the action of high water and soil pressure, the structural safety margin of the water-rich fine sand section of the Taidacun Tunnel is small, and waterproof and drainage design optimization is required. Combined with the proposed average pressure reduction coefficient, the influence of the water level and annular blind pipe spacing on the water pressure of the lining is proved, and then the optimal annular blind pipe spacing in the water-rich area of the tunnel is determined. A structural safety evaluation method based on the bending moment curvature model is proposed. Two models of elastic beam and moment–curvature beam are used to analyze the mechanical characteristics and optimization effects of the structure under optimal annular blind pipe spacing.

Study on drainage mode and anti-clogging performance of new waterproofing and drainage system in a tunnel

With an increase in tunnel construction and retention, traditional waterproofing and drainage systems have been unable to meet the needs of tunnels in heavy rainfall areas, and disasters such as tunnel lining cracking, leakage, and even collapse, occur frequently. In order to ensure the safe operation and maintenance of tunnels, this paper analyses the characteristics of the traditional waterproofing and drainage system, and puts forward a new drainage structure through numerical simulation and indoor testing. This structure removes the circular drainage blind pipe and adds a convex shell drainage plate between the waterproof board and the secondary lining. The research shows that the new drainage system greatly decreases the water pressure in the easily blocked area of the drainage structure. With the special surface discharge model, the external water pressure of the lining far away from the blocked area can quickly fall back to the normal level. In addition, the drainage capacity of different waterproof and drainage boards is different. With an increase in support pressure, the drainage capacity decreases; the geotextile decreases the most, followed by the capillary drainage board and then the convex shell drainage board. At the same time, after the muddy water drainage test of the three materials, it is found that the convex shell type drainage plate has the best anti-sludge performance. The research in this paper provides a beneficial attempt for the design of waterproofing and drainage structure of a water-rich karst tunnel, and provides a guarantee for the safe operation and maintenance of the tunnel.

Experimental Study on the Effect of Hydraulic Deterioration of Different Drainage Systems on Lining Water Pressure

With the increasing operation time of tunnels, the drainage system cannot fulfil its proper function as a result of the deterioration of traditional waterproof and drainage systems (TWDS), such as the blockage of drainage blind pipes and the failure of drainage boards. Therefore, the lining bears a high water pressure and even causes disasters such as tunnel leakage and lining cracking. An effective solution to mitigate these issues is to adjust the tunnel drainage scheme. In view of this, a composite waterproof and drainage system (CWDS) is proposed in this paper. To verify the effectiveness of the proposed system, a series of model experiments were conducted to study the change law of the seepage field of two drainage systems under different blockage conditions. The study results showed that longitudinal blind pipe blockage caused a more significant increase in water pressure than circular blind pipe blockage. In the case of blind pipe blockage, the water pressure of the TWDS tunnels rise rapidly, while the CWDS tunnels could effectively drain and reduce pressure.

Research on waterproofing and drainage optimization scheme for karst tunnel lining in water-rich areas

In the presence of heavy rainfall on the earth’s surface, a series of water-induced problems often appear in karst tunnels, such as lining cracks and invert uplift. An effective method of alleviating these problems is the adjustment of the tunnel drainage scheme. In this study, three waterproofing and drainage optimization schemes were studied using numerical simulation and model tests. Numerical results show that, when the conventional waterproofing and drainage scheme is adopted in water-rich karst tunnels, the water pressure at the tunnel invert cannot be effectively reduced by the drainage system. When the water head height of the tunnel crown is 50 m and the distance between circumferential drainage blind pipes is reduced from 5 to 2 m, the rate of water pressure reduction at the invert from 21 to 27%. When a longitudinal drainage blind pipe is added at the bottom of the invert, the rate of reduction is increased to 84%; however, it is increased to 96% when the central drainage ditch is set at the bottom of the invert. Therefore, placing the central drainage ditch at the bottom of the invert has the most significant effect on reducing the water pressure. Model test results indicate that when the water head height of the tunnel crown is 12 m, the reduction rates of water pressure at the invert corresponding to the placement of a central drainage ditch at the bottom of the invert are 66%. The model test results were found to be consistent with numerical results.

Petrographic, geochemical, and isotopic evidence of crustal assimilation processes in the Indaiá-II kimberlite, Alto Paranaíba Province, southeast Brazil

ABSTRACTThe Indaiá-I and Indaiá-II intrusions are hypabyssal, small-sized ultrabasic bodies belonging to the Cretaceous magmatism of the Alto Paranaiba Alkaline Province (southeast-central western Brazil). While Indaiá-I is classified as an archetypal group-I kimberlite, Indaiá-II (its satellite intrusion) presents several petrographic and chemical distinctions: (1) an ultrapotassic composition (similar to kamafugites), (2) lower volumes of olivine macrocrysts, (3) diopside as the main matrix phase (in contrast with the presence of monticellite in Indaiá-I), (4) high amounts of phlogopite, and (5) abundant felsic boudinaged and stretched microenclaves and crustal xenoliths. Disequilibrium features, such as embayment and sieve textures in olivine and clinopyroxene grains, are indicative of open-system processes in Indaiá-II. Mineral reactions observed in Indaiá-II (e.g., diopside formed at the expense of monticellite and olivine; phlogopite nearby crustal enclaves and close to olivine macrocrysts) point to an increase in the silica activity of the kimberlite magma; otherwise partially melted crustal xenoliths present kalsilite, generated by desilification reactions. The high Contamination Index (2.12–2.25) and the large amounts of crustal xenoliths (most of them totally transformed or with evidence of partial melting) indicate a high degree of crustal assimilation in the Indaiá-II intrusion. Calculated melts (after removal of olivine xenocrysts) of Indaiá-II have higher amounts of SiO2, Al2O3, K2O, slightly higher Rb/Sr ratios, lower Ce/Pb and Gd/Lu ratios, higher 87Sr/86Sr, and lower 143Nd/144Nd than those calculated for Indaiá-I. Crustal contamination models were developed considering mixing between the calculated melts of Indaiá-I and partial melts modeled from the granitoid country rocks. Mixing-model curves using major and trace elements and isotopic compositions are consistent with crustal assimilation processes with amounts of crustal contribution of ca. 30%. We conclude that (1) Indaiá-II is representative of a highly contaminated kimberlitic intrusion, (2) this contamination occurred by the assimilation of anatectic melts from the main crustal country rocks of this area, and (3) Indaiá-I and Indaiá-II could have had the same parent melt, but with different degrees of crustal contamination. Our petrological model also indicates that Indaiá-II is a satellite blind pipe linked to the main occurrence of Indaiá-I.

Grouting Design of Rich Water Tunnels and the Calculation of Distance between Annular Blind Pipes

The rich water tunnel often uses “water blocking and drainage limiting” waterproofing and drainage systems. On the one hand, the drainage system is set behind the lining to reduce the water pressure. On the other hand, the stratum grouting is used to control the discharge flow of groundwater. In the drainage system, it is important to determine the distance between the annular blind pipes, but there is no clear calculation formula, which leads to the designer often relying on experience. First, the groundwater drainage system is constructed. Based on Darcy’s law and the law of conservation of mass, the formula for calculating the seepage discharge and the seepage pressure with the parameters of annular blind pipe spacing is derived. At the same time, the design parameters of the grouting circle are optimised, and then the formula of annular blind pipe spacing is derived according to the design value of the antiwater pressure of the secondary lining structure and the allowable seepage discharge of the tunnel. Finally, based on the case study of the Hongtu extra‐long tunnel under construction, it is verified by field monitoring data. The results show that (1) grouting reinforcement is an important means to reduce water seepage, and tunnel water seepage can be adjusted by changing the thickness and permeability coefficient of the grouting reinforcement circle, in which the thickness of the reinforcement circle should not be too large, and the permeability coefficient should not be less than 1/80 of the surrounding rock permeability coefficient; (2) according to the derived formula, the water pressure of the secondary lining structure decreases in a parabolic manner from the middle of the two rows of annular blind pipes to the place where the annular blind pipes are set; (3) the allowable water seepage of the tunnel and the design value of the water pressure resistance of the lining structure should be considered when determining the distance between annular blind pipes; and (4) based on the derived formula, the distance between the annular blind pipes in the test section of the Hongtu extra‐long tunnel is determined to be 8 m.

The Mechanical Analysis of an All-Glass Solar Evacuated Tube With Spiral Inner Tube for Seawater Desalination

Solar desalination is an important way to obtain fresh water. Nowadays, the all-glass evacuated tube with only one open end (blind pipe) is widely used in hot-water system, and the glass-metal evacuated tube is commonly used in solar trough concentrating system in medium temperature area. But both of them have drawbacks for seawater desalination. The former cannot quickly heat seawater to 100 °C, and the latter is expensive and fails to make full use of its high temperature advantage. A new design of a medium-temperature full-glass evacuated tube whose inner tube is wound by a spiral structure is proposed in to achieve a more cost-effective solar trough concentrating system for solar desalination. The sealing stress between inner and outer tube is analyzed and the thermal performance is tested. The results showed that the evacuated tube could withstand temperature of 250 °C, quickly heat seawater, and has good corrosion resistance and can keep a long-term vacuum. Such a tube enables seawater to flow directly without oil heat-exchange system, so it is a more promising solution for seawater desalination.

Experimental and numerical study of secondary flow in a T-type bend of a CFB riser

Periodic flow behavior was investigated in a T-type bend of a circulating fluidized-bed riser. With the geldart group A particle, experimental observations suggested that a periodic flow behavior formed under certain conditions. The gas velocity in the T-type bend was simulated using a renormalization group k-ε turbulence model and measured by hot-wire anemometry. Flow patterns in the T-type bend were numerically studied under different superficial gas velocities. Preliminary results suggested that there was a pair of vortices moving periodically in the T-type bend, appearing, increasing, decreasing, and shedding in a cycle, which possessed partial characteristics of a Karman vortex street and Dean vortex. When the superficial gas velocity Vg was low (<10 m/s), flow patterns presented periodic changes with a stable, symmetrical structure of two vortices. In contrast, when the superficial gas velocity reached a certain magnitude (10 m/s), the stable structure disappeared, switching to a pair of alternately swinging vortices; this process was demonstrated by a series of pressure contour measurements. Fourier transformation of continuous local static pressure data from two near-wall points allowed frequency analysis of static pressure fluctuations under different conditions. It was found that the main pressure frequency in the T-type bend increased with increased superficial velocity in the riser. Complex flow characteristics in the T-type bend were mainly due to its specific structure, including a 90° bend with a blind pipe, which played a significant important role in vortex vibrations.

Blind Pipe Type Fiber Bragg Grating Hydrostatic Gauge

A blind pipe type fiber Bragg grating hydrostatic gauge is developed to measure the pressure of liquid. In the hydrostatic gauge, the inside of elastic tube is suffered by the pressure of liquid and drives the wavelength shift of a fiber Bragg grating mounted on the outside of elastic tube. For eliminating the disturbance of temperature variation, the other grating is mounted on the n type sheet metal and is immune to the applied stress strain of elastic tube. The hydrostatic experiment indicates that the pressure sensitivity of the hydrostatic gauge is 0.425 nm/MPa, when the original Bragg wavelength of pressure-sensitized grating is 1557.510 nm.

Collaborative demonstration of optical‐layer service‐differentiation and load‐balancing in intelligent optical network

Optical-layer service-differentiation (Diff-Serv) and load-balancing abilities are achieved by collaborative implementation of OpenFlow (OF) switches and intelligent optical adapt unit (IOAU) prototypes. Experimental demonstration shows that by adapting OF-switches as edge routers, optical-layer Diff-Serv can be realised by mapping services of different priorities into different lightpaths. Thus, optical fibre is service-aware rather than merely a blind pipe. In addition, the load-balancing function of the IOAU can be used to gain reasonable wide area network (WAN) link utilisation. By combining these two abilities, many interesting experimental scenarios and meaningful upper layer applications can be devised.

Sub-volcanic development of kimberlite pipes: Evidence from the Lace and Voorspoed (Group II) kimberlites, South Africa

The Lace and Voorspoed kimberlites occur on the Kaapvaal Craton (South Africa), and form part of the Kroonstad Group II kimberlite (orangeite) cluster. The Lace kimberlite is composed of a main pipe and a satellite blind pipe, the latter of which does not reach the current land surface (~30m below the current land surface), and is not observed connecting with the main pipe at depth. The main pipe increases in size from ~100m to ~250m in diameter at depth. The Voorspoed kimberlite pipe is the largest of the cluster and is dominantly infilled with massive layers (up to 200m thick) of resedimented volcaniclastic kimberlite (RVK). Coherent kimberlite (CK), identified at all three pipes, is described here in order to constrain their formation.Distinct volcaniclastic kimberlite (VK) at the Lace main pipe is also described here and is characterised by a highly clastic fragmental, quartz-rich, and mud-rich interclast material. The VK is interpreted to form by resedimentation of extra-crater deposits into a deep (~1600m) open vent.The CK from both Lace occurrences is characterised by coherent to globular segregationary textures, generally high proportions of crustal xenoliths, and the complete absence of Karoo basalt xenoliths; which are ubiquitous in VK infilling South African Cretaceous kimberlites. The increase in pipe size with depth associated with the occurrence of CK at the main pipe and the occurrence of CK within the satellite blind pipe strongly favours an interpretation of formation in a hypabyssal setting, rather than by pyroclastic processes. CK is also described from the Voorspoed kimberlite where it occurs at depth along the south-western margin of the pipe. The CK is xenolith-rich, the xenolith population is entirely from the immediate sidewall lithologies, and has an incipient globular segregationary texture. The contact with the RVK in the centre of the pipe is sharp, indicating that the CK was cross-cut by a period of eruption prior to the formation of spatially associated RVK. The pipe margins at similar depths along the northern and eastern sections of the pipe are characterised by the occurrence of contact breccias, which have a gradational change to lower degrees of brecciation away from the pipe. The CK at Voorspoed is interpreted to form by the intrusion of magmatic kimberlite at depth, which invades a previously formed contact breccia and incorporates large proportions of crustal xenoliths from the immediate sidewall.The CK occurring at the Lace and Voorspoed kimberlite are interpreted to form in a sub-volcanic hypabyssal setting during a stage of pre-conditioning of the country rock prior to eruptive emplacement of the pipe. A model for the development of a sub-volcanic embryonic pipe is presented for the formation of CK at the Kroonstad kimberlite cluster.

The Water Control Technique of Horizontal Well Completion Strings With an Inner-located Nozzle in a Nonhomogeneous Bottom Water Reservoir

Horizontal well has been used successfully in small block and offshore reservoirs and reservoirs with bottom water. But with the oilfield development, horizontal well has also exposed some questions gradually. Vertical well has a long water cut production period, but water cut of the horizontal well increases dramatically after water breakthrough, which affects horizontal well development seriously. The coupled model was established and solved according to the characteristics of the completion strings with inner-located nozzle. The authors found that compared with a simple implementation of blind pipe or adjust the size of the nozzle, the implementation of external casing packer or the implementation of external casing packer in conjunction with the implementation of blind pipe (or adjust the size of the nozzle) can adjustment the production profile by a wide margin. Because the high-permeability zone is the major water flooded zone, and also the major producing zone, therefore, unduly limit of the liquid producing capacity may not be able to achieve preferable results. The best results can be obtained when coefficient of variation is about .6; the effect of these measures is not obvious when coefficient of variation is too small or too large.

Tunnel Waterproofing Board Construction Process Analysis

This article from preparation befor the job, blind pipe with fixed and waterproof plate laying geotextile, analysis of waterproof board laid before the preparatory work, waterproof board laid process related indicators of control, and offer reference for the construction of the tunnel.

A Numerical Study of Flow Field and Oil Water Separation in Vertical Deadlegs

Deadleg is a kind of blind pipe connected with a main pipe used for fluid transportation, which has distinct flow characteristics. This work aims to investigate the complex flow, oil/water separation and the relation between fluid flow and water concentration of a vertical deadleg. The investigation was based on the solution of algebraic slip mixture model, which calculated the continuity and momentum equations for the mixture of oil and water, and solved the volume fraction equation for the secondary phase. The computed results indicated that the mixing zone of the deadleg consists of two circulation vortexes and the whole mixing length depends on the inlet flow intensity. Furthermore, distinct oil/water stratification forms in the stagnant zone, and the maximum water volumetric concentration is related to the length of stagnant zone and also influenced by the flow intensity of the main pipe, which could increase from 25% to 72% with inlet velocity ranges from 0.75m/s to 5m/s.

Diagnostic analysis of farmers' skimming well technologies in the Indus Basin of Pakistan

Farmers are using skimming wells tosupplement their canal deliveries. Toensure sustainable groundwater extraction,proper design and operational guidelinesfor these skimming wells are required. Thestarting point of such guidelines is tolook at farmers' existing groundwaterextraction practices, their extent andassociated problems. For this purpose, afield survey was conducted in the IndusBasin of Pakistan. Participatory ruralappraisal identified several design andoperational problems with farmers' skimmingwells. These include; depth of well,number of strainers, horizontaldistance of strainers, priming, water quality, sand in pumped water,and reduction in well discharge withtime. To investigate these problems,diagnostic analysis was carried out. A testborehole was drilled to get water samplesalong the aquifer depth during drilling.The depth of well was then decided on thebasis of these water quality analyses. Todecide the number of strainers, a pumpingtest was conducted at test borehole toestimate the contribution of individualstrainer and then the numbers wereincreased according to the desireddischarge. Similarly, placing non-returnvalve between blind pipe and strainersolved the priming problem. Operating wellsintermittently rather than continuouslysolved the problems of water quality andreduction in well discharge. The systematicapproach adopted in the study helped thefarmers to rectify the problems.