Extra High-Pressure High-Temperature (XHPHT) Flowlines: Design Considerations and Challenges

This paper presents a coupled design analysis for a Pipe-in-Pipe (PIP) Steel Catenary Riser (SCR) and Flowline (FL) system in 5000ft of water under high pressure and high temperature (HP/HT) conditions in the Gulf of Mexico (GOM). The finite element program ABAQUS is used to model the inner and outer pipes of the PIP system, the centralizer, the SCR hangoff, the flowline lateral and end supports, and pipe-soil interactions on the seabed. Thermal stresses and stress ranges caused by repeated temperature transients, axial and lateral displacements of SCR and flowline, as well as by the dynamic responses of the coupled riser and flowline system, are presented. Comparisons are also made with results by ABAQUS models with beam and pipe elements, and results obtained by coupled and de-coupled analysis. The sample vessel motion was obtained for an example Spar platform in GOM.

Development of deep water oil reservoirs is presently being considered in the Gulf of Mexico (GoM) where the flowline product temperatures approach 177°C (350°F), and water depths to 3,000 meters (10,000ft). The design of these flowlines requires the use of advanced ‘local’ and ‘global’ Finite Element (FE) analysis models, integrated with limit state design methods. This paper presents the ‘local’ and ‘global’ FE models developed to investigate the limit state design of Extra High Pressure High Temperature (XHPHT) flowlines. The ‘global’ PIP FE model is used to conduct design sensitivity analyses and provide the input loads for limit state design checks. Using the global FE model, investigations are undertaken to examine design issues such as effectiveness of thermal expansion buckle management, application of inner pipe pre-tension and load sharing device, and the effect of operating temperature. The ‘local’ full size PIP FE model is used to verify the global PIP FE model at a local level. Global and local FE models present comparable results in term of pipeline stress response. A 3D helical arrangement of the inner pipe subjected to high temperature is observed. This helical shape is sensitive to temperature and material thermal expansion coefficient. The investigation's goal is bridging technology gaps by pushing the boundaries of PIP designs for XHPHT applications in the GoM. These innovative, cutting edge finite element models could be used by the pipeline for future deep water PIP XHPHT projects. Introduction The pressure and temperature of the oil and gas contents coming out of the ground and well head may be high, and this can be a key design challenge for pipelines. High Pressure / High Temperature (HP / HT), with pressures in the order of 700bar (10,000PSI), and temperatures being considered up to 160°C (320°F) are not uncommon. High Pressure and High Temperature (HPHT) reservoirs are typically, but not exclusively, gas condensate fields. They are technically more complex to develop because of the inherently higher energy in the well fluid. Although initially developed exclusively by dry tree systems, subsea HP / HT developments are now common place. To keep the heat in a pipeline, and especially over long tie-back lengths, is a real engineering challenge. One way that this is overcome is to use a PIP design. This is where the pipe carrying the contents is inside an outer pipe separated by an annulus filled with thermal insulation. PIP technology is a design challenge, and is normally used when a low Overall Heat Transfer Coefficient (OHTC) value is required (<1 W/m2K). High Pressure (HP) has a major impact on the design of wellhead and other equipment, such as manifold valves, in terms of strength, materials and reliability. For piping, flowlines and risers, HP can also lead to very high wall thicknesses. Equipment manufacture and linepipe fabrication and installation become more complex. High Temperature (HT) has a wider impact, as the whole system has to operate over a greater temperature range between non-producing situations, such as: installation and shut down, and the operational case. Also, due to the uncertainty of material response at elevated temperatures, the industry Codes of Practice is approaching their limits of applicability. Additionally, corrosion and corrosion protection throughout the system becomes a challenge for hotter systems.

The pipe-in-pipe (PIP) offshore flowline is gaining popularities in ultra deep water developments due to its better characteristics in thermal insulation, thermal expansion, seabed stability, free span and maintenance. So far most of the larger size PIP flowline are installed using J-lay method. During the pipe welding and lowering process, the vessel tensioner grabs the outer pipe with the inner pipe free-standing inside the outer pipe. Therefore a large top lay tension is applied to the outer pipe while the inner pipe is under a sizable compression due to its own weight. A bulkhead is welded to the both inner and outer pipes with a predetermined spacing. As the PIP is being lowered toward the sea floor, the large lay tension on the outer pipe is gradually released, and the outer pipe tends to go back to its original length. This results in a push to the inner pipe from the outer pipe and develops a locked-in compression in the inner pipe and a locked-in tension in the outer pipe. In the ultra deep water PIP case, the locked-in loads and locked-in stresses could be critical if they are not well addressed. The solution to limit the locked-in effects to the inner and outer pipes is to apply a predetermined pretension to the inner pipe before both the pipes are welded together through the bulkhead. The pretension is a function of water depth, pipe length, lay angle, bottom lay tension, soil friction, pipe wall thickness, content density, content temperature, content pressure and bulkhead spacing, installation sea state and vessel motion. The accurate prediction of the pretension demands significant resources and time through utilizing the advanced nonlinear finite element analysis (NLFEA) tools such as ABAQUS. This paper proposes analytical formulations to estimate the pretension requirement to the inner pipe. The formulations are validated using ABAQUS modeling. The proposed formulations can be used as a cost effective alternative to the more time consuming and cost driven FEA method, especially when only a high level analysis is needed such as in the FEED stage or as a starting point for the detailed design stage. Introduction With the ever increasing demand for oil and gas and the fast depleting surface reservoirs, oil and gas companies are forced to search for new oil reservoirs, and hence the project requirements for pipeline systems are intensifying. Currently, subsea systems are being designed for water depths to 10,000 feet, high product temperatures and high pressures. Designing pipelines to transport high pressure and high temperature (HPHT) oil and gas from these deepwater locations is challenging. Pipe-in-pipe (PIP) flowlines are widely used to address this challenge because of their superior insulation capacity [Ref. 1, 2, and 3]. With PIP flowlines, the pipe carrying the hot oil or gas is placed inside another pipe; thermal insulation in the ringshaped space between the two pipes minimizes blockages or hydrates that can form in the pipeline by providing an adequate thermal barrier to reduce heat loss [Ref. 1]. Further, PIP flowlines are gaining popularity due to their good characteristics in thermal expansion, seabed stability, free span and maintenance.

Foam injection has been promoted as a reliable method for improving the sweep efficiency in heterogeneous carbonate reservoirs by modifying the properties of the injected gas and hence, providing mobility control effect. However, the conditions of the Middle Eastern carbonate reservoirs are quite detrimental to foam performance, leading to unoptimized mobility control. This challenge has motivated the improvement and development of different foaming agent formulations that can withstand the harsh conditions in carbonate reservoirs of high temperature and high salinity. In this study, the effect of different amphoteric and switchable surfactants on bulk foam performance were investigated and later the optimum formulation was evaluated in carbonate porous media for EOR under high salinity and temperature conditions. For this purpose, the solutions containing different commercial amphoteric and amine-based switchable surfactants were prepared in high salinity brine (20 wt%) at high temperature conditions (80 °C). Initial screening was performed by conducting series of foamability and foam stability tests at high temperature. Foam generation and endurance were also investigated in the presence of crude oil. Foam performance was evaluated in carbonate core samples under different foam qualities and at reservoir conditions. After selecting the optimal foam quality for effective foam generation, the oil recovery experiment was then performed to recover the remaining oil after secondary N2-gas flood. The results from bulk foam experiments demonstrated the superior properties of betaine-based surfactant (B-1235), in which the highest foam generation and foam stability performance were achieved. Foam endurance of B-1235 was also found comparable to the foam produced by switchable diamine (DTTM) surfactant; however, DTTM surfactant showed poorer foamability performance. In the presence of crude oil, B-1235 surfactant was able to maintain the foam properties, compared to other tested surfactants. The optimum concentrations for B-1235 in the absence and presence of crude oil were found to be 0.25 wt% and 0.5 wt%, respectively. The injection of foam stabilized by the B-1235 was able to pronouncedly increase the mobility reduction factor (MRF) at all the tested foam qualities under high-pressure and high-temperature conditions. Coreflood investigations indicated an optimal foam quality at 70% for all tested surfactant concentrations. The cumulative oil recovery after foam injection was found to be 67%, including 25% tertiary incremental oil recovery by foam flooding. The overall performance of the tested betaine-based surfactant is promising as an effective mobility control during foam EOR process and promotes further application in difficult Middle Eastern carbonate reservoir conditions.

Guvermectin is a recently discovered microbial N9-glucoside cytokinin compound extracted from Streptomyces sanjiangensis NEAU6. Although some research has reported that N9-glucoside cytokinin compounds do not have the activity of cytokinin, it has been noted that guvermectin can promote growth and antifungal activity in Arabidopsis. Maize is an important food crop in the world and exploring the effect of guvermectin on this crop could help its cultivation in regions with adverse environmental conditions such as a high temperature. Here, we investigated the effects of guvermectin seed soaking treatment on the growth of maize at the seedlings stage and its yield attributes with different temperature stresses. The maize (cv. Zhengdan 958) with guvermectin seed soaking treatment were in two systems: paper roll culture and field conditions. Guvermectin seed soaking treated plants had increased plant height, root length, and mesocotyl length at the seedlings stage, and spike weight at maturity in the field. But only root length was increased at the paper roll culture by guvermectin seed soaking treatment. Guvermectin seed soaking treatment reduced the adverse effects on maize seedling when grow at a high temperature. Further experiments showed that, in high temperature conditions, guvermectin treatment promoted the accumulation of heat shock protein (HSP) 17.0, HSP 17.4 and HSP 17.9 in maize roots. Comparative transcriptomic profiling showed there were 33 common differentially expressed genes (DEGs) in guvermectin treated plants under high temperature and room temperature conditions. The DEGs suggested that guvermectin treatment led to the differential modulation of several transcripts mainly related with plant defense, stress response, and terpenoid biosynthesis. Taken together, these results suggested that the guvermectin treatment promoted the growth and tolerance of high temperature stresses, possibly by activation of related pathways. These results show that guvermectin is a novel plant growth regulator and could be developed as an application to maize seeds to promote growth in high temperature environments.

Nanoparticle/polymer-enhanced alpha olefin sulfonate solution for foam generation in the presence of oil phase at high temperature conditions

Anthocyanins are ubiquitously accumulated in diverse plant species and play crucial roles in plant development. In addition, anthocyanin pigmentation is associated with significant characteristics in the flowers and fruits of horticultural products. Notably, anthocyanin biosynthesis and storage are known to be affected by environmental factors. High ambient temperatures often suppress anthocyanin accumulation in flowers and fruits, raising concerns regarding the increase in atmospheric temperatures caused by global warming. Therefore, a comprehensive understanding of the mechanisms underlying the effects of high ambient temperatures on the regulation of anthocyanin biosynthesis and storage is necessary to maintain pigment quality and quantity of the products. In this review, we provide comprehensive information on the role of high-temperature-related signaling pathways in the regulation of anthocyanin biosynthesis. The expression of genes involved in anthocyanin biosynthesis is mainly regulated by R2R3-MYB activators, R2R3-MYB repressors, and R3-MYB negative regulators. The expression levels of R2R3-MYB activators decrease under high-temperature conditions, as observed in many flowers and fruits. The upregulation of R2R3-MYB repressors and R3-MYB negative regulators has also been demonstrated in some plant species under high-temperature conditions. The high-temperature-related signaling pathways have been evaluated mainly in the vegetative organs of Arabidopsis and apple fruits. In these organs, light strongly influences anthocyanin biosynthesis in addition to ambient temperatures. The CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1)-ELONGATED HYPOCOTYL 5 (HY5) module and B-box proteins upregulate the R2R3-MYB activators under light conditions, while they downregulate the R2R3-MYB activators under high-temperature conditions. However, the pathways that transduce high-temperature signals in flowers are poorly understood. Unlike in fruits and vegetative organs, light exerts relatively small effects on anthocyanin pigmentation in flowers, suggesting that the COP1-HY5 module-independent pathway could be responsible for the regulation of R2R3-MYB regulators in many flowers. Further research to clarify the related signaling pathways in flowers is needed to find solutions to overcome the problem of color fading caused by high ambient temperatures. In addition, exceptional cases have been reported in which high temperatures do not inhibit or enhance the anthocyanin pigmentation of flowers. Such species can prove helpful in elucidating the mechanisms underlying temperature-mediated regulation of anthocyanin pigmentation and as parental materials for crossbreeding.

BackgroundThermo-sensitive genetic male sterile (TGMS) lines have been widely used in two-line hybrid rice breeding. The two-line hybrids have increased rice yields substantially. However, the effect of environmental temperatures on the fertility conversion is still not fully clear. In this study, we performed a tandem mass tag (TMT)-based proteomic analysis on the anthers of the TGMS line AnnongS-1 grown under permissive (low) temperature (21 °C) and restrictive (high) temperature (> 26 °C) conditions in an attempt to explore the effect of temperature on the fertility of the male sterile line.ResultsAfter the AnnongS-1 plants were induced under either permissive or restrictive conditions, morphological observations and I2-KI staining confirmed that the pollen grains formed under high temperature conditions were abortive while those formed under low temperature developed normally. In comparison to the plants grown under permissive conditions, the restrictive high-temperature conditions led to the differential accumulation of 89 proteins in the anthers, of which 46 were increased in abundance and 43 were decreased in abundance. Most of the subcellular compartments of the anther cells had one or more proteins that had been differentially accumulated, with the cytoplasm and chloroplast having the greatest accumulations. More than 40% of the differentially abundant proteins (DAPs) were enzymes involved in photosynthesis, energy metabolism, biosynthesis and catabolism of cellular components, metabolic regulation, defense and stress, etc. The DAPs related to protein metabolism accounted for the largest proportion (21.35%), followed by those related to defense and stress (12.36%), metabolic regulation (10.11%) and carbohydrate metabolism (8.99%), indicating that such biological processes in anther cells were more susceptible to high temperature stress.ConclusionsThe restrictive temperature induction caused fertility-sterility conversion in the TGMS line AnnongS-1 mainly by adversely affecting the metabolism of protein, carbohydrate and energy, and decreasing the abundances of important proteins closely related to defense and stress, thereby impeding the growth and development of the pollen and weakening the overall defense and ability to endure stress of AnnongS-1. These data are helpful for deepening our understanding of the molecular mechanism underlying fertility conversion in TGMS lines.

Climate change caused by global warming, is predicted to have severe consequences for ecosystems and economic sectors. In the agricultural industry, it is predicted that there will be decreased crop yields resulting from shifting planting seasons, as well as higher temperature and water stress which significantly reduce crop productivity. Kimchi cabbage, a cold-loving plant, is particularly vulnerable to high-temperature stress which can lead to stunted growth, increased susceptibility to pests like soft rot, reduced yield, and lower quality that will negatively impact the Kimchi cabbage market. Kimchi cabbage can be cultivated in highland regions with low summer temperatures and reduced pest occurrence, but rising temperatures and water stress are expected to increase pest pressure, resulting in a rapid decrease in the potential cultivation area of Kimchi cabbage. Currently, research is being conducted around the world to identify physiological mechanisms of heat tolerance at the molecular level, selection of heat-tolerant material, and studies on cellular responses of plants under high-temperature conditions. Despite numerous studies on physiological and biochemical responses of Brassica crops to high temperatures, there is a need to develop heat-tolerant Kimchi cabbage cultivars that can adapt to rapidly changing climates, new strategies for pest control under high-temperature conditions, and mitigation measures to ensure stable cultivation and production.

High temperature is a critical barrier in most cotton growing areas, limitingcotton growth and development. The present study aimed to evaluate theeffects of foliar spray on KC 3 cotton variety grown under ambient (32.66°C)and high temperature (37.21°C) stress in open-top chamber (OTC) with atemperature of 5°C from the ambient temperature for 10d from flowering toboll development stage. Foliar spray of kaolin @ 3% and calcium carbonate @5% were sprayed separately to the set of pots both in ambient and elevatedtemperature on 70th day of flowering. Observations on morphological andphysiological parameters were recorded on viz., plant height (cm plant-1), leafarea (cm2 plant-1), relative water content (%), canopy temperature (°C), SPAD,chlorophyll fluorescence (Fv/Fm ratio). Kaolin @ 3% foliar spray significantlyincreased the plant height, leaf area, relative water content, chlorophyllcontent and reduced the canopy temperature both in high temperature andambient temperature conditions. Among these treatments, T2 - kaolin 3%(Ambient) followed by T5 - Kaolin 3% (elevated temperature of 5 °C) recordedhigher values as compared to calcium carbonate treatment both in ambienttemperature and high temperature condition.

In order to deal with the complex working conditions of high temperature and high pressure and improve the bearing capacity of expansion joint, the reinforced bellows expansion joint with reinforcing ring is often used in engineering. At present, most of the studies on the strength performance of the reinforced bellows expansion joint do not consider the influence of the assembly gap between the reinforcing ring and the bellows on the strength performance of the expansion joint, and ignore the thermal stress caused by the temperature difference between the inner and outer surfaces of the bellows under high temperature conditions. In this paper, the effect of the gap between the stiffeners and bellows on the high temperature strength of the expansion joint was studied by full thermodynamic coupling numerical analysis method. The maximum Mises stress of the expansion joint with the gap between the stiffeners and bellows under different temperature differences was obtained. The strength performance of the expansion joint can be effectively improved by selecting the optimal clearance between the stiffening ring and the bellows, and due to the different temperature difference between the inner and outer surfaces of the bellows, the clearance value of the stiffening ring is different. The conclusion provides reference for the theoretical research, optimization design and manufacture of the reinforced bellows expansion joint under high temperature and high pressure conditions.

Significant amount of oil and gas reserves contain CO2 and H2S. Leakage of these gases to fresh water aquifers and their escape to the surface compromises human health and safety and create unthinkable environmental hazards. Cement exposed to these acid gases degrade, thereby promoting their release through the wellbore to overlying fresh water formations and/or the environment. This study investigates how these contaminants aid the corrosion of well cement in high pressure-high temperature (HPHT) environment. Experiments were conducted under two broad test conditions. In the first case, cement cores were aged at 100°F in CO2-H2S brine solution. The total test pressure was varied from 3000 psi to 9000 psi. In the second case, cement cores were exposed to brine saturated with gas mixture comprising H2S, CO2, and CH4 at total test pressure of 6000 psi. Temperature was varied from 100°F to 350°F. The compressive strength, shear bond strength, porosity, and permeability of the aged and unaged specimens were measured to quantify the alteration in these critical cement properties. Observations are supported with FTIR, SEM and EDS analyses. As temperature increases, the presence of H2S shows more impact on the loss of mechanical strengths and increase in transport properties of Class G cement than Class H cement. Variation of H2S concentration also shows significant impact on cement integrity. Compared to previous study involving the exposure of cement to pure CO2, the presence of H2S improves the relative strength of cement. However, transport properties are compromised. FTIR mineralogy confirms that the extent to which cement is carbonated by CO2 is limited by the presence of H2S. In addition, SEM and EDX indicate that ettringite was formed at low temperature (100°F). However, it dissolves at high temperature (350°F) without significantly compromising the structural integrity of cement. The most significant new finding in this study is that the presence of H2S and its coexistence with CO2 under HPHT conditions minimizes the loss of the structural integrity of well cement by pure CO2. This is important because it narrows down the most significant factor to consider when designing acidresistant cements for HPHT wells.

The high temperature and high in-situ stress geological environment can significantly affect the mechanical properties, failure modes, and deformation characteristics of deep shale reservoirs. In this study, real-time high temperature triaxial compressive tests simulating the deep shale formation environment (temperature: 25–150 °C, confining pressure: 0–100 MPa) are carried out. The GSI-strength degradation and constitutive models are derived based on the Hoek–Brown criterion. The results show that in low confining pressure conditions, the mechanical behavior of shale is greatly influenced by temperature. Compared with shale at 25 °C, the compressive strength of shale at 150 °C decreases by up to 13.7%, and the elastic modulus decreases by up to 36.9%. The peak strain was increased by a factor of up to 1.4, and the yield stress level was advanced by as much as 7.4%. However, in high confining pressure conditions, the shale plasticity characteristics are significantly enhanced and the failure mode is relatively single. The GSI-strength degradation model can well characterize the variation law of shale strength with confining pressure under high temperature conditions. The statistical damage constitutive model matches the actual stress–strain curve very well, and it can fully reflect the deformation and failure characteristics of deep shale. The findings of this study can help us better understand the variation of mechanical properties of deep shale.

An effort was made after detailed literature survey and few experiments, conducted at Laboratory conditions about the VAM fungus inoculated plants; they have large surface area and more photosynthetic rate, can assimilate more CO2, even can grow in drought condition including water deficiency and high temperature. For this purpose, a greenhouse pot experiment was conducted in which soil manifested with fungi was used and Conocarpus erectus L (common on green belt of Karachi Streets) was selected for testing the fungal engineering. Results demonstrated a well-developed strong roots system and branching pattern of shoots rather than larger surface area of leaves of the fungal engineered plant when compared with non-treated ones. The long root system indicates the stability of plant and water transport system in high temperature and low water conditions. While increased branching pattern of areal part may be directly related to an increase in net photosynthetic rates or increase CO2 absorption in the fungal inoculated plants. This investigation showed an interesting use of VAM services for technology development of root organ culture development in areas of low water availability and high temperature condition with elevated concentration of CO2. A mechanism of absorption of CO2 related with the alteration in plant bio-physical metabolism is discussed in relation with phosphorus uptake under VAM inoculation.

Reciprocal transfer study of north temperate and subtropical populations of Mesocyclops edax (Copepoda: Cyclopoida)