Browsing by Author "Falcone, Gioia"
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Item Open Access Assessment of deep geothermal energy exploitation methods: The need for novel single-well solutions(Elsevier, 2018-06-28) Falcone, Gioia; Liu, Xiaolei; Radido Okech, Roy; Seyidov, Ferid; Teodoriu, CatalinGeothermal energy is a constant and independent form of renewable energy and plays a key role towards the world's future energy balance. In particular, deep geothermal resources are largely available across continents and can help countries become less dependent on energy imports and build a broader base in their future energy mix. However, despite its significant potential, the total contribution of the geothermal sector to global power generation remains relatively small. The International Energy Agency has recommended devising plans to address technology-specific challenges to achieve faster growth and improving policies tackling pre-development risks for geothermal energy. Reaching considerable depths is a requirement to exploit deep geothermal resources, but experience gained to date from the implementation of complex, engineered deep geothermal projects has unveiled technical and economic challenges, lower-than-expected performance and poor public image. There is therefore an urgent need for alternative, more sustainable well designs. This paper critically assesses conventional and unconventional deep geothermal well concepts, focusing on the basic Borehole Heat Exchanger (BHE) concept. The discussions are supported by numerical simulations of a BHE design that includes heat conductive fillers to enhance the heat exchange with the surrounding formation, while avoiding direct fluid interaction with the latter.Item Open Access CFD modeling of a high enthalpy geothermal context(2018-02-28) Renaud, Théo; Stebel, Michal; Verdin, Patrick G.; Falcone, GioiaThe promising development of highly energetic geothermal resources could considerably enhance geothermal power production worldwide. The first attempt at tapping supercritical/heated fluids was made by the Iceland Deep Drilling project (IDDP), but unfortunately a magma layer at a depth of 2,100m was encountered, and the drilling was abandoned. Yet, this drilling operation failure generated new opportunities for assessing the potential power generation close to shallow magmatic intrusions. Detailed numerical methods are required to assess the heat transfer and fluid thermodynamics at wellbore and reservoir scale at near supercritical conditions to provide production scenarios and forecasts as accurate as possible. A primary steady-state study of reservoir and wellbore heat extraction from a geothermal well near a magmatic chamber has been performed with Computational Fluid Dynamics (CFD) techniques. Using simplified geological assumptions based on the IDDP-1 well description, a 2D axisymmetric single phase flow model was developed and its results were compared to those obtained with a full 3D CFD model. The simulated output power simulations reached 25 MW at 350°C and a wellhead pressure of 140 bars. Methodology and results from this study show that CFD techniques can be successfully used to assess geothermal energy outputs for unconventional geothermal wells and can provide details of a vapor superheated flow structure at wellbore-reservoir scale.Item Open Access Characterization of gas-liquid flows in annuli.(2019-07) Eyo, Edem Nsefik; Lao, Liyun; Falcone, GioiaGas–liquid two–phase flow in annulus is encountered during certain operations in the nuclear, chemical and petroleum industries. In the Oil and Gas industry, the knowledge of gas liquid two-phase flow in annuli is important during underbalanced drilling of wells and hole clean operations. This technique offers several advantages over the conventional drilling method including reducing formation damage, preventing fluid losses and enhancing the safety and efficiency of operation. Proper design of underbalanced drilling operations hinges on the accurate prediction and monitoring of gas-liquid two-phase flow parameters such as flow regimes, liquid holdup and pressure drop; however the complexities associated with two-phase flows coupled with complex geometry makes this difficult. Limited studies exist in literature for gas-liquid flow hydraulics in horizontal annuli and no studies have been undertaken on the effects of annulus eccentricity on two-phase flow parameters including flow regimes, liquid holdup and pressure drop. In order to provide an improved fundamental understanding of gas-liquid two-phase flow in horizontal annulus and give insight necessary for accurate model development, detailed systematic experimental studies are conducted at atmospheric conditions in horizontal concentric and fully eccentric annulus formed using a 3 inch outer and 2 inch inner pipes. Flow parameters including flow regimes, liquid holdup and pressure drop are investigated using high speed camera, conductance probes and pressure transducers, with air and water as testing fluids. Results show that annulus eccentricity affects the flow regimes, liquid holdup and pressure drop. Predictive models are compared with experimental data and new models are proposed for flow regime identification and liquid holdup prediction, while a new real-time objective flow regime identification tool is developed using Support Vector Machine (SVM). The data generated from this study can be used for developing models which would be incorporated into commercial software for study of flow through annulus.Item Open Access A comprehensive assessment of correlations for two-phase flow through Venturi tubes(Elsevier, 2020-04-17) Liu, Xiaolei; Lao, Liyun; Falcone, GioiaThe objective of this study is to comprehensively evaluate established correlations for two-phase (gas-liquid) flow through Venturi tubes. Two-phase flow metering plays a critical role in the oil and gas industry and several commercial metering solutions incorporate a Venturi. However, despite its significance, there is no widely accepted standard for two-phase flow metering applications. In this paper, sixteen differential pressure correlations are critically assessed from literature and international standards, focusing on the Venturi tube. The discussions are supported by an independent dataset obtained from a two-phase flow test rig with an installed Venturi tube (following ISO 5167-4 2005) to assess correlations' performance within their own respective application range. The wide literature review and the obtained comparison results trended to inform that the homogeneous model performs better in most scenarios.Item Open Access Conjugated numerical approach for modelling DBHE in high geothermal gradient environments(MDPI, 2020-11-21) Renaud, Théo; Verdin, Patrick; Falcone, GioiaGeothermal is a renewable energy source that can be untapped through various subsurface technologies. Closed geothermal well solutions, such as deep geothermal heat exchangers (DBHEs), consist of circulating a working fluid to recover the available heat, with less dependency on the local geological settings than conventional geothermal systems. This paper emphasizes a double numerical method to strengthen the assessment of DBHE performances. A computational fluid dynamics (CFD) commercial software and the 1D coupled wellbore-reservoir geothermal simulator T2Well have been used to investigate the heat transfer and fluid flow in a vertical DBHE in high geothermal gradient environments. The use of constant water properties to investigate the energy produced from DBHEs can lead to underestimating the overall heat transfer at high temperature and low mass flow rate. 2D axisymmetric CFD modelling improves the understanding of the return flow at the bottom of the DBHE, readjusting and better estimating the pressures losses commonly obtained with 1D modelling. This paper highlights the existence of convective cells located at the bottom of the DBHE internal tubing, with no significant effects due to the increase of injected water flow. Both codes are shown to constrain the numerical limitations to access the true potential of geothermal heat extraction from DBHEs in high geothermal gradient environments and demonstrate that they can be used for geothermal energy engineering applications.Item Open Access Dataset for "Conjugated Numerical Approach for Modelling DBHE in High Geothermal Gradient Environments"(Cranfield University, 2020-12-07 09:10) Verdin, Patrick; Renaud, Théo; Falcone, GioiaNumerical data corresponding to the journal paper entitled: "Conjugated Numerical Approach for Modelling DBHE in High Geothermal Gradient Environments"Item Open Access Dataset for "Numerical Analysis of Enhanced Conductive Deep Borehole Heat Exchangers",Cranfield University,CC BY 4.0,https://creativecommons.org/licenses/by/4.0/ Wadi et al. Pap1 CORD-Updated.xlsx,Wadi(Basil, 2021-06-14 09:00) Verdin, Patrick; Renaud, Théo; Falcone, Gioia; Doran, Hannah; Pan, LehuaNumerical data corresponding to the journal paper entitled: "Numerical Analysis of Enhanced Conductive Deep Borehole Heat Exchangers"Item Open Access Development of a real-time objective gas-liquid flow regime identifier using kernel methods(IEEE, 2019-04-22) Eyo, Edem; Pilario, Karl Ezra; Lao, Liyun; Falcone, GioiaCurrently, flow regime identification for closed channels have mainly been direct subjective methods. This presents a challenge when dealing with opaque test sections of the pipe or at gas-liquid flow rates where unclear regime transitions occur. In this paper, we develop a novel real-time objective flow regime identification tool using conductance data and kernel methods. Our experiments involve a flush mounted conductance probe that collects voltage signals across a closed channel. The channel geometry is a horizontal annulus, which is commonly found in many industries. Eight distinct flow regimes were observed at selected gas-liquid flow rate settings. An objective flow regime identifier was then trained by learning a mapping between the probability density function (PDF) of the voltage signals and the observed flow regimes via kernel principal components analysis (KPCA) and multi-class Support Vector Machine (SVM). The objective identifier was then applied in real-time by processing a moving time-window of voltage signals. Our approach has: (a) achieved more than 90% accuracy against visual observations by an expert for static test data; (b) successfully visualized conductance data in 2-dimensional space using virtual flow regime maps, which are useful for tracking flow regime transitions; and, (c) introduced an efficient real-time automatic flow regime identifier, with only conductance data as inputsItem Open Access Estimation of plugging and abandonment costs based on different EU regulations with application to geothermal wells(Stanford University, Stanford, USA, 2018-02-15) Osundare, Olusegun Samson; Teodoriu, Catalin; Falcone, Gioia; Ichim, AdonisThis paper presents the cost of plugging and abandonment (P&A) of the Horstberg Z1 well and shows how the well history is considered in the P&A planning process together with existing European regulations. Three different design plans are presented, based on innovative ideas and best practices in the oil and gas industry. Horstberg Z1, located in Germany, was originally a gas well, converted to a scientific geothermal well to prove the single well concept. After serving as a geothermal well for several years, the well has been proposed for P&A. The three designs presented in this work fulfill the purposes of well P&A, and meet the BVOT requirements, which are standard requirements for wells in Lower Saxony, Germany. Following a financial analysis of the designs, it is noted that rig costs are the largest element of the total expenditure, contributing over 50% in the design plans considered. As the number of cement plugs and round trips increase per design plan, the implementation period also increases, which impacts on the total cost. Based on the investigations made in this project, a minimum of USD 1,275,500 is required for the plug and abandonment cost of the well, excluding the well site re-cultivation. A rigless solution for pulling heavy casing out of the wellbore, to avoid the use of a conventional workover rig, would significantly reduce the plug and abandonment cost of the Horstberg Z1 well.Item Open Access Experimental validation of multiphase flow models and testing of multiphase flow meters: A critical review of flow loops worldwide(WIT Press (Wessex Institute of Technology), 2016) Bello, O. O.; Falcone, Gioia; Teodoriu, C.Around the world, research into multiphase flow is performed by scientists with hugely diverse backgrounds: physicists, mathematicians and engineers from mechanical, nuclear, chemical, civil, petroleum, environmental and aerospace disciplines. Multiphase flow models are required to investigate the co-current or counter-current flow of different fluid phases under a wide range of pressure and temperature conditions and in several different configurations. To compliment this theoretical effort, measurements at controlled experimental conditions are required to verify multiphase flow models and assess their range of applicability, which has given rise to a large number of multiphase flow loops around the world. These flow loops are also used intensively to test and validate multiphase flow meters, which are devices for the in-line measurement of multiphase flow streams without separation of the phases. However, there are numerous multiphase flow varieties due to differences in pressure and temperature, fluids, flow regimes, pipe geometry, inclination and diameter, so a flow loop cannot represent all possible situations. Even when experiments in a given flow loop are believed to be sufficiently exhaustive for a specific study area, the real conditions encountered in the field tend to be very different from those recreated in the research facility. This paper presents a critical review of multiphase flow loops around the world, highlighting the pros and cons of each facility with regard to reproducing and monitoring different multiphase flow situations. The authors suggest a way forward for new developments in this area.Item Open Access Gas-liquid flow regime maps for horizontal pipelines: predicting flow regimes using dimensionless parameter groups(Begell House, 2022-10-27) Osundare, Olusegun Samson; Elliott, Alexander; Falcone, Gioia; Lao, LiyunFlow regime maps are essential to gas-liquid flow applications in many industrial processes to accurately identify the flow regimes before estimating multiphase features. Flow regime classifications were originally based on visual observations of two-phase flow experiments. The observations were mapped on two-dimensional plots (called “flow regime maps”) and the boundaries between regimes determined. Over the years, different coordinates have been proposed for the maps (e.g., superficial velocities and momentum fluxes), in search for parameters that are independent of the given experimental set-up. This paper reports a study on developing new flow regime maps with a broader range of applications by using dimensionless parameter groups as the map coordinates. Various flow regime maps were developed with the use of different combinations of these parameter groups, then they were examined and assessed using datasets from published experimental research and the MultiFlowMet II project for validation. This initial feasibility study develops proof-of-concept flow regime maps that demonstrate the potential of dimensionless parameter groups to more accurately characterise multiphase flow in horizontal pipes, with the optimisation of these maps being considered in future works. The analysis revealed that combinations of the mixture Froude number (Frm) versus the ratio of gas superficial velocity to liquid superficial velocity (vSG/vSL), with the liquid phase Froude number (FrL) versus the gas phase Froude number (FrG) show potential for unambiguous identification and mapping of flow regimes, even for datasets with a wider range of operating conditions.Item Open Access Heat transfer in unconventional geothermal wells: a double numerical modelling approach(Springer, 2021-06-02) Renaud, Théo; Verdin, Patrick; Falcone, GioiaGeothermal energy aims at producing electricity or heat from underground resources. Worldwide geothermal energy extraction and use is still limited, despite its estimated high potential. To date, the efficiency and viability of enhanced geothermal system (EGS) and deep unconventional geothermal resources (e.g. superheated/supercritical systems) via conventional heat recovery techniques have led to limited success due to technology issues. Research on superheated/supercritical geothermal systems is highly active in Europe, notably triggered by the Iceland Deep Drilling Project (IDDP) [1]. Supercritical resources could deliver more energy than conventional resources thanks to the increase of enthalpy and the sharp decrease of density around the critical point of water [2]. The first well from IDDP was drilled at a depth of 2072 m after unintentionally drilling into magma between 2092 and 2104 m. The wellhead temperature reached 450°CC, with a superheated steam at a pressure of 140 bars (Palsson et al. in Geothermics 49:23–30, 2014).Item Open Access Heat transfer modelling of an unconventional, closed-loop geothermal well(2021-10-27) Renaud, Théo; Verdin, Patrick; Falcone, Gioia; Pan, LehuaWith approximately 13 GW installed capacity worldwide in 2017, the geothermal energy sector represents less than 1% of the total renewable energy mix. Although the Enhanced Geothermal System (EGS) concept faces technical and economic validation challenges and suffers from public acceptance issues, such system is considered to have the capability to unlock the significant deep geothermal potential worldwide. The development of unconventional deep well designs can help to improve the efficiency and reliability of EGS systems. An integrated reservoir-wellbore approach to model alternative EGS well designs is key to assess their long-term hydraulic and thermal performance, particularly in unconventional geological settings. A coupled wellbore-reservoir simulator, T2WELL/EOS1, is used to compare the estimated energy recovery with experimental results available in the public domain from a downhole coaxial heat exchanger (DCHE) installed in Hawaii, where a temperature of 358°C has been measured at a depth of 1962 m. Numerical results are also compared with analytical-based results from the literature, showing good agreement and demonstrating that the heat recovery from deep borehole heat exchangers can be accurately simulated. Thermal performance and economic viability of a hypothetical DCHE with conducting fillers in high thermal gradient areas are also discussed, based on the results from the Hawaii case study. The findings provide guidance to assess the operating range of closedloop single-well EGS designs in future studies.Item Open Access An investigation into job role localisation in the oil and gas industry: a case study(2018-03) Pegram, Jack; Falcone, Gioia; Kolios, Athanasios; Craig, JonathanThis study investigates the viability of localising job roles in the oil and gas industry and whether job role localisation can reduce staffing costs. The principal barrier to job role localisation is high standards required by oil and gas companies and immature labour markets that do not meet these standards. A four stage mixed methods approach is taken. The first stage addresses the global level using a survey about local content issues. The second stage focuses on the national level using interviews to investigate how national factors can affect job role localisation. The third stage addresses the company level, using a decision tree methodology on a sample of ten job roles within one oil and gas company operating in Ghana to assess the viability of localising particular job roles. The fourth stage uses training and development investment timelines to model whether the costs of employing expatriates are greater than training, developing and employing Ghanaians to do the same job roles. The findings show that different stakeholders often share opinions about local content issues. At the national level there are many national context specific factors that affect job role localisation including legislations, culture, attitudes and experience within the labour market. The decision tree methodology developed in this study is an effective tool to assess the viability of localising different job roles over time. Training and development investment timelines show that it is more cost-effective to invest in the education, training and development of local people than it is to employ expatriates. This study finds that localisation is becoming increasingly prevalent worldwide. Oil and gas companies must adapt their localisation strategies to the national context where they are operating. Whilst not all job roles should be localised, decision trees can support companies to decide which job roles should be localised. Furthermore, companies can reduce costs if they train, develop and employ local people rather than employing expatriates.Item Open Access Investigation of the Effect of Sand on Annular Flow Behaviour in Horizontal Pipes(Cranfield University, 2017-10) Osokogwu, Uche; Falcone, GioiaAnnular flow is encountered in petroleum production systems, where reservoir fluids are conveyed to surface via wells and transport lines and also nuclear power plants, chemical and refining processes (e.g. reactors, heat exchangers). In this type of flow regime, the gas, together with the entrained liquid droplets, flows within the core of the pipe at high velocities, while the liquid flows as a film along the pipe walls. Experimental investigations on annular flow behaviour, sand transport and its effect on annular flow in horizontal pipe are presented, with the aim of progressing the understanding of such flow and facilitate the optimum design of hydrocarbon production systems. The experiments were conducted using a closed-loop horizontal pipe with an internal diameter of 2-inch (0.0504m). The experiments could be categorized into: water/air flow, water/sand flow, water/air/sand annular flow and sand sampling. The water/air flow experiments could be subdivided into water/air flow (Plug, Slug, Stratified-smooth and stratified-wavy flows) and water/air annular flow. The results of water/air flow were plotted on flow regime map to aid the recognition of the different flow regimes. For the water/air annular flow experiments, key flow features are presented, with discussion on liquid hold up, film thickness, wave frequency and pressure gradient. The water/sand flow experiments investigated sand saltation, sand streaks, moving dunes and sand beds. Also, sand particles of 212microns and 500microns for water/air/sand annular flow were investigated. Similarly, sand sampling experiments were also carried out. The OLGA dynamic multiphase flow simulator was run against the experimental results. The OLGA simulations of the water/air annular flow shows a better liquid hold-up match at lower superficial liquid velocities. For sand transport, OLGA also identified sand flow in annular flow as no bed. The main contributions of this study are: presenting the minimum transport velocities for water/sand flow in horizontal pipe. For water/air annular flow, the contributions are: detailed annular flow behaviours in horizontal pipes with annular-wavy slug flow at low superficial liquid and gas velocities, and full symmetrical annular flow from superficial gas velocity of 12m/s at low Vsl. The study proves that superficial liquid velocity has impact and significance on wave frequency: This has refuted Setyawan et al., (2014), whose report presented superficial liquid velocity to be insignificant in wave frequency. The study also identified that the higher the Vsl, the higher the interfacial shear stress but the lower the wave velocity. Also, the higher the Vsl, the higher interfacial friction factor/shear stress, but the lower the wave frequency. For water/air/sand annular flow, this study identifies saltation and suspension as the two main sand distribution in annular flow, with small-size particles being transported at the gas core and the bigger particles at the bottom (i.e. in the liquid film) along in the horizontal pipes. Finally, sand particles’ size does not appear to have an impact on wave velocity and wall shear stress, while sand concentration affects wall shear stress, but not wave velocity. Lastly, presence of sand particles in the liquid film is associated with increase in wave amplitude in annular flow, as more energy is being dissipated from the gas phase to keep the waves in motion.Item Open Access Liquid loading in gas wells: experimental investigation of back pressure effects on the near-wellbore reservoir(Elsevier, 2016-10-28) Liu, Xiaolei; Falcone, Gioia; Teodoriu, C.A large-scale core-flooding experimental setup was designed and constructed to investigate the back pressure effects on transient flow through porous medium, and so mimic the physical process of liquid loading and reservoir response. Between initial and final steady-state flowing conditions, where inlet pressure was maintained at a constant level while initiating a transient pressure build up at the core sample end, an “U-shaped” temporal distribution of pore fluid pressure within the medium itself was observed, which is in direct contrast to the conventional reservoir pressure profile.Item Open Access Liquid loading in gas wells: From core-scale transient measurements to coupled field-scale simulations(Elsevier, 2017-08-12) Liu, Xiaolei; Falcone, Gioia; Teodoriu, CatalinLiquid loading is a major operational constraint in mature gas fields around the world. It manifests itself as an increasing back pressure on the reservoir due to a rising liquid column in the well, which initially decreases deliverability, then ultimately causes the gas well to cease production. Theoretically, every gas well will experience this debilitating phenomenon in the latter stages of its producing life. In this paper, both laboratory experiments and numerical simulations are presented to shed more light on the physical process of liquid loading, with a focus on reservoir responses. On the one hand, core-flooding experimental setups of different scales were designed and constructed to investigate back pressure effects on transient flow through the near-wellbore region of the reservoir. On the other hand, the modelling of a gas well undergoing controlled flow and shut-in cycles was performed to validate core-scale observations at reservoir scale, using commercial integrated numerical software that connects a transient wellbore model to a transient reservoir model. The simulated transient characteristics of short-term downhole dynamics (e.g. liquid re-injection and co-current/counter-current flows) supported the U-shaped concept observed in the experiments. The detected temporal distribution of pore fluid pressure within the reservoir medium itself (referred to as the U-shaped pressure profile) was observed both experimentally at the core-scale and numerically at the reservoir-scale. This pressure distribution can be used to explain re-injection of the denser phases into the near-wellbore region of the reservoir.Item Open Access Liquid-liquid flow pattern prediction using relevant dimensionless parameter groups(MDPI, 2020-08-24) Osundare, Olusegun Samson; Falcone, Gioia; Lao, Liyun; Elliott, AlexanderAccurate predictions of flow patterns in liquid-liquid flow are critical to the successful design and operation of industrial and geo-energy systems where two liquids are jointly transported. Unfortunately, there is no unified flow pattern map, because all published maps are based on limited ranges of dimensional parameters. Dimensional analysis was performed on oil-water horizontal flows, to obtain some relevant dimensionless parameter groups (DPG) for constructing flow pattern maps (FPM). The following combinations of DPG were used: (i) the ratio of mixture Reynolds number to Eötvös number versus water fraction, (ii) the ratio of Weber number to Eötvös number versus water fraction, (iii) the mixture Froude number versus water fraction, (iv) the water Froude number versus oil Froude number, (v) the ratio of gravity force to viscous force versus water fraction. From twelve published experimental studies, 2696 data points were gathered and analysed covering a variety of flow patterns including stratified, stratified mixed, dispersed oil in water, dispersed water in oil, annular and slug flows. Based on the performed analysis, it was found that flow patterns could occupy more than one isolated region on the DPG-based flow pattern map. None of the combinations of DPG can mark out all the considered flow patterns, however, some combinations of DPG are particularly suitable for marking out the regions associated with some flow patternsItem Open Access A microwave cavity resonator sensor for water-in-oil measurements(Elsevier, 2018-02-02) Sharma, Prafull; Lao, Liyun; Falcone, GioiaOnline monitoring of Water-Liquid Ratio (WLR) in multiphase flow is key in petroleum production, processing and transportation. The usual practice in the field is to manually collect offline samples for laboratory analysis, which delays data availability and prevents real time intervention and optimization. A highly accurate and robust sensing method is needed for online measurements in the lower end of WLR range (0%–5%), especially for fiscal metering and custody transfer of crude oil, as well as to ensure adequate flow assurance prevention and remedial solutions. This requires a highly sensitive sensing principle along with a highly precise measurement instrument, packaged together in a sufficiently robust manner for use in the field. In this paper, a new sensing principle is proposed, based on the open-ended microwave cavity resonator and near wall surface perturbation, for non-intrusive measurement of WLR. In the proposed concept, the electromagnetic fringe field of a cylindrical cavity resonator is used to probe the liquid near the pipe wall. Two of the cylindrical cavity resonance modes, TM010 and TM011 are energized for measurements and the shift in the resonance frequency is used to estimate liquid permittivity and the WLR. Electromagnetic simulations in the microwave frequency range of 4 GHz to 7 GHz are used for proof-of-concept and sensitivity studies. A sensor prototype is fabricated and its functionality demonstrated with flowing oil-water mixtures in the WLR range of 0–5%. The frequency range of the proposed sensors is 4.4–4.6 GHz and 6.1–6.6 GHz for modes TM010 and TM011, respectively. The TM011 mode shows much higher sensitivity (41.6 MHz/WLR) than the TM010 mode (3.8 MHz/WLR). The proposed sensor consists of a 20 mm high cylinder, with a diameter of 30 mm and Poly-Ether-Ether-Ketone (PEEK) filler. The non-intrusiveness of the sensor, along with the high sensitivity in the resonance shift, makes it attractive for practical applications.Item Open Access Modelling an unconventional closed-loop deep borehole heat exchanger (DBHE): sensitivity analysis on the Newberry volcanic setting(Springer, 2021-02-15) Doran, Hannah R.; Renaud, Théo; Falcone, Gioia; Pan, Lehua; Verdin, Patrick G.Alternative (unconventional) deep geothermal designs are needed to provide a secure and efficient geothermal energy supply. An in-depth sensitivity analysis was investigated considering a deep borehole closed-loop heat exchanger (DBHE) to overcome the current limitations of deep EGS. A T2Well/EOS1 model previously calibrated on an experimental DBHE in Hawaii was adapted to the current NWG 55-29 well at the Newberry volcano site in Central Oregon. A sensitivity analysis was carried out, including parameters such as the working fluid mass flow rate, the casing and cement thermal properties, and the wellbore radii dimensions. The results conclude the highest energy flow rate to be 1.5 MW, after an annulus radii increase and an imposed mass flow rate of 5 kg/s. At 3 kg/s, the DBHE yielded an energy flow rate a factor of 3.5 lower than the NWG 55-29 conventional design. Despite this loss, the sensitivity analysis allows an assessment of the key thermodynamics within the wellbore and provides a valuable insight into how heat is lost/gained throughout the system. This analysis was performed under the assumption of subcritical conditions, and could aid the development of unconventional designs within future EGS work like the Newberry Deep Drilling Project (NDDP). Requirements for further software development are briefly discussed, which would facilitate the modelling of unconventional geothermal wells in supercritical systems to support EGS projects that could extend to deeper depths