Sadiq Zarrouk
The University of Auckland, Engineering Science, Faculty Member
Sterilization of liquid food in cans was studied and analyzed using computational fluid dynamics (CFD). In all the simulations studied, saturated steam at 121oC was used as the heating medium. The different liquid foods studied in this... more
Sterilization of liquid food in cans was studied and analyzed using computational fluid dynamics (CFD). In all the simulations studied, saturated steam at 121oC was used as the heating medium. The different liquid foods studied in this work were assumed to have constant specific heat, thermal conductivity and volume expansion coefficient, while the viscosity was taken as a function of temperature. Density variations were governed by the Boussinesq approximation. The software package code PHOENICS was used, which is based on finite volume method of analysis (FVM). The results of the simulations were presented in the form of transient temperature and velocity profiles. The shapes and movement of the slowest heating zone were followed throughout the sterilization time. The simulations show clearly the action of natural convection, which forces the slowest heating zone (SHZ) to migrate towards the bottom of the can as expected.
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... Oil & Gas Journal, 99: 40 - 45. Stricker, GD, Flores, RM, McGarry, DE, Stilwell, DP, Hoppe, DJ, Stilwell, KR, Ochs, AM, Ellis, ME, Osvald, KS, Taylor, SL, Thorvaldson, MC, Trippi, MH, Grose, SD, Cockett, FJ, Shariff, AA, 2006. Gas... more
... Oil & Gas Journal, 99: 40 - 45. Stricker, GD, Flores, RM, McGarry, DE, Stilwell, DP, Hoppe, DJ, Stilwell, KR, Ochs, AM, Ellis, ME, Osvald, KS, Taylor, SL, Thorvaldson, MC, Trippi, MH, Grose, SD, Cockett, FJ, Shariff, AA, 2006. Gas desorption ...
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ABSTRACT Pressure, Temperature and Spinner (PTS) probes/tools are commonly used in the characterization of geothermal wells during drilling, completion testing, and monitoring throughout the life of the well. These well tests include... more
ABSTRACT Pressure, Temperature and Spinner (PTS) probes/tools are commonly used in the characterization of geothermal wells during drilling, completion testing, and monitoring throughout the life of the well. These well tests include static formation temperature testing, water loss surveys, injection fall-off tests, drawdown build-up tests, warm-up surveys, flowing surveys, and other tests. The challenge when using these tools is to ensure that the electronic components of the different sensors, signal processing, and memory are not affected by the heat generated from the tool's internal energy use, internal supply (battery), and from the high temperatures inside the well. This buildup of heat limits the working time available for the tool down the geothermal well and can affect/limit the acquisition and quality of the data. A survey was conducted on the current state of electronics and electronic packaging for the use in geothermal, and oil and gas probes/tools. Techniques for high temperature performance were reviewed including the use of Dewar flasks for the thermal insulation of electronic components of the PTS tool and the use of electronics for operation at higher temperatures. An in-depth analysis of the performance of the widely used commercial PTS tool developed by MB Century Ltd. was completed using SolidWorks™ thermal simulation software. The model was optimized and compared to PTS probe test data taken from five different test cases. The calibrated model was used to evaluate several different heat sink materials, with results showing that the current tool design cannot be easily optimized further. However, predictions based on the calibrated model showed an alternative operating procedure that can provide an increase in the operating down-hole time of the tool.
Resource estimates in geothermal "green" fields involve significant inherent uncertainty due to poorly constrained subsurface parameters and multiple potential development scenarios. There is also limited published information... more
Resource estimates in geothermal "green" fields involve significant inherent uncertainty due to poorly constrained subsurface parameters and multiple potential development scenarios. There is also limited published information on probabilistic resource assessments of geothermal prospects. This paper explores the applications of a systematic experimental design (ED) approach to a geothermal reservoir simulation model to generate probabilistic resource assessment results. A Plackett-Burmann design was used to build 12 simulation experiments for a geothermal system, investigating six model parameters at two levels. A probabilistic 30-yr power capacity was successfully generated from the resulting response surface. Analysis of the response also showed that the power capacity was significantly affected by only three of the tested parameters: reservoir temperature, permeability, and well depth. Volumetric methods, both "heat in place" and mass in place, were applied to...
Lake Waikare, situated within the Huntly coalfield in North Waikato, is host to a small island (Punikanae Island) where a silica sinter-depositing spring is located. This is the only sinter depositing spring known outside the Taupo... more
Lake Waikare, situated within the Huntly coalfield in North Waikato, is host to a small island (Punikanae Island) where a silica sinter-depositing spring is located. This is the only sinter depositing spring known outside the Taupo Volcanic Zone. The chemical analysis from the two spring samples complimented by geological information gathered during a short field visit and other technical data available in the literature are the sets of information used in this study. Based on the Cl-SO 4 -HCO 3 ternary plot that was used to classify the geothermal waters with respect to major anion composition and the Na-K-Mg ternary plot to classify fluids according to the state of equilibrium at given temperatures, the origin of the geothermal system that feeds the spring is thought to be mature neutral chloride waters that probably originate from an up-flow zone beneath Punikanae Island with the Maungaroa Fault as its main conduit. Up-flow zones are generally characterized by silica sinter depos...
Geothermal energy training is a very specialised area with only two established postgraduate programmes available worldwide, in Iceland and New Zealand. In this paper we discuss the background, teaching philosophy, course content, student... more
Geothermal energy training is a very specialised area with only two established postgraduate programmes available worldwide, in Iceland and New Zealand. In this paper we discuss the background, teaching philosophy, course content, student cohort, and the funding of the New Zealand course. The Post Graduate Certificate in Geothermal Energy Technology (PGCertGeothermTech) is taught at the University of Auckland, New Zealand. The inaugural course was in 2007, and the course has been taught every year since then. It is a one-semester (5 month) course for Science and Engineering graduates, developed in response to the increasing demand for trained engineers and scientists to work in geothermal exploration and development nationally and internationally. The precursor to this course was the two-semester geothermal PG Diploma at the Geothermal Institute, the University of Auckland which ran from 1979 till 2002 (Hochstein, 2005). The programme is industry-oriented and is designed to bring to...
A TOUGH2 reservoir model has been developed for the Habanero EGS, located in the Cooper Basin. The reservoir, interpreted to be the sub-horizontal Habanero fault, was defined by the extent of the stimulated seismic cloud. A 1D natural... more
A TOUGH2 reservoir model has been developed for the Habanero EGS, located in the Cooper Basin. The reservoir, interpreted to be the sub-horizontal Habanero fault, was defined by the extent of the stimulated seismic cloud. A 1D natural state model was used first to calibrate the rock properties: specific heat capacity, thermal conductivity, heat generation and the heat flux at the base of the model. The temperature distribution was matched against measured down-hole data from well Habanero 1. A 3D model was then developed with 9 horizontal layers and aligned along an impermeable eastern boundary fault. Gravity potentially plays an important role so the model was tilted to the west-south-west. Since the fine 72,000 cell model only extends to 20 km 2 whilst the reservoir rock (Innamincka Granite) extends to over ~1,000 km 2 , Dirichlet boundary condition (large block volumes) was used for the sides with closed boundaries at the top and bottom. These large cells simulate the extension o...
Pressure, Temperature and Spinner (PTS) probes/tools are commonly used in the characterization of geothermal wells during drilling, completion testing, and monitoring throughout the life of the well. These well tests include static... more
Pressure, Temperature and Spinner (PTS) probes/tools are commonly used in the characterization of geothermal wells during drilling, completion testing, and monitoring throughout the life of the well. These well tests include static formation temperature testing, water loss surveys, injection fall-off tests, drawdown build-up tests, warm-up surveys, flowing surveys, and other tests. The challenge when using these tools is to ensure that the electronic components of the different sensors, signal processing, and memory are not affected by the heat generated from the tool's internal energy use, internal supply (battery), and from the high temperatures inside the well. This buildup of heat limits the working time available for the tool down the geothermal well and can affect/limit the acquisition and quality of the data. A survey was conducted on the current state of electronics and electronic packaging for the use in geothermal, and oil and gas probes/tools. Techniques for high temp...
The Mount Apo Geothermal Field is located on the northwestern flank of Mount Apo the Philippines’ highest peak. Out of the 40 wells drilled in the field, 20 production and 8 injection wells are used to run the two 52 MWe plants... more
The Mount Apo Geothermal Field is located on the northwestern flank of Mount Apo the Philippines’ highest peak. Out of the 40 wells drilled in the field, 20 production and 8 injection wells are used to run the two 52 MWe plants commissioned in 1997 and 1999 respectively. During the cementing of the production casing of well T7, cement invaded the production zone of well T4 causing it to cease producing. Pressure transient data were collected and analyzed from injection/fall-off tests at different stages: post-drilling, after cement-damaged, after mechanical clearing and after acid stimulation. The preliminary analysis of the four sets of data is done using well test analysis and interpretation software (Saphir™). Three different numerical models were also developed to model the pressure transient for each test using: (a) a 3D model with a refined grid, (b) a radial model, and (c) a 3D model with a radial grid embedded into the injection block. For the radial-grid, three different ty...
The continuous measurement of mass flow rates during output testing from a geothermal production well 2H-21 of Hatchobaru geothermal field, Japan are relatively short. Field data from a horizontal discharge into a twin separator was used... more
The continuous measurement of mass flow rates during output testing from a geothermal production well 2H-21 of Hatchobaru geothermal field, Japan are relatively short. Field data from a horizontal discharge into a twin separator was used to evaluate and understand the transient behavior of the near-well characteristics. The data was recorded every second for: the pressure drop across the steam orifice plates, the pressure at the separators, and the water level at weir box. The atmospheric pressure was also measured daily. The valve opening was changed three times during the measurement to obtain the output curve of the well. The measured mass flow rates and pressure at the wellhead then were used as input data to wellbore simulator. The results of calculated well bottom pressures then were inputted into AWTAS (Automated Well-Test Analysis System) to evaluate the properties of the reservoir. Three different types of radial reservoir model were used including uniform porous media, dua...
The steam-water separator is a vital component in liquid dominated geothermal steam field equipment. While various designs exist, the vertical cyclone separator dominates the design used worldwide. Most current designs are based on... more
The steam-water separator is a vital component in liquid dominated geothermal steam field equipment. While various designs exist, the vertical cyclone separator dominates the design used worldwide. Most current designs are based on Bangma's experience in Wairakei in 1961, and Lazalde-Crabtree's (1984) empirical approach. Although the design of a vertical cyclone separator is relatively simple, understanding of the fluid behaviour within the separator is still limited. Challenges arise from the difficulty in predicting the flow regime, pressure distribution and the separation efficiency inside the separator vessel. Due to this complexity, a numerical approach from Computational Fluid Dynamics (CFD) software is needed. This paper simulates the two-phase fluid movement inside a geothermal cyclone separator using the Fluent® CFD software package. The inlet fluid characteristics were varied to see how the change in enthalpy and mass flow affected the cyclone separator performance. The effect of inlet shape design on separator performance was also studied. In order to model the swirling flow with a high degree of turbulence, as normally occurs inside the separator, the Renormalization Group (RNG) k-ε turbulence model was implemented. The separator efficiency was calculated by injecting liquid droplets after a converged solution was achieved. The Harwell technique was used to get an approximate estimate of the average liquid droplet size. The CFD simulation results demonstrated a promising method for optimizing the separator design.
The present-day surface activity at Orakei Korako dominantly occurs on the eastern side of the Lake Ohakuri with only minor surface activity on the western bank. A 30 m deep drill hole (OKM3) was drilled on the western bank to monitor the... more
The present-day surface activity at Orakei Korako dominantly occurs on the eastern side of the Lake Ohakuri with only minor surface activity on the western bank. A 30 m deep drill hole (OKM3) was drilled on the western bank to monitor the shallow groundwater level. Continuous core was recovered providing the first core from the western side of Lake Ohakuri, as previously reported cored drillholes are located on the eastern side of Lake Ohakuri. Examination of OKM3 core involved identifying the lithology and stratigraphy which consists of pyroclastic rocks of Taupo Pumice alluvium and Akatarewa breccias. At 22 m depth a thin (~10 cm) siliceous sinter horizon is present, indicating historic surface discharge of alkali chloride thermal water. X-Ray Diffraction (XRD), petrographic microscopy, Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Ray Spectroscopy (EDS) were used to examine hydrothermal alteration within the core. Hydrothermal alteration minerals identified include z...
Travertine is a common geothermal surface feature that forms by the deposition of carbonate from discharging bicarbonate thermal water. Travertine samples from two sites: Silver Peak, Nevada, USA, and Waikite, New Zealand, were examined... more
Travertine is a common geothermal surface feature that forms by the deposition of carbonate from discharging bicarbonate thermal water. Travertine samples from two sites: Silver Peak, Nevada, USA, and Waikite, New Zealand, were examined to contrast their mineralogy, morphology, and chemical composition. These sites were chosen as they provided examples of travertine formed in different countries and in different geothermal settings. Travertine formed at Silver Peak is related to a deep-reaching heat-sweep system, Travertine at Waikite contains silica and is related to a flat terrain geothermal system where the heat source appears to be extensive, hot rhyolitic crustal rock. X-ray Powder Diffraction (XRPD) determined differences in the travertine mineralogy of Silver Peak samples were calcite, whereas samples from Waikite consisted of calcite with some samples also conteining silica (opal-A). Based on the XRPD trace samples from Waikite were slightly more crystalline than those from ...
As the opportunities for developing further conventional geothermal resources become increasingly limited, the development of deep supercritical reservoirs is attracting more interest. If the associated exploration, modelling and... more
As the opportunities for developing further conventional geothermal resources become increasingly limited, the development of deep supercritical reservoirs is attracting more interest. If the associated exploration, modelling and engineering challenges can be addressed, supercritical reservoirs represent a potentially large and untapped source of high-enthalpy fluid for power generation. To investigate production from supercritical reservoirs, a simple idealized two-dimensional numerical model has been developed, using a supercritical version of TOUGH2 simulator. The model is 7 km deep and produces fluid from 4 – 5 km, a reasonable drillable depth. Numerical experiments indicated that steady-state supercritical conditions at this depth will be found only when permeability below it is low, of the order of 0.1 mD. Simulations of production showed that reservoirs with higher porosity will give higher mass flows but lower flowing enthalpy, as expected. They also showed that, as in conve...
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Andesites are minor rock types in the Taupo Volcanic Zone (TVZ) and most occur near the Tongariro Volcanic Centre (TVC), White Island, Putuaki and Rolles Peak near Rotokawa. However, several subsurface andesites have also been intersected... more
Andesites are minor rock types in the Taupo Volcanic Zone (TVZ) and most occur near the Tongariro Volcanic Centre (TVC), White Island, Putuaki and Rolles Peak near Rotokawa. However, several subsurface andesites have also been intersected by wells drilled at the Ngatamariki, Rotokawa, Wairakei, Waiotapu, Kawerau and Tauhara geothermal fields. The Spa Andesite at Tauhara, at least 201 meters thick, comprises interbedded lavas and breccias between 390 and 591 m depth. It was intersected only in well THM18 in the Spa Bowl area. Some of rocks are intensely altered. This study characterizes the Spa Andesite and compares it with other andesites within the TVZ. Twelve cores were chosen to cover the vertical extent of the andesite as well as differences in its hydrothermal alteration. The samples were examined by petrography, X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) and fluid inclusion geothermometry. The Spa Andesite cores have silica contents ranging from basalt to dacite (52.2 t...
Rotorua township is situated on top of a shallow geothermal reservoir within the Taupo Volcanic Zone of New Zealand. The resource is easy to access for private users and is commonly used for domestic and commercial heating. The Rotorua... more
Rotorua township is situated on top of a shallow geothermal reservoir within the Taupo Volcanic Zone of New Zealand. The resource is easy to access for private users and is commonly used for domestic and commercial heating. The Rotorua Hospital is located on one of the up flows of the geothermal reservoir and uses a doublet geothermal heating system that
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The paper first discusses the real fluids circulating in the earth's crust, and justifies the need to examine the natural convection in a porous medium of a simple pure fluid with properties resembling those near the thermodynamic... more
The paper first discusses the real fluids circulating in the earth's crust, and justifies the need to examine the natural convection in a porous medium of a simple pure fluid with properties resembling those near the thermodynamic critical point. The literature on natural convection in a homogenous porous medium between isothermal horizontal plates, the lower one hotter, is then reviewed.
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Viscous fingering is a hydrodynamic instability that can be caused by a viscosity difference across a travelling thermal front. The equations governing the instability of radial flow through porous media are cast, and a linear... more
Viscous fingering is a hydrodynamic instability that can be caused by a viscosity difference across a travelling thermal front. The equations governing the instability of radial flow through porous media are cast, and a linear perturbation analysis was performed numerically. Transient growth of temperature perturbations show which wave number, and hence fingering displacement shape, will be most unstable. Results illustrate that there are two parameters that define the stability: the Péclet number and the log-mobility ratio (for homogeneous media). These critical parameters provide limits on reinjection temperature and flow rate for a given reservoir temperature that will cause thermal stability. In addition, the TOUGH2.2 numerical simulator was used to model fluid flow displacement patterns that occur during reinjection in geothermal reservoirs. Results show that a critical Péclet number and log-mobility ratio exist for the onset of viscous fingering. Moreover, in cases where the p...
Low enthalpy geothermal systems are widely spread in New Zealand although their exploration and utilization has been relatively limited. There are approximately 105 low-temperature geothermal systems in New Zealand. Approximately thirty... more
Low enthalpy geothermal systems are widely spread in New Zealand although their exploration and utilization has been relatively limited. There are approximately 105 low-temperature geothermal systems in New Zealand. Approximately thirty of them are found within the Waikato region, which is also host to most of the high-temperature systems in New Zealand. This study focuses on Ohinewai low-enthalpy geothermal system, which is located to the North West of the Waikato region in the central north island of New Zealand. A field survey was carried out in Ohinewai geothermal prospect to assess the field potential. Geothermal water samples were collected from self-discharging and pumped warm-water wells. The samples were analyzed for their geochemical signature. The geothermal waters have been classified with respect to their anion and cation contents. The Cl-SO 4 -HCO 3 ternary diagram classifies the geothermal water as dilute alkali chloride waters with relatively lower concentrations of ...
ABSTRACT The pressure derivative method is one of the most significant developments in the history of pressure transient analysis (PTA). PTA results that would otherwise be difficult to interpret can have a clear and characteristic... more
ABSTRACT The pressure derivative method is one of the most significant developments in the history of pressure transient analysis (PTA). PTA results that would otherwise be difficult to interpret can have a clear and characteristic pressure derivative. The application of this technique in groundwater, coalbed methane, mineral exploration and oil and gas wells has been widespread. However application to geothermal wells is still very limited. The usefulness of the pressure derivative method is demonstrated in this study. Despite the challenges of geothermal wells it remains a key diagnostic tool to determine the processes taking place during a test and therefore the models to apply during analysis. Three common issues which affect PTA in geothermal wells are: (1) downflows, (2) slow valve closing and (3) two-stage pump shut-down. Issue 1 involves downflows of fluid from a higher permeable zone to a deeper one of lower pressure. Issue 2 is the inevitable delay when manually opening or closing a valve to control the flow rate during a test. Issue 3 of two-stage pump shut-down occurs when using pumps for injection and not all pumps cease injection at the same time. Both Issues 2 and 3 effectively produce non-zero flow early in the PFO and can look similar. For each issue some real examples are given. The characteristic anomalies these issues produce in a derivative plot are presented. Some analyses and discussion are presented of the extent to which these issues affect the results obtained for permeability (k) and skin factor (s) by treating these as standard analyses.
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The Huntly coalfield has significant coal deposits that contain biogenically-sourced methane. The coals are subbituminous in rank and Eocene in age and have been previously characterised with relatively low to moderate measured gas (CH4)... more
The Huntly coalfield has significant coal deposits that contain biogenically-sourced methane. The coals are subbituminous in rank and Eocene in age and have been previously characterised with relatively low to moderate measured gas (CH4) contents (2–4 m3/ton). The CO2 holding capacity is relatively high (18.0 m3/ton) compared with that of CH4 (2.6 m3/ton) and N2 (0.7 m3/ton) at the same pressure (4 MPa; all as
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The Poihipi power station utilizes dry steam from a shallow zone near the margin of the Wairakei geothermal reservoir. The station has been in operation for several years, with daily variations in the fluid production rate following... more
The Poihipi power station utilizes dry steam from a shallow zone near the margin of the Wairakei geothermal reservoir. The station has been in operation for several years, with daily variations in the fluid production rate following variations in time-of-day pricing of electricity. The corresponding varying pressure history provides a good database for testing models of the geothermal reservoir.Three different
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ABSTRACT Since the development of the liquid dominated geothermal reservoir at Wairakei, New Zealand in 1950s, various separator designs have been utilised to enable the separation of steam and water from two-phase geothermal fluid. This... more
ABSTRACT Since the development of the liquid dominated geothermal reservoir at Wairakei, New Zealand in 1950s, various separator designs have been utilised to enable the separation of steam and water from two-phase geothermal fluid. This is to ensure that only dry and clean steam enters the turbine and generates electricity. Information from several existing geothermal fields shows that there are two common separator designs, the vertical cyclone separator and the horizontal separator. Both designs are reported to have high separation efficiency in the order of 99.9% or higher. The vertical cyclone separator is normally found at power stations with strong influence by the technology from New Zealand. The horizontal separator is normally found at power stations with strong influence by technology from Iceland, Japan, Russia and the US.
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Mines are heavy energy consumers and energy costs are significantly high for remote mines located far from the grid, due to considerable spending on fuel and fuel transportation. The mining industry is also increasingly aware of the need... more
Mines are heavy energy consumers and energy costs are significantly high for remote mines located far from the grid, due to considerable spending on fuel and fuel transportation. The mining industry is also increasingly aware of the need to shift towards cleaner energy sources in order to reduce its environmental impact. As a reliable source, capable of delivering very high availability factors, geothermal is an important, though often overlooked, energy option for the mining industry. For mines that are located in areas of high geothermal potential, geothermal energy can provide for parts of a mining operation's electrical power needs. Geothermal fluids are utilized in a variety of ways during the operational life cycle of a mine. In the production stage, hot fluids are used directly in applications such as raffinate heating in copper production and enhanced heap leaching for the extraction of gold and silver. Underground mines in areas of high geothermal potential must deal with higher ventilation loads; these can be partially provided for by in-situ geothermal power generation. Geothermal fluids can also provide energy for space heating, typically a substantial load for northern mines. In the closure and post-closure phases of a project, hot water irrigation can enhance reclamation rates, while an operating power plant that is turned over to the local community results in jobs creation, and can support community development through projects such as geothermal district heating. In addition, geothermal energy helps reduce a mine's environmental impact and Greenhouse Gas (GHG) emissions and improves its reputation within local communities, while "greening" its portfolio and contributing to sustainable development and the process of acquiring and retaining a social license to operate. The main factors affecting the successful integration of geothermal energy in a mining development are: the presence of a proven, accessible, and extractable resource; the relative price of alternate energy options; the distance from/to the grid; the potential for coproduction and/or minerals extraction; and the availability of communities and other industries in the vicinity of the mine. This paper outlines the synergies between mining and geothermal energy, and explores the ways in which geothermal energy can contribute to the development and operation of a mine.