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Collaborating Authors
Sahand University of Technology
Estimating Rock Mechanical Properties with Nondestructive Tests
Hamzaban, M. T. (Sahand University of Technology) | Jakobsen, P. D. (Norwegian University of Science and Technology) | Touranchehzadeh, A. (Sahand University of Technology)
Uniaxial compressive strength (UCS), modulus of elasticity (E), and Brazilian tensile strength (BTS) are some of the most common rock mechanical properties, which are used frequently in the geomechanical design of rock engineering projects. The accurate measurement of these properties needs a precise sample preparation process and well-controlled loading conditions. Moreover, in some geomechanical projects, especially in petroleum engineering, access to proper rock samples is very difficult. Generally, there is not any tendency to perform destructive rock mechanical tests on the samples, which have been obtained from exploratory oil wells. Therefore, the estimation of intact rock mechanical properties from non-destructive tests is a common procedure in rock engineering. In this study, the correlation between rock mechanical properties (UCS, E, and BTS) and the nondestructive parameters of density, P-wave velocity (Vp), and Schmidt hammer rebound number (N) has been investigated. The experimental investigations included testing on six different rock types. Different linear models were developed based on ฯ, Vp, and N values to predict the mechanical properties. The results showed that a linear combination of Vp and N values provides acceptable accuracy for estimating the mechanical properties of intact rock samples.
- North America > United States (1.00)
- Asia > Middle East > Turkey (0.28)
Seismic response of soft water-bottom sediments
Yilmaz, Oz (Anatolian Geophysical) | Mavko, Gerald M. (Stanford University) | Jodeiri, Hossein (Sahand University of Technology)
ABSTRACT The Municipal Government of Istanbul plans to construct a second subsea tunnel across the Bosphorus Waterway between the European and Asian sectors of the city, and a submerged tube tunnel across the Golden Horn Waterway. High-resolution 2-D sparker seismic surveys with the source bandwidth up to 1,600ย Hz were conducted to delineate geometry of the sub-bottom sedimentary sequence and geometry of the sediment-bedrock interface, and to determine the locations and depths of the geotechnical boreholes. In this paper, we discuss aspects of the seismic response of water-bottom sediments. Unlike the usual behavior of water-bottom multiples with alternating polarity observed in the Bosphorus case, we find that the polarity of the water-bottom primary and first-order water-bottom multiples are the same in the Golden Horn case. The polarity behavior of the water-bottom multiples in the Golden Horn is a convincing evidence of the low-velocity sub-bottom sediments that can be described as a gas-charged suspension โ a composition that consists of particles suspended in water with only slight grain-to-grain contact and biogenic gas. The results of the velocity analysis of the Golden Horn seismic data confirm the presence of a low-velocity (550โ650ย m/s) soft water-bottom sediments with an average thickness of 18 m above the bedrock. This makes it imperative to design the foundation pillars for the submerged tube-tunnel with sufficient penetration deep into the bedrock. Presentation Date: Tuesday, October 16, 2018 Start Time: 8:30:00 AM Location: 207A (Anaheim Convention Center) Presentation Type: Oral
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.73)
Abstract This paper presents an investigation on the effect of foaming agents perpropeties in tetms of surfactant concentration, interfacial tension (IFT) and foam strength during foam flooding in porous media in the absence of oleic phase. The experiments consisted of the co-injection of gas and various surfactant solutions with three different formulation properties in terms of IFT reduction and foaming strength capability into Bentheimer sandstone samples initially saturated with the surfactant solution. Experiments were performed using Bentheimer sandstone cores during, where X-ray CT images were taken during foam generation to find out the stability of advancing front of foam propagation and to map the gas saturation for both the transient and steady-state flow regimes. Then, a series of numerical simulation was conducted to investigate the effect of surfactant concentration on pressure drop across the core for the foam flooding in the absence of oil. The foam model implemented is based on a local equilibrium and describes dependency of foam mobility reduction factor using several independent functions, such as liquid saturation, foam velocity, oil saturation and capillary number. To this end, the dry-out and gas velocity functions in the foam model were determined from the experimental data obtained at low and high-quality regimes of foam flow at a constant injection velocity. Next, pressure drop profiles of foam flooding at two different surfactant concentrations were modelled to determine the parameters of the surfactant-dependent function in the foam model. The simulation results fit the experimental data of pressure drops very well.
- North America > United States (0.46)
- Europe (0.28)
Integrated Method for Numerical Simulation of Foam Flooding in Porous Media in the Absence and Presence of Oil
Hosseini-Nasab, S. M. (Amirkabir University of Technology) | Douarche, F.. (IFP Energies Nouvelles) | Nabzar, L.. (IFP Energies Nouvelles) | Simjoo, M.. (Sahand University of Technology) | Bourbiaux, B.. (IFP Energies Nouvelles) | Roggero, F.. (IFP Energies Nouvelles)
Abstract This paper presents an novel integrated approach for numerical simulation of foam core-flood experiments in the absence and presence of oil. The experiments consisted of the co-injection of gas and Alpha-Olefin Sulfonate (AOS) surfactant solution into Bentheimer sandstone samples initially saturated with the surfactant solution [see (Simjoo & Zitha, 2013)]. The foam model implemented is based on a local equilibrium and describes dependency of foam mobility reduction factor using several independent functions, such as liquid saturation, foam velocity, oil saturation and capillary number. First, a series of numerical simulation was conducted to investigate the effect of surfactant concentration on pressure drop across the core for the foam flooding in the absence of oil. To this end, the dry-out and gas velocity functions in the foam model were determined from the experimental data obtained at low and high-quality regimes of foam flow at a constant injection velocity. Next, pressure drop profiles of foam flooding at two different surfactant concentrations were modelled to determine the parameters of the surfactant-dependent function in the foam model. The simulation results fit the experimental data of pressure drops very well. Then, the numerical simulations investigated the oil displacement, by foam where the main goal was to determine the foam model parameters dedicated to the oil saturation-dependent function. The pressure drop across the core, oil-cut, and oil recovery factor were modelled, and an excellent match was obtained between the pressure profile and the oil recovery obtained numerically compared with those obtained from the corresponding core-flood experiments.
Experimental Investigation of the Effects of Slotted Cone-Shaped Piers on Scour Reduction Due to Steady Flows
Mehrzad, Razieh (Sahand University of Technology) | Hakimzadeh, Habib (Sahand University of Technology)
Abstract Local scouring at bridge piers can be regarded as one of the main reasons for bridge collapses at river crossings. Bridge failure can cause severe damages and can result in serious injury or death. Hence, the investigation of the control of scouring at bridge piers plays an important role in bridge design. The main aim of this study was to evaluate the effectiveness of the slotted conical-shaped piers in reducing local scour when compared with a circular-shaped pier. Two sets of experimental tests were carried out under clear water conditions for the duration of eight hours and with relatively uniform sediments. For the first set, the model piers with different lateral slopes were tested, and the experimental results showed that the maximum scour depth was mainly reduced by a decrease in the lateral slope of the model piers. With the mildest lateral slope angle of 78.69ยฐ the maximum scour depth was reduced by as much as 32%. In addition, the combination of the slotted and conical shape could further reduce the maximum scour depth by up to 55%. Thus, the experimental results showed that the combination of the slotted and conical shape can be regarded as a very effective countermeasure tool against local scouring at bridge piers. Introduction There are many reports about the failure of bridges around the world due to the scouring process. These reports clearly show the motivation of this study of scouring and any possibility of scour reduction. The used methods of controlling the scour around bridge piers can be divided into two categories including direct and indirect methods. The first methods may be achieved by the increase in the streambed resistance. This is usually done by placing a riprap layer around the bridge piers (Worman, 1989; Yoon et al., 1995; Chiew, 2008). Indirect methods, however, can be achieved by changing the flow pattern around the piers. These methods may be done, for instance, by the use of a collar around the pier or alternatively by the use of a slot within the pier. Another method in the second category is to use a section of variable depth. Application of Cone-Shaped Structure with Respect to Side Slope Sumer et al. (1994) measured the bed shear stress for a cone-shaped structure to observe the influence of the side slope on the shear stress amplification. They found that the overall effect of the side slope in front of the cone-shaped structure was the reduction of the bed shear stress. Sumer and Fredsoe (1997) measured scour around a cone-shaped structure in a follow-up study. The results revealed that the scour mainly decreases through the reduction of the side slope. The scour-reduction efficiency of conical piers has already been established by Sumer and Fredsoe (2002) and confirmed numerically by Besharati and Hakimzadeh (2008). However, the projected area (the blockage ratio) of the conical piers was reduced when compared with that of the cylindrical piers. This reduction was due to the decrease in the lateral slopes in the structures at both the experimental and numerical model piers.
- Research Report > New Finding (1.00)
- Research Report > Experimental Study (0.88)
Wavelet Estimation and Seismic Deconvolution using Seprable Nonlinear Least Squares
Gharibi, Mojtaba (Sahand University of Technology) | Shadmanaman, Navid (Sahand University of Technology) | Kazemi, Kazem (Pars Petro Zagros) | Mirzakhanian, Marzieh (NIOC Exploration Directorate)
Summary Deconvolution is one of the main steps in seismic data processing. It compresses the wavelet in order to improving resolution. Wiener deconvolution is one of the famous deconvolution method that uses the early part of autocorrelation of seismic trace as a representation of seismic wavelet. The smoothed amplitude spectrum of seismic data assumed to be the amplitude spectrum of seismic wavelet. Each trace can be assumed to be a linear combination of a number of Ricker wavelet with different peak frequency, center time and phase (Liu and marfurt, 2007), therefore its amplitude spectrum is a function of or depends on significant Ricker wavelets. The result of deconvolution greatly depends on the wavelet estimation. Here, we aim to introduce an alternative way for wavelet estimation based on fitting Ricker wavelet spectra on the seismic spectrum. Separable nonlinear least square (SNLS) method is applied to optimum determination of peak frequencies of main Ricker wavelets in order to fit seismic spectrum. Results of our synthetic and real tests indicate that proposed method have significant improvements on deconvolution outputs, comparing with Wiener deconvolution. Introduction The main goal of seismic deconvolution is to improve temporal resolution of seismic images by compressing seismic wavelet. Mathematically, seismic trace, x(t), is defined as convolution of the seismic wavelet, w(t), with the earthโs imp ulse resp onse, e(t), with addition of the random ambient noise caused during the data acquisition (Yilmaz, 2001). ??(??) = ?? (??) * ??(??) + ??(??). (1) The earthโs imp ulse resp onse, e(t), is what we exp ect from earth responding to an impulse seismic source. Thus, e(t) involves primary reflectivity series and all possible multiples. Usually, seismic wavelet is not known, thus we try to estimate it from the recorded seismogram using statistical methods. Almost all deconvolution methods require some assumptions including random reflectivity and minimum phase wavelet. The seismic deconvolution can be done by designing deconvolution operator or inverse filter of seismic wavelet. Convolution of the inverse filter with the recorded seismogram y ields the earthโs imp ulse resp onse. Seismic deconvolution is most widely done using Wiener deconvolution method in which the optimum Wiener filter convert the seismic wavelet into any desired shape, usually into a spike (Robinson and Trietel, 1967). Wiener deconvolution uses the early part of autocorrelation of seismic trace as a representation of seismic wavelet and then try to achieve its inverse in the standard least square sense using Levinson recursion algorithm. The result of seismic deconvolution intensively depends on properly estimation of seismic wavelet.
- Information Technology > Data Science (0.49)
- Information Technology > Artificial Intelligence (0.47)
Effect of Oil Gravity and Pore Volume Injected (PVI) of Steam to PVI of Foam During Enhanced Oil Recovery by Steam-CO2-Foam Flooding
Daraei, H. Nejatian (Sahand University of Technology, National Iranian South Oil Company (NISOC)) | Sahraei, E.. (Sahand University of Technology) | Solouk, A.. (Sahand University of Technology)
Abstract In spite of CO2mobility reduction during CO2and surfactant solution co-injection, CO2-foam flooding in heavy oil reservoirs has relatively poor sweep efficiency due to the high viscosity the oil. Therefore, reducing the oil viscosity is necessary to improve CO2-foam sweep efficiency. For this reason, steam is injected initially during steam-CO2-foam flooding to reduce oil viscosity. Displacement process is followed using CO2and surfactant solution co-injection. In our previous experimental study, in order to highlight the potential of steam-CO2-foam flooding, three different oil recovery experiments were conducted using medium heavy crude oil (19 ยฐAPI), including CO2-foam flooding after water flooding, CO2-foam flooding and steam-CO2-foam flooding. The results showed that steam-CO2-foam flooding increases oil recovery dramatically by simultaneous mechanisms such as oil viscosity reduction by steam, CO2dissolution in oil and emulsification by steam and surfactant. Furthermore, the effect of high surfactant concentration slug injection on steam-CO2-foam flooding performance was investigated. The results showed that slug causes the formation of viscous micro emulsions in front of CO2-foam flood and improves CO2-foam sweep efficiency. In this paper, the effects of oil gravity and pore volume injected (PVI) of steam to PVI of foam on the oil recovery during steam-CO2-foam flooding have been studied. The experiments are conducted using heavy oil (12 ยฐAPI) and sand pack models under reservoir conditions of 1550 psi and 131ยฐF. In order to investigate the effect of PVI of steam/PVI of foam ratio on the oil recovery, three different oil recovery scenarios have been conducted using heavy crude oil, including CO2-foam flooding only, steam-CO2-foam flooding including 0.14 PVI of steam/PVI of foam ratio and steam-CO2-foam flooding including 0.34 PVI of steam/PVI of foam ratio. The results show that in spite of decreasing oil recovery by decreasing API gravity of the oil during steam-CO2-foam flooding, increasing PVI of steam improves oil recovery. The steam-CO2-foam flooding process has the following benefits. (1) Combination of steam injection and CO2-foam flooding as a novel enhanced oil recovery (EOR) method to achieve favorable oil recovery. (2) The applicability of this EOR method in heavy and medium heavy oil reservoirs.
- North America > United States > Texas (0.47)
- North America > United States > Oklahoma (0.47)
A New Chemical Enhanced Oil Recovery Method?
Hosseini-Nasab, S.M.. M. (Delft University of Technology) | Zitha, P.L.J.. L.J. (Delft University of Technology) | Mirhaj, S.A.. A. (Aker Solution) | Simjoo, M.. (Sahand University of Technology)
Abstract Alkali-Surfactant-Polymer (ASP) is one of the most attractive chemical EOR methods. In properly designed ASP formulations, the alkali-surfactant provides ultralow interfacial tension (IFT) between drive aqueous fluid and the displaced oil whereas polymer ensures a good mobility control. Nevertheless, the efficiency of ASP can be much less than expected under various reservoir conditions including low permeability, high temperature, high formation brine salinity, presence of divalent cations (Ca+2, Mg+2) in the formation brine. This is due to polymer degradation or precipitation, low injectivity, scaling in well and surface equipment. This paper reports an experimental study of new a chemical EOR which has the potentially to overcome above drawbacks. The chemical formulation consists of the combination of no-polymeric viscosity enhancement compound and a blend of two surfactants. The performance of this chemical formulation was evaluated by a series of core-flood tests on Bentheimer sandstone cores, under stable gravity conditions, with the aid of X-ray Computed Tomography. A significant reduction of the residual oil saturation was observed by constructing the capillary desaturation curves (CDC) suggesting that proposed formulation is potentially a rather good chemical EOR agent.
- North America (0.68)
- Asia > Middle East > Iran (0.28)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.68)
- South America > Suriname > North Atlantic Ocean > Guyana-Suriname Basin > Tambaredjo Field (0.99)
- South America > Guyana > North Atlantic Ocean > Guyana-Suriname Basin > Tambaredjo Field (0.99)
- Europe > Austria > Vienna Basin > Matzen Field (0.99)
Oil Relative Permeability During Enhanced Oil Recovery by Foam Flooding
Heins, R.. (Sahand University of Technology) | Simjoo, M.. (Sahand University of Technology) | Zitha, P. L. (Delft University of Technology) | Rossen, W. R. (Delft University of Technology)
Abstract A previous study (Simjoo and Zitha, 2013) reports enhanced oil recovery by foam injection in corefloods: that is, reduction in oil saturation in the core below waterflood residual. This reduction is achieved by foam in a process with reduced oil-water interfacial tension and increased pressure gradient. Those results, combined with bubble-column experiments, suggest that a new mechanism of oil recovery is involved in these floods: emulsification of oil into the Plateau borders between the bubbles of the foam and transport of oil along with the foam bubbles. Using these data we compute the oil relative permeability during this process of enhanced oil recovery. There is an initial oil bank with oil relative permeability of order 0.1. Thereafter, during the period of highest capillary number and oil production attributed to emulsified oil droplets, oil relative permeability is between 0.001 and 0.0001: far less than with surfactant flooding, for instance, at similar capillary number. Over time in these experiments, the final oil saturation is greater than, but is slowly approaching, that expected at the large capillary number of the experiment. Since in the proposed mechanism emulsified oil must travel with the foam, which has extremely large effective viscosity, but oil relative permeability is computed based on the much-smaller oil viscosity, the low oil relative permeability can be seen to be result of strongly adverse viscous coupling between the phases. Efficient oil recovery by the mechanism of emulsified oil droplets would require a large volume fraction of oil within the foam, a less-viscous foam, and/or a more-viscous oil. Other studies of foam displacing oil briefly examined here reflect a larger oil relative permeability during foam displacement, in large part because of a smaller contrast between foam and oil viscosity, or even a foam effective viscosity less than that of the oil it displaces.
- North America > United States > California (0.46)
- North America > Canada > Alberta (0.46)
- North America > United States > Texas (0.28)
- Asia > Middle East > Iran (0.28)
- North America > United States > California > San Joaquin Basin > Midway-Sunset Field > Webster Formation (0.99)
- North America > United States > California > San Joaquin Basin > Midway-Sunset Field > Monterey Formation (0.99)
- Europe > Norway > North Sea > Northern North Sea > East Shetland Basin > PL 375 > Block 34/7 > Snorre Field > Statfjord Group (0.99)
- (11 more...)
Simulation of Wave Propagation over a Submerged Breakwater on a Sloped Bed by SPH Method
Mahmoudi, Amin (Sahand University of Technology) | Hakimzadeh, Habib (Sahand University of Technology) | Ketabdari, Mohammad Javad (University of Technology, Tehran,)
In this paper a space-averaged Navier-Stokes approach has been deployed to simulate wave propagation over a submerged breakwater. The developed model is based on the smoothed particle hydrodynamic (SPH) method, which is a pure Lagrangian approach and can handle large deformations of the free surface with high accuracy. For this study, the large eddy simulation (LES) model was chosen as the turbulence model to couple with the weakly compressible version of the smoothed particle hydrodynamics (WCSPH) method to simulate the wave propagation over a submerged breakwater on a sloped bed. The results of numerical simulations were compared with experimental results and a good agreement was achieved. Finally, it is shown that the WCSPH method provides a useful tool to investigate the wave transmission and performance of the submerged breakwaters.
- Europe (0.94)
- Asia > Middle East > Iran (0.28)