Permeable Sand Research Articles

Research on the Deposition Mechanisms and Production Characteristics of Untabulated Reservoirs in the X Oilfield of the Songliao Basin

In the late stage of the ultra-high water cut development, the untabulated reservoir (not included in the submitted reserve sheet) is considered an important part of production sustainability in the X oilfield. According to the coring well data of 5 wells in the eastern district, the untabulated reservoir is associated with higher heterogeneity. Specifically, it develops not only the conventional low and ultra-low permeability sands but also medium-high permeability sands with thickness below 0.2 m. Given this, the research investigates the sedimentary models, spatial distribution, and heterogeneity of the different types of untabulated sand bodies, based on the core analysis. Moreover, the physical model water flooding experiments are carried out and the production characteristics of the different sand bodies in the untabulated reservoir with the different recovery approaches are clarified. The findings of this research effectively solve the development contradictions of the untabulated reservoir and lay down the foundation for the further potential tapping of the untabulated reservoir.

The effect of liquefaction on mineral breakage physical in the Palu City, Central Sulawesi Province, Indonesia

The Central Sulawesi province had a 7.4 magnitude earthquake in 2018, which was followed by liquefaction in Palu City, Donggala Regency, Sigi Regency, and Parigi Moutong Regency. The boulder sediments, sand, silt, and clay make up the liquefaction material. The extent of mineral damage, mineral surface area, porosity, and sand permeability were all evaluated in this study. By digging a 1 x 1 x 2 m trench at 27 sites, a vertical sampling of liquefaction material was done in both liquefaction-affected and unaffected areas. Smear slides for petrographic investigation were created after the separation of grain sizes. Quartz, biotite, orthoclase, hornblende, plagioclase, and opaque minerals were among the minerals found. Mineral area values in the liquefaction area are lower than in the unaffected area. The Petobo liquefaction area has the highest value of mineral damage, followed by Balaroa, while Sibalaya has the lowest value. In the liquefaction area, where quartz and opaque minerals are less damaged than other minerals, the percentage of mineral damage exceeds 40%. A factor in the deterioration in the carrying capacity of residential land is liquefaction, which causes significant mineral damage but little change in the value of the mineral area. It is suggested that the Petobo and Balaroa areas be designated as green spaces and water catchment areas, while the Sibalaya area can be repurposed as a set of regulated and constrained residential communities.

Experimental Study on the Permeability of Microbial-Solidified Calcareous Sand Based on MICP

In the construction of artificial islands in distant seas, calcareous sand has been widely used as a foundation filler due to its excellent mechanical properties and extensive availability in the marine environment. How to store more fresh water on the artificial islands by reducing its permeability is currently a great challenge. Microbial-induced carbonate precipitation (MICP) has always been considered as a great potential method to improve the cemented properties of calcareous sand, but the effect of grain gradation on the permeability of MICP-improved calcareous sand remains unclear. In this research, a self-made device was developed to conduct MICP grouting and permeability tests, where the permeability coefficient (k) under different grain gradations (curvature coefficient (Cc) and uniformity coefficient (Cu)) was measured. A CT scan was conducted to investigate the variation in the porosity (n) of sand samples before and after MICP treatment. The weighting method was adopted to measure the content of induced calcium carbonate (M). A scanning electron microscopy (SEM) technique was used to further study the micromechanism of the MICP treatment. Finally, the correlations between the k of MICP-treated sand and Cu, as well as Cc, were semiquantitively analyzed. The results show that the magnitude of M, k and n changes are closely related to Cc and Cu. The reduction amount of k and n increased with the rise in Cc and Cu, and the increased amount of M increased with the rise in Cc and Cu. The SEM results show that the particle surface became rough due to the coating effect of CaCO3 crystals, and the pore spaces were reduced because of the partially filling effect of the crystals, which was responsible for the decrease in permeability and porosity. Furthermore, k fitted well with Cu and Cc, respectively, and the fitting curve reveals that larger Cu (Cu ≥ 6.0) and smaller Cc (2.0 > Cc > 0.5) were more suitable for MICP treatments and lead to a large reduction in permeability. The above results indicate that the grain gradation of calcareous sand had a significant influence on its permeability improved by MICP.

DEVELOPMENT OF OPTIMAL COMPOSITION OF DRILLING FLUID FILLER FOR OPEN HOLE WELL COMPLETION

Experimental studies were carried out to determine the effect of inert fillers on the filtration properties of clay cakes during their formation. The sequence of experiments corresponds to the sequence of stages: formation of the main structure of the filter cake (simulation of the opening process by drilling), treatment of the bottomhole zone to restore the initial permeability (for example, during chemical destruction of the filter cakes) and washing out of process fluid filtrates from the bottomhole zone into the well. The solid phase in the drilling fluid can be represented by both structure-forming clay particles and fillers (barite, crushed cuttings, bridging agents, etc.). Moreover, fillers can have individual particles of a size of a colloidal degree of dispersion and significantly affect the filtration performance of drilling suspensions. It is especially important to evaluate the influence of the composition of the solid phase of the clay suspension on the filtration properties at the stage of formation of the main structure of the filter cake. This stage is characterized by a non-stationary filtration process. In essence, the bulk of the studies of filtration processes is carried out in this mode. In our case, it is necessary to determine the dependence of the filtration index of solutions Пр on the composition of the solid phase. In the course of experimental studies, it was confirmed that subsequent filtration through the cakes formed at stage 1 equally depends on the magnitude and nature of the drawdown application, as in stage 1, as well as on the permeability of the filter cake and the clogging zone. Therefore, the research methodology at stage 2 required supplementing experiments with the formation and modification of filter cakes during filtration through permeable sand packs.

Verification of bounding surface plasticity model with reversal surfaces for the analysis of liquefaction problems

This paper presents the verification of a new bounding surface plasticity model with reversal surfaces when used in boundary value problems related to liquefaction. The model is implemented in a commercial finite-difference code using an explicit stress integration algorithm. After validating the model against element tests on Nevada sand, the paper employs the same set of values of model parameters for ascertaining the model's simulative potential at the system level, via comparisons with data from 8 dynamic centrifuge tests performed on the same sand. These pertain to: a) the free-field response of a horizontal liquefiable layer, b) the lateral spreading response of a gently sloping liquefiable layer and c) the seismic response of rigid foundations on a single-layered and two-layered horizontal liquefiable ground profiles. Parametric analyses emphasize the effects of non-constant sand permeability coefficient and excitation intensity on the liquefied system response. Similar analyses highlight the importance of post-liquefaction strain accumulation and the avoidance of stress-strain overshooting, both constitutive attributes of the new model.

Accounting for Modeling Errors in Linear Inversion of Crosshole Ground‐Penetrating Radar Amplitude Data: Detecting Sand in Clayey Till

AbstractMapping high permeability sand occurrences in clayey till is fundamental for protecting the underlying drinking water resources. Crosshole ground penetrating radar (GPR) amplitude data have the potential to differentiate between sand and clay, and can provide 2D subsurface models with a decimeter‐scale resolution. We develop a probabilistic straight‐ray‐based inversion scheme, where we account for the forward modeling error arising from choosing a straight‐ray forward solver. The forward modeling error is described by a Gaussian probability distribution and included in the total noise model by addition of covariance models. Due to the linear formulation, we are able to decouple the inversion of traveltime and amplitude data and obtain results fast. We evaluate the approach through a synthetic study, where synthetic traveltime and amplitude data are inverted to obtain slowness and attenuation tomograms using several noise model scenarios. We find that accounting for the forward modeling error is fundamental to successfully obtain tomograms without artifacts. This is especially the case for inversion of amplitude data since the structure of the noise model for the forward modeling error is significantly different from the other data error models. Overall, inversion of field data confirms the results from the synthetic study; however, amplitude inversion performs slightly better than traveltime inversion. We are able to characterize a 0.4–0.6 m thick sand layer as well as internal variations in the clayey till matching observed geological information from borehole logs and excavation.

Effect of warp and weft uniaxial tension on the permeability of sand covered with geotextile

The permeability of sand covered with geotextile is affected by the permeability of geotextile, which is related to the tensile state of the geotextile. Considering the weaving mode of geotextile, the effects of warp tension and weft tension on the permeability of sand covered with geotextile were studied by experiment. Four different specifications of geotextiles were selected for warp and weft tension respectively. The changes of permeability parameters of sand covered with geotextile under non tension, warp and weft tension were measured by vertical permeability instrument, and the effects of warp and weft tension on permeability parameters such as seepage velocity, sand loss and gradient ratio were analyzed. The test results show that the water permeability and anti silting performance of the geotextile increase with the increase of tensile strain, and the soil conservation performance decreases with the tensile strain increasing. Meanwhile, the relationship between permeability and warp tensile strain is not monotonic. When the warp tensile strain 3%, the water permeability and anti silting performance of geotextile are the weakest, and the soil conservation performance is the strongest.

Improved interpretation of groundwater-surface water interactions along a stream reach using 3D high-resolution combined DC resistivity and induced polarization (DC-IP) geoelectrical imaging

Common approaches for characterizing streambed architecture, and its influence on groundwater-surface water (GW-SW) exchanges, are generally limited by their invasiveness and low spatial sampling density, which is a particular issue in streambeds that typically have high spatial heterogeneity. Combined DC resistivity and induced polarization (DC-IP) imaging can provide rapid, non-invasive and continuous information on streambed lithology; however, its full potential remains unrealized, leading to its underutilization for streambed investigations. The objective of this study is to demonstrate the value of DC-IP imaging, in both 3D and high-resolution, for characterizing streambed architecture and interpretating GW-SW exchange patterns. The study focused on a 50 m long stream reach located in Kintore, Ontario, Canada. Traditional methods – streambed temperature mapping, vertical head gradient measurements, streambed porewater quality, and sediment cores – were used to qualitatively identify spatial GW-SW exchanges. Underwater 3D DC-IP surveying was then conducted across the stream reach to obtain high-resolution distributions of resistivity and chargeability. Resistivity first identified three distinct zones along the stream reach: Zone 1 (0–12 m) and Zone 3 (38–50 m) exhibits high resistivity (>100 ohm-m), while Zone 2 (12–38 m) exhibits relatively low resistivity (<40 ohm-m). Chargeability highly complements resistivity by confirming that the shallow streambed contains only non-clayey materials; therefore, the more resistive Zones 1 and 3 is attributed to more permeable coarse sand and gravel, while the more conductive Zone 2 is attributed to less permeable finer sand, and consequently, increased porewater EC due to longer residence times and hyporheic exchanges. This geoelectrical interpretation is well-supported by information from traditional methods (e.g., higher temperature and hydraulic gradients correspond to the more permeable Zone 1 and Zone 3). This study demonstrates the unrealized value of spatially continuous, high-resolution DC-IP information for mapping streambed architecture and its control on GW-SW exchange patterns.

Experimental Study on Phenol-Formaldehyde Resin Aggregates as In-Depth Conformance Control Agents Stabilized by Polymer.

To improve the dispersion stability of phenol-formaldehyde resin (PFR) particles in simulated oilfield injection water and their propagation ability in petroleum reservoir, a hydrophobically associating polymer (HAP) was employed as a stabilizer in this paper. The dispersion stability of PFR in the injection water was studied by measuring turbidity as a function of time. In addition, the migration property of the PFR/HAP dispersion was evaluated by both cellulose membrane filtration and sand packs-flooding experiments. The results show that HAP can stabilize the PFR dispersion prepared with the simulated injection water by forming PFR/HAP complex molecular aggregates. These aggregates can migrate in sand packs with strong flow resistance due to deformation or disaggregation of the aggregates when passing through the pore throat. Oil recovery was improved by up to 21.1% on the basis of water flooding, and the higher the concentration of PFR/HAP dispersion system, the better the oil recovery effect. Moreover, the cycle of log-jamming/dispersion of the aggregates leads to their penetrations through the bigger pores in the sand packs with a higher flow resistance than water. This process can improve the conformance of water in high permeability sand packs on a micro/macro scale and thus divert more water into low permeability sand packs. Therefore, more oil could be recovered from the low permeability sand packs. Moreover, the bigger the sand pack’s permeability ratio, the lower the oil recovery rate by waterflood, and the more the incremental oil can be recovered by the PFR/HAP flood.

Investigation on Different Compositions of Clay and Water to the Permeability of the Silica Sand Used in Greensand Casting Mould

Greensand casting is a casting process that uses mixture of silica sand with addition of control additions which are bentonite clay and the presence of water. Control additions influence the mechanical properties of greensand casting mould, for this study focuses on the permeability. Bentonite clay acts as a binder and activated by water to develop strength and plasticity thus the greensand casting mould can be formed. Permeability is ability of gas to pass through the moulding mixture aggregates in order to reduce the defects due to trapped gasses in mould cavity such as blow holes or pin holes. The objective of this study is to investigate the effect of control addition (water and clay) on the permeability number of silica sand sample (tailing sand) from former tin mine site in Tronoh, Perak. Experiments are conducted according to American Foundrymen Society (AFS) standard of procedures. Sand sample is sieved using mechanical sieve shaker to size of 425 µm. Cylindrical test pieces dimensioning of Ø50 mm×50 mm in height from various mixtures of sand-clay–water ratios are compacted by applying three ramming blows of 6666 grams using Ridsdale-Dietert metric standard rammer. The test pieces are tested for permeability with Ridsdale-Dietert permeability meter. The results show that clay and water have affected the permeability of silica sand sample and when more water and clay added, into the moulding mixture, the permeability is found decreased. The appropriate allowable water and clay content are crucial for permeability number of greensand casting mould.

Oil Recovery by Low-Rate Waterflooding in Low-Permeability Water-Wet Sandstone Cores

Summary Smart water or low-salinity (LS) water injection are environmentally friendly methods for efficient hydrocarbon recovery. Wettability alteration toward more water-wet conditions and increased spontaneous imbibition (SI) of water are responsible for enhanced oil production. Wettability alteration and SI to expel oil from the low-permeability matrix are time-dependent processes and both injection rate and oil viscosity are important factors affecting the contribution of capillary and viscous forces to oil production. Low flooding rate must be applied in laboratory corefloods to allow for SI and improved sweep to take place. Residual oil saturation by waterflooding and SI has previously been determined in low-permeability limestone and in higher permeability sands under various flooding rates, wetting conditions, and initial oil saturations. In this study, the effect of flooding rate on oil displacement from low-permeability, water-wet Bandera Brown outcrop sandstone cores has been examined. Viscous forces have been varied by injection at two different rates in addition to SI experiments and using mineral oils with different oil viscosities. The results showed small differences in oil recovery by SI and viscous flooding at high and low rates, indicating that capillary forces contribute significantly to the oil mobilization and production process from this low-permeability, water-wet rock. By varying the oil viscosity, the results indicated that capillary forces were especially important for oil displacement at higher oil viscosity as the ultimate oil recovered by low-rate injection was higher than that from the high-rate injection. Capillary number calculations indicated that viscous forces should be dominant in the recovery tests; however, the experiments showed that capillary forces were important for efficient oil displacement from the low-permeability, water-wet cores used in this study. There was no direct link observed between generated pressure drops at high and low injection rates, including SI, and the ultimate oil recovery. Thus, to simulate oil production in the middle of the reservoir, it was concluded that low-rate waterflooding is needed in laboratory tests to allow SI into the matrix to displace oil by positive capillary forces. The combination of using oils that differ in viscosity at different injection rates could add some additional information to the literature on how to increase the efficiency of waterflooding with a low injection rate.

Dynamic interaction of coral sand-pile-superstructure during earthquakes: 3D numerical simulations

The seismic safety of piles and superstructures in coral sand deserves attention. To explore the particular dynamic interaction of the coral sand–pile-superstructure during earthquakes, fully nonlinear, 3 D numerical models were established using the Fast Lagrangian Analysis of Continuum (FLAC3D). Hysteresis damping was adopted to indicate the particular stress–strain relationship and shear modulus attenuation of coral sand. The results show that increasing the pile diameter reduces the superstructure settlement but amplifies the bending moment of the piles and superstructures. Specifically, when the pile radius increases from 0.05 m to 0.25 m, the superstructure settlement is reduced by 30.0%, while the moments of the piles and superstructures are increased by an average of 993.9% and 29.5%, respectively. Although the excess pore pressure ratio decreases when the coral sand permeability increases, the pile bending moment increases with an increase in permeability. Effectively balancing the superstructure settlement, pile bending moment and coral sand liquefaction should be considered in the earthquake resistance of coral sand.

Optimal design of the field hydrate production test in the offshore India: Insights from the vertically heterogeneous hydrate reservoir model

Recently, the hydrate-bearing sand reservoirs were founded with high saturation in the offshore India by the National Gas Hydrate Program Expedition 02 (NGHP-02). Based on the detailed geological data at the NGHP-02-16 site, a more realistic reservoir model is constructed to analyze the unique multiphase flow and hydrate phase change behaviors from the geologically descriptive hydrate reservoirs. The main goals of this work are to optimize the adjustable production parameters and to predict the long-term gas production performance for guiding the upcoming field hydrate production test in India. The results indicate that gas production rates increase, but water production rates decrease slowly with time from the heterogeneous hydrate-reservoir. This is completely different from the previous prediction of multiphase flow behavior based on homogeneous hydrate-reservoir models. A non-uniform hydrate dissociation front is formed in the hydrate-reservoir due to the reservoir heterogeneity promote the horizontal dissociation of solid-hydrate within the high permeability sand layers. The maximum distance of free gas zone expands to outside more than 500 m from the production well. This indicates that the field fault system should be carefully concerned during the long-term production. Sensitivity analysis results suggest that the complete perforation in the hydrate-bearing layer and the underlying water saturated layer is beneficial for improving the hydrate production performance. Over the 5 years depressurization, a total of 2.08 × 107 ST m3 methane gas can be produced using the recommended well placement. The average gas-to-water ratio and energy ratio reach 10.22 ST m3 CH4/m3 H2O and 30.14, respectively, showing a high gas production potential from this hydrate site.

Application of waste eggshell as a source of calcium in bacterial bio-cementation to enhance the engineering characteristics of sand.

A technique to produce bio-cementation in sandy soil using the microbially induced calcium carbonate precipitation (MICP) process and calcium ions generated from eggshell is presented in this research. This research also focused on the application of S. pasteurii bacteria and L. fusiformis bacteria along with eggshell and calcium chloride cementing chemicals on the strength properties of sand. The experimental variables maintained in this research are bacteria type (S. pasteurii and L. fusiformis), cementing chemical type (eggshell and calcium chloride) and molarity of the cementing chemical (0.25, 0.50, 0.75 and 1.0). The engineering behaviour of bacteria treated sand was estimated by executing the unconfined compression test and permeability test in the laboratory. From the experimental findings, it is identified that the unconfined compressive strength of sand is enhanced and the value is in the range of 650kPa. In addition to that, the permeability of sand is minimized in the order of two from 6.3 × E-3 to 3.2 × E-5cm/s. The best improvement of Young's modulus and calcium carbonate content estimated in this research are 28.9MPa and 17.9% when the sand is treated with S. pasteurii along 0.50 molarity of eggshell cementing chemical. The experimental findings are validated with the help of microstructural studies of scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). This research showed that bio-cementation technology in the form of S. pasteurii and eggshell can be effectively adopted to enhance the engineering characteristics of sand.

Numerical modeling of viscous slurry infiltration in sand

Current numerical methods for describing slurry infiltration fail to take into account the viscous effect of slurry. This paper develops a one-dimensional slurry infiltration model accounting for the viscosity of the slurry. The permeability of sand is first modified by introducing the slurry’s viscosity. Then governing equations are established using the modified permeability and solved by the finite difference method. Three infiltration tests with a wide range of slurry viscosities: 1.8, 58, and 2248 mpa·s are performed and simulated to validate the developed model. Good agreement between numerical and experimental results are obtained. Analysis of coupling behaviours indicates that an optimum slurry of viscosity can be recommended for engineering applications. Unlike previous studies describing incomplete behaviours, the proposed numerical model validates all coupling behaviours involving slurry particle transportation, hydraulic characteristics, and soil deformation. The proposed model can also simultaneously predict the results of slurry infiltration, including adequate infiltration depth, controllable soil deformation, and low-permeability cake.

Modeling a well-characterized perfluorooctane sulfonate (PFOS) source and plume using the REMChlor-MD model to account for matrix diffusion

Two of the most important retention processes for per- and polyfluoroalkyl substances (PFAS) in groundwater likely are sorption and matrix diffusion. The objective of this study was to model concentration and mass discharge of one PFAS, perfluorooctane sulfonate (PFOS), with matrix diffusion processes incorporated using data from a highly chemically- and geologically-characterized site. When matrix diffusion is incorporated into the REMChlor-MD model for PFOS at this research site, it easily reproduces the field data for three key metrics (concentration, mass discharge, and total mass). However, the no-matrix diffusion model produced a much poorer match. Additionally, after about 40 years of groundwater transport, field data and the REMChlor-MD model both showed the majority (80%) of the measured PFOS mass that exited the source zones was located in downgradient low permeability zones due to matrix diffusion. As such, most of the PFOS mass is not available to immediately migrate downgradient via advection in the more permeable sands at this site, which has important implications for monitored natural attenuation (MNA). Plume expansion over the next 50 years is forecasted to be limited, from a 350-m plume length in 2017 to 550 m in 2070, as matrix diffusion will attenuate groundwater plumes by slowing their expansion. This phenomenon is important for constituents that do not degrade, such as PFOS, compared to those susceptible to degradation. Overall, this work shows that matrix diffusion is a relevant process in environmental PFAS persistence and slows the rate of plume expansion over time.

Study on the matching relationship between dispersed droplet size in O/W emulsion and reservoir permeability

Formation and percolation of emulsion are important to enhance heavy oil recovery through emulsification. The percolation behavior of emulsion is affected by permeability, concentration of emulsion, oil-water ratio, etc. To ensure the stable flow of emulsion in porous media and improve the oil-carrying capability of emulsion, it is necessary to study the matching relationship between dispersed droplet size in emulsion and reservoir permeability. The emulsion was prepared by a mulser, and then a series of sand pack flow tests were conducted to investigate the effects of the size of dispersion droplet, permeability and oil-water ratio on percolation. Based on the analysis of displacement pressure, variation of droplet size and oil-carrying capability, the paper established a matching relationship between droplet size and permeability. Due to the shear effect of throat and pore, injection pressure increased, and droplet size became smaller as the injection volume increased in the low permeability sand packs, which shown a poor matching relationship. Then, the permeability increased gradually until the flowing droplet size was remained constant, and the injection pressure was relativity stable. At the point, it can be confirmed that the permeability and the injected droplet size matched well. The study of Influencing factor indicated that the matched droplet size increased with the increase of reservoir permeability. In detail, when the permeability was about 2.76 μm2, the matched droplet median diameters (D50) was about 3.60 µm. When the permeability was about 4.34 μm2, the matched D50 was about 7.04 μm. When the permeability was about 5.60 μm2, the matched D50 was approximately 11.03 μm. In addition, increasing the oil-water ratio of emulsion contributed to shortening the breakthrough time of the emulsion, thus the matched droplet size became a little smaller.

Predicting the permeability coefficient of polydispersed sand via coupled CFD–DEM simulations

Permeability is one of the most fundamental properties of soil, which governs many geotechnical engineering problems. However, among the published equations that predict the permeability coefficient k, the influence of a wide range of particle size distributions (PSDs) on k was not considered accurately. This research aims to quantify the influence of PSD on k and propose a prediction equation for k. Coupled computational fluid dynamics–discrete element method (CFD–DEM) simulations were conducted to reproduce the constant head permeability tests of different soil samples. The results show that among the various drag models implemented in the CFD–DEM, the Syamlal–O’Brien drag model leads to the highest accuracy in simulating sand permeability. The permeability coefficient is proportional to the square of the Sauter mean diameter of the polydispersed particle system. Therefore, the prediction equation for k considering the PSD of the particle system is proposed based on the particle gradation and the size characteristics Cu, Cc, and d10. The proposed equation is verified well by published experimental data. Additionally, the proposed equation can calculate the k of irregular calcareous sand by representing the effect of particle irregularity with the Kozeny–Carman (KC) constant.

Effect of temperature on two-phase gas/oil relative permeability in unconsolidated sands

Thermal Enhanced Oil Recovery (TEOR) for heavy oil reservoirs involves the simultaneous flow of oil and steam, mimicking the gaseous phase with an elevation in the temperature. While implementing the TEOR process, reservoir performance prediction tools require the water/oil and gas/oil relative permeability data. Many studies reported the temperature effect on two-phase water/oil relative permeability despite knowing that steam or vapor is conventionally injected, mimicking the gaseous phase during heavy oil recovery. Thus, this requires the knowledge of temperature effect on two-phase gas/liquid relative permeability as well. However, limited studies are reported in the literature regarding the temperature dependency of relative permeability in gas/liquid systems; offer no census about its effects. The scarcity of such studies in the literature is due to the lack of systematic experimental studies and complications observed while conducting the higher temperature tests to mimic the thermal EOR. Hence, the objective of this study was to examine the temperature effect on two-phase gas/liquid relative permeability at varying temperatures from 64 to 132 °C using a systematic and reliable experimental process.In this study, Poly Alpha Olefin (PAO-100) was used as the oleic phase, deionized water as the immobile phase, and nitrogen gas as the displacing phase in a clean unconsolidated sandpack under the confining pressure around 1000 psi. Furthermore, Johnson-Neumann-Bossler (JBN) method was opted to interpret the two-phase gas/liquid relative permeability curves from the displacement data, i.e., cumulative oil production and pressure drop measured across the sandpack. The experimental observation suggests that irreducible water saturation and endpoint oil relative permeability are temperature independent. The residual oil saturation decreased with the increase in temperature and led to a higher endpoint relative permeability to gas. On the other hand, the oil relative permeability at equal saturation uplifted, suggesting the enhanced mobility of oil through pores with increasing temperature. On the other side, the gas relative permeability at equal saturation was temperature-insensitive other than at residual oil saturation. Also, the two-phase flow region increased with the rise in temperature as both the relative permeability curves shifted upwards, and the broader curve was observed. Hence, this study strongly suggests that the reservoir engineers or commercial reservoir simulators should account for the temperature effects on two-phase gas/oil relative permeability to efficiently predict heavy oil reservoir performance and management during the thermal enhanced oil recovery process (TEOR).

Kinematic response of single vertical and batter piles to bidirectional ground motions in liquefiable soil

Kinematic responses of single fixed head vertical and batter piles in liquefiable soil under bidirectional ground motions have been studied with fully-coupled three-dimensional nonlinear dynamic analyses. Pressure dependent multi-yield constitutive model has been adopted for modeling the liquefiable sand behavior. The variable permeability of saturated sand during the process of liquefaction process has also been considered. The analyses are carried out for combinations of bidirectional earthquake loading conditions. For this, combination of longitudinal and transverse ground motions as well as combination of longitudinal and vertical motions are considered. The responses of the soil-pile systems under liquefying ground conditions, subjected to these bidirectional ground motions, are compared with the unidirectional loading conditions. Further, the effect of sloping ground on the response of the piles under bidirectional ground motions is also investigated. The developed sectional forces in both vertical and batter piles are lesser under bidirectional motions in comparison to unidirectional ground motion in both level and sloping grounds. However, the pile displacement is more in case of sloping ground under bidirectional ground motions comparing to unidirectional motion.