Water Saturation Changes Research Articles

Electrical resistivity monitoring of lower Rio Grande River-Groundwater intermittency

• Time-lapse electrical resistivity before, during, and after the intermittent river flooding. • Resistivity used to characterize the transient and spatial connectivity transitions. • Resistivity changes due to water saturation characterized connectivity transitions. • Resistivity changes after connection occurred were dominated by river temperature. • Resistivity sensitivity to temperature was also used to characterized infiltration. In the current era of rapid environmental changes, more rivers are projected to dry up and transition to disconnected systems in unprecedented duration and frequency. However, river-groundwater interactions, including connectivity, remain a challenge to characterize, especially for managed-ephemeral rivers such as the lower Rio Grande in southern New Mexico, where conjunctive use for irrigated agriculture is prevalent. This investigation used a noninvasive and spatially distributed geophysical method for mapping the disconnection/connection of groundwater with the Rio Grande River, which has been validated with ancillary data that includes river flow, water levels in the river and adjacent wells, and river and groundwater temperature and electrical conductivity. Time-lapse monitoring of electrical resistivity before, during, and after the river flooding season was used to characterize the transient and spatial connectivity of the water table with the Rio Grande, from disconnection to connection, and back to disconnection. The relationships between electrical conductivity from the geophysical analysis versus the large array of ancillary data helped to narrow down the driver of observed temporal changes in connectivity after the transition from disconnection to connection. The results convey that water temperature is potentially the main influence on the changing electrical conductivity after the connectivity transition. The surface water temperature showed a direct and strong correlation to the electrical conductivity of shallow sediments, which was similar to the river stage/groundwater elevation drivers of infiltration. Time-lapse electrical resistivity can be used to monitor river-groundwater connectivity throughout the intermittency cycle, due to its sensitivity to changes in both water saturation and temperature.

High‐Resolution Monitoring of Controlled Water Table Variations From Dense Seismic‐Noise Acquisitions

AbstractWater‐resource management has become a major global issue in a world threatened by climate change. High‐resolution geophysical methods may be of valuable help in monitoring the water masses, both in space and time. Passive seismic interferometry takes advantage of ambient seismic noise to recover the variations in seismic wave velocity induced by changes in groundwater. We present hereafter the time and space monitoring of an hydraulic dome artificially formed to prevent biological and chemical pollutants from entering the exploitation field of Crépieux‐Charmy (Lyon, France). We use a dense seismic network to passively monitor the water table changes induced by infilling of an infiltration basin at the water supply facility for the two million inhabitants of the Lyon Metropolis (France). We assess the hourly seismic velocity variations over 19 days, during which two filling and drainage cycles were performed. The use of a dense three‐component seismic network allows fine characterization of the seismic wavefield, and offers the possibility to include the analysis of 4,851 raypaths in a robust inversion algorithm based on ray theory. The velocity variations are mapped with high resolution. They are directly related to the water table variations and to residual water saturation changes within the unsaturated zone. This seismic experiment highlights the three‐dimensional (3D) implementation and evolution of a hydraulic dome under the infiltration basin. This dynamic information helps in the understanding and modeling of water flows between the water table and a river, which represents a fundamental issue for discussions on the effectiveness of the barrier.

Experimental and Numerical Study on the Insulation Performance of a Photo-Thermal Roof in Hot Summer and Cold Winter Areas

The use of a solar architecture system is a feasible way to reduce the energy consumption of a building. The system also has important significance to the “Dual-carbon” plan. In this study, the heat transfer characteristics of a photo-thermal roof were analyzed in hot summer and cold winter zones; a model to calculate insulation performance was established. In the summer climate, the thermal performances of the photo-thermal roof and an ordinary roof were explored through experiments and simulations. The results showed that the heat transfer and temperature of the photo-thermal roof were lower than those of the ordinary roof. Heat transfer through a photo-thermal roof can be changed by adjusting the water flow of collectors. The water saturation of insulation materials is an important factor that affects the insulation performance of a roof. Compared with the ordinary roof, the change in water saturation was shown to have less impact on the insulation performance of the photo-thermal roof. The water saturation increased from 0 to 30%, while the heat transfer per unit area of the photo-thermal roof only increased by 0.9 W/m2; 97.3% lower than that of the ordinary roof. The effect of reducing the insulation material thickness was less for the photo-thermal roof than for the ordinary roof. When the insulation material thickness was reduced from 100 mm to 0 mm, the average temperature in the indoor non-working area reached 38.5 °C and 27.1 °C in the ordinary roof and the photo-thermal roof, respectively. The insulation thickness of the photo-thermal roof had little effect on the indoor air temperature. The research results provide a reference for the roof energy-saving design of new buildings and the roof energy-saving transformation of existing buildings.

Impact of pore characteristics on displacement processes of air and water flow: Modelling and experimental investigation

Air-water two-phase flow is a common phenomenon during irrigation or intense rainfall in soils. The competition between air and water phases has been recognized for long, but few attempts have been made to study the effect of pore size distribution on the air–water displacement processes at pore scale. In this study, micro-computed tomography experiments and pore network simulations are employed to study air–water flow in the pore space. Experimental and simulated results show that as the water saturation changes, the diameters of water-occupied pores change more quickly than air-occupied pores, while the connectivity of air clusters is more fragile than water clusters. Compared with single-phase conditions, air–water two-phase flow is more sensitive to pore network connectivity. It can also be found that, due to the decreasing diameter of water-occupied pores and decreasing connectivity of air clusters, the air–water flow rate decreases as the pore size distribution becomes skewed.

Hydrate formation from liquid CO2 in a glass beads bed

CO 2 sequestration in marine sediments as solid hydrates is a potential way to capture and store anthropogenic CO 2 . In this study, hydrate formation from liquid CO 2 in marine sediments was simulated in a glass beads bed, and the factors affecting the kinetics of hydrate formation were investigated. The results indicated that the rapid initial hydrate formation with a high driving force always increases the mass transfer resistance, which slows down hydrate growth. The final ratio of water conversion is higher under conditions of low temperature and higher pressure. A smaller particle size is conductive to initial CO 2 hydrate growth, but the water conversion ratio in a bed with larger particles is slightly higher. Compared with other factors, the change in water saturation has an obvious effect on the final water conversion. To inhibit the initial hydrate formation during the injection process, in this paper, a kinetic inhibitor is proposed for pre-injection into marine sediments. This work shows that at a low pressure, a low-concentration inhibitor has an obvious inhibition effect on hydrate growth. However, at a high pressure, it is necessary to increase the concentration of inhibitor to produce an obvious inhibition effect.

Reservoir Monitoring by Inversion of Reservoir Pressure and Saturation Changes from Time-Lapse Avo Differences and Time-Shifts

The main storage-related challenges for accelerated deployment of CCS are capacity, confidence and cost. These challenges are to be addressed by focusing on improving strategies for monitoring and management of the pore pressure distribution in the CO2 storage reservoir. Pressure-driven decision support protocols are to be developed for safe and cost-effective reservoir monitoring. These protocols will enable the operator to maximize CO2 storage capacity and quickly turn monitoring data indicating non-conformance into plans for corrective actions. A new extended method is developed for inverting and de-noising reservoir pressure and water saturation changes from time-lapse AVO differences and time-shifts for the purpose of CCS monitoring and conformance. Detailed reservoir pressure and saturation fronts are obtained for seismic timelapse data in the Norwegian offshore, honouring reservoir compartments and fault boundaries found in comparative studies. Applications on CCS and non-CCS fields offshore Norway were researched in synthetic and field data cases for purposes of benchmarking, pre-storage analysis, monitoring plans and conformance studies. Back-estimations of pressure and saturation changes were successful for both synthetic and field data and have made this method substantially more credible for field cases and seismic history matching.

Influence of High Pressure Fluid on the Competence of Porous Clastic Rock

In porous clastic rocks, the uneven distribution of high-pressure fluid will cause changes in water saturation and frequent changes in wavelength. The purpose of this article is to study the effect of high-pressure fluid on the competence of porous clastic rocks. First, according to the dynamic high pressure technology of the two-stage light gas gun and the compressed gas target technology, the principle of dynamic high pressure loading is introduced and the rock competence in the rheological process is analyzed. The traditional Gassmann equation is adjusted to match the temperature to verify the fluid mechanism model of the porous medium. The impact of high-pressure jet on the rock surface of porous clastic rock and the influence factors of high-pressure pulse jet on rock are discussed. The experimental results show that the rock damage effect is better when the distance between adjacent pulsed jets is 9mm.

Influence of water on elastic deformation of coal and its control on permeability in coalbed methane production

The permeability of the coal reservoir is affected by the stress caused by water production and matrix shrinkage caused by methane desorption, and its change rate is mainly affected by the elastic parameters of coal, namely Young's modulus (E) and Poisson's ratio (v). E and v will change with the change of coal water saturation, which will affect the reservoir permeability, but there is little research on it. Therefore, in this study, triaxial compression experiments were carried out on high volatility bituminous coal samples with different water saturation to obtain the variation law of E and v with water saturation. Combined with gas permeability experiments of coal samples with different water saturation and finite element method, the influence of E and v on permeability change were analyzed based on the P&M permeability evolution model. The results showed that E decreases linearly with the increase of water saturation, while v increases linearly, and the change rate was affected by the fracture of coal and stress. The existence of fractures makes the mechanical properties of coal show great heterogeneity, resulting in the reduction of water action, and the stress will close the fractures to be as a whole, more prone to elastic deformation and greater deformation. The change of E and v will lead to a decrease of permeability faster or slower, which depends on the initial E and v and their change rate. Because the effects of E and v on permeability are different and nonlinear, the control effects of E and v on permeability are also different, depending on the E and v value. The quantitative numerical analysis showed that the variation of E can increase permeability change range by at least 32%. When the E is less than 3000 MPa and greater than 4000 MPa, the influence degree is greater, more than 60%, which means that the change of E has a significant control effect on permeability change. The change of v has little effect on the permeability change range with the maximum permeability change range is only 31%. The permeability of coal reservoir generally exceeds 3000 MPa, which means that more attention should be paid to the influence of E and v change with water production on permeability, especially the change of E.

Calculation Model of Relative Permeability in Tight Sandstone Gas Reservoir with Stress Sensitivity

During the development of tight gas reservoir, the irreducible water saturation, rock permeability, and relative permeability change with formation pressure, which has a significant impact on well production. Based on capillary bundle model and fractal theory, the irreducible water saturation model, permeability model, and relative permeability model are constructed considering the influence of water film and stress sensitivity at the same time. The accuracy of this model is verified by results of nuclear magnetic experiment and comparison with previous models. The effects of some factors on irreducible water saturation, permeability, and relative permeability curves are discussed. The results show that the stress sensitivity will obviously reduce the formation permeability and increase the irreducible water saturation, and the existence of water film will reduce the permeability of gas phase. The increase of elastic modulus weakens the stress sensitivity of reservoir. The irreducible water saturation increases, and the relative permeability curve changes little with the increase of effective stress. When the minimum pore radius is constant, the ratio of maximum pore radius to minimum pore radius increases, the permeability increases, the irreducible water saturation decreases obviously, and the two-phase flow interval of relative permeability curve increases. When the displacement pressure increases, the irreducible water saturation decreases, and the interval of two-phase flow increases. These models can calculate the irreducible water saturation, permeability and relative permeability curves under any pressure in the development of tight gas reservoir. The findings of this study can help for better understanding of the productivity evaluation and performance prediction of tight sandstone gas reservoirs.

On conditions of geodynamic tension and oil-gas bearing content of Garbi Absheron structure based on advanced models

In the context of Garbi Absheron structure the significance of increase of accuracy for searching and exploration of oil-gas fields with the purpose of avoiding technological complications in the drilling considering conditions of geodynamic tension, as well as the necessity of the implementation of perfect methods of modeling based on the geophysical and seismological data in the specification of the site of drilled wells and operation of productive layer has been defined for the first time. Considering the results of facies analysis, as well as the petrophysical and geophysical logging data of the wells drilled in various areas of Garbi Absheron field, 2D and 3d models characterizing the lithology of the layers, have been developed. The maps showing petrophysical scale of horizon layers, as well as the changes of porosity, permeability, water and oil saturation and clay content of the layers in geological sections have been developed using “Petrel” software. Favorable permeable horizon in the central part of the structure and the highest oil saturation degree in the central area of 3D models have been revealed during the research of porosity, water and oil saturation and clay content.

Electrical Resistivity Tomography (ERT) Monitoring for Landslides: Case Study in the Lantai Area, Yilan Taiping Mountain, Northeast Taiwan

Water saturation in the bedrock or colluvium is highly related to most landslide hazards, and rainfall is likely a crucial factor. The dynamic processes of onsite rock/soil mechanics could be revealed via monitoring using the electrical resistivity tomography (ERT) technique and Archie’s law. This study aims to investigate water saturation changes over time using time-lapse ERT images, providing a powerful method for monitoring landslide events. A fully automatic remote resistivity monitoring system was deployed to acquire hourly electrical resistivity data using a nontraditional hybrid array in the Lantai area of Yilan Taiping Mountain in Northeast Taiwan from 2019 to 2021. Six subzones in borehole ERT images were examined for the temporal and spatial resistivity variations, as well as possible pathways of the groundwater. Two representative cases of inverted electrical resistivity images varying with precipitation may be correlated with water saturation changes in the studied hillslope, implying the process of rainfall infiltration. Layers with decreased and increased electrical resistivity are also observed before sliding events. Accordingly, we suggest that high-frequency time-lapse ERT monitoring could play a crucial role in landslide early warning.

Ultrasonic S-wave responses of single rock joints filled with wet bentonite clay

Clay minerals are prevalent in rock discontinuities and have significant effects on mechanical, hydraulic and seismic properties of rock masses. Understanding seismic behaviours across individual clay-rich rock joints is of great importance in the fields of geology and earth sciences. However, the wave responses of individual clay-rich rock joints have not been well understood until now. This paper reports a laboratory investigation of ultrasonic S-wave propagation and attenuation across single rock joints filled with bentonite clays with varying degree of water saturation. In this study, a series of acoustic measurements were conducted on specimens of the bentonite clay-filled rock joint using a self-developed ultrasonic pulse-transmission test system that equipped with a S-wave transducer pair with a dominant frequency of 250 kHz. Based on the obtained laboratory data, the wave velocity, transmission ratio and the time-frequency-energy distribution of the S-waves transmitted through the bentonite clay-filled joint were calculated and evaluated. The experimental results show that the degree of water saturation of the bentonite clay greatly affects S-wave responses of the filled rock joint. In particular, an increase in the degree of saturation causes a nonlinear decrease in S-wave velocity. In addition, as the water saturation of the bentonite clay increases, the wave attenuation decreases; the minimum wave attenuation is reached at a saturation degree of 71.4% and then the attenuation increases slightly. Additionally, with the increase of the water saturation, the magnitudes of the S-wave energy transmitted across the bentonite clay-filled joint firstly increases and then decreases. The S-wave energy is mostly stored in the frequency range of 150 - 300 kHz regardless of the degree of water saturation of the bentonite clay. This finding indicates that the frequency partition of the transmitted S-waves rarely changes with the changing water saturation. The present work could not only compensate for the lack of laboratory-based research on wave behaviours across clay-rich rock joints but also provides insights into the interpretation of acoustic data from field tests for detecting, characterizing and monitoring rock discontinuities.

Quantitative seismic interpretation of the Lower Cretaceous reservoirs in the Valdemar Field, Danish North Sea

A quantitative seismic interpretation study is presented for the Lower Cretaceous Tuxen reservoir in the Valdemar Field, which is associated with heterogeneous and complex geology. Our objective is to better outline the reservoir quality variations of the Tuxen reservoir across the Valdemar Field. Seismic pre-stack data and well logs from two appraisal wells form the basis of this study. The workflow used includes seismic and rock physics forward modelling, attribute analysis, a coloured inversion, and a Bayesian pre-stack inversion for litho-fluid classification. Based on log data, the rock physics properties of the Tuxen interval reveal that the seismic signal is more governed by porosity than water-saturation changes at near-offset (or small angle). The coloured and Bayesian inversion results were generally consistent with well-log observations at the reservoir level and conformed to interpreted horizons. Although the available data have some limitations and the geological setting is complex, the results implied more promising reservoir quality in some areas than others. Hence, the results may offer useful information for delineating the best reservoir zones for further field development and selecting appropriate production strategies.

Unsupervised machine learning for time-lapse seismic studies and reservoir monitoring

Time-lapse (4D) seismic analysis plays a vital role in reservoir management and reservoir simulation model updates. However, 4D seismic data are subject to interference and tuning effects. Being able to resolve and monitor thin reservoirs of different quality can aid in optimizing infill drilling or in locating bypassed hydrocarbons. Using 4D seismic data from the Maui field in the offshore Taranaki Basin of New Zealand, we generate typical seismic attributes sensitive to reservoir thickness and rock properties. We find that spectral instantaneous attributes extracted from time-lapse seismic data illuminate more detailed reservoir features compared with those same attributes computed on broadband seismic data. We have developed an unsupervised machine-learning workflow that enables us to combine eight spectral instantaneous seismic attributes into single classification volumes for the baseline and monitor surveys using self-organizing maps (SOMs). Changes in the SOM natural clusters between the baseline and monitor surveys suggest production-related changes that are caused primarily by water replacing gas as the reservoir is being swept under a strong water drive. The classification volumes also facilitate monitoring water saturation changes within thin reservoirs (ranging from very good to poor quality) as well as illuminating thin baffles. Thus, these SOM classification volumes indicate internal reservoir heterogeneity that can be incorporated into reservoir simulation models. Using meaningful SOM clusters, geobodies are generated for the baseline and monitor SOM classifications. The recoverable gas reserves for those geobodies are then computed and compared with production data. The SOM classifications of the Maui 4D seismic data seem to be sensitive to water saturation change and subtle pressure depletions due to gas production under a strong water drive.

The Biophysical Role of Water and Ice Within Permafrost Nearing Collapse: Insights From Novel Geophysical Observations

AbstractThe impact of permafrost thaw on hydrologic, thermal, and biotic processes remains uncertain, in part due to limitations in subsurface measurement capabilities. To better understand subsurface processes in thermokarst environments, we collocated geophysical and biogeochemical instruments along a thaw gradient between forested permafrost and collapse‐scar bogs at the Alaska Peatland Experiment site near Fairbanks, Alaska. Ambient seismic noise monitoring provided continuous high‐temporal resolution measurements of water and ice saturation changes. Maps of seismic velocity change identified areas of large summertime velocity reductions nearest the youngest bog, indicating potential thaw and expansion at the bog margin. These results corresponded well with complementary borehole nuclear magnetic resonance measurements of unfrozen water content with depth, which showed permafrost soils nearest the bog edges contained the largest amount of unfrozen water along the study transect, up to 25% by volume. In situ measurements of methane within permafrost soils revealed high concentrations at these bog‐edge locations, up to 30% soil gas. Supra‐permafrost talik zones were observed at the bog margins, indicating talik formation and perennial liquid water may drive lateral bog expansion and enhanced permafrost carbon losses preceding thaw. Comparison of seismic monitoring with wintertime surface carbon dioxide fluxes revealed differential responses depending on time and proximity to the bogs, capturing the controlling influence of subsurface water and ice on microbial activity and surficial emissions. This study demonstrates a multidisciplinary approach for gaining new understanding of how subsurface physical properties influence greenhouse gas production, emissions, and thermokarst development.

INVESTIGATION OF THE WATER CONTENT OF CH4-H2 SYSTEM

Hydrogen, as the clean energy carrier of the future can play a significant role in climate policy efforts in the near future. The study National Energy Strategy 2030 published in January 2020 defines the natural gas network as a seasonal energy storage. Several European countries have investigated whether hydrogen predominantly from renewable sources can be introduced to the natural gas system to reduce GHG emission. One of the important parameters of the natural gas fed into the gas network is the water vapor content, its maximum value of which is regulated by law. In this article, the authors examined whether hydrogen, which differs significantly from the properties of methane, causes a significant change in water saturation. The investigated pressure and temperature ranges cover every state found in the processing and transportation of natural gas. To carry out the calculations the Aspen HYSYS program was used.

Dynamic Variation of Water Saturation and Its Effect on Aqueous Phase Trapping Damage During Tight Sandstone Gas Well Production.

Dynamic variation of water saturation near a wellbore may cause serious aqueous phase trapping (APT) damage in gas well production, especially in partly water-saturated tight sandstone gas reservoirs. In this paper, a prognosis model was deduced and used to characterize the dynamic variation of water saturation. In addition, experimental evaluations of APT damage were conducted to reveal the influence of water saturation changes on APT damage. The results showed that the new model used for the prognosis of the water saturation consists of immobile water and a water film and has good reliability. The results obtained from the model and experiments agreed with each other well; the error is very little and only 2.94%. Decrease of drawdown pressure or increase of hydrostatic pressure will result in increasing water saturation, which is positively correlated with APT damage. The chart curve of APT damage degree versus water saturation indicates that the APT damage degree will increases from 23.14 to 68.27 and 91.37% during the middle-later stages of tight sandstone gas well production, respectively. Finally, results of a sensitivity analysis showed that the surface tension and wetting contact angle have a great significant impact on water saturation. The interfacial modifier could effectively enter the reservoir pores in a near-wellbore zone and continuously act on the reduction of surface tension and increase of wetting contact angle, which is very helpful for releasing APT damage.

Investigation on water phase trapping mechanisms in tight gas reservoirs: Pore-scale visualization observation and core-scale flooding analysis

Water phase trapping (WPT) is one of severe formation damage issues for the safe production in tight gas reservoirs. In this work, both pore-scale and core-scale investigation of the formation process of WPT were performed. Real-time observation of the water invasion and formation of trapped gas was achieved using visualized micromodel. Meanwhile, core flooding experiments including water imbibition and drainage experiments were conducted to analyze the responses of gas permeability and water saturation changes to the formation of WPT. The micromodel visualization experiments presented an intuitive gas-water two-phase flow scenarios which revealed the microscopic mechanisms of the WPT vividly. It pointed out that snap-off and circumfluous flow are the two major mechanisms to break the bulk gas flow and generate the trapped gas during WPT formation. The results of core flooding provided a causality link between the changes of gas permeability and water saturation, which showed a macroscopic consequence to the gas flow ability caused by WPT damage. These findings will benefit a better understanding of the formation process and damage mechanisms of WPT.

In-Situ Capabilities of Lab-Based X-Ray Microscopy for Polymer Electrolyte Fuel Cells

X-ray Computed Tomography has proven to be a crucial method to properly characterize and understand a wide variety of materials applications. Due to the non-destructive 3D imaging capabilities, this imaging methodology provides unique insight into material properties with comparatively minimal sample processing. One limitation, however, has been resolution capabilities. Previously, X-ray tomography imaging has utilized the principle of geometric magnification to obtain resolution. This has several limitations, the main impact being the realistic resolution achievable for a given sample size. Recently, the application of using a photon-converting scintillator and objective lens magnification has enabled much higher resolution imaging [1]. A unique ability of this system architecture is to enable non-destructive, multi-length scale visualization for relatively large sample sizes; with an imaging field of view range from tens of millimeters down to tens of micrometers, and resolution capabilities reaching 500 nm in instruments such as the ZEISS Xradia Versa. This architecture provides capabilities perfectly suited for complex device visualization, such as polymer electrolyte fuel cell (PEFC) systems, as well as the ability to image in-situ.By combining 3-dimensional visualization through repeated identical location tomography scans at various temporal stages, powerful in-situ investigations of dynamic material properties can be obtained. This methodology is often termed as 4DCT (4-dimensional computed tomography) and is particularly well suited to study various dynamic and evolutionary processes in PEFCs due to their complex multi-layered and entangled system. Detailed images of the membrane electrode assembly (MEA) can be periodically obtained while the cell is still assembled in its operational housing as well as while it is producing current, to observe transient liquid water pathways [2, 3].Extraction of quantitative information regarding material/geometrical properties, such as thickness, porosity, saturation, and local deformation, as well as temporal changes to these properties and morphology during degradation processes is facilitated by advanced image processing and visualization methodologies [3,4,5]. In this presentation, custom tools, workflows, and analysis methods are showcased that allow for insight into the lifetime changes of cathode catalyst layer morphology, water saturation, and crack propagation. It has been found through ageing that morphological interaction between different layers can have considerable impact on degradation mechanisms [5,6,7]. We present an overview of the 4DCT approach applied to various fuel cell degradation studies as well as GDL water distribution during in situ imaging. These visualization methods uncover unique evidence around the strongly interactive nature of material degradation within a fuel cell that has previously been unobserved.Figure 1: Overview of lab-based in-situ imaging methodology within the Zeiss Xradia Versa system. A model of the X-ray microscope is shown with an ‘opened’ in-situ fuel cell device. Resulting segmented liquid water and cathode catalyst layer before and after ageing are shown with GDL, ionomer membrane and anode catalyst layer removed for visualization. Acknowledgements The authors would like to acknowledge the support from Monica Dutta and Ballard Power Systems in providing samples and discussion of the presented work, as well as all members of the Fuel Cell Research Lab for their kind support.

A New Methodology of Production Performance Prediction for Strong Edge-Water Reservoir

Abstract Material balance is a basic principle in reservoir engineering, which is still used as a quick and easy analytical tool for reservoir evaluation. In this article, a new methodology of production performance prediction for water-flooding reservoir was proposed based on the material balance principle, which considers the water saturation change caused by water injection and natural water influx, and its effect on transient gas–oil ratio. Among them, the cumulative water production was calculated based on Tong’s water-driver performance curve; the cumulative water influx was obtained by the Fetkovitch method; the transient gas–oil ratio can be acquired by Darcy’s law and Baker’s relative permeability model. Comparisons have been made between the new methodology and commercial reservoir simulator for two different reservoirs. The results show that there is good similarity between these two tools, which verifies the correctness of the new methodology.