Reservoir Shape Research Articles

Toward Improved Simulations of Disruptive Reservoirs in Global Hydrological Modeling

AbstractAccurate simulation of reservoirs has been a challenge for global hydrological models due to highly discontinuous water management and uncertainties in reservoir shape representation. In addition, at a global scale, it is crucial to consider those reservoirs that disrupt the downstream flow regime. We augment the mesoscale Hydrological Model with a newly developed lake module (LM) that incorporates an existing reservoir regulation scheme with non‐consumptive demand predictions from random forest. We also evaluate the sensitivity of reservoir shape on streamflow and evaporation for three shape approximations of varying complexities. We tested the LM across 31 non‐consumptive reservoirs covering an extensive range of hydroclimatic characteristics and demonstrate the applicability by using freely available global reservoir information. Streamflow simulations with reservoirs and model calibration show a median Kling‐Gupta Efficiency improvement of +0.94 (calibration) and +0.77 (validation) when compared against model simulations without reservoirs and default parameter set. We find reservoir evaporation highly sensitive to reservoir shape with half‐pyramid approximation consistently resulting in best fit at reservoirs with surveyed bathymetry. In contrast, the linear approximation (rectangular prism) produced a median bias of +114% relative to half‐pyramid, for estimating evaporation, across all the reservoirs. Streamflow simulations were insensitive to the reservoir shape. Our analysis shows that 30% of the non‐consumptive hydropower reservoirs of the GRanD data set are non‐disruptive and can be excluded without loss to model realism. Further work is necessary for testing the regulation approach in reservoirs with consumptive water usage.

A comprehensive analysis of transient rate and rate derivative data of an oil well intercepted by infinite-conductivity hydraulic fracture in closed systems

This paper presents a method for analyzing constant-pressure drawdown test of infinite-conductivity fractured wells in bounded reservoirs. The presented method is based on the Tiab direct synthesis approach. The fracture and reservoir parameters are directly determined from the rate and rate derivative of the well test data. New equations describing the elliptical flow regime and the transition from the pseudoradial regime to the boundary-dominated regime of different rectangular reservoirs are also presented. The various flow regimes occurring during the well test are easily identified based on the shape of the plotted data and the slope of each flow regime. The unique features of the slopes of the various regimes and their intersection points are utilized to determine the fracture half-length, formation permeability, skin factor, well drainage area, and reservoir shape factor. Moreover, new equations defining the intersection points of the straight lines corresponding to different flow regimes are presented. These equations are very important for confirming the precision of the calculated results. A systematic process demonstrating the application of the proposed method to linear, elliptical, pseudoradial, and boundary-dominated regimes is well delineated. Comprehensive examples are presented to validate the efficiency of the proposed technique. The examples show that even if some of the flow regimes are not fully developed, the method can still be used to determine the formation and fracture properties using information obtained from the remaining flow regimes. This is one of several advantages of the proposed technique over conventional techniques.

A New Fracturing Method to Improve Stimulation Effect of Marl Tight Oil Reservoir in Sichuan Basin

China’s argillaceous limestone reservoir has a lot of oil and gas resources, and hydraulic fracturing of the argillaceous limestone reservoir faces many difficulties. The first problem is that the heterogeneity of the argillaceous limestone reservoir is strong, and it is difficult to optimize fracturing parameters. The second problem is that there are a lot of natural fractures in the argillaceous limestone reservoir, which leads to a lot of fracturing fluid loss. The third problem is that the closure pressure of the argillaceous limestone reservoir is high, and the conductivity of fractures decreases rapidly under high closure pressure. The last problem is that the fracture shape of the argillaceous limestone reservoir is complex, and the law of proppant migration is unclear. The main research methods in this paper include reservoir numerical simulation, fluid-loss-reducer performance evaluation, flow conductivity tests and proppant migration visualization. To solve the above problems, this paper establishes the fracturing productivity prediction model of complex lithology reservoirs and defines the optimal hydraulic fracturing parameters of the argillous limestone reservoir in the Sichuan Basin. The 70/140 mesh ceramide was selected as the fluid loss additive after an evaluation of the sealing properties of different mesh ceramides. At the same time, the hydraulic fracture conductivity test is carried out in this paper, and it is confirmed that the fracture conductivity of 70/140 mesh and 40/70 mesh composite particle-size ceramics mixed according to the mass ratio of 5:5 is the highest. When the closure pressure is 40 MPa, the conductivity of a mixture of 70/140 mesh ceramic and 40/70 mesh ceramic is 35.6% higher than that of a mixture of 70/140 mesh ceramic and 30/50 mesh ceramic. The proppant migration visualization device is used to evaluate the morphology of the sand dike formed by the ceramsite, and it is clear that the shape of the sand dike is the best when the mass ratio of 70/140 mesh ceramsite and 40/70 mesh ceramsite is 6:4. The research results achieved a good stimulation effect in the SC1 well. The daily oil production of the SC1 well is 20 t, and the monitoring results of the wide-area electromagnetic method show that the fracturing fracture length of the SC1 well is up to 129 m.

Magma reservoir growth and ground deformation preceding the 79 CE Plinian eruption of Vesuvius

The 79 CE eruption of Vesuvius is the first documented Plinian eruption, also famous for the archaeological ruins of Pompeii and Herculaneum. Although much is known regarding the eruption dynamics and magma reservoir, little is known about the reservoir shape and growth, and related ground deformation. Numerical modelling by Finite Element Method was carried out, aimed at simulating the reservoir growth and ground deformation with respect to the reservoir shape (prolate, spherical, oblate) and magma overpressure. The modelling was tuned with volcanological, petrological and paleoenvironmental ground deformation constraints. Results indicate that the highest magma overpressure is achieved considering a prolate reservoir, making it as the most likely shape that led to eruption. Similar deformations but lower overpressures are obtained considering spherical and oblate reservoirs. These results demonstrate that ground deformation may not be indicative of eruption probability, style/size, and this has direct implications on surveillance at active explosive volcanoes.

A novel semi-analytical model for transient pressure behavior in fracture-cave carbonate reservoirs

Fracture-cave carbonate reservoirs represent a significant amount of oil and gas resources worldwide, while their intrinsic complex pore network, large caves and tectonic fractures bring challenges to reservoir characterizations and productions. Many models have been proposed to solve the pressure transient analysis (PTA) solutions for such reservoirs. With recent explorations, the position of fractures and caves can be determined by seismic data. However, models using the position information with the coexistence of discrete fractures and caves were not reported in the literature. This paper proposes a novel semi-analytical model based on the Boundary Element Method (BEM), to describe the transient pressure behavior of the fracture-cave carbonate reservoirs. Basically, the proposed model treats the cave edge as an inner boundary and includes the fracture-cave fluid interchanges. As a results, the model's solution is proved to be flexible for arbitrary cave and reservoir shape. A typical system consisting of one fracture and one case is discussed in detail. The result indicates the well location is the key factor to the pressure response, where the pressure response is mostly affected by the cave volume and fracture conductivity when the well is on the cave and fracture, respectively. The sensitivities of three major parameters on the pressure response are analyzed. In addition, the proposed model is applied in two field cases. The result shows the proposed model is reliable and accurate.

Saturation and Pressure Prediction for Multi-Layer Irregular Reservoirs with Variable Well Patterns

The well pattern and boundary shape of reservoirs determine the distribution of the remaining oil distribution to a large extent, especially for small-scale reservoir blocks. However, it is difficult to replicate experiences from other reservoirs directly to predict the remaining oil distribution because of the variety of irregular boundary shapes and corresponding well patterns. Meanwhile, the regular well pattern can hardly suit irregular boundary shapes. In this paper, we propose a well placement method for undeveloped irregular reservoirs and a multi-step prediction framework to predict both oil saturation and pressure fields for any reservoir shape and well pattern. To boost the physical information of input characteristics, a feature amplification approach based on physical formulae is initially presented. Then, 3D convolution technology is employed for the first time in 3D reservoir prediction to increase the spatial information in the vertical direction of the reservoir in the input. Moreover, to complete the two-field prediction, the concept of multi-task learning is adopted for the first time, improving the rationality of the forecast. Through the loss-based ablation test, we found that the operation we adopt will increase the accuracy of prediction to some extent. By testing on both manually designed and real irregular-shape reservoirs, our method is proven to be an accurate and fast oil saturation prediction method with its prediction loss less than 0.01 and calculation time less than 10 s in the future one year.

Monitoring and Modelling of Sediment Flushing : A Review

With ever decreasing potential for suitable new dam sites, sustainable use of existing water reservoirs is of paramount importance. In absence of appropriate measures, reservoir storage is continually reduced due to sedimentation. One option to remove sediment deposits is hydraulic flushing. During the flushing operation, bottom outlets are open and water and sediment released. Whether flushing successfully removes sediment depends on a number of factors, such as bottom outlets capacity, reservoir shape and water availability. Modelling is often used to assess viability of flushing for sediment management in the reservoir, as well as to design the operations and optimize their scheduling. One-dimensional numerical models are preferred for long term simulations, assessments on of a large number of scenarios, and optimization studies. Two- and three-dimensional numerical models and physical models can be used, each on their own or in combination as hybrid models, to understand local scouring near the gates and other details of operation. Monitoring of flushing operations can help improving their efficiency while at the same time limit downstream impacts. General monitoring of the reservoir and its catchment can help understanding the sedimentation problem and thus facilitate preparation of efficient sediment management strategies. Live monitoring of sediment concentrations is possible with modern equipment though not without challenges, and reservoir survey can be performed faster. Earth observation techniques are also an attractive option, allowing to monitor large areas and areas of difficult access, as well as to provide historical information going back several decades. This paper reviews monitoring and modelling approaches published in the literature, as well as presents some previously unpublished analyses.

Estimation of an ephemeral cooling for silicic magma reservoirs using thermal simulation

• A thermal simulation is to constrain the cooling time of silicic magma reservoirs. • The cooling time is dominantly controlled by pluton’s shape and emplacement depth. • Shallow magma reservoirs require extra heat to maintain liquid for a longer time. • A cooling time of ∼20 kyr is proposed for the ca. 44 km 2 Jiuxiantang intrusion. Understanding the processes involved in magmatic evolution is one of the most fundamental aspects of geological research. The limitations of available chronological and geophysical methods hinder their precise depictions of the short residence time of small-volume magma reservoirs in the upper crust, while thermal simulation may provide an alternative solution for the key issue. In this contribution, a numerical simulation is built to constrain the processes of magma reservoirs in terms of heat conduct. The sensitivities of magma cooling time on relevant factors (including pluton shape, size, emplacement depth, heat dissipation efficiency, and thermal gradient) are explored. Our simulation suggests that the depth and shape (size and radius/thickness ratio) of magma reservoirs affect the cooling time significantly. An ephemeral cooling time of ∼20.4 kyr (thousand years) from liquidus (994 ℃) to solidus (664 ℃) for the homogeneous ca 820 Ma (million years ago) Jiuxiantang intrusion in South China is revealed. An overall ‘mush’ state of the magma reservoir is proposed for the most lifetime of the intrusion. This contribution provides a unique perspective to understanding the thermal budget of the magma system and the residence time of magma reservoirs in the upper crust.

Sress-strain analysis and optimization of the geometric shape of cylindrical oilfield reservoirs

The paper sets forth an approach for calculating and optimizing the geometric shape, taking into account the physical nonlinearities of the material of oilfield reservoirs and the end conditions of supports. An effective calculation technique based on finite difference methods has been developed. On the basis of the developed methods, a computational algorithm was created, a set of applied programs was compiled. An analysis of the calculation results based on the developed computational technique showed that the solution of the problems of determining the stress-strain behavior of shells must be carried out taking into account the physical nonlinearity. The influence of various factors on the stress-strain behavior of the reservoir was found out. A general method for the linearization of a thin structure with changeable geometric parameters is proposed, which has accelerated convergence. Based on the results of the calculations, concrete formulas and diagrams have been compiled that can be used in engineering practice. Keywords: shell; cylindrical oilfield reservoir; nonlinear model; finite difference method.

Petrologic imaging of the magma reservoirs that feed large silicic eruptions

Large silicic explosive eruptions are one of Nature's most hazardous phenomena. Very few have been witnessed and unravelling the complex conditions that lead to these eruptions remains a difficult task because the characteristics of the feeding magma reservoirs are still insufficiently constrained from geophysical imaging. Here we show that a barometer based on the composition of amphibole in equilibrium with plagioclase and biotite, common minerals in the eruptive products of large silicic eruptions, records the thickness and depth of magma reservoirs with uncertainties of 0.8 and 2.7 km, respectively. Pressures are given by the equation: P (MPa) = 892 · VI Al + 101, where VI Al is the octahedral aluminum content of the amphibole. With the example of a Miocene Turkish ignimbrite, we show that reservoirs feeding large silicic eruptions can be pancake-shaped. Our new barometer, valid between 650 and 950 °C, can be used in combination with volcanological and geophysical data to infer the size, shape and depth of magma reservoirs and may serve as a tool for monitoring future activity. This temperature-independent barometer is also applicable to any volcanic or plutonic rock containing amphibole + plagioclase + biotite and is in excellent agreement with previously published temperature-dependent barometers within their calibration range. • Developpement of a new temperature-independent Al-in amphibole geobarometer • Depth of emplacement of plutons and magma reservoirs with an uncertainty of 2.7 km • Shape of erupted magma reservoirs accessible from petrological and volcanological observations

Mechanisms of shape transfer and preheating in indirect-drive double shell collisions

Implosions of Hohlraum-driven double shell targets as an alternative inertial confinement fusion concept are underway at the National Ignition Facility. The double shell system relies on a series of energy transfer processes starting from thermal x-ray absorption by the outer shell, followed by collisional transfer of kinetic energy to a heavy metal inner shell, and finally, conversion to the internal energy of the deuterium-tritium fuel. During each of these energy transfer stages, low-mode asymmetries can act to reduce the ideal transfer efficiency degrading double shell performance. Mechanisms, such as hard x-ray preheat from the Hohlraum, not only decrease the efficiency of kinetic energy transfer but may also be a source of low-mode asymmetry. In this article, we evaluate the shape transfer processes through the time of shell collision using two-dimensional integrated Hohlraum and capsule computations. We find that the dominant mode of the shape transfer is well described using a “radial impulse” model from the shape of the foam pressure reservoir. To evaluate the importance of preheat on inner shell shape, we also report on first measurements of Au L-shell preheat asymmetry in a double shell with a tungsten pusher. These measurements showed a 65% higher preheat velocity at the pole of the capsule relative to the equator. We also found that the experiments provided rigorous constraints by which to test the Hohlraum model settings that impact the amount and symmetry of Au L-shell preheat via the plasma conditions inside the outer cone Au bubble.

Quantification of Volcano Deformation Caused by Volatile Accumulation and Release

AbstractCrustal‐stored magma reservoirs contain exsolved volatiles which accumulate in the reservoir roof, exerting a buoyancy force on the crust. This produces surface uplift and sudden loss of volatiles through eruption results in syn‐eruptive subsidence. Here, we present three‐dimensional, visco‐elasto‐plastic, numerical modeling results which quantify the ground deformation arising from the growth and release of a volatile reservoir. Deformation is mostly independent of crustal thermal distribution and volatile reservoir shape, but is a function of volatile volume, density and depth and crustal rigidity. We present a scaling law for the volatiles' contribution to syn‐eruptive subsidence and show this contributes ∼20% of the observed subsidence associated with the 2015 Calbuco eruption. Our results highlight the key role that volatile‐driven buoyancy can have in volcano deformation, show a new link between syn‐eruptive degassing and deflation, and highlight that shallow volatile accumulation and release may have a significant impact on ground deformation of volcanoes.

Influence of stress redistribution and fracture orientation on fracture permeability under consideration of surrounding rock in underground gas storage

UGS (underground gas storage) is of great significance for ensuring emergent supply and CCUS (Carbon Capture, Utilization, and Storage). However, very different from gas reservoir development, some stress changes in reservoir, caprock, and bottom support rock may affect its operation. Sichuan Basin is rich in natural-gas resources and geological targets for the UGS rebuilt from fractured carbonate reservoirs. Moreover, gas storage is featured by rapid injection and production, and the change of in-situ stress affects intensively the permeability of reservoir fracture. However, most existing models on the fracture permeability assume that the surrounding-rock stress is constant. So, a new model has been established for the fracture permeability based on the Eshelby theory, considering the effect of both direct caprock and bottom support rock (also called surrounding rock) and the stress redistribution mechanism of the entire geological body during UGS injection and production. Results show that for the fracture, the permeability is related to not only its compressibility and orientation, but also reservoir shape and elastic property of the entire geological body including reservoir and surrounding rock. In most disk-shaped or elliptical reservoirs, vertical fracture is less susceptible to pore pressure than horizontal one. The surrounding-rock elastic property is also an important factor in the fracture-permeability model. Hard surrounding rock can reduce the stress sensitivity in fracture. When the elastic modulus ratio (elastic modulus of reservoir vs. that of surrounding rock) is 0.1, the fracture permeability decreases by only 15%. This model is also applicable to multiple fractures. Using the superposition principle, it is found that the main direction of permeability and the degree of permeability anisotropy may change when there are multiple fractures in the reservoir in spite of the same fracture compressibility.

A New Fluid Mobility Calculation Method Based on Frequency-Dependent AVO Inversion

Fluid mobility (i.e., permeability to viscosity ratio) is a key parameter that can evaluate the reservoir permeability and delineate the fluid characteristic in hydrocarbon-saturated reservoirs. Based on the asymptotic representation for the frequency-dependent reflections in the fluid-saturated pore-elastic media and frequency-dependent AVO inversion, we propose a novel method for estimating fluid mobility from poststack seismic data. First, we establish the relationship between fluid mobility and frequency-dependent AVO analysis. Then, the fluid mobility is estimated using the theory of frequency-dependent AVO inversion. Tests on synthetic data reveal that the fluid mobility shows excellent imageability for the fluid-saturated reservoirs and can accurately delineate the spatial distribution shape of the gas-saturated reservoir. The application of field data examples demonstrates that the fluid mobility calculated by the proposed method produces less background interferences caused by elastic layers compared with the conventional frequency-dependent fluid indicator. The frequency-dependent fluid mobility takes into account the dispersion features associated with hydrocarbon reservoirs, and it provides a new way to detect the location of hydrocarbon reservoirs and characterize their spatial distribution.

To optimize well pattern during miscible gas injection process via heuristic techniques

To detect optimum well locations for new injection wells one must generally notice to existing well locations, reservoir shape, capital cost per well construction in each area as well as recovery increase relevant to new well layout. Designing injection process presents inverse optimization issue whereas adjusting exploitation wells prior to primary recovery exhibits classic optimization problem. Most important design factor namely injection well layout has no unique explicit solution to solve via analytical or numerical techniques thus one can propose meta or hyper heuristic approaches to solve such problems. Our main novelty in this work is that here we cooperate four heuristic optimization approaches with our self made fast simulation technique to optimize well locations for two exemplar miscible gas injection processes. We employ MATLAB software to construct artificial porous media prototypes with different uncertainties to investigate optimization technique performances in low rather than high risk media. Outcomes illustrate that approaches like artificial immune system or particle swarm optimization which exhibit strong local search can effectively detect optimal well locations in high risk porous media. Results also show that solution techniques such as Monte Carlo that have strong global search capabilities at expense of weak local search can discover optimum well locations only in media with low uncertainty.

Management of suction cup induced palatal bone resorption in xerostomia patient with sunken cheek appearance: A therapeutic and esthetic treatment option- A case report

Salivary reservoir in maxillary denture offers an effective, non-invasive approach in the treatment of edentulous patients afflicted with xerostomia. It is always desirable to have large volume reservoir in order to decrease the inconvenience of repeated refilling, however, increased bulk of palatal reservoir often leads to discomfort in speech, swallowing and acceptance of such prosthesis. In designing of size and shape of reservoir in the present case, large volume was achieved utilizing circular palatal resorption area, and proper shape was ensured by duplication of functional palatal contour. Adequate voluntary wetting of mouth was effected by “swallowing control saliva release” mechanism of the flexible reservoir lid. Sunken cheek appearance was addressed by using an easy, economical, and effective method of detachable cheek plumpers.

Investigation of Hydrodynamic Characteristics of Flow Caused by Dam Break around a Downstream Obstacle Considering Different Reservoir Shapes

Investigation of Hydrodynamic Characteristics of Flow Caused by Dam Break around a Downstream Obstacle Considering Different Reservoir Shapes

Comparative Analysis & Design of Elevated Storage Reservoir (ESR) By Manually & Software

Abstract: Water tanks are important public utility and industrial structure. The design and construction method used in reinforced concrete are influenced by the prevailing construction practices ,the physical property of the material and the climatic conditions water tanks are classified on the basis of their shape and position of structure storage reservoirs and overhead tank are used to store water all tanks are designed as crack free structure to eliminate any leakage . The principle objective of this project is to plan, analysis and design a circular overhead tank of 750lakh litters capacity. In this project all structural elements of circular water tank are analysed and design by using manually and ETAB software . this project giuesin brief ,The theory behind the design of liquid retaining structures (Elevated circular water tank ) using limit state method with reference to IS: 3370 (2009)and IS456:2000 The behaviour of structure for the parameters like story drift ,displacement stiffness ,deflection ,storey shear ,base shear , area of steel ,for circular water tank are studied on ETAB software and then comparison of the results is made between manually design By this study we say that the circular water tank analysis and design on ETAB software is more economical and safe than manually design of water tank. Keywords: Circular water tank , Seismic pressure, Population Forcasting, Limit state method ,working stress method , ETAB .

Characterization and Redesigning of Mada Batu Small Scale Irrigation Scheme, West Arsi Zone of Oromia Region

Irrigation enhances agricultural production, improves the food supply and income of rural population in Ethiopia. From this important viewpoint irrigation projects were widely studied, planned and implemented throughout the country. However, little or no attention was given to the monitoring and evaluation of the performance of already established schemes. The aim of this study was to characterize and redesign of Mada-Batu small scale irrigation scheme in order to improve the performance of the irrigation system. Firstly, scheme was characterized in terms of capacity, dimensions and functionality of reservoir, main and secondary canal and then redesign of the scheme was done depending on the current command area of the scheme. The scheme has trapezoidal shape of reservoir with a capacity of 2604 m 3 live storage along with trapezoidal shape of main canal with average size of 161, 59, 38.2 cm at the top, bottom and depth respectively and maximum discharge capacity when gate was fully opened at off take was 70 l/sec. The overall efficiency of the scheme is rated at reasonable category. The current redesigned capacity of main canal was 524 l/s and dimensions of 253.9, 74 and 60 cm at the top, bottom and depth respectively. Keywords: Mada-Batu, small scale irrigation scheme, characterization, command area, redesigning DOI: 10.7176/CER/13-3-01 Publication date: May 31 st 2021

Investigation of Nonlinear Behaviour of Semiburied Cylindrical Concrete Reservoir without Dynamic Load Effect

This study aimed to examine the effect of rigid and flexible foundations on the response by a semiburied water storage reservoir. In this study, the reservoir support conditions of both flexible and inflexible states were studied. The seismic behaviour of reinforced and prestressed concrete reservoirs was compared based on their support conditions. The powerful numerical method FEM was used to study about the nonlinear behaviour of cylindrical reservoirs using static and dynamic nonlinear analysis. The values of the results correcting factor in the design codes and standards were evaluated. Moreover, the response correcting behaviour (R) was evaluated based on the findings from a push-over and nonlinear dynamic analysis. This research finding indicated that the reservoir shapes and support types affect the deformability of the reservoirs. Reservoirs with prestressed concrete show less flexibility compared to reinforced concrete reservoir. Finally, it is resulted that displacement, base shear, and wave height obtained from time history analysis are more than those of response spectrum analysis, indicating insufficiency of response spectrum analysis.