Comparative Analysis of Tracers Against Pressure Pulse Code Interference Testing based on the Numerical Simulations of the Synthetic Oilfields with Complicated Geology

2021 ◽  
Author(s):  
Artur Mikhailovich Aslanyan ◽  
Rushana Rinatovna Farakhova ◽  
Danila Nikolayevich Gulyaev ◽  
Ramil Anvarovich Mingaraev ◽  
Ruslan Ildarovich Khafizov
Keyword(s):  
Numerical Simulations ◽  
Pressure Pulse ◽  
Accurate Estimation ◽  
Reservoir Properties ◽  
Advantages And Disadvantages ◽  
Well Spacing ◽  
Reservoir Permeability ◽  
The Cross ◽  
Specific Implementation ◽  
Synthetic Models

Abstract The main objective of the study is to compare the results of the cross-well tracers survey against the pulse code pressure interference testing (PCT) for the complicated geological structures. The study was based on the numerical simulations on the synthetic 3D models with popular geological complications, such as faults, vertical and horizontal reservoir anisotropy and pinch-outs. The study has set a special focus on quantitative analysis of the reservoir properties estimated by tracers and PCT as against the known values. This provides a text-book examples of advantages and disadvantages of both surveillance methods in different geological environment. Pulse code testing is specific implementation of pressure interference testing by creating a series of injection/production rate changes accordingly to a preset schedule to create a "pressure code" and monitoring the pressure response in the offset wells. The use of high-resolution quarts gauges is highly beneficial in case of large cross-well intervals scanning or poor reservoir quality in case of regular inter-well spacing. The tracer survey is based on injecting a liquid with chemical markers and subsequent capturing the markers at surface samples in the offset wells. The modern markers are relatively cheap and can be captured at very low concentrations thus making the cross-well scanning available even for high inter-well spacing. For synthetic models with vertical inhomogeneity the PCT provides a close estimate for compound dynamic reservoir properties (transmissibility and pressure diffusivity). For synthetic models with lateral inhomogeneity the PCT provides an accurate estimation for effective reservoir thickness and permeability. Tracers survey is not able to assess the reservoir thickness. The popular methods to assess reservoir permeability from tracers survey show a substantial deviation from the true reservoir permeability for synthetic models with vertical and lateral heterogeneity. This leads to conclusion that the most reliable application of racers survey is a qualitative assessment of cross-well connectivity and quantitative estimate of permeability in homogenous reservoirs. The first study of quantitative comparison of tracer survey against pressure pulse-code interference survey. Tracer survey and PCT efficiency was compared on 3D numerical models. Presence of synthetic models, describing geological complications, which may be seen very often on real reservoirs, provides a reliable basis for comparison.

The Clipper Field, Blocks 48/19a, 48/19c, UK North Sea

2003 ◽  
Vol 20 (1) ◽  
pp. 691-698
Author(s):  
M. J. Sarginson
Keyword(s):  
North Sea ◽  
Upper Permian ◽  
Lower Permian ◽  
Reservoir Properties ◽  
Gas Field ◽  
Field Development ◽  
Matrix Permeability ◽  
Recoverable Reserves ◽  
Reservoir Permeability ◽  
Sandstone Formation

AbstractThe Clipper Gas Field is a moderate-sized faulted anticlinal trap located in Blocks 48/19a, 48/19c and 48/20a within the Sole Pit area of the southern North Sea Gas Basin. The reservoir is formed by the Lower Permian Leman Sandstone Formation, lying between truncated Westphalian Coal Measures and the Upper Permian evaporitic Zechstein Group which form source and seal respectively. Reservoir permeability is very low, mainly as a result of compaction and diagenesis which accompanied deep burial of the Sole Pit Trough, a sub basin within the main gas basin. The Leman Sandstone Formation is on average about 715 ft thick, laterally heterogeneous and zoned vertically with the best reservoir properties located in the middle of the formation. Porosity is fair with a field average of 11.1%. Matrix permeability, however, is less than one millidarcy on average. Well productivity depends on intersecting open natural fractures or permeable streaks within aeolian dune slipface sandstones. Field development started in 1988. 24 development wells have been drilled to date. Expected recoverable reserves are 753 BCF.

scholarly journals Discussion on the Theoretical Basis for Cross-Over Method Applied to Downhole Wave Velocity Test

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Qing Dong ◽  
Zheng-hua Zhou ◽  
Su Jie ◽  
Bing Hao ◽  
Yuan-dong Li
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Wave Velocity ◽  
Theoretical Basis ◽  
Influence Factors ◽  
P Wave ◽  
Engineering Practice ◽  
S Wave ◽  
Simulation Results ◽  
The Cross

At engineering practice, the theoretical basis for the cross-over method, used to obtain shear wave arrival time in the downhole method of the wave velocity test by surface forward and backward strike, is that the polarity of P-wave keeps the same, while the polarity of S-wave transforms when the direction of strike inverted. However, the characteristics of signals recorded in tests are often found to conflict with this theoretical basis for the cross-over method, namely, the polarity of the P-wave also transforms under the action of surface forward and backward strike. Therefore, 3D finite element numerical simulations were conducted to study the validity of the theoretical basis for the cross-over method. The results show that both shear and compression waves are observed to be in 180° phase difference between horizontal signal traces, consistent with the direction of excitation generated by reversed impulse. Furthermore, numerical simulation results prove to be reliable by the analytic solution; it shows that the theoretical basis for the cross-over method applied to the downhole wave velocity test is improper. In meanwhile, numerical simulations reveal the factors (inclining excitation, geophone deflection, inclination, and background noise) that may cause the polarity of the P-wave not to reverse under surface forward and backward strike. Then, as to reduce the influence factors, we propose a method for the downhole wave velocity test under surface strike, the time difference of arrival is based between source peak and response peak, and numerical simulation results show that the S-wave velocity by this method is close to the theoretical S-wave velocity of soil.

scholarly journals Discharge Estimation Using Tsallis and Shannon Entropy Theory in Natural Channels

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1786
Author(s):  
Jitendra Kumar Vyas ◽  
Muthiah Perumal ◽  
Tommaso Moramarco
Keyword(s):  
Flow Velocity ◽  
Surface Flow ◽  
Tsallis Entropy ◽  
Accurate Estimation ◽  
Mean Flow ◽  
Flow Area ◽  
Cross Sectional ◽  
The Cross ◽  
Discharge Estimation ◽  
Mean Flow Velocity

Streamflow measurements during high floods is a challenge for which the World Meteorological Organization fosters the development of innovative technologies for achieving an accurate estimation of the discharge. The use of non-contact sensors for monitoring surface flow velocities is of interest to turn these observed values into a cross-sectional mean flow velocity, and subsequently, into discharge if bathymetry is given. In this context, several techniques are available for the estimation of mean flow velocity, starting from observed surface velocities. Among them, the entropy-based methodology for river discharge assessment is often applied by leveraging the theoretical entropic principles of Shannon and Tsallis, both of which link the maximum flow velocity measured at a vertical of the flow area, named the y-axis, and the cross-sectional mean flow velocity at a river site. This study investigates the performance of the two different entropic approaches in estimating the mean flow velocity, starting from the maximum surface flow velocity sampled at the y-axis. A velocity dataset consisting of 70 events of measurements collected at two gauged stations with different geometric and hydraulic characteristics on the Po and Tiber Rivers in Italy was used for the analysis. The comparative evaluation of the velocity distribution observed at the y-axis of all 70 events of measurement was closely reproduced using both the Shannon and Tsallis entropy approaches. Accurate values in terms of the cross-sectional mean flow velocity and discharge were obtained with average errors not exceeding 10%, demonstrating that the Shannon and Tsallis entropy concepts were equally efficient for discharge estimation in any flow conditions.

Physician judgment in clinical settings: methodological influences and cognitive performance

1993 ◽  
Vol 39 (7) ◽  
pp. 1468-1480 ◽  
Author(s):  
N V Dawson
Keyword(s):  
Decision Making ◽  
Cognitive Biases ◽  
Critical Evaluation ◽  
Medical Decision ◽  
Accurate Estimation ◽  
Advantages And Disadvantages ◽  
Cognitive Limitations ◽  
Intuitive Judgments ◽  
Analytical Approaches

Abstract Understanding the quality of physicians' intuitive judgments is essential in determining the appropriate use of their judgments in medical decision-making (vis-a-vis analytical or actuarial approaches). As part of this process, the quality of physicians' predictions must be assessed because prediction is fundamental to common clinical tasks: determining diagnosis, prognosis, and therapy; establishing monitoring intervals; performing screening and preventive maneuvers. Critical evaluation of predictive capabilities requires an assessment of the components of the prediction process: the data available for prediction, the method used for prediction, and the accuracy of prediction. Although variation in and uncertainty about the underlying data elements are often acknowledged as a source of inaccurate predictions, prediction also can be confounded by both methodological and cognitive limitations. During the past two decades, numerous factors have been recognized that may bias test characteristics (sensitivity and specificity). These same factors may also produce bias in intuitive judgments. The use of cognitive processes to simplify judgment tasks (e.g., the availability and representativeness heuristics) and the presence of certain biases in the judgment process (e.g., ego, regret) may present obstacles to accurate estimation of probabilities by physicians. Limitations on the intuitive use of information (cognitive biases) have been demonstrated in both medical and nonmedical decision-making settings. Recent studies have led to a deepening understanding of the advantages and disadvantages of intuitive and analytical approaches to decision making. Here, many aspects of the basis for this understanding are reviewed.

Experimental Study and Pore Network Modeling of Formation Damage Induced by Fines Migration in Unconsolidated Sandstone Reservoirs

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Xiaodong Han ◽  
Liguo Zhong ◽  
Yigang Liu ◽  
Tao Fang ◽  
Cunliang Chen
Keyword(s):  
Water Injection ◽  
Three Dimensional ◽  
Experimental Results ◽  
Ion Concentration ◽  
Formation Damage ◽  
Fluid Viscosity ◽  
Pore Scale ◽  
Reservoir Properties ◽  
Reservoir Permeability ◽  
Sandstone Reservoirs

Abstract Fine migration is always considered as one of the major mechanisms that are responsible for formation damage. The unwanted reduction of reservoir permeability would result in the decline of water injection and consequent oil production, especially for the unconsolidated sandstone reservoir. For better understanding, the mechanisms of formation damage in pore-scale, a new three-dimensional pore-scale network model (PNM) is proposed and developed to simulate formation damage caused by particle detachment, migration, and capture in pore throats based on force analysis. Experiments are also conducted on the formation damage characteristics of an unconsolidated core. Both X-ray diffraction and scanning electron microscope (SEM) are applied to understand the microscopic reservoir properties. The experimental results show that the studied core has a strong flowrate sensitivity. A comparison between experimental results and PNM simulation results is conducted. The simulated results agree well with the experimental data, which approves the efficiency and accuracy of the PNM. Sensitivity analysis results show that larger particle sizes, higher flowrate, higher fluid viscosity, and lower ion concentration of the fluids would contribute to the formation damage, which could provide guidance for the development of unconsolidated sandstone reservoirs with strong sensitivity.

Influence of the Exhaust System on Performance of a 4-Cylinder Supercharged Engine

1998 ◽  
Vol 120 (4) ◽  
pp. 855-860 ◽  
Author(s):  
F. Trenc ◽  
F. Bizjan ◽  
A. Hribernik
Keyword(s):  
Pressure Pulse ◽  
Exhaust System ◽  
Medium Size ◽  
Advantages And Disadvantages ◽  
Available Energy ◽  
Good Utilization ◽  
The Individual ◽  
Radial Turbines ◽  
Manifold System ◽  
Four Cylinders

Twin entry radial turbines are mostly used to drive compressors of small and medium size 6-cylinder diesel engines where the available energy of the undisturbed exhaust pulses can be efficiently used to drive the turbine of a turbocharger. Three selected cylinders feed two separated manifold branches and two turbine inlets and prevent negative interaction of pressure waves and its influence on the scavenging process of the individual cylinders. In the case of a four-stroke, 4-cylinder engine, two selected cylinders, directed by the firing order, can be connected to one (of the two) separated manifold branches that feeds one turbine entry. Good utilization of the pressure pulse energy, together with typically longer periods of reduced exhaust flow can lead to good overall efficiency of the “two-pulse” system. Sometimes this system can be superior to the single manifold system with four cylinders connected to one singleentry turbine. The paper describes advantages and disadvantages of the above described exhaust systems applied to a turbocharged and aftercooled 4-cylinder Diesel engine. Comparisons supported by the analyses of the numerical and experimental results are also given in the presented paper.

Using the Characteristic Equation to Estimate the Initial Values for Numerical Forecasts

2016 ◽  
Vol 20 (7) ◽  
pp. 1147-1151
Author(s):  
Eiichi Matsunaga ◽  
◽  
Tomomasa Ohkubo
Keyword(s):  
Wave Equation ◽  
High Resolution ◽  
Numerical Simulations ◽  
Shallow Water ◽  
Characteristic Equation ◽  
Governing Equation ◽  
Water Wave ◽  
Accurate Estimation ◽  
Initial Value ◽  
Shallow Water Wave

Japan is an island nation that experiences frequent earthquakes. When an earthquake occurs, it is important to forecast its resultant tsunami: its size, location, time of arrival, etc. These forecasts are made using numerical simulations. The initial conditions are very important for numerical simulations, but the small number of tide stations makes it difficult to make highly precise forecasts. The distance between stations is normally several tens of km, and this lowers the precision of the initial data afforded by them. It is therefore common to use data interpolated from the sparse observation data at timet=0. Even so, high-resolution interpolation cannot be expected since the original data is of poor quality. In addition, the interpolated values may not be physically valid because the governing equation may not have been considered when the data were interpolated. We therefore propose a new method of estimating the initial value by using a characteristic equation. In this method, we replace the spatial resolution with time resolution. This results in a high-resolution initial value because the same place is measured more than once. In addition, the characteristic equation is based on the governing equation. Therefore, in this method, an accurate estimation of initial value is considered to be possible. In this paper, we show two applications of this approach, one for a dimensional shallow water wave equation and one for Euler’s equation. The shallow water wave equation is for the tsunami, and the Euler equation is the governing equation of the numerical weather forecast.

scholarly journals Estimating the Probability of Compound Floods in Estuarine Regions

2020 ◽  
Author(s):  
Wenyan Wu ◽  
Seth Westra ◽  
Michael Leonard
Keyword(s):  
Frequency Analysis ◽  
Flood Risk ◽  
Data Availability ◽  
Flood Frequency Analysis ◽  
Accurate Estimation ◽  
Flood Events ◽  
Advantages And Disadvantages ◽  
Comparative Review ◽  
Flood Probability

Abstract. The quantification of flood risk in estuarine regions relies on accurate estimation of flood probability, which is often challenging due to the rareness of flood events and their multi-causal (or compound) nature. Failure to consider the compounding nature of estuarine floods can lead to significant underestimation of flood risk in these regions. This study provides a comparative review of alternative approaches for estuarine flood estimation; namely, traditional univariate flood frequency analysis applied to both observed historical data and simulated data, and multivariate frequency analysis applied to flood events. Three specific implementations of the above approaches are evaluated on a case study – the estuarine portion of Swan River in Western Australia, highlighting the advantages and disadvantages of each approach. The theoretical understanding of the three approaches, combined with findings from the case study, enable generation of guidance on method selection for estuarine flood probability estimation, recognising issues such as data availability, complexity of the application/analysis process, location of interest within the estuarine region, computational demands and whether or not future conditions need to be assessed.

scholarly journals Estimating the probability of compound floods in estuarine regions

2021 ◽  
Vol 25 (5) ◽  
pp. 2821-2841
Author(s):  
Wenyan Wu ◽  
Seth Westra ◽  
Michael Leonard
Keyword(s):  
Frequency Analysis ◽  
Flood Risk ◽  
Data Availability ◽  
Flood Frequency Analysis ◽  
Accurate Estimation ◽  
Flood Events ◽  
Advantages And Disadvantages ◽  
Comparative Review ◽  
Flood Probability

Abstract. The quantification of flood risk in estuarine regions relies on accurate estimation of flood probability, which is often challenging due to the rareness of hazardous flood events and their multi-causal (or “compound”) nature. Failure to consider the compounding nature of estuarine floods can lead to significant underestimation of flood risk in these regions. This study provides a comparative review of alternative approaches for estuarine flood estimation – namely, traditional univariate flood frequency analysis applied to both observed historical data and simulated data, as well as multivariate frequency analysis applied to flood events. Three specific implementations of the above approaches are evaluated on a case study – the estuarine portion of Swan River in Western Australia – highlighting the advantages and disadvantages of each approach. The theoretical understanding of the three approaches, combined with findings from the case study, enable the generation of guidance on method selection for estuarine flood probability estimation, recognizing issues such as data availability, the complexity of the application/analysis process, the location of interest within the estuarine region, the computational demands, and whether or not future conditions need to be assessed.

Dual and single hedging strategy: a novel comparison from the direct and cross hedging perspective

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yun Feng ◽  
Yan Cui
Keyword(s):  
Exchange Rates ◽  
Foreign Exchange ◽  
Oil Prices ◽  
Performance Criteria ◽  
Foreign Exchange Rates ◽  
Hedging Strategy ◽  
Content Type ◽  
Advantages And Disadvantages ◽  
Cross Hedging ◽  
The Cross

PurposeThe purpose of this paper is to deeply study and compare the dual and single hedging strategy, from the direct and cross hedging perspective.Design/methodology/approachThe authors not only first consider the dual hedge of integrated risks in this oil prices and foreign exchange rates setting but also make a novel comparison between the dual and single hedging strategy from a direct and cross hedging perspective. In total, six econometric models (to conduct one-step-ahead out-of-sample rolling estimation of the optimal hedge ratio) and two hedging performance criteria are employed in two different hedging backgrounds (direct and cross hedging).FindingsResults show that in the direct hedging background, a dual hedge cannot outperform the single hedge. But in the cross dual hedging setting, a dual hedge performs much better, possibly because the dual hedge brings different levels of advantages and disadvantages in the two different settings and the superiority of the dual hedge is more obvious in the cross dual hedging setting.Originality/valueThe existing literature that deals with oil prices and foreign exchange rates mostly concentrates on their relationship and comovements, while the dual hedge of integrated risks in this setting remains underresearched. Besides, the existing literature that deals with dual hedge gets its conclusions only based on a single specific background (direct or cross hedging) and lacks deeper investigation. In this paper, the authors expand the width and depth of the existing literature. Results and implications are revealing.

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