bluuebunny/crossref_metadata_2025_split huggingface dataset:
Arps Transient Analysis: 10 Simple Steps for Tight Gas Evaluation
Authors: Creus Fernando Luis , Terrasanta Gustavo Ramón 
Published: May 2017

Abstract
It has been more than 70 years since J.J. Arps1 firstly documented the empirical equations used to analyse production trends. With the development of the unconventional reservoirs, other more complex techniques were presented to forecast the production history and determine the estimated ultimate recovery (EUR). Arps Transient Analysis seems to be in the opposite direction.
Arps formulas are widely used and highlypopular because of their simplicity and easy understanding. However, the cited author published his research in a context where the boundary-dominated flow period described the common behaviour of a field. On the other hand, unconventional reservoirs are characterized by the transient flow, and therefore, using Arps in this context, without the appropriate knowledge of the flow regimes involved, will certainly lead to incorrect conclusions.
Many other authors have already discussed the close relationship between the hyperbolic and diffusivity equations. Once the hyperbolic formulas start to be combined with flow regimes identification plots, the Arps formulations become a reliable transient analysis methodology.
Based on the complementation of hyperbolic and diffusivity equations, this paper provides a compiled methodology for tight gas evaluation. The first part introduces the Arps Transient Analysis and its final goal: a sound EUR calculation. The second part provides a comprehensive methodology to deeply understand the flow regimes present in the reservoir, both for gas and water, and how each flow parameter can be related to the well productivity and the ultimate recovery.
A Variant of Particle Swarm Optimization for Uncertainty Quantification
Authors: Babin V. , Yaubatyrov R. R. , Ushmaev O. , García D. Kremer , Golitsyna M. , Semenikhin A. , Ciaurri D. Echeverría 
Published: May 2017

Abstract
In this paper we present an enhanced and new optimization algorithm based on Particle Swarm Optimization (PSO) that can be used in reservoir characterization applications to determine multiple solutions that reproduce measurements within satisfactory accuracy. The method is illustrated on a history-matching problem where significant speed-up is obtained with respect to a standard PSO implementation.
PSO is a global-search iterative technique where the solution space is explored using a swarm of particles. In every PSO iteration each particle is individually attracted to: the best point (in terms of objective function) in the swarm during last iteration, the best point visited by that particle in all iterations, and the best point found by any particle in all iterations. In the PSO variant proposed here, rather than single points, collections of points carefully selected are used as attractors. The algorithm ensures by a series of mechanisms that the number of attractors is adequate and that the solutions progressively determined are sufficiently different from one another.
A series of experiments were performed with a synthetic model based on a real oil field for which nine years of historical data were generated. Both standard PSO and the PSO variant were tested to obtain several models that reproduced well rates within acceptable accuracy. In order to determine multiple solutions via standard PSO (which usually returns only one solution), a number of independent runs with different initial conditions were considered (i.e., standard PSO was run in multi-start fashion). In our experiments, which had a budget of 3,072 simulations in the two cases, the number of solutions found on average by standard PSO and by our PSO variant was 8 and 837, respectively. That is, multi-start standard PSO may require, on average, around 100 times more simulations than our PSO variant to compute a comparable number of models (possibly) distributed in similar manner in the solution space. These results may be explained by noticing that the search for multiple solutions may be more efficient when all information is considered simultaneously than separately by means of a number of independent runs.
Standard PSO, when applied to many uncertainty quantification problems, may provide only one solution because the particles in the swarm generally tend to converge to essentially a single point. The Ensemble Kalman Filter (EnKF), which has lately become a very popular history-matching algorithm, presents a similar problem because the ensemble sometimes collapses into one solution. The PSO variant introduced in this work can be an efficient alternative to these algorithms in reservoir characterization since it has been designed to provide multiple and different solutions in a single run.
EOR Simulation of Convection and Diffusion in Fracture During CO2 Injection in Tight Oil Reservoir
Authors: Fang Xin , Yue Xiangan , Fang Wei , Lu Shuyun , Geng Zhi 
Published: May 2017

Abstract
Fractures always play a significant role in tight oil reservoir development. Due to the high conductivity, the efficiency of mass transfer between fracture and matrix determines the ultimate development effectiveness especially during gas injection process. Convection and diffusion in fracture have been recognized as two dominant mechanisms affecting the mass transfer. In current studies, many authors illustrate this process by reducing the fracture to a lower-dimensional structure and imposing inconsistent boundary conditions on fracture surface. However, it hardly reveals the continuity of mass transfer between fracture and matrix in this kind of simplification.
In this paper, we studied the effect of convection and diffusion in fractures on the fracture-matrix mass transfer as well as the final recovery by developing a coupled model considering mass transfer continuity on the fracture wall. The model accounts for convection and two dimensional diffusions in the fracture, vertical convection and diffusion in the matrix. The interaction between matrix and fracture is expressed by exposing a consistent boundary condition. Subsequently, a numerical method was applied to solve the model. The model was validated by available experimental data. And then we compared the results generated by model under inconsistent boundary condition. Finally, we discussed the effect of injection rate and matrix permeability on convection-diffusion mass transfer efficiency.
The results show that convection and two dimensional diffusions in fracture promoted material transport between fracture and matrix during CO2 injection process. And convection in fracture favors transversal vertical diffusion both in fracture and matrix, which is the main mechanism for mass transfer in fracture-matrix system. In addition, with decreasing matrix permeability, transverse vertical diffusion in matrix dominated in mass transfer gradually.
The proposed model sheds some light on mechanism of mass transfer during gas injection in tight oil reservoirs. The method provides EOR practice for reference.
Integrated Prospect Evaluation and Characterization Using Pre-Stack Seismic Data, Mansoura Area, onshore Nile Delta, Egypt
Authors: Fathy W. , Shams A. 
Published: May 2017

Abstract
In 2003, an aggressive drilling program started in Mansoura area in the onshore Nile Delta, with high success ratio. The program benefited from the direct hydrocarbon indicators provided by the post stack seismic data. After proving hydrocarbon presence in the field many reservoirs explored, however some challenges appeared lately. The most important challenges are the lithology and fluid discrimination due to the shale behavior, furthermore, the delineation of different reservoir properties like clay content, water saturation, and porosity proved to be challenging.
Analysis of pre-stack seismic data for different reservoir properties prediction is commonly used for reservoir characterization. To enhance pre-stack seismic data quality some seismic gathers preconditioning flowcharts have been applied on the pre-stack data. The wavelet spectral analysis has been performed after conditioning the data then different techniques like the AVO simultaneous inversion, AVO analysis and density inversion have been applied on both west Dikirnis and west Khilala fields.
Building rock physics model was carried out in the onshore Nile Delta to link the elastic properties and the reservoir properties. The model implemented in the unexplored areas within the concession to minimize the drilling risk of the delineated prospects. The rock physics model built in the area of study helped significantly to discriminate between wet sand, shale and gas sands. The middle and late Messinian are typically sand rich sections with excellent reservoir quality encountered in the drilled wells within both fields. Different reservoir properties predicted using the advanced inversion techniques in addition to the well data showing strong correlation at the well locations.
The reliability of the far and ultra-far seismic data was encouraging. The cross-plot of the acoustic impedance versus shear impedance represents a useful technique in the onshore Nile Delta for sand and shale discrimination. Using Elastic impedance logs we can discriminate the water bearing sand, hydrocarbon sand and shale especially at the ultra-far angle.
Regional Scale 3D Geomechanical Modeling For Evaluating Caprock Integrity And Fault Leakage Potential During Underground Gas Storage Operations In A Produced Field
Authors: Sun Junchang , Wang Jieming , Zheng Dewen , Xu Hongcheng , Li Chun , Zhao Kai , Zhong Rong 
Published: May 2017

Abstract
This paper presents a regional scale 3D geomechanical modeling study of the HB large produced gas field located in the northwest of China, which was converted to UGS facility in June 2013. The reservoir is approximately 3500m deep and there are three faults completely penetrate the caprock. The potential of the caprock failure and reservoir-bounding faults leakage after 14 years depleted production and their dynamic containment during UGS operations must be comprehensively evaluated.
In this study, a multi-disciplinary approach was used to build the static regional-scale 3D geomechanical model through interagrated analysis of geologic, seismic, well drilling, logging and rock experimental data. Gas-bearing reservoir, primary and secondary caprock, three main faults as well as underburden were all covered in this model. Comparing to the reservoir model, the regional scale geomechanical model is expanded laterally by about 5 times. Reservoir pressure during gas production and subsequent annual gas injection/withdrawal was passed to the model using Eclipse software.
The 3D fluid-dynamical geomechanical model was calibrated using the surface vertical displacements measured by InSAR interferometry over the second operation cycle. Simulation indicated that the change of reservoir pressure has a significant impact on the state of the regional-scale stress. Significant differences of in-situ stress have occurred on the both sides of the faults after gas production. It was found that the caprock failure and fault slip had not occur during past gas production, thus ensuring the safety of the UGS conversion. However, distribution of the in-situ stress became more heterogeneous due to high rate gas injection and withdrawal during the UGS operations that may have a significant impact on well integrity. Shear failure and hydraulic fracture of the caprock will not occur during the long term gas storage operations. But the model predicted a maximum shear slip up to 5 cm associated with cyclic gas injection and extraction and the slip tendency of the Southern fault is increasing with the UGS operations which will be weak spot of the UGS integrity. Consequently, it is strongly recommended to strengthen the dynamic monitoring of the Southern fault.
This paper provides a comprehensive geomechanical simulation method for assessment of the risk of caprock integrity failure and fault leakage of large UGS in produced gas filed during long term operations. This work is particularly important in the selection and design of UGS in complex faulted depleted gas filed in China.
Application of Multi-Level and High-Resolution Fracture Modeling in Field-Scale Reservoir Simulation Study
Authors: Gong Bin , Thakur Ganesh , Qin Guan , Peng Xian , Xu Wei 
Published: May 2017

Abstract
Carbonate formations are usually highly fractured. The fractures exist at all length scales ranging from microscopic fissures to kilometer-size structures. Consequently, it is vitally important to rigorously characterize the multi-scale fracture system and to accurately model the fluid flow in such highly fractured porous media. In this paper, we will present an integrated workflow for characterization of natural fracture system and accurate numerical modeling of fluid flow in fractured rocks. We have then applied the workflow in a field-scale reservoir simulation study, and the simulation results demonstrate significant advantages of the proposed workflow over the conventional dual-porosity/dual-permeability modeling approach.
The fracture characterization usually involves the integration of multiple data sources including core analysis, image logs and seismic interpretations etc., at different scales. The fracture mappings are thus required to perform at different length scales and resolutions. In this study, we present a systematic approach that characterizes the actual fracture distribution with seismic and log interpretations. Firstly, the small-scale fractures are interpreted using image logs and seismic anisotropy analysis with a co-Kriging and stochastic modeling approach. The small-scale fractures are initially constructed in an explicit fashion, and are then incorporated in the matrix medium using a flow-based upscaling procedure. Secondly, the large-scale fractures are mapped out from post-stack seismic data with ant-tracking and maximum curvature analysis. The reservoir is then gridded into unstructured tetrahedral or prism meshes to fully resolve these large fractures. This discrete fracture model (DFM) is employed in a reservoir simulation study based on such grid system.
We apply the procedure for simulation study and history match on a portion of a gas reservoir which is highly fractured in Longwangmiao formation in Southwest China. Currently, there are 7 horizontal and 2 vertical wells in operation in this block and some large-scale fractures are connected to edge water causing early water breakthrough. We partition the reservoir block into about 0.6 million cells, in which 153 large-scale and thousands of small-scale fractures are fully resolved. The simulation study is carried out and history match is successfully achieved using an extended Ensemble Karman Filter (EnKF) algorithm. Due to the fast edge water invasion, both gas and water rates exhibit sharp changes in a short time period. The proposed simulation procedure is able to efficiently capture such extreme flow dynamics and achieve good history match. The simulation results clearly demonstrate the major advantages in efficient multi-scale fracture characterization and numerical simulation in the proposed workflow.
Low-Salinity Fines-Assisted Waterflooding: Multiscale Analytical and Numerical Modelling
Authors: Borazjani S. , Behr A. , Genolet L. , Kowollik P. , You Z. , Bedrikovetsky P. 
Published: May 2017

Abstract
The aim of this work is the development of mathematical models for oil–water flow with varying injected water compositions in oil reservoirs. The model accounts for two main mechanisms of low salinity waterflooding (LSW): wettability alteration and salinity-variation-induced fines migration. Analytical and numerical models are developed and applied to low salinity fines-assisted core flood tests.
In large reservoir scale, the general system of equations permits for an analytical solution. The solution is obtained by recently developed splitting technique, where the stream function is used as a variable instead of time. Large-scale approximation assumes that six dimensionless groups for dissipative and non-equilibrium effects are negligibly small. Numerical results are obtained for the general system, which accounts for dissipative and non-equilibrium effects.
The effects of fines migration and wettability variation on oil recovery are discovered as two separate mechanisms in LSW. The significant EOR-effects of both mechanisms are observed under the typical oil reservoir conditions.
Utilization of Geosciences, Geostatistics, and Fluid Flow Simulations to Evaluate Well Placement Sensitivity
Authors: Salahuddin Andi A. , Qureshi Zaghum U. , Bandyopadhyay Indrajit , Seiari Jamila M. , Hammadi Khaled E. 
Published: May 2017

Abstract
The paper is continuation of SPE-175682 and SPE-182963. This work illustrates horizontal well placement optimization studies conducted on a Cretaceous complex carbonate reservoir with thin oil column and strong water drive reservoir. A further complication for the well placement is the presence of some thin high permeability streaks intervals with permeability value of up to 1 Darcy. Early water breakthrough encountered in the existing oil producers is a serious problem which results in lower oil production rates, lower oil recovery, and increased lifting cost. In addition, premature water breakthrough would leave behind bypassed oil zones. Hence determining the optimum location of the wells is a critical and crucial decision to be made during a field development plan.
In this study, we apply integrated geosciences, geostatistical, and flow simulations to assess options for well placement. Base case porosity, permeability, and water saturation realization was selected from multi-realizations performed in the static model which was then used for sensitivity in fluid flow simulations. Flow simulation was used to analyze the performance of the well considering horizontal wells length, well azimuth, well inclination, wells position relative to the reservoir top as well as its position relative to the water contact. In addition, multi-scenarios of well placement relative to the high permeability intervals were created to see the impact on the oil rate, plateau, and water breakthrough time.
The flow simulation results show that the 4000 feet horizontal well that penetrating the upper high permeability streak gives the best performance in most of the cases. In contrast, the performance of the horizontal wells deteriorated rapidly once the well hit the lower high permeability streaks.
Some producers in the studied reservoirs have been drilled using the multidiscipline study recommendation. Actual property derived from the newly drilled wells displayed a very reasonable match to the expected property from model. In addition, production test and well commissioning result also showed comparable match with what was expected from dynamic simulation.
Delayed Sowing Improved Barley Yield in a No‐Till Rainfed Mediterranean Agroecosystem
Authors: Plaza‐Bonilla Daniel , Álvaro‐Fuentes Jorge , Bareche Javier , Masgoret Albert , Cantero‐Martínez Carlos 
Published: May 2017

Core Ideas
Sowing delay and cultivar effects on cereal production and water and N use efficiencies were studied.
Sowing delay increased grain yield due to greater number of grains per m2.
Sowing delay maximized the efficiency in the use of resources.
The effect of delaying sowing date and maturity class on no‐till (NT) winter cereal performance was studied over two periods of 3 yr each. A 3 (sowing date) × 2 (maturity class) randomized complete block design was run for 3 yr with barley (Hordeum vulgare L.) (B‐) (2006–2007 to 2008–2009) and soft wheat (Triticum sp.) (W‐) (2009–2010 to 2011–2012) in northeastern Spain. Sowing dates corresponded to October (D1‐ the standard farming practice), November (D2), and December (D3). Maturity classes corresponded to early (‐EC) and medium (‐MC). Crop aboveground biomass, grain yield, and yield components were analyzed. The water use efficiency of aboveground biomass (WUEb) and grain yield (WUEy), and nitrogen use efficiency (NUE), were calculated. Averaging barley maturity classes and cropping seasons, D2 and D3 increased their grain yields 59 and 46%, respectively, when compared to D1. A greater number of grains per spike, as well as higher WUEb and NUE were observed in D2 and D3 compared to D1 in two of the three barley seasons. A greater thousand kernel weight (TKW) and higher WUEy were observed when sowing was delayed. Averaged across years, WEC presented a greater yield and aboveground biomass for D2 and D3 compared to D1, while for WMC there were no grain yield differences seen between the sowing dates, aboveground biomass or yield components. Our results demonstrate that, in western Mediterranean areas, sowing delay under NT can increase grain yield, WUE and NUE of winter barley, and also of wheat but only during wet years.
Impact of Early Sowing on Winter Wheat Receiving Manure or Mineral Fertilizers
Authors: Christensen Bent T. , Jensen Johannes L. , Thomsen Ingrid K. 
Published: May 2017

Core Ideas
Grain yield benefits of early sown wheat was 0.5 and 1.0 Mg ha−1 for mineral fertilizers and animal manure.
Over‐winter N uptake was 11 kg N ha−1 higher in early than in timely sown wheat.
At harvest, 19 kg N ha−1 more N was removed in early than in timely sown wheat.
The beneficial effect of early sowing compares to that of N catch crops.
Surface‐applied cattle slurry provides a poor N use efficiency and grain protein.
To reduce over‐winter nitrate leaching from temperate soil, nitrate catch crops can be grown between main crops. We hypothesize that earlier sowing can replace catch crops sown before winter wheat (Triticum aestivum L.) and improve wheat yields and N uptake. Early sown (late August) and timely sown (late September) wheat were tested over two cropping seasons (2011–2012 and 2013–2014) using two contemporary cultivars (Hereford and Mariboss) and increasing rates of N (0–300 kg total N ha−1) with animal manure (AM; cattle slurry) or mineral fertilizers (NPK), surface applied in late March. We measured over‐winter N uptake in wheat, harvest yields, and N concentrations in grain and straw. Over‐winter N uptake was 11 kg ha−1 higher for early than for timely sown wheat; at harvest this benefit increased to 19 kg N ha−1. Mariboss yielded more straw than Hereford whereas grain yields did not differ. Early sowing increased grain yields by 0.5 and 1.0 Mg ha−1 for NPK and AM, respectively, regardless of N rate. Grain and straw N concentrations were higher with NPK than with AM, and NPK showed higher N use efficiency (0.48–0.53) than AM (0.15–0.22). Moving sowing of winter wheat from late September to late August provided higher grain and straw yields; the increased over‐winter N uptake suggests that the beneficial effect of earlier sowing may surpass that of a catch crop. Cattle slurry surface applied in late March gave poor N use efficiency and low grain protein content.