bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deformation Processes in Reservoir Engineering of the Limestone and their Influence on the Engineering Calculations
Authors: Belanozhka Aliaksei 
Published: October 2017

Abstract
In the process of developing hydrocarbon deposits in terms of changing baric conditions, not only formation fluids are transformed, but also the rock itself, which possesses elastic properties and is capable of deforming. The article presents approaches to identifying, analyzing and interpreting the manifestations of deformation processes in the development of hydrocarbon deposits in the limestones of the Republic of Belarus. The article presents the methods for the justification and calculation of the values of critical pressures at which the deformation processes in the beds or formations appear.
The main methods by which critical pressure values were determined were:
a method for assessing of the critical bottomhole pressure based on the interpretation of well-test (change in productivity during the removal of PC); a method for determining the critical reservoir pressure, taking into account the construction of specific selection curves for closed deposits; a direct laboratory method for determining critical effective pressures, which significantly reduces permeability, which is associated with deformation processes (studies should be carried out at a constant sample crushing pressure and a variable pore pressure).
Deformation processes significantly (by several orders of magnitude) reduce permeability and are not reversible. In this case, the presence of these processes is noted both in the test of individual wells, and in the process of developing the whole deposit. It is noted that according to the results of studies in 63% of cases, the decrease PI with increasing depression is associated with deformations in the bottomhole zone.
Knowledge of these pressure values allows the correct application of the material balance method to assess hydrocarbon reserves and adapt hydrodynamic reservoir models, to plan efficiently and rationally the implementation and modernization of reservoir pressure maintenance systems and also to predict the change depending on the pressure of the productive characteristics of the wells.
The new thing of this work is in identification and systematizing cases of deformation processes in the limestones of the Republic of Belarus, to justify simple methods for understanding and implementing methods for determining the critical values of pressures at which deformation of collectors occurs. A new method for estimating the reservoir type by the capacitive component is proposed, which evaluates the compressibility of the capacitance during the deformation process, as well as the capacitance volume susceptible to deformation.
Effect of Saturation Alteration on Wellbore Stability during WAG Injection
Authors: Bataee M. , Hamdi Z. , Irawan S. , Ashena R. , Ghassemi M. F. 
Published: October 2017

Abstract
Nowadays, enhanced oil recovery (EOR) injection methods are very popular due to its simplicity and effectiveness in increasing the recovery. The water alternating gas (WAG) injection method shows higher sweep efficiency and recovery than the one-phase fluid injection. However, extremely high injection pressure will fracture the wellbore. Moreover, the saturation alteration changes the rock mechanical properties and stress values around the wellbore. The purpose of this study is to study the effects of saturation alteration on wellbore stability. This study has implemented with modelling procedure regarding the obtained experimental results from modified triaxial testing device. The core holder for this device is exclusively designed to prepare the favourable data of rock mechanical properties for different saturation schemes. The parameters of pressures, saturations, and stresses were obtained for the WAG flow using numerical modelling. For the pressures and saturation values, finite difference method (FDM) was used and to solve the rock stress values, finite volume method (FVM) was applied. According to experimental results, the recorded maximum axial stress was higher than the water and oil saturated cases (48.19 respected to 42.33 and 41.28). It indicates that the formation was more resistive to failuire for gas injection. However, after modelling, it was concludedthat the formation was more unstable in the gas injection case because of higher pressure transient. Therefore, the possibility of wellbore failure was higher during gas injection rather than water injection.
Operative Localization Technique of Current Mobile Oil Reserves for Mature Reservoirs Based on Material Balance
Authors: Aleev A. , Syrtlanov V. , Kovalyova Ye. 
Published: October 2017

Abstract
This paper proposes real-time evaluation of distribution of residual oil reserves in mature oil fields developed with water flooding system and localization of zones with higher density of reserves for the selection of areas/wells for well intervention and for optimization of water flooding system. Examples of application of this procedure on the facilities and oil fields in West Siberia are provided below.
Foam Acid Treatment - The Key to Stimulation of Carbonate Reservoirs in Depleted Oil Fields of the Samara Region
Authors: Letichevskiy Alexander , Nikitin Alexey , Parfenov Alexey , Makarenko Vitaliy , Lavrov Ilya , Rukan Gleb , Ovsyannikov Dmitry , Nuriakhmetov Ruslan , Gromovenko Alexander 
Published: October 2017

Abstract
Oil fields of the Samara region are at a late stage of development, which is reflected in declining of their production level and rapid growth of watercut. About 30% of the region's industrial hydrocarbon reserves are concentrated in carbonate reservoirs, which require stimulation. Low reservoir pressure, heterogeneity of the formation and the proximity of water-saturated interlayers significantly complicate the task of efficient field development and exploitation. In such conditions, the use of traditional methods for treating the bottomhole zone of carbonate rocks does not bring the expected results, and the worsening stock of exploited objects makes it necessary to look for new promising methods for increasing oil recovery.
Carbonate reservoirs stimulation in the Samara region is carried out using a spectrum of various technologies of hydrochloric acid treatments, both to extend the life of old wells and to efficiently start new wells after drilling. In order to increase the effect from the performed hydrochloric acid treatments in 2016, the foam diverting technology was applied in the framework of pilot projects. This technology uses a stable non-damaging agent to form a nitrogen foam of 65% quality at the bottom hole. After the treatment, the foam breaks down into liquid and nitrogen, which in turn improves well flow back and helps to restore the natural flow.
Despite the high degree of field development, the use of foam made it possible to achieve a 69% greater initial well productivity index than other methods. At the same time, the starting production rate of wells increased almost 2 times. The technology also allowed to reduce the specific volume of injected acid per meter of oil saturation by 25% without compromising the efficiency of the treatment, what has key importance from the point of view of economic feasibility. Based on the results of the performed pilot operations, nitrogen-foam acid treatments were included in the regular program of wells stimulation.
Reservoir Surveillance Informative Value on Brown Field
Authors: Bogatyreva I. , Metelkina N. , Mustafin R. 
Published: October 2017

Abstract
Matured oil field development poses different set of problems to be solved. As the geological structure is understood by this time, the most important tasks for reservoir surveillance becomes localization of residual reserves and the identification of promising zones for the production enhancement. Considering that the effect of potential geological and technical measures in the matured oilfield will not be that significant, the monitoring methods should be cost effective and at the same time deliver sufficient information. In our case, the main surveillance techniques were measurements of reservoir pressure, joint measurements of bottomhole pressure and well production rate, and targeted well tests. In addition, production logging was widely used to build the inflow and injection profile, identify sources of watering, and commingled production control. Authors implemented technology to assess the current skin factors without stopping such wells for special tests, only on the basis of the results of joint measurements of bottomhole pressure and well production.
The main low-cost method to remove the colmatation of the bottomhole zone was re-perforation, significantly increasing the flow rate of oil wells. In general, a comprehensive production analysis was carried out, including recovery evaluation by the zones of the reservoir and an areal analysis based on facies heterogeneity information. It was possible to achieve stabilization and even an increase in oil production after the suggested well intervention program was implemented in the field.
Mechanism Study on Foam Flooding for Daqing Reservoirs After Polymer Flooding
Authors: Qingfeng Hou , Donghong Guo , Youyi Zhu , Jian Ouyang , Zhe Wang 
Published: October 2017

Abstract
Polymer flooding has been carried out widely in Daqing oilfield. The average oil recovery was 53% and the water cut was more than 90% after polymer flooding. The remaining oil was highly dispersed in distributary channels. New EOR techniques with better profile control ability than polymer flooding need to be applied. The mechanism on foam flooding after polymer flooding was studied based on core flood experiments and X-ray computed technology (CT) in this paper.
The EOR effect for foam flooding after polymer flooding was evaluated employing both 2D and 3D core flood experiments. Artificial three-layer positive rhythm sand-packed cores were employed. The length, width and height for 2D cores were 28.0 cm, 4.5 cm and 4.5 cm, respectively. And the length, width and height for 3D cores were 50.0 cm, 50.0 cm and 20.0 cm, respectively. 1/4 five-spot pattern was employed for 3D core flood experiments. Particularly, the oil saturation profile was monitored with CT during whole 2D flooding process. The fluid distribution and sweep efficiency during the flood were described based on CT images.
EOR effect evaluation with 2 D and 3D models indicated that foam flooding could contribute 11.7% and 16.1% OOIP recovery even if the recovery after polymer flooding was more than 50%, respectively. The obvious increasing in injection pressure during the foam flooding indicated that foam fluid had stronger profile control ability than polymer. The distribution of residual oil in three-layer cores during the flooding was monitored. Firstly, the injected water mainly fingered through high-permeability zones during water flooding. The residual oil after water flooding was mainly distributed in the middle and low permeability layers. Next, polymer flooding could subsequently increase sweep efficiency by the deceasing in mobility ratio. The residual oil after polymer flooding was highly dispersed. In the end, foam could be employed to further recover considerable oil after polymer flooding. Pore blocking effect might play a great role in EOR mechanism for foam flooding. The evolution of fluid distribution was demonstrated clearly during foam propagation. The difference among the CT value of three phases (eliminating the contribution of the rock) was contributed to the addition of sodium iodide in aqueous phase.
Core flooding experiments monitored with CT proved that foam flooding could become a further EOR method for Daqing reservoirs after polymer flooding. Foam demonstrated better pore blocking ability than polymer within middle and high permeability layers. Foam could effectively block thief zone for highly heterogeneous reservoirs and increase sweep efficiency significantly after polymer flooding. It might become a promising EOR method for Daqing reservoirs after polymer flooding due to its profile control ability.
Additional Appraisal Program Optimisation with the Value of Information Aproach
Authors: Asmandiyarov R. N. , Onegov A. V. , Nigamatov S. A. , Vashevnik A. M. , Goncharov A. S. , Mityaev M. Y. , Sizykh A. V. , Fedorov E. G. 
Published: October 2017

Abstract
The work is aimed at the optimum program of additional appraisal for the object with high investment risk level. The investigated object is related to non-structural oil reserves and stands along from the infrastructure nodes with exploitation wells. Therefore, the work consist of the probability based reserves estimation for the all possible project ways and maximum effective way choice with the save of economically profitability.
Optimization program is concerned as to the project realization way as to the additional appraisal program. In the case of additional appraisal program three pilot wells drilling time and expenditures were considered. All three wells planed and calculated with standard well logging tools. As an alternative the exploration wells re-entry were considered. Facies distribution features and petrophysical properties were examined as uncertainties. The main point was haw they influence on the exploitation method. For this point of view, approximately 3000 realizations with different combinations of petrophysical properties, sedimentation facies geometrical sizes and type of exploitation were calculated. Result of optimization shoed that the optimum way is connected with consistent exploration wells re-entry, in spite of possible long term operations because of possible troubles. These optimization calculations give decision tree with probability and parameters values for every decision point for the further operations.
Geologist, reservoir engineers or economists who deals with the high investment risk projects where geology, exploitation and infrastructure uncertainties take place may use similar approach.
Accounting of Stationary Liquid Unloading Criteria in Simulation Model for Downhole Equipment and Regime Optimization and Prolongation of Gas Wells Operation
Authors: Maksimovskiy I. V. , Minikaev F. M. , Mangushev R. R. , Mingazov A. A. 
Published: October 2017

Abstract
The problem of liquid loading in well bores for a great number of gas wells is considered. This problem is observed in the framework of production calculations using the simulation model. It is determined that groundless assignment of wells decommissioning criteria leads to significant errors in the assessment of cumulative gas production and well stop flowing time.
Using the results of data after water breakthrough and wells stop flowing, the liquid unloading criteria in the gas wells were formed. The stationary unloading criteria depend on elevator equipment construction and critical production rates. They were evaluated, based on agreement procedure of calculated and actual liquid unloading parameters, by means of hydraulic well models. At the same time, applicability conditions for this technique were determined.
In this paper, simple and sufficiently reliable methods and algorithms are proposed. They are used for accounting stationary liquid unloading criteria which are needed for right well decommission time. Moreover, the criteria make it possible to improve the predictive potential of the integrated field models and to arrange the operations for prolongation of well life. For instance, technological regime optimization and running additional tubings of smaller diameter made from coiled tubing (velocity strings) can be proposed.
Carbonate Core: Research Features, Complexities, Prospects
Authors: Kovalev K. M. , Grishin P. A. , Gabsia B. K. , Kurochkin A. D. , Kolesnikov M. V. , Levchenko A. C. 
Published: October 2017

Abstract
Carbonate cores require special approaches and techniques to obtain appropriate data from core analysis due to their complex nature.
This paper discusses various challenges faced and presents an integrated approach to the study of carbonate cores.
Comparative analysis of the results obtained from standard and special carbonate rocks core analyses are presented. While carbonate rocks operations key difficulties encountered from core acquisition to long term storage are highlighted.
Mosaic Hydrophobization of the Surface of Organic-Mineral Matrix from Rocks of Bazhenov Formation
Authors: Bogdanovich N. N. , Borisenko S. A. , Kozlova E. V. , Spasennykh M. Yu , Rudakovskaya S. Yu. 
Published: October 2017

Abstract
By data of laboratory studies of mineral composition, analytical estimation of hydrophobicity of rocks by adsorption and NMR methods, pyrolytic studies of organic matter of Bazhenov Formation rocks, dependencies were determined between organo-mineral matrix composition and wettability of the solid surface. Influence of secondary effects on changes in hydrophobization of rocks were revealed. For carbonate minerals, catagenetic substitution of calcium cations for magnesium and iron results in polar changes in attitude of the rock to water fluids. Evaluation was made of the proportion of generated autochthonous and parautochthonous hydrocarbons of the oil series, heteroatomic compounds and kerogen in the overall balance of the organic component of the Bazhenov rocks, and an attempt was made to establish dependency of these proportions versus measured hydrophobicity of rocks. After dissolution of the light fraction of petroleum hydrocarbons, a decrease in combustion rate of the residual organic matter in air flow was observed for hydrophobic varieties. There are no obvious dependencies of surface hydrophobization versus mineral composition and organic matter of a rock in the ‘rock-water-oil’ system.
Investigation of Relationships of Geomechanic Properties of Layered Rocks Depending on Hydrostatical Pressure
Authors: Aliev Mekhrali , Baiburova Minsariya , Ibragimov Ildar , Ismagilova Zulfiya , Lutfullin Azat 
Published: October 2017

Abstract
The paper presents the investigation results to determine the mechanical characteristics of multilayered shales. The results are based on shearing and breaking off tests along certain planes of specimen. The modified Mohr-Coulomb criterion including an alternating angle of internal friction and variable cohesion is used as a strength criterion. Both the angle of internal friction and cohesion are considered as parameters depending on orientation. To determine the transverse strength at different orientations three rock test designs and two equations are proposed. In the case of breaking off the rock another strength criterion proposed by G.Geniev is used. It was investigated by authors of the paper for various anisotropic materials. Here strength characteristics are determined via calculations. They are based on results of two simplified tests (along and across the foliation), that is simple stretching test or the so-called "Brazilian test". Examples of calculations of the rock strength characteristics using the proposed models are given and considered in a critical manner.
Laboratory Modeling of Residual Oil Mobilization in Flooded Reservoirs
Authors: Melekhin Sergey V. , Mikhailov Nikolay N. , Russian Gubkin 
Published: October 2017

Abstract
Currently more and more oil fields reach their final development stage, characterized by increased water cut and decline of the oil production flow. Having said that, the residual oil saturation is still high, which means a presence of significant residual recoverable reserves within the flooded fields. Efficient recovery of these reserves is impossible without a prior analysis of their structure and location within the reservoirs.
Modern approaches to evaluation of residual oil saturation and displacement efficiency are based on determination of only one parameter and its relationship with porosity and permeability. With these methods residual oil saturation values are simulated on the bases of unlimited flow and unified predetermined filtering parameters, which correspond to the reservoir mean values. The methods are also based on maximum injection rates, ten times higher than the average injection rate values. As a result of reservoir development simulation, flooded zones will have the lowest residual oil saturation, while the residual oil saturation will be concentrated within the unflooded areas.
An experimental research was carried out to assess the impact of displacement parameters on oil displacement efficiency. A special test procedure was developed, which involves special core preparation so that the samples retain their surface properties. The obtained data allow for a conclusion, that there is a relationship between capillary and hydrodynamic forces (capillary number) and rate of oil recovery from the core pore space. Conditionally mobile residual oil saturation values and their relationship with the rock surface properties were determined.
Spectral Inversion Methods and its Application for Wave Field Analysis
Authors: Butorin A. V. , Krasnov F. V. 
Published: October 2017

Abstract
The article describes different methods of spectral decomposition on model seismic traces. The main methods are considered: windowed Fourier transform, continuous wavelet transform and algorithms of spectral inversion.
As a result the spectral inversion methods based on the approximation of an input trace in a library of wavelets with the help of Lp-regularization, provide a much more accurate spectral representation of the signal.
Several possible ways of geological interpretation using spectral inversion are shown in the article as a practical result. Considered approaches could be divided into custom – related to the all types of spectral inversion and specific – forwarded to specific features of spectral inversion results.
Randomized Crossover Trial of Blood Volume Monitoring–Guided Ultrafiltration Biofeedback to Reduce Intradialytic Hypotensive Episodes with Hemodialysis
Authors: Leung Kelvin C.W. , Quinn Robert R. , Ravani Pietro , Duff Henry , MacRae Jennifer M. 
Published: October 2017

Background and objectives
Intradialytic hypotension (IDH) is associated with morbidity. The effect of blood volume–guided ultrafiltration biofeedback, which automatically adjusts fluid removal rate on the basis of blood volume parameters, on the reduction of IDH was tested in a randomized crossover trial.

Design, setting, participants, & measurements
We performed a 22-week, single blind, randomized crossover trial in patients receiving maintenance hemodialysis who had >30% of sessions complicated by symptomatic IDH in five centers in Calgary, Alberta, Canada. Participants underwent a 4-week run-in period to standardize dialysis prescription and dry weight on the basis of clinical examination. Those meeting inclusion criteria were randomized to best clinical practice hemodialysis (control) or best clinical practice plus blood volume–guided ultrafiltration biofeedback (intervention) for 8 weeks, followed by a 2-week washout and subsequent crossover for a second 8-week phase. The primary outcome was rate of symptomatic IDH.

Results
Thirty-five participants entered, 32 were randomized, and 26 completed the study. The rate of symptomatic IDH with biofeedback was 0.10/h (95% confidence interval, 0.06 to 0.14) and 0.07/h (95% confidence interval, 0.05 to 0.10) during control (P=0.29). There were no differences in the rate or proportion of sessions with asymptomatic IDH or symptoms alone. Results remained consistent when adjusted for randomization order and study week. There were no differences between intervention and control in the last study week in interdialytic weight gain (difference [SD], −0.02 [0.8] kg), brain natriuretic peptide (1460 [19,052] ng/L), cardiac troponins (3 [86] ng/L), extracellular water–to–intracellular water ratio (0.05 [0.33]), ultrafiltration rate (1.1 [7.0] ml/kg per hour), and dialysis recovery time (0.43 [19.25] hours).

Conclusion
The use of blood volume monitoring–guided ultrafiltration biofeedback in patients prone to IDH did not reduce the rate of symptomatic IDH events.