bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficient Acoustic Wave Equation Modeling in TTI Media
Authors: Nikonenko Yury Andreevich , Charara Marwan 
Published: September 2020

Abstract
We present a new effective method for the acoustic wave modeling in transversely isotropic media with the tilted axis of symmetry. It makes novel accurate techniques of migration, such as Reverse Time Migration (RTM), computationally affordable in terms of memory usage and speed. Our modeling is based on pure acoustic wave equation derived from the fundamental physical laws – Hooke's law and the equation of motion. There is no need to approximate the pseudodifferential operator for the decomposition motivation in our approach, which was the primary problem in solving the acoustic wave equation. First, we perform the rotation of the operator in the spectral domain in accordance with the parameters of the tilted transversely isotropic (TTI) media. Next, we make a discrete inverse Fourier transform of the desired frequency response contained in the pseudodifferential operator to build the corresponding spatial operator and, finally, truncate the operator with a window to reduce edge effects. As a result, the obtained spatial TTI operator is applied locally to the wavefield through a simple convolution. Taking advantage of fast convolution algorithms, this equation can be efficiently solved, resulting in an explicit numerical scheme. There is no need to deal with the implicit schemes resulting from various approximations of the pseudodifferential operator with our method. It greatly facilitates the calculations for the full modeling. The most significant advantage of our approach lies in its locality, which means that our spatial TTI operator can be implemented in any selected area individually. Our approach can be combined with classical fast finite-difference schemes, e.g. when the media are isotropic and elliptical. Also, the modeling is performed without generating any spurious modes, which greatly reduces the total computational time and memory usage as well as improves the quality of seismic image. We demonstrate the stability, accuracy, and the absence of the residual S-wave artifacts with several numerical modeling examples including complex heterogeneous case.
An Integrated Earth Image Modelling for Safe Exploration Drilling
Authors: Shtun Sergey Urievich , Alekseev Andrey Germanovich , Kireev Evgeniy Vitalievich , Sibilyov Mikhail Aleksandrovich , Topolyan Maria Urievna , Golubtsov Ruslan Vyacheslavovich , Kuzakov Vitaly Radikovich , Sadykov Lenar Alfatovich , Bayukansky Yury Feliksovich , Petrakova Natalia Nikolaevna , Kashcheev Denis Evgenievich , Yang Sherman 
Published: September 2020

Abstract
Construction of offshore exploration wells in harsh pressure and temperature environment involves a high risk of geological complications. This is particularly relevant for exploration operations in insufficiently explored areas where the well design is based on seismic data, while the nearest drilled wells are at a considerable distance and do not reflect the specific geological conditions at the point of the new target. This paper presents a comprehensive approach to the detailed study of the geological structure of the Caspian shelf exploration area by processing 3D seismic data for the purpose of forecasting and monitoring hydraulic fracturing pressure and pore pressure prior to construction and during well drilling. Optimized algorithm of data processing in a 7×7 km near-wellbore seismic volume, including detailed tomographic analysis using the Seismic Guided drilling (SGD) method, real-time updating of the geomechanical model, updating of the structural framework and forecasting of properties allows to effectively reduce risks during well construction. Taking into account the experience of geological complications during drilling through Neogene and Quaternary sediments in North Caspian it is also shows the application and integration of geotechnical engineering survey data to refine the upper section model.
Test Results of Active Thermometry Technology Using a Distributed Temperature Measurement System
Authors: Rymarenko Konstantin , Nukhaev Marat , Grishchenko Sergey , Zaytsev Alexander , Golubtsov Alexander , Aitkaliev Galymzhan , Dadakin Nikita 
Published: September 2020

Summary
One of the most important tasks when developing oil fields with horizontal or directional wells is the inflow distribution monitoring along the wellbore. Possible irregularities in the inflow are primarily associated with heterogeneity in the filtration distribution and capacitive properties along the wellbore, unevenness in the depression distribution, possible overfilling of the wellbore, partial or complete blockage of sand filters by mechanical impurities or clay material, imperfect development of the wells (when part of the mud cake remains on the wall of the well), gradual clogging of the bottomhole zone pores, water breakthroughs and gas outs, or other reasons.
Inflow profile monitoring allows identifying why the well performance has decreased and timely planning and carrying out appropriate geological and technical measures. Also, this information allows timely updating hydrodynamic models of field development to properly make strategic decisions.
This paper presents the results of bench tests of a new active thermometry technology using a distributed temperature measurement system
Complex Using of Conventional Production Logging and Indicator Technologies in Tight Oil Reservoir Study
Authors: Bukov Oleg Vladimirovich , Basov Artem Vladimirovich , Lazutkin Dmitriy Mikhailovich , Kashapov Denis Vagizovich , Ovchinnikov Kirill Nikolaevich , Buyanov Anton Vitalyevich , Drobot Albina Viktorovna , Novikov Igor Leonidivich 
Published: September 2020

Resume
Constant growth of commercial hydrocarbon (HC) consumption requires for the oil and gas industry to be involved into exploitation of unusual oil and gas reserves, preventing HC supply shortage on the global market. The fields with conventional reservoirs being actively developed during the last century have a tendency now to reduction of routine parameters of HC production.
Now more and more attention is being attracted to tight reserves, which have to be studied in unconventional ways. This article focuses precisely on complex reservoirs, in which reserves are classified as tight. A complex quantitative assessment using several different technologies for long-term monitoring under difficult conditions has shown favorable results.
Integration of Petrophysical Log Data with Computational Intelligence for the Development of a Lithology Predictor
Authors: Amir Syed Muhammad , Khan Mohammad Rasheed , Panacharoensawad Ekarit , Kryvenko Serhii 
Published: September 2020

Abstract
Wrong manual interpretation from the log data about the formation type and other important information can be catastrophic for the company-operator. With Machine-Learning (ML) (a branch of Artificial Intelligence) algorithms, the interpretation of formation type from the log data has been addressed. As a result, we have successfully developed a program able to accurately predict the type of formation.
Using the conventional Machine Learning technique of splitting the data into training, validation and test sets, we tried six different ML algorithms to fit with the training part of the data and then verify their prediction accuracy with cross-validation scores and cross-validation predictions which tests the performance of the classifiers (ML algorithms) on the validation set. The three best performing classifiers were selected and further improved by a search of classifier's best hyperparameters. These improved classifiers are further tested on unseen data to produce a comparative analysis.
Our prediction accuracy with Receiver Operating Characteristic (ROC) scores and ROC-Area Under-the-Curve (ROC-AUC) for each type of formation from the log data lies in the range of 95-99%, except for formations such as shaly sandstone and shale (50% and 84% respectively). The reason for this seemed to be under-fitting i.e., during the training, the classifiers did not see enough instances of these types of formation to know exactly what characteristics of the data make the type of formation to be shaly sandstone or shale. The issue of under-fitting was verified by skimming through the data. To resolve this problem, we suggest training classifiers with a larger data with more targets (types of formation). Furthermore, during the data cleaning (prior to classifier training) and data analysis phases we have discovered important relationships between well logs and defined relative importance of each well log for different formations. This observation can be investigated further to help eliminate the use of multiple well logs while dealing with some formations (based on prior geological knowledge) and reduce the cost of the well logging operations. Using our program with a larger well log data consisting of more formation type instances, we can train the classifiers to accurately predict the formation type irrespectively of differences in formation type.
Our program is dynamic in the sense that with different targets, i.e., type of formation fluid instead of type of formation or both together, it can successfully predict either or both targets. Increasing the numbers of data instances resulted in a better training and thus, more accurate predictions. Utilization of the program will make the formation-evaluation process easier, faster, automated and more-precise.
Innovative Completion and Stimulation Approach to Increase Gas Production from Water-Sensitive, Low-Temperature Turonian Formation
Authors: Vorobyev Vladislav Viktorovich , Dmitruk Vladimir Vladimirovich , Zavyalov Sergey Alexandrovich , Yudin Alexey Vladimirovich , Loginov Arkadii Vladimirovich , Novikov Maxim Igorevich , Vikulin Nikita Anatolievich , Burdin Konstantin Valerievich , Shmarin Iliya Sergeevich , Mukhametshin Ilkam Rashitovich , Doronin Sergey Vladimirovich 
Published: September 2020

Abstract
The Turonian siltstone is widely spread through the Siberian region in northern Russia. It is a laminated, heterogeneous and high-shale content formation with low permeability (1-3 mD) and low reservoir temperature (15 degC), with more than 300 trillion m3 of natural gas in place. Hydraulic fracturing is a necessity for economic and sustained development of the field in the described geological conditions. High montmorillonite contentand extremely low temperatures make the Turonian reservoir a true challenge for frac experts.
A pilot stage of project development has been executed with horizontal drilling and multistage fracturing. A well has been constructed with 168-mm casing and 114-mm liner, with the liner separated into discrete segments with hydraulic packers. Each zone is equipped with filters integrated with the inflow control devices (ICD)plus frac portsenabling multistage frac jobs and subsequent controlled, solids-free production.Frac ports and ICDs are shifted using coiled tubing (CT) equipped with a downhole hydraulic key.
Significant innovations were implemented for the frac fluid design in terms of a noveldiesel-based fluid breaker package.Additionallab investigation of proppant transport capacity has revealed some elastic properties of diesel-based fluid, that are not typical for crosslinked guar-borate water-based fluids. This provided the opportunity to significantly increase proppant concentration and frac design aggressiveness for the successful completion of a trial campaign.With the optimized fluid, the engineering team has achieved outstanding results in frac design, when large-sized proppant has been pumped at concentrations up to 1400 kg/m3 during multistage frac operations in horizontal wells.The combination of technologies led to rapid well cleanup with a quick transition to stable gas flow to sales.
New achievements in well completion techniques andwater-free frac fluid optimization can be implemented when dealing with similar low-temperature reservoirs with high content of water-sensitive clays.
The Influence of External Conditions on the Behavior of Products Made of Soluble Metals
Authors: Peshchansky Alexey , Mikhalitsyn Egor 
Published: September 2020

Abstract
Even though products made of soluble metals are widely used in the oil and gas industry, the issue of the cumulative effect of downhole conditions on the rate and nature of dissolution of products in the well is still insufficiently studied. This problem is especially acute when predicting the time of dissolution of frac balls. The generally accepted methods for testing frac balls for dissolution rate do not allow predicting with enough accuracy two most important parameters: the time during which the ball retains the ability to provide hydraulic isolation of the fracturing intervals and the time of complete dissolution of the ball.
In this paper, the dependence of the rate of dissolution of frac balls on the geometry of the unit in which dissolution occurs, the temperature of the unit heating, the pressure in the well, and the influence of various technological media are considered. A test procedure is proposed that allows one to consider the combined effect of the above factors on the dissolution of frac balls. The work of the presented technique is illustrated by the example of validation tests of a frac ball in downhole conditions.
Non-Guar Synthetic Hydraulic Fracturing Gels – Successful Concept of Choice
Authors: Churakov Artem Vladimirovich , Pichugin Maxim Nikolaevich , Fayzullin Ildar Gayazovich , Gainetdinov Ruslan Ramilevich , Makarevich Stepan Bronislavovich , Mikhaylov Dmitry Yurevich , Williams Benjamin , Hu Thomas 
Published: September 2020

Abstract
Fluids capable of transporting proppant with the least formation and fractures contamination are one of the most relevant areas of the technological development of hydraulic fracturing treatment. In the world in recent years, there has been a tendency to switch from cross-linked guar-based fracturing fluids to synthetic ones. Highly viscous friction reducers find wider application in the new concept of modern industry development. Unlike traditional guar-borate-based fluids, these fluids have a number of advantages - they provide higher residual fracture conductivity, are less sensitive to the mineral composition and temperature of the water source, contain fewer chemical elements in the working formulation and, as a rule, are less demanding of equipping a hydraulic fracturing fleet. Also, in addition to the above features, note the possibility of making changes to an engineering solution immediately in the work process, ensured by the simplicity of fluid making-up and high hydration rate.
Despite the obvious advantages in using synthetic fluid systems over standard guar-based systems, until now they have not been widely used in conventional reservoirs. This is supported by poor knowledge of the practical application associated with proppant transport and the absence of selection criteria based on the system rheological properties which significantly affect the hydraulic fracturing success rate.
The paper describes a set of rheological studies, including building viscosity and elasticity profiles, as well as an assessment of the fluid system thermal stability. The viscosity behavior was also studied in a wide range of shear rates. The effects of elastic moduli were studied by conducting vibrational-shear tests in a spectrum of various frequencies. Quantitative and qualitative comparative measurements were carried out to study the settling rate of proppant, as well as its viscoelastic properties in a flow.
The result of the study is generalized analytical findings on synthetic fluid systems confirmed by practical application in real conditions of conventional reservoirs in West Siberia. This paper will help to understand the key factors affecting the choice of fracturing fluid formulations based on high-viscosity friction reducers and, in the future, may become the basis for creating a methodology for testing synthetic gels.
New Fracturing Fluid Viscosity Model to Cure Power Law Mistakes
Authors: Vernigora Denis , Sypchenko Stella , Fedorov Andrey , Olennikova Olesya 
Published: September 2020

Abstract
Rheology of fracturing fluids described by power law model. The coeffects n and K of this model is using for all fracturing stimulators. Rheology measurements of real fracturing fluid frequently provide values with n &gt;1, which is contradicted with Power Law model.Transfer this number to a fracturing simulator software gives wrong fracture simulation. The paper describes a new approach for modeling of fluid viscosity which resolves wrong assumptions of previously used model.
Fluid viscosity measured with high-pressure-high-temperature (HPHT) rotational rheometer. The conventional fluid testing procedure based on ISO 13503-1 standard requirements provided erroneous and inexplicable results. The investigation of fluid rheological behavior was done by measurement of fluid viscosity in extended range of shear rates. Contrary to usual measurements of viscosity at 25, 50, 75 and 100 s-1, during this approach shear rates range was extended to 340 s-1 and 5 s-1. Fluid behavior was analyzed using log-log regression approach. Base on this analysis the corrected rheology numbers calculated and used tor a stimulation software.
As a result of laboratory research, Power Law model inapplicability in several cases was confirmed. Number of rheological measurements revealed boundary conditions for implementation of Power Law model and enlighten the factors which causes non-linear relation of viscosity at log-log plot. It has been found that pH, temperature and polymer degrading material cause abnormal fluid behavior at 1-100 s-1 shear rates range. Therefore, limitations for measurements according to ISO 13503-1 standard was stated.
Additionally, impact of recently introduced oil and gas producing companies’ fracturing fluid quality standards on fluid viscosity behavior was evaluated. It was revealed that tough requirements for fracturing fluid viscosity recovery after passing through high shear rate region provoke abnormal viscosity loss at low shear rates and errors in determination of consistency and behavior indexes.
Finally impact of wrong data obtained with Power Law approximation on fracture geometry calculated with currently available fracturing simulators was estimated and requirements for next-generation fracturing simulators in terms of fluid viscosity modeling was claimed.
The study shows weak points in implementation of currently used Power Law fluid viscosity model for fracturing simulation. Implementation of practices described in this study allow to either don't cross the border of power law model or to enrich fracturing simulators with more precise rheology model.
Geosteering Improvement by Geological Uncertainties Assessment
Authors: Kazancev Gleb Vladimirovich , Nikitin Ivan Andreevich , Zunde Dmitry Alexeevich , Chuchalina Kristina Yuryevna 
Published: September 2020

Abstract
Today, the acute question is the possibility of using seismic data in the process of drilling horizontal wells, in particular, on continental deposits, which are characterized by high lithological and facies heterogeneity. In particular, the results of seismic inversion, which are widely used during well planning and geological modeling, are often not taken into account in the geosteering process. This is due to the fact that the drilling results do not always confirm the forecast made with the use of seismic data. In order to increase the convergence of wells and seismic data and wells efficiency, the authors propose to use the uncertainty analysis of the geological model and wellbores position when drilling horizontal wells.
Fracture Hits in Unconventional Reservoirs: A Critical Review
Authors: Gupta Ishank , Rai Chandra , Devegowda Deepak , Sondergeld Carl H. 
Published: September 2020

Summary“Fracture hit” was initially coined to refer to the phenomenon of an infill-well fracture interacting with an adjacent well during the hydraulic-fracturing process. However, over time, its use has been extended to any type of well interference or interaction in unconventional reservoirs. In this study, an exhaustive literature survey was performed on fracture hits to identify key factors affecting the fracture hits and suggest different strategies to manage fracture hits. The impact of fracture hits is dictated by a complex interplay of petrophysical properties (high-permeability streaks, mineralogy, matrix permeability, natural fractures), geomechanical properties (near-field and far-field stresses, tensile strength, Young’s modulus, Poisson’s ratio), completion parameters (stage length, cluster spacing, pumping rate, fluid and proppant amount), and development decisions (well spacing, well scheduling, fracture sequencing). It is difficult to predict the impact of fracture hits, and they affect both parent and child wells. The impact on the child wells is predominantly negative, whereas the effect on parent wells can be either positive or negative. The “child wells” in this context refer to the wells drilled with pre-existing active/inactive well(s) around. The “parent well” refers to any well drilled without any pre-existing well around. Overall, fracture hits tend to negatively affect both the production and economics of lease development. The optimal approach rests in identifying the reservoir properties and accordingly making field-development decisions that minimize the negative impact of fracture hits. The different strategies proposed to minimize the negative impact of fracture hits are simultaneous lease development, thus avoiding parent/child wells (i.e., rolling-, tank-, and cube-development methods); repressuring or refracturing parent wells; using far-field diverters and high-permeability plugging agents in the child-well fracturing fluid; and optimizing stage and cluster spacing through modeling studies and field tests. Finally, the study concludes with a recommended approach to manage fracture hits. There is no silver bullet, and the problem of fracture hits in each shale play is unique, but by using the available data and published knowledge to understand how fractures propagate downhole, measures can be taken to minimize or even completely avoid fracture hits.