bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced Method of Controlled Core Scratching as a Source of Geomechanical Data
Authors: Toropetsky Konstantin Victorovich , Borisov Gleb Alexandrovich , Samoilov Mikhail Ivanovich , Eltsov Igor Nikolaevich
Published: September 2020

The established practice of geomechanical testing includes the procedures of core sampling and marking, as well as core plug drilling out and testing. The key challenge is that a selection of core plugs is physically or economically limited. The classical core analysis offers a limited and discrete data set. Along with that, the tests carried out on a set of core plugs are dependent upon the core quality and the accuracy of selection of the core plugs sharing identical properties. These constraints impair accuracy and reliability of geomechanical models.

This paper describes controlled core scratching (CST) as a method of geomechanical testing of full-size cores. Physically, the CST method is based on resistance measurements of the of full-size cores to scratching. Depending on the cutter penetration depth and the core sample scratching rate, the force characterizes unconfined compressive strength (UCS) and/or fracture resistance of the rock.

The principal CST advantage is that it provides accurate and diverse continuous geomechanical rock properties. The application of the CST method enhances comprehensive core analysis accuracy, synthetic physical & mechanical parameters reliability and, therefore, geomechanical modeling precision. In practice, the CST method applied in conjunction with the classical geomechnical core analysis enhances the quality of drilling, completion, frac'ing, and field development support in general.

This paper presents a comparative study of geomechanical models that incorporate synthetic curves for unconfined compressive strength (UCS), Brazilian tensile strength (BTS) and cohesion strength (CS), derived from the CST and well logging data, using a well that is drilled through halocarbonates and clastics as an example. The comparative study of the CST-based and log-based geomechanical models demonstrated that the CST-based model outputs robust correlations and detailed distinctive curves of physical & mechanical properties and clear stratification boundaries.
Multi-Objective Optimization as a Tool for Scenario Modeling of a Company's Portfolio
Authors: Zhigach Sergei Alexandrovich , Yudina Elizaveta Nikolaevna
Published: September 2020

The aim of the work is to create a scenario modeling technique based on adaptation of metaheuristic multi-objective optimization algorithms to construct Pareto-optimal investment portfolios taking into account multiple restrictions on the company's portfolio.

Investment portfolio is a tool for company's resources management. The process of portfolio construction through a combination of individual investment projects aims to optimize available resources utilization. Currently, there is no single approach to determining the optimal portfolio, since portfolio requirements depend on a particular company. Due to its simplicity in terms of implementation, approaches based on the ranking of projects according to individual technical and economic indicators are widely used. However, if a company needs to take into account several indicators, then this approach is not applicable. An effective solution to this problem is to create a technique that allows to find Pareto-optimal portfolios.

In this work, the problem statement and analysis of existing solving approaches were carried out. Based on that, methodology of scenario modeling of a company's portfolio was created. The posed problem belongs to the class of NP-hard problems and for its efficient solving it is necessary to use metaheuristic algorithms. These algorithms include genetic algorithms, variable neighborhood search, bees algorithm, etc. Genetic algorithm NSGA-II is widely used for solving multi-objective optimization problems due to its high performance and ease of use. This algorithm was adapted to solve proposed problem. Based on it, a methodology was developed for the formation of Pareto-optimal investment portfolios, taking into account financial and infrastructural restrictions. Testing of the methodology was carried out on a dataset of synthetic projects simulating real investment projects. Various combinations of this projects simulated investment portfolios. The optimization objectives were maximization of net present value (NPV), maximization of cumulative oil production and minimization of total investments. In order to control the quality of the results obtained using genetic algorithm, the problem was also solved by using variable neighborhood search. However, the quality of the results obtained using genetic algorithm was higher. Analysis of the results allows us to consider the use of multi-objective optimization as a tool for forming a pool of investment portfolios, which provides flexible company management.

In the proposed work, it is shown that the problem of scenario-based modeling of company's investment portfolio can be considered as a multi-objective optimization problem. Based on the existing metaheuristic algorithms, a Pareto-optimal investment portfolio search methodology has been developed. Proposed methodology can effectively solve the problem of managing company resources.
Bolshekhetskaya Depression Concept Selection Study
Authors: Mamedov Emil Adalatovich , Lysov Alexey Gennadyevich , Avchikhanov Arsen Sultanovich
Published: September 2020

A concept has been developed for gas, gas-condensate and oil fields exploitation planning in the Arctic region, taking into account the limitations of the existing external and internal infrastructure. The work was carried out as part of an integrated project management system to determine business opportunities and initiate the transition of field development projects to the pre - project development phase (Pre - FEDD).

The paper considers the formations and geological structures of the Bolshekhetskaya Depression in the license areas: License area "Nakhodkinskiy"Licensed area "Pyakyakhinsky"License area "South Messoyakhsky"License area "Halmerpayutinsky"License area "Salekaptsky"Licensed area "West Tazovsky"License area "Vareisky"

The choice of the profile of the horizontal section of the well is one of the main issues in the design and affects not only the final gas and condensate recovery, but also helps to clarify the geological structure of the formation during the well construction, as well as include all productive layers in the development, reduce the risk of complications during operation. Usage of longer horizontal wells will reduce drill footage; to increase the flow rate and profitability of wells; it is more rational to use formation energy due to lower values of depression on the formation and correspondingly reduced losses of condensate in the formation.
Method for Optimal Well Pattern Estimation for Oil Rim Fields
Authors: Nekhaev Sergey Aleksandrovich , Perevozkin Igor Vladimirovich , Reshetnikov Dmitriy Anatolevich , Samolovov Dmitriy Alekseevich
Published: September 2020

The effective development of thin oil rims by horizontal wells is an urgent area of technological development of oil and gas companies in the context of an increase in the portfolio of new fields with significant reserves of free gas. A key feature of the development of oil rims is gas coning and therefore it is necessary to limit the productivity of wells, which leads to a high sensitivity of project profitability to reservoir properties, economic conditions and the development system. For successful development it is necessary to optimize all the components of the project – wells count, downhole equipment, transport system.

Some works relating to the theory and methodology of developing oil rims describe approaches to calculating the optimal well spacing [Khasanov et.al.], the number of wells per bush [Samolovov, Mozhchil et.al.], and ground facility [Povyshev et.al.]. Special cases of comparing different well placement systems are widely represented in the literature, for example, in [Sugaipov et.al.]. An increase in the share of oil rims production leads to the need to find common solutions to such optimization problems.

In this paper, we consider the question of determining the optimal location of wells by systematic selection of an in-line or radial development system. When horizontal wells are placed on oil rims in the form of an in-line development system, optimal conditions are created for the uniform production of oil reserves, since the distance between the horizontal wells is the same for all cross sections of the well and the gas cone is formed uniformly along the direction of the horizontal wells. However, when combining well trajectories into one bush, in this case there is a need for large reach from the wellhead or in a small number of wells in the bush. When horizontal wells are placed on oil rims in radial development system, optimal conditions are created to minimize well reach, however, interference occurs between wells in the reservoir due to the distance between wells changing along the direction of the horizontal wellbore. The purpose of the work is to determine the conditions under which in-line or radial well placement is optimal.
Promising Methods for Increasing the Efficiency of Exploitation of Thin Low-Pressure Gas Deposits with Underlying Water
Authors: Urvantsev Roman Vadimovich , Ibragimova Dina Renatovna
Published: September 2020

The main problem of exploitation of thin low-pressure gas deposits with underlying water is the constantly increasing water cut. As a result, this leads to wells liquid loading and the impossibility of further work. Various technologies exist to solve this problem. In this paper, we consider technologies based on the principle of removing water from the bottom of the wells with its further disposal. An analysis of literary sources containing experience in the application of various technologies at analogous facilities has been performed. In addition, the conditions under which produced water is removed from the bottom hole are evaluated.

A feasibility study of technologies applicability was carried out in the context of unique gas field, the main reserves of which are associated with Cenomanian deposits.

All calculations were performed on the hydrodynamic model including the gas-gathering system option.
The Balance Between Oil and Gas Options in Case of J2-6 Oil Rim Development of Novoportovskoye Field
Authors: Varavva Valentina , Bogdanov Evgenii , Chameev Igor , Sherstoboev Evgenii , Isakov Kirill , Virt Vitaliy , Shorokhov Aleksei , Kashapov Denis
Published: September 2020

The paper considers gas option beginning and forcing in case of U2-6 reservoir of oil and gas condensate Novoportovskoye field, which is an underlaying-typed oil rim with a massive gas cap. Based on conducted analysis the recommendations for the further gas option development with oil production losses minimization and gas production maximization were formulated.
Production Enhancement in Deep Sour Gas Field: A Case Study in China
Authors: Guo Hongzhi , Li Huigeng , Weng Zhiyong , Tao Ke , Wang Dong
Published: September 2020

Puguang is the biggest sour gas field in China with 17% H2S and 9% CO2 concentration and is the major gas sources for the pipeline from Sichuan to Shanghai. It's important to keep the gas wells healthily and steadily producing. However, the production is continually declining due to water coning, scale buildup and formation pressure dropping. It's urgent to perform well intervention effectively and economically to increase the well production.

Production logging in multiple wells identified that inflow zones were less than 30% of perforation interval because of formation invasion and perforation tunnel plugging from initial completion. To release the potential productivity from nonproducing zones, reopening the perforations is critical to reverse the trend of production decline. To pass through the 3.5-in tubing with minimal restriction of 2.7-in and to effectively perforate the 7-in production casing and the carbonate formation, a 2.5-in spiral-exposed perforation system was finally selected as the optimized solution that can achieve the deepest formation penetration compared with conventional carrier system from simulations with rock-based perforation model.

The spiral-exposed perforation system was modified to be H2S resistant, and wellbore dynamic simulation was conducted to minimize the gun shock to avoid gun drop during detonation. The detailed job design and risk mitigation plan were made as well to avoid any failure in such a highly corrosive environment with well depth up to 6,000 m. The first reperforation job was conducted successfully, and the well production increased 130,000 m3/day or 22.8%, and afterward, production logging confirmed that zonal production had significantly improved from the newly perforated interval. Then another seven wells were reperforated with an interval of 30 m to 45 m and average 100,000 m3/day gas production increment or 20% per well was achieved. It's proven that reperforation with redesigned exposed perforation system is the effective and economical way to increase production in the Puguang gas field.

This paper illustrates how and what we do for exposed system improvement, candidate well selection, planning, and executing the through-tubing exposed perforation in such extremely challenging conditions. It also discusses lessons learnt and recommendations for future well intervention to steadily increase the well production in the Puguang gas field.
Digital Core Analysis – Innovative Approach for EOR Agent Screening at Pore-Scale for Achimov Rocks
Authors: Yakimchuk Ivan , Evseev Nikolay , Korobkov Dmitry , Dinariev Oleg , Ridzel Olga , Khan Vladimir , Semkov Vyacheslav , Zhonin Alexander , Kravets Dmitry
Published: September 2020

The digital core analysis technology with direct hydrodynamic modeling based on the density functional method was applied for the first time for the EOR screening and evaluation of the EOR agent efficiency at pore scale for Achimov reservoir rocks. The technology consists of scanning core samples by X-ray microtomography (microCT), constructing the corresponding digital core models of the pore space geometry, and performing multiphase hydrodynamic modelling at the pore scale based on the density functional method (DFT).

The required spatial resolution of digital models for the studied sample was about 1 μm, and the size of the representative elementary volume on which multiphase hydrodynamic modeling was performed was 750 × 750 × 750 voxels.

Despite the extremely low permeability values (less than 1 mD) of the test sample, digital core analysis allowed a series of digital experiments to calculate the absolute permeability, the creation of residual water saturation using different approaches (simulation of the laboratory protocol and geological process) and the determination of oil displacement when injecting various EOR agents (formation water, carbon dioxide and smart water). For the first time, the dependence of the displacement coefficient both on the method of modeling the initial conditions (residual water saturation) and on the type and mechanism of the considered EOR agents for Achimov reservoir rocks was studied.
Core Column Filtration Testing Supplemented by Measurements of Oil Optical Properties
Authors: Burkhanov Ramis Nurutdinovich , Lutfullin Azat Abuzarovich , Ibragimov Ildar Ilyasovich , Maksyutin Alexander Valeryevich
Published: September 2020

The composition and properties of oil change during its flow through the reservoir, which is associated with the high molecular weight resins and asphaltenes retained in the pores. Oil is retained in the thinnest capillaries and narrow contacts of hydrophilic mineral grains (capillary-retained oil) and as a film on the surface of hydrophobic minerals (oil films). To confirm this, core analysis tests were performed on three pre-prepared core columns made up of standard core samples with different porosity ϕ, absolute permeability k, irreducible water saturation Swir and other properties. Oil was flowing through the column and displaced by water with pre-determined physical properties. The properties of the core specimens, oil and water, as well as the thermobaric conditions of flow experiments were selected so that they corresponded to the reservoir conditions of the Pashian horizon of the Romashkinskoye oilfield of the Republic of Tatarstan. In the case of the mature Romashkinskoye oilfield, the relevant objective is to quantify and localize the remaining reserves of capillary-retained oil and oil films and substantiate effective technologies for their extraction. To prove that the composition of oil change during flow through porous media, the light absorption coefficient of oil kla was investigated that depends on the relative content of resins and asphaltenes in the oil. Oil was studied using a photometer in a continuous mode during the entire period of oil displacement test. Oil samples were collected and subjected to preparation at the inlet and outlet of the core column, their optical density D, light absorption and transmission coefficients were measured in vitro, and statistical data were processed. It has been found that regular changes in the oil kla occur both at the stage of the core column saturation with oil (a regular decrease), and as oil is displaced from the core samples by water (a regular increase). The identified patterns are the function of the rock and oil properties, the established rate of the column saturation with oil and oil displacement by water, and the amount of residual and displaced oil. The obtained data have shown the promising outlook for continuing laboratory experiments to study not only changes in the properties of oil when it is displaced by water, simulating the development processes, but also those occurring in the column as it is saturated with oil, simulating the processes of primary migration and accumulation of oil in a natural reservoir.
Efficient Acoustic Wave Equation Modeling in TTI Media
Authors: Nikonenko Yury Andreevich , Charara Marwan
Published: September 2020

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

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

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

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

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

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

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

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 >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

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.
Russian Oil and Gas Industry Technology Priorities
Authors: Zhdaneev Oleg
Published: September 2020

This report represents the findings of a survey of managers and specialists of state and private enterprises from oil and gas sector of the Russian Federation. The survey findings reflect technological needs of the industry, plans for technological development of the enterprises in the short-, medium- and long-term periods as well as the readiness of enterprises for technological cooperation.
Fracture Hits in Unconventional Reservoirs: A Critical Review
Authors: Gupta Ishank , Rai Chandra , Devegowda Deepak , Sondergeld Carl H.
Published: September 2020

“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.
Assessment of Optometrists’ Knowledge, Skills and Practice on Cataract: A Cross-Sectional Study from Kisumu County, Western Kenya
Authors: Muma Shadrack , Obonyo Stephen
Published: September 2020

Background: Cataract not only contributes to blindness which is avoidable, but also impact negatively on the quality of life. The total prevalence of blindness in Kenya is estimated at 0.7%, however cataract contributes almost half (43%) of the total blindness in Kenya. Optometrists are well placed to assess and refer cataract patients however, little is known on their skills, practice and knowledge. Therefore, this study was designed to assess optometrists’ knowledge, skill and practice on cataract in Kisumu, Kenya. Methods: A cross-sectional study design was used. The study was conducted from June 2019 to August 219 using self-administered questionnaire. Basic socio-demographic characteristics were collected and participants’ knowledge, skills and practice on cataract investigated. The primary outcome measures were the proportions of participants who identified the questions related to knowledge, skills and practice on cataract. Chi-square analysis was performed to assess the association between demographic characteristics with practice, knowledge and skills. Results: A total of 49 optometrists were interviewed with a male to female ratio of 2:1, mean age of 30.4 years and mean duration of practice of 1-10 years. Most optometrists had good knowledge on various aspects of cataract. For example (98%) had a good knowledge on the types of cataract. Almost three quarter (75.5%) of the optometrists reported that they could diagnose cataract correctly based on skills. However, half (57.1%) of the optometrists could not identify nuclear cataract. Being a self reported practice and not observed practice, most optometrists (61.2%) reported that they do not screen patients aged 40 years and above for cataract. Almost half (52.6%) of the optometrists reported that they always do a routine eye examination but they do not know the importance of examining the crystalline lens for patient above 40 years. Conclusion The study established that despite the good level of knowledge among optometrist on cataract, there exist a gap on skills and practice. The results of this study calls for more clinical based activities among optometrists and other cadres. This will eases diagnosis of cataract and its management so as to reduce its burden in Kenya.
Effects of STIP1 and GLCCI1 polymorphisms on the risk of childhood asthma and inhaled corticosteroid response in Chinese asthmatic children
Authors: Huang Juan , Hu Xiaolei , Zheng Xiangrong , Kuang Jian , Liu Chentao , Wang Xia , Tang Yongjun
Published: September 2020

Background: Asthma is a common chronic lung disease in children. We aimed to determine the associations between stress-induced phosphoprotein 1 (STIP1) and glucocorticoid-induced transcript 1 (GLCCI1) polymorphisms and susceptibility of childhood asthma and inhaled corticosteroid (ICS) response in children. Methods: A total of 263 Chinese Han asthmatic children were recruited from the Xiangya Hospital, Central South University. Pulmonary function tests were performed before the treatment and 3 months after the treatment. 150 non-asthmatic children were recruited. Each participant's DNA was extracted from the peripheral blood and Method of MassARRAY was used to genotype the single-nucleotide polymorphisms (SNPs). Results: STIP1 rs2236647 wild-type homozygote (CC) was associated with increased asthma risk of children (OR=1.858，95% CI：1.205-2.864), but not associated with the ICS response. GLCCI1 rs37969, rs37972 and rs37973 polymorphisms were not associated with the risk of childhood asthma. However, rs37969 mutant genotypes (TT/GT) were significantly associated with less improvement in PD20 (p = 0.028). We also found significant associations between rs37969, rs37972 and rs37973 mutant genotypes and less improvement in maximal midexpiratory flow (MMEF) after ICS treatment for 3 months (p=0.036, p=0.010 and p=0.003, respectively). Conclusions: STIP1 rs2236647 was associated with asthma risk of children and GLCCI1 rs37969 mutant genotypes were associated with less improvement in airway hyper-responsiveness. GLCCI1 rs37969, rs37972 and rs37973 polymorphisms might be associated with pulmonary function in childhood asthma patients after ICS treatment.
The Detrimental Impacts of Negative Age Stereotype on Episodic Memory of Older Adults: Does Social Participation Moderate the Effects?
Authors: Chan Stephen Cheong Yu , Au Alma May Lan , Lai Simon Man Kin
Published: September 2020

Background: Older adults' cognitive abilities can be impaired through priming of negative age stereotypes. However, it is unclear whether the effects of negative priming can be extended to episodic memory, which is believed to be the most age-sensitive type among the long-term memory systems, in Asian populations. Social participation has recently emerged as a potential protective factor for maintaining the cognitive function of older adults. The purpose of this study was to examine the effects of negative age stereotype priming on episodic memory and the moderating role of social participation in the priming effect.Methods: A total of 105 community-dwelling older adults residing in Hong Kong were randomly allocated to two experimental conditions. Participants were primed either with negative age stereotype words (n = 53) or neutral words (n = 52) using an implicit priming task. Episodic memory performance was assessed using the Hong Kong List Learning Task (HKLLT), which includes total learning, two delayed recalls and a recognition task. Analysis of covariance (ANCOVA) was used to assess group differences in the priming task and memory performance, while a series of moderation analyses were performed to examine the moderating effects of social participation.Results: The group that received negative age stereotype priming performed significantly worse than the group that received neutral words in their episodic memory test. Additional analyses showed that socially active individuals might be less prone to the effects of negative age stereotypes for the recognition task only.Conclusions: Older adults who are more socially active might be more immune to the effects of negative age stereotype priming on episodic memory. These results provide initial support for the hypothesis that social participation might act as an effective strategy to ward against negative age stereotype priming. Trial registration: ClinicalTrials.gov: NCT04202120 (first posted December 17, 2019), (Retrospectively registered)