bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Natural Fractures on Wormhole-Propagation Behavior
Authors: Mou Jianye , Yu Xiaoshan , Wang Lei , Zhang Shicheng , Ma Xinfang , Lyu Xinrun 
Published: October 2018

Summary
Natural fractures have significant influence on flow fields, thus affecting wormhole pattern in acidizing. This paper summarizes our research on wormholing behavior in naturally fractured carbonates. First, statistical natural-fracture models are established using the Monte Carlo method. Second, a two-scale continuum wormhole model is established to simulate wormhole propagation with natural fractures. Finally, extensive numerical simulation is conducted to investigate wormhole behavior and the effect of the natural-fracture parameters on wormhole pattern. In addition, possible wormhole-penetration distance is discussed. This study provides a theoretical basis for matrix-acidizing designs in naturally fractured carbonates.
On Subcool Control in the SAGD Producers—Part III: Efficiency of Subcool Trapping in the Nsolv Process
Authors: Irani Mazda , Gates Ian 
Published: October 2018

Summary
Steam-assisted gravity drainage (SAGD) is currently the preferred thermal-recovery method used to produce bitumen from Athabasca deposits in Alberta, Canada. SAGD is, however, an energy-intensive process with large amounts of greenhouse-gas (GHG) emissions and required water treatment. One option to reduce emissions and water usage is with solvent-based techniques, such as the Nsolv™ process. Suncor and Nsolv have been working together on a bitumen-extraction solvent-technology (BEST) field demonstration at Suncor's Dover test site. The solvent-injection–produced-oil ratio (SvOR) is among the key performance indicators (KPIs) of the BEST facility. Solvent breakthrough caused by inefficiency of thermodynamic trapping, such as subcool trapping, contributes to SvOR and affects the facility's economic and artificial-lift efficiencies. Subcool is the temperature difference between the injected butane (at saturated condition) and produced fluids (mixture of butane condensate, upgraded bitumen, and formation water). One of the unknowns in this process is the efficiency of thermodynamic trapping. On the basis of field results, it is shown that, like the SAGD process, liquid-pool depletion presents a critical control on the performance of the recovery process. Although the produced fluids are depleted from the liquid pool at the base of the chamber, because liquid-butane viscosity dependency on temperature is not strong and its viscosity changes slightly with temperature, thermodynamic trapping (or subcool trapping) is not efficient. Stability analysis of BEST data suggests that vapor breakthrough is part of the process but can be minimized by operating at temperatures greater than the second subcool limit. The second subcool limit (or Nsolv optimal reservoir subcool) will vary over time, and it is shown to occur at slightly less than 4°C after liquid-pool development.
Thermal Effects of Liquid/Supercritical Carbon Dioxide Arising From Fluid Expansion in Fracturing
Authors: Li Xiaojiang , Li Gensheng , Yu Wei , Wang Haizhu , Sepehrnoori Kamy , Chen Zhiming , Sun He , Zhang Shikun 
Published: October 2018

Summary
Liquid/supercritical carbon dioxide (L/SC-CO2) fracturing is an emerging technology for shale gas development because it can effectively overcome problems related to clay swelling and water scarcity. Recent applications show that L/SC-CO2 fracturing can induce variations in temperature. Understanding of this phenomenon is rudimentary and needs to be carefully addressed to improve the understanding of CO2 thermodynamic behavior, and thus helps to optimize CO2 fracturing in the field.
In this paper, we develop a numerical model to assess the impact of thermal effect on fracture initiation during CO2 fracturing. The model couples fluid flow and heat transfer in the fracture, and is verified by a peer-reviewed solution and observation in laboratory experiments. The velocity, pressure, and temperature are calculated at various time to demonstrate the thermodynamic behavior during fracture initiation. A pseudo shock wave is observed, associated with a compression wave and an expansion wave, which finally leads to an increase in temperature in the new fracture and a decrease in temperature in the initial fracture. The thermal stress is derived to investigate the difference between hydraulic fracturing and CO2 fracturing. The results show that thermal stress, resulting from CO2 fracturing initiation, is comparable to the rock strength, which will help induce microfractures, and thus promote the fracture complexity. The formation pressure after CO2 fracturing is also calculated to evaluate the pressure-buildup potential. This work highlights the importance of CO2 expansion during and after fracturing. It is one of the unique features that differs from hydraulic fracturing. For field-design recommendations, to enhance the thermal effect of CO2 fracturing, it is a good strategy to pump CO2 at high pressure and low temperature into the reservoirs with high Young's modulus, low Poisson's ratio, low permeability, and high geothermal temperature (or large depth).
This paper does not address the dynamics of fracture propagation under the influence of thermal effect. Rather, it intends to demonstrate the potential of the thermal effect of CO2 fluid in assisting the fracture propagation, and the importance of incorporating the compressibility of CO2 into fracture modeling and operation design. Failing to account for this thermal effect might underestimate the fracture complexity and stimulated reservoir volume.
Preformed Partial Gel Injection Chased by Low-Salinity Waterflooding in Fractured Carbonate Cores
Authors: Alhuraishawy Ali K. , Bai Baojun , Wei Mingzhen , Almansour Abdullah 
Published: October 2018

Summary
Fractures and oil-wet conditions significantly limit oil recovery in carbonate reservoirs. Gel treatment has been applied in injector wells to modify the prevailing reservoir streamlines and significantly reduce fracture permeability, whereas low-salinity waterflooding has been applied experimentally to modify rock wettability toward water-wet for improved oil recovery. However, both processes have limitations that cannot be resolved using a single method. The objective of this study was to test whether low-salinity water could enable gel particles to move deeply into fractures to efficiently increase oil recovery and control water production. A semitransparent fracture model of carbonate cores and acrylic plates was built to study the effect of low-salinity waterflooding, fracture width, gel-injection volume, and fracture uniformity on oil recovery and to redirect the flow path to unswept zones. Preformed partial gel (PPG) and brine movements were visible through the model's transparent acrylic plate. Seawater was used for brine flooding and to prepare swollen particles; the seawater was diluted 100 times to create low-salinity water. A light crude oil was used, with 10-cp viscosity. Low-salinity water was injected after gel placement to test the gel-plugging efficiency. The results showed that the low-salinity water could improve gel propagation into the fracture and increase oil recovery because the gel strength (apparent viscosity) decreased as the brine concentration decreased. The gel-injection volume had a significant effect on the oil-recovery factor when seawater flooding followed the gel-injection process, although there was less of an effect when the gel was followed by low-salinity waterflooding. Moreover, the effect of low-salinity waterflooding on gel propagation decreased as the fracture width decreased. In addition, the resulting fracture uniformity illustrates a viable effect of the in-depth water-diversion treatment.
Drilling with Digital Twins
Authors: Nadhan Derek , Mayani Maryam Gholami , Rommetveit Rolv 
Published: October 2018

Abstract
The industry is undergoing a transition into efficient technologies and it has digitalization written all over it. Digitalization not only should be about data, a fancy software, touchscreens and the internet, it is important that solutions are able to connect within existing work processes and with people for companies to truly lead to more efficient and safer drilling operations.
Oil and gas industries are now moving towards using Digital Twin's during the life-cycle of well construction. The concept of Digital Twins was first introduced by Dr. Michael Grieves at the University of Michigan in 2002 through Grieves’ Executive Course on Product Lifecycle Management. Digital Twin is a digital copy of the physical systems and act as a connection between physics and digital world. The digital system gets the real-time data from the mechanical systems which include all functionality and operational status of the physical system. An example from another industry; A Formula 1 team uses data from many sensors used in the car, harnessing data and using algorithms to make projections about what's ahead, and apply complex computer models to relay optimal race strategies back to the driver. Ultimately, to drive faster and safer.
By means of the digital twin of the drilling wells during the life cycle of the drilling by combining digital and real-time data together with predictive diagnostic messages there is seen a lot of advantageous in the improvement of accuracy in decision making and results. This again will help the industry to increase safety, improve efficiency and gain the best economic-value-based decision. A Digital Twin driven by real-time data helps to give operations the optimal plan with focus on safety, risk reduction and improved performance.
In this paper, the concept will first be explained in creating and utilizing a Digital Twin of your well for drilling and how it will directly influence how Drilling/well engineers, managers and supervisors plan, prepare and monitor their drilling operations and then implement learnings on future wells; for faster and improved decision making with direct relation to predicting and avoiding/mitigating NPT while also optimizing operations along with it. Case examples will be shared, showing value from use of the Digital Twin from first introduced in 2008 up until now where operators around the globe have implemented it for multiple uses in the drilling lifecycle.
An Experimental Study on Carbonated Water Injection of Core Samples from Tight Oil Reservoirs from Ordos Basin
Authors: Zou Jiandong , Liao Xinwei , Li Xiaoming , Zhu Zengguo , Chu Hongyang , Yuan Zhou , Luo Weiyun , Shen Xudong 
Published: October 2018

Abstract
Carbonated water injection (CWI) is considered to be a win-win association for enhancing oil recovery and reducing environmental footprint. Therefore, the study of CWI potential has gained tremendous attention recently. Unfortunately, the dedicated research so far focus heavily on conventional reservoirs. In order to expand the application scope of CWI, the objective of this study is to carry out a coreflooding investigation of core samples from tight oil reservoirs.
The experiments were carefully designed to assess the performance of CWI and to quantify the potential of additional oil recovery and CO2 storage capacity under various experimental conditions. We presented the results of a series of CWI coreflood experiments using the reservoir cores of tight sandstone with live crude oil. It is found that the ultimate oil recovery by CWI is higher than the conventional water injection in both secondary and tertiary recovery mode. The complex mechanisms are also investigated including CO2 content of injected carbonated water (CW), oil swelling and viscosity reduction.
It was observed that both secondary and tertiary CWI could recover a significant amount of additional oil compared to conventional water injection. The results revealed that the oil recovery would be lower if CO2 concentration is reduced, but the extent of oil recovery reduction would be much less than the level of reduction in CO2 concentration. Oil swelling as a result of CO2 diffusion into the oil raised the pressure, and the reduction of subsequent oil viscosity were amongst the main mechanisms of oil recovery by CWI, which were obtained by the high pressure coreflood models and PVT studies. Higher oil recovery was obtained with the higher permeability and higher carbonation level. At the end of the injection period, an encouraging amount of dissolved CO2 was stored in the brine and the residual oil of the tight sandstone.
The experimental results clearly indicate the potential of CWI for improving oil recovery and CO2 storage capacity in tight oil reservoirs. It is particularly attractive for the implementation of CWI for reservoirs that have limited access to large amounts of CO2. To the best of our knowledge, this is the first time to experimentally investigate CWI potential in tight oil reservoirs.
Prospects for the Spectral Noise Logging Application in the Analysis of Stimulated Reservoir Volume in Horizontal Wells with Multistage Fracturing
Authors: Nagimov Vener , Alekseev Aleksey , Tolmachev Evgeny , Maslennikova Yulia , Shigapov Ilnur 
Published: October 2018

Abstract
The most effective technique of low-permeability reservoir development is multistage hydraulic fracturing (hydrofrac) in horizontal wells. One of the specific features in operating such wells is that in the vast majority of cases flow rates from the created fractures are insignificant and remain below the sensitivity threshold of most tools that are part of the conventional production logging suite. In addition, development of unconventional reservoirs, such as Bazhenov formation, requires application of special hydraulic fracturing techniques. Therefore, estimation of the contribution from each frac stage into the total production and diagnostics of active fracs are essential and challenging tasks. To solve these tasks, the production logging suite that was run in a horizontal well to Bazhenov formation included Spectral Noise Logging tool which can not only locate the flow zones but is also suitable for identification of the flow zone type. This paper discusses the approaches to Spectral Nose Logging data analysis focused on the problem mentioned above and provides several case studies dealing with application of the production logging suite supplemented with SNL in a horizontal well drilled in Palyanovo area of Kranoleninsk field where multistage fracs had been carried out in the Bazhenov Deposits.
Approach to Understanding the Stimulated Reservoir Volume in Unconventional Oil Reservoirs
Authors: Dvoretskaya Ekaterina Alexandrovna , Salishchev Mikhail Vsevolodovich 
Published: October 2018

Abstract
At the early stage of unconventional oil field exploitation under circumstances by lack of geomechanical reservoir model the way to estimate drainage volume of fractured horizontal well is considered.
In order to create connected reservoir volume and to improve reservoir sweep efficiency though the initiating drainage channels in unconventional reservoirs multiple hydraulic fracturing is used. It improves the recovery of oil from previously impermeable vast pore volume. In this case the target of stimulation is not a planar fracture with definite length and height but the supreme rock failure directed to development induced fracturing network and therefore hydraulic techniques distinguishes from standard one. Generally this complex network is achieved by specific hydraulic fluids injection at elevated rates. As a result artificial fractured rock volume is created in the reservoir and provides the draining of a great previously unavailable hydrocarbon reserves which sustaining high production rates and acceptable cummulative oil production per well.
The concept of stimulated reservoir volume is used for the purpose of characterizing the rock volume subjected to stimulation. In the result of this treatment the complex hydraulically communicated fracture network is generated around the horizontal well. It defined by extensive improved filtration properties due to permeability of induced fractures. Initial stock tank oil in place is governed by rock capacities and saturation of mobile hydrocarbons.
Effects associated with fractures are the key ones for production intensification since they define the distribution of fluid's flow paths in the reservoir. The possibility of their accounting in the simulation modelling is an important challenge since it directly defines the history matching quality and therefore the forecast of long-term production.
During the application of the concept of stimulated reservoir (SRV) penetrating with multi-fractured horizontal well the necessity in stimulated reservoir volume characterization is arised. This characterization concerned with the base properties which exert the impact on well productivity index and on the oil recovery factor. Then as a result, the use of mathematical modeling to solve the inverse problem to clarify the structure and properties of unconventional formation by reproducing the history of development authors state three basic geological and technological parameters which define the well production performance of unconventional reservoir with SRV – the volume of stimulated zone, shape-factor and effective permeability of fractured zone.
At the early stage of exploitation the unconventional reservoir, which characterized by the availability of production history and the drawback of geomechanical data, the approach is presented which provides an opportunity to create the fluid-flow reservoir model ensures with higher degree of accuracy and more reliable long-term production forecast.
On the Mechanisms of the Formation of Zones with Abnormally High Rock Pressure and Methods for Predicting them in Undeveloped Rock Systems
Authors: Islamov Azamat , Kolupaev Dmitriy , Faskhutdinov Ruslan , Vereschagin Sergei 
Published: October 2018

Abstract
To the list of the most serious and uncontrolled geological complications arising during the drilling of wells, it is well known the Oil, Gas and Water Shows (OGWS) which often happens in areas with formed waterflooding zones. Risks result from the lack of the ability to predict the location of Abnormally High Reservoir Pressures zones (AHRPZ) due to high uncertainties in the movement of the injected fluid in formation.
Oversight of the meeting of reservoir zones with high reservoir pressure is conducted on the basis of a number of analytical tasks: making water-oil factor maps, ping the front of the injection water in formation, pressure (isobar) maps, drilling history, special field geophysical tests for formation cross-flows, CO-logs across not perforated productive intervals.
However, by using the classical development tools, it is possible to solve the issues with predicting the potential high pressure zones in the flooded reservoirs, but how we can predict the abnormal pressure systems in reservoirs that are not under development and carry exclusively technogenic genesis?! In this paper we will talk about the forecasting possibility of the abnormal pressures in the transit reservoir systems using the example of the Priobskoye oilfield. Those systems are not involved in the development process either because of the lack of hydrocarbon reserves or because of the absence of the reservoir at all. The authors hope that this materials allow to describe the tools that will protect other colleagues from complications related with well drilling and their re-drilling with associated material costs.
The First Experience of Formate Based Drilling Fluids Application in Russia
Authors: Ryabtsev Peter Leonidovich , Khomutov Anton Yuryevich , Korolev Andrey Vladimirovich 
Published: October 2018

Summary
Notwithstanding significant advantages of the oil-base mud systems, their application inherent in a number of disadvantages that have been primarily attributable to environmental restrictions. In 2017 AKROS LLC and GAZPROMNEFT ran full-scale field-testing of potassium and sodium formate mud systems enabling them to analyze the performance of such systems and define the key application features. Conclusions on the application features of these systems and their perspectives in Russia are based on the results of the work performed.
To implement potassium and sodium formate drilling fluids in GAZPROMNEFT fields, the full-scale laboratory testing was performed. The outcomes enabled the identification of fluid formulations for field applications and procedures for the maintainance of mud properties when drilling.
Two intervals on «Gazpromneft-Khantos»' LLCs Yuzhno-Priobskoye Field and three intervals on
«Gazprom Neft Shelf» LLC's Prirazlomnoye Field were drilled with potassium formate-base formulations.
Field testing proved the high efficiency of potassium formate mud systems allowing them to: –achieve high drilling performance indicators;–gain experience in horizontal well drilling without lubricating additives demonstrating loads and torques similar to or lower than values observed in mud systems treated with lubricants;–develop the procedure for interval treatment of a high-density drilling fluid;–confirm the possibility of achieving a high density up to 1.41 g/cm3 without barite;–implement the technology ensuring mitigation of environmental risks connected with drilling fluids;–drill horizontal section and production casing intervals using one type of drilling fluid instead of two, facilitating reduced waste and prepared volumes.
The potassium formate mud system proved to be efficient and has impressive perspectives in Russia as an alternative to oil-base drilling fluids, particularly for high formation pressure drilling. Based on field application results, practical application procedures and optimum recommendations for controlling mud properties were developed. Comparative tests for inhibition effectiveness, reducing friction factor, achieving high drilling performance were conducted.
Design and Process Engineering of Slotted Liner Running in Extended Reach Drilling Wells
Authors: Kunshin Andrey , Dvoynikov Mikhail 
Published: October 2018

Abstract
In this paper, the process of developing an improved design of slotted liner, which makes it possible to increase the efficiency of running into extended-reach wells is considered. The options of running a liner with the filter through the power sub or swivel are discussed. Each option of running is estimated and the optimal method is selected. A scenario is proposed with changing the filter part of the assembly to optimize the strength and dynamic characteristics during well completion and subsequent field operation. Existing models of filters are considered, their shortcomings are discovered and, on this basis, a digital filter prototype is proposed.
A filter assembly with guiding turbulators, their number and arrangement are proposed. The prototype is designed and printed on a 3D-printer.
The calculations result of the friction moment during its running are presented. The criteria for installing guiding turbulators on a filter are established, which prevents the filter body to deflect from its own weight and contact with the borehole wall.
Technical and economic indicators are calculated, which show the attractivity of the project in several criteria (blocks).