bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Continental Shale Gas with Integrated Geoscience-Engineering Approach
Authors: Zhang Lixia , Ma Fujian , Jiang Chengfu , Xian Chenggang , Liu Chao , Zhao Xianran , Gao Yagang , Wang Qing , Guo Chao , Pan Yuanwei 
Published: April 2019

Abstract
Marine shale gas plays have been well developed worldwide; however, continental shale plays have been untapped until recently. Globally, there are no or few successes for continental shale gas development, although marine shale gas has been commercially exploited worldwide for decades. Ordos Basin, China is a rich continental shale gas play in Mesozoic and Paleozoic target zones. The proven resource is about 1600×108m3 (5.6 Tcf). The first geoengineering project for continental shale gas globally was conducted in this play in China.
The paper presents a case study that illustrates the challenges of a lacustrine shale gas well from integrated study to fracturing and well testing. Although an integrated geoscience-engineering workflow is used in the study, only results from drilling and logging are presented in the paper. Discussions and recommendations for future exploitation are presented.
The deep or semi-deep lacustrine deposits in the Triassic Yanchang formation, Ordos basin is the interval of interest in the study. The study area is in the southeastern part of Ordos basin, China, and the area is characterized by a single westerly dipping monocline with undeveloped faults . The interpretation of the seismic data showed no obvious faults. However, natural fractures were interpreted with ant tracking analysis, and these may influence reservoir and completion quality.
Numerical Study on Proppant Transport and Placement in Complex Fractures System of Shale Formation Using Eulerian Multiphase Model Approach
Authors: Yang Ruoyu , Guo Jianchun , Zhang Tao , Zhang Xudong , Ma Jian , Li Yang 
Published: April 2019

Abstract
Slick-water fracturing treatment is one of the most effective method to develop shale reservoir, which creates complex fracture system by connecting the pre-existing natural fractures. However, the proppant transport and placement behavior is quite different from that in conventional bi-wing fractures due to the low viscosity fluid system and intersections between fractures. The goal of this work is to simulate and understand the characteristic of proppant transport behavior in Complex Fractures network.
A Eulerian multiphase model is introduced to simulate the transport and settling behavior in the hydraulic fracture network, which takes turbulence effects and friction stress between the proppant particles into consideration and fully couple the fluid phase with particle phase. Simulation work was conducted to investigate the control mechanism and influencing factors for proppant transportation from main fracture into secondary and tertiary fractures.
The simulation results indicate that a small proppant dune quickly forms in the main fractures first, and almost no proppant enters the lower grade fracture until the proppant dune in the intersection reaches a specific height. With continuous injection of slurry fluid, majority of the proppant enters in the lower grade fracture which is controlled by gravity rolling from the dune in main fractures and fluid drag force, and the proppant settles quickly and gradually reach their own equilibrium height. Parametric study shows that smaller proppant density and particle size can also help proppant transport into secondary fractures and form a higher equilibrium height dune, resulting in larger effective propped area. Moreover, when the lower grade fracture is closer to the inlet entrance, the proppant is more likely to transport in, and the height of sand dunes formed in the fractures is higher.
The proppant transport process in complex fracture systems is simulated by Eulerian Multiphase Model in this paper. This study extends the understanding of the process and mechanism of proppant transport in complex fracture system and controlling factors, which helps optimize hydraulic fracturing design in shale formation.
Use of Data Analytics to Incorporate Geophysical Surface Uncertainty into Subsurface Modelling
Authors: Hardy Madeline , Lockwood Andrew , Thomas Peter 
Published: April 2019

AbstractUncertainty is present at every stage of the subsurface modelling workflow and understanding it is an ongoing challenge for the petroleum industry. Quantifying this uncertainty is a rapidly growing field of study as increasingly available high-performance computing enables the application of traditional statistical methods to this problem. However, the extension of these methods to spatial data remains a challenge for which there is no immediate solution. This paper describes the use of data analytics techniques to incorporate spatial uncertainty in reservoir surfaces into subsurface modelling. A metric usually applied in image analytics, the Modified Hausdorff Distance, is adapted for this purpose. The workflow involves sampling the domain of possible surface realisations, characterising them using this metric and determining the most efficient subset to represent the entire data set. The value of this process is that the selected subset captures spatial uncertainty in the surface rather than only gross rock volume. The proposed technique proved to be a simple process that was able to easily select these surfaces from a stochastically generated set and has been successfully applied to the top reservoir surfaces in two fields.
Accumulation Stages Division of Carbonate Hydrocarbon Pool in the Western Yingxiongling Area of Qaidam Basin
Authors: Wu Kunyu , Zhang Yongshu , Zhang Shenqin 
Published: April 2019

Abstract
The Qaidam Basin is a big intermountain Mesozoic-Cenozoic petroliferous basin in western China. The huge thickness Cenozoic strata and tectonic deformation formed a good combination of hydrocarbon sources, reservoirs and caps, leading to huge hydrocarbon potential of the basin. The Western Yingxiongling Area locates in the western part of the Qaidam basin, during the Cenozoic era a special tectonic dynamics background was formed by the joint control of the sinistral strike-slip fault of the East Kunlun and the sinistral strike-slip fault of the Altun (Fu et al., 2016). The tectonic deformation in this area is very strong, which makes the distribution of hydrocarbon pools extremely complicated. The breakthrough of wells Shi 20 and Shi 24 in the Western Yingxiongling Area in the 1980s confirmed that there are high oil and gas enrichment zones in this region. However, the distribution characteristics of oil and gas reservoirs in this area are not ascertained due to the lack of technical means and theoretical understandings. In recent years, based on the results of three-dimensional seismic exploration, studies on sedimentology and reservoir, and hydrocarbon geochemical evaluation, the geological characteristics of deep reservoirs in this area were systematically recognized. The structure of this area is characterized by "double layer", with large trap area and diverse types. At the same time, the region is in the favorable source depression area of the basin with sufficient hydrocarbon sources (Jin et al., 2001). The latest reservoir research discovered the commonly developed dolomite intergranular pores and the dissolution pores, which changed the former understanding of single fractured reservoir (Li and Wang, 2001). Since 2015, the exploration of the Western Yingxiongling Area has made remarkable progress on the basis of new theoretical understandings and technical application, and has successfully drilled a batch of high-yield wells such as Shi 38, Shi 205 and Shi 1-3 et al. In order to gain better understandings on the hydrocarbon pool in the Western Yingxiongling area, performing a systemic analysis on hydrocarbon pool stage division is necessary.
Weight-on-Bit Self-Adjusting Dual-Diameter Bit Leads a Step Change in Drilling Bit Technology
Authors: Hu Huaigang , Guan Zhichuan , Wang Bin , Liang Deyang , Sun Meiwei , Wang Xiaohui , Chen Weiqing 
Published: April 2019

Abstract
With the deepening of the large-size well section, mitigating drilling vibrations and pushing the upper limit of performance while drilling in a single bit run remains a challenge for PDC bits, and the problem of slow rate of penetration (ROP) has seriously affected the drilling cycle and cost of the whole well. Recently, new Weight-on-Bit(WOB) Self-Adjusting Dual-Diameter Bit (WSDB) technology was introduced to help overcome these challenges.
The structure of the bit is designed, the stress state of the stepped bottom hole is analyzed by using the general finite element software. The results of theories are corroborated with testing in the laboratory, which also demonstrates the ability of the technology to reduce drilling vibrations and push the performance envelope. The bit is mainly composed of four parts, the pilot section, the reaming section, the WOB regulating spring, and the transmission assembly. The technology provides the bit with the ability to continuously adjust its depth of cut control(DOCC) characteristics to suit the drilling environment and to mitigate of stick/slip vibrations. Because of the presence of the pilot section, the stress concentration area on the shoulder of the reaming bit is obviously reduced, and the stress unloading area in the junction of the reaming bit and the pilot bit is larger, therefore the rock breaking mechanical specific energy is reduced greatly in stress releasing area, thus the rock breaking efficiency is improved. Through the indoor comparison test, it is found that compared with the conventional PDC bit, the ROP of WSDB can be increased by up to 325% when drilling in limestone, which also indicates that Bit B has the characteristics of faster and more efficient drilling with low TOB.
A method to make full use of bottom hole stress releasing effect and reduce rock compressive strength to improve the rock-breaking efficiency is put forward, and a matched WSDB is developed. The mechanical specific energy required in the rock-drilling process can be greatly reduced, at the same time DOC characteristics of the bit are dynamically adjusted, which could remit the stick-slip vibration caused by a rapid change of DOC, thus the rock-breaking efficiency is improved.
Development of an Erosion Dynamics Model and its Application to Wells and Facilities
Authors: Wang Jason , Sami Muhammad , Troshko Andrey , Gallo Federico , Mayer Christian , Tenny Matthew 
Published: April 2019

Abstract
When producing hydrocarbons from an oil well, managing erosion of both surface and subsurface components caused by solids in the flow stream is critical to maintaining operations integrity in both land and offshore assets. Although component lifetime prediction has advanced in the past few decades, the prediction's accuracy remains a major oil and gas industry challenge. Current computational models only provide an initial erosion rate which is usually assumed constant until equipment failure. However, observed erosional rates vary as a function of time due to the geometrical changes caused by equipment material loss, which result in variations in solid particle impingement velocity [1] thereby either accelerating or slowing the erosional process. The constant rate simplified erosion model often produces inaccurate results that can lead to unexpected equipment failures or unnecessary equipment upgrades depending on whether the rate accelerates or decelerates. Therefore, developing a transient erosion model to capture the variations of erosional rate is needed for an accurate prediction of equipment lifetime.
This paper presents an implementation of an erosion dynamics model in ANSYS FLUENT, a commercial computational fluid dynamics (CFD) software, to capture the progression of transient erosion. The model has the capability to capture the effects of surfaces receding from erosion at each time interval. By dynamically adjusting these surfaces and recalculating the local flow conditions in the area, this method can predict new erosion rates for each time interval and achieve fully coupled geometry-flow-erosion interactions.
This new erosion dynamics model was validated against experimental data from both literature and physical testing, and was determined to have accurately captured the observed erosion trends over time in terms of location and magnitude. The model was then employed to study two real world applications: 1) in evaluating the erosion risk for a high-rate water injector, it predicted the evolution of damage to a coupler designed to connect different diameter pipes, and 2) in analyzing facility piping systems connected to an unconventional well, it predicted the transient erosion trend from proppant flowback, which allowed for pipe geometry optimization to increase in erosional life expectancy.
Efficient Flow Rate Profiling for Multiphase Flow in Horizontal Wells Using Downhole Temperature Measurement
Authors: Zhang Shuang , Zhu Ding 
Published: April 2019

Abstract
The downhole temperature measurements have become a powerful tool for fracture diagnosis. Multiphase flow is common in fractured horizontal wells, and its effects on temperature behavior are noteworthy. To interpret downhole temperature measurement quantitatively, we need an integrated flow and thermal model to handle multiphase flow with reasonable computational efficiency while maintaining maximum accuracy that can be achieved. This study presents the multiphase black-oil thermal and flow model and shows its applications on temperature interpretation.
The integrated multiphase black-oil thermal and flow model can simulate the transient temperature behavior during the injection of the hydraulic fracturing, shut-in, and the production. The model simulates reservoir flow (pressure and velocity) and thermal (temperature) for a multi-stage hydraulic fractured horizontal well. Previously developed wellbore model for two-phase flow is adopted in this study. The reservoir model solves the mass balance, Darcy's law and energy balance in three dimensions. We assume that the oil and water components are immiscible, and the gas component is only soluble in oil but not in water. The reservoir model and wellbore model are coupled interactively through boundary conditions to each other.
The multiphase black-oil thermal/flow model is validated against the compositional model. The results show the consistency between these two models, and the multiphase black-oil thermal/flow model significantly reduces the computational time. This study gives guidance on when and how to apply this black-oil thermal model to fulfill its full advantages. This work proposes a modified inversion workflow particularly for liquid production based on the previous study and presents a field example of implementing this developed thermal model to interpret temperature data to flow rate profile for a multistage fractured horizontal well with the multiphase flow. The results reveal this multiphase black-oil thermal model is efficient and can be used to interpret temperature measurements for multiphase flow quantitatively with reasonable assumptions.
The Study of Surfactant Huff and Puff of Horizontal Well with SRV in Tight Oil Reservoirs
Authors: Weirong Li , Zhenzhen Dong , Gang Lei , Cai Wang , Huijie Wang 
Published: April 2019

Abstract
A local refined model, using micro-seismic data to model fracture geometry, is presented to study huff-n-puff surfactant injection in a tight oil reservoir. The goal of this study is to understand the key parameters that control the surfactant huff-n-puff performance in tight oil reservoirs.
In this new approach, natural fractures in tight oil reservoir is described by dual permeability model, and stimulated reservoir volume (SRV) based on micro-seismic datais is modeled by local refined grid. In the study, sensitivity analysis is carried out to optimize oil recovery, such as wettability change, interfacial tension, surfactant adsorption, huff-n-puff cycle, etc.
The results indicate that surfactant injection is a favorable method to mobilize oil in tight oil reservoirs; wettability alteration and interfacial tension of surfactant are the dominant mechanisms for the oil recovery through surfactant injection; surfactant adsorption is a key element to the success of the wettability alteration process; and soaking time does not have obvious impact on recovery. The incremental oil recovery factor over primary production for 15 years of total production is up to 3.5% of OOIP that doubles the recovery from the primary production.
The study gives new method to study surfactant injection in the tight oil reservoirs when micro-seismic data available. It can be helpful for modeling other EOR process in tight oil reservoirs. The results also can guide surfactant injection in field development for similar tight oil field.
Accurate Original Resistivity Inversion in a Heterogeneous Thick Flooded Reservoir Through Electrical Interpretation Unit Classification
Authors: Liu Huan , Xu Jinxiu , Cui Yunjiang , Lv Zuobin , Shi Xinlei 
Published: April 2019

Low resistivity is a main feature of flooded reservoir in injection fields. The key to evaluate flooding severity is to reconstruct resistivity in its' original condition. In this process, the routine method is to find a relationship between resistivity and other logs to rebuild unflooded resistivity. However, it is very sensitive to formation parameters and prone to have larger error due to ignoring the difference of lithology, reservoir and electrical properties driven by geological background.
This paper proposes a method to classify reservoir into different electrical interpretation units to address the problem that routine methods have. Firstly, reservoir was divided into different logging facies through multi-resolution graph-based clustering(MRGC). Secondly, a database of the relationship between logging facies and lithology in aimed reservoir was built based on the core, petrophysical logging data and so on. Eventually, electrical interpretation units were obtained based on the database and reservoir resistivity. Resistivity models of origin field were built for each electrical interpretation unit, which could improve the accuracy of original resistivity calculation dramatically.
In the studied field, five logging facies were defined in a coring well using MRGC method. The relationship between each logging facie and its lithology were constructed as well. Each logging facie can be recognized though cross-plots from conventional logs. Meanwhile, considering reservoir fluid properties, through finding similar electrical properties in the reservoir with same logging facies and lithology, the studied well could be further divided into three interpretation units. With similar lithology and reservoir properties, reservoir heterogeneity from the same electrical interpretation unit decreases, plus bearing similar electrical property, the influence from saturation difference of the original field has weakened. Through the previous illustrated model, it has demonstrated a good effect in evaluating the original resistivity in thick layers of the M field from Bohai Bay. Comparing with the result from routine method, the resistivity from the proposed method has a better match with the resistivity from unflooded area, consequently, increase the evaluation accuracy dramatically.
Eventually, the classification of logging facies and electrical interpretation units from key wells can be spread to flooded wells to calculate the unflooded resistivity, as a result, a more accurate flooding severity evaluation could be obtained. It could provide more reliable data for further residential oil development.
3D Permeability Characterization Based on Pore Structure Analysis and Multi-Parameters Seismic Inversion and Its Application in H Oilfield
Authors: Chen Xin , Wang Guihai , Wang Zhaofeng , Liu Zundou , Liu Zhaowei , Cui Yi , Tian Wenyuan , Wei Xiaodong , Hou Liugen , Yang Ke , Chen Gang , Xia Yaliang , Yan Xiaohuan , Zhang Zeren , Liu Jingluan 
Published: April 2019

Abstract
To improve the accuracy of permeability prediction, seismic constraint and sedimentary facies has often been adopted in conventional methods. However, it is porosity that both of them constrain, rather than permeability, and different pore structure with different permeability, the accuracy of permeability prediction cannot be radically improved. To address the problem of permeability prediction in carbonate reservoir, new permeability prediction technique workflow were summarized based on pore structure analysis and multi-parameters seismic inversion: division reservoir types based on the pore structure, construction of the rock types identification curve, carry out a rock type inversion and a porosity inversion constrained by seismic impedance respectively, and then get a final permeability prediction volume according to the porosity-permeability relationship and pore structure of core samples. It breaks the bottleneck that is difficult for seismic impedance (continuous variable) to constrain rock type (discrete variable), then constrains pore structure (continuous variable) related to rock type instead, and converts it into rock type using multi-parameters seismic inversion. According to the certification of new wells, this workflow have been applied successfully in carbonate reservoir of H oilfield in Middle East, it not only improves the prediction of rock type in space, but also permeability prediction accuracy.
The Rock Mechanical Properties of Lacustrine Shales from Ordos Basin
Authors: Yu Hongyan , Li Xiaolong , Wang Zhenliang , Rezaee Reza , Gan Litao 
Published: April 2019

Abstract
Abundant shale oil and gas resources have been discovered in the Zhangjiatan shale of the Yanchang formation in ordos basin in recent years. Zhangjiatan shale is a typical lacustrine shale, which is different from Marine shale in physical properties. Most previous research has focused on Marine shale. In order to understand the rock mechanical properties of Zhangjiatan shale, we conducted dynamic and static elastic properties experiments. We selected argillaceous shale and silty laminae shale in Zhangjiatan shale as samples. In order to obtain the static Young's modulus and Poisson's ratio, we use the triaxial pressure test. We use the dipole log to measure the acoustic velocity down the hole, and then we calculate the dynamic Young's modulus and Poisson's ratio of the sample based on acoustic velocity. Young's modulus of argillaceous shale is slightly smaller than that of silty laminae shale and the Poisson's ratio of argillaceous shale is also smaller than that of silty laminae shale. The brittleness of argillaceous shale are greater than that of silty laminae shale, as a result, argillaceous shale is much easier fracturing under pressure. We plotted the cross-plot of RCS, elastic properties and TOC and reached a conclusion that the mass ratio of clay to quartz and feldspar determined the brittleness and deformability of rock, while organic matters also affected the elastic properties of rock. Therefore, the elastic properties of shale are not controlled by a single factor, instead of multiple factors.