A numerical method for simulating planar 3D multi-fracture propagation in multi-stage fracturing of horizontal wells

To resolve the issue of design for multi-stage and multi-cluster fracturing in multi-zone reservoirs, a new efficient algorithm for the planar 3 D multi-fracture propagation model was proposed. The model considers fluid flow in the wellbore-perforation-fracture system and fluid leak-off into the rock matrix, and uses a 3 D boundary integral equation to describe the solid deformation. The solid-fluid coupling equation is solved by an explicit integration algorithm, and the fracture front is determined by the uniform tip asymptotic solutions and shortest path algorithm. The accuracy of the algorithm is verified by the analytical solution of radial fracture, results of the implicit level set algorithm, and results of organic glass fracturing experiment. Compared with the implicit level set algorithm(ILSA), the new algorithm is much higher in computation speed. The numerical case study is conducted based on a horizontal well in shale gas formation of Zhejiang oilfield. The impact of stress heterogeneity among multiple clusters and perforation number distribution on multi-fracture growth and fluid distribution among multiple fractures are analyzed by numerical simulation. The results show that reducing perforation number in each cluster can counteract the effect of stress contrast among perforation clusters. Adjusting perforation number in each cluster can promote uniform flux among clusters, and the perforation number difference should better be 1-2 among clusters. Increasing perforation number in the cluster with high in situ stress is conducive to uniform fluid partitioning. However, uniform fluid partitioning is not equivalent to uniform fracture geometry. The fracture geometry is controlled by the stress interference and horizontal principal stress profile jointly.

Implementation of a Subjective Visual Vertical and Horizontal Testing System Using Virtual Reality

Subjective visual vertical(SVV)and subjective visual horizontal(SVH)tests can be used to evaluate the perception of verticality and horizontality,respectively,and can aid the diagnosis of otolith dysfunction in clinical practice.In this study,SVV and SVH screen version tests are implemented using virtual reality(VR)equipment;the proposed test method promotes a more immersive feeling for the subject while using a simple equipment configuration and possessing excellent mobility.To verify the performance of the proposed VR-based SVV and SVH tests,a reliable comparison was made between the traditional screen-based SVV and SVH tests and the proposed method,based on 30 healthy subjects.The average results of our experimental tests on the VR-based binocular SVV and SVH equipment were−0.15◦±1.74 and 0.60◦±1.18,respectively.The proposed VR-based method satisfies the normal tolerance for horizontal or vertical lines,i.e.,a±3◦error,as defined in previous studies,and it can be used to replace existing test methods.

Numerical modeling calculation for the spatial distribution characteristics of horizontal field transfer functions

Applying 3-dimension finite difference method, the distribution characteristics of horizontal field transfer functions for rectangular conductor have been computed, and the law of distribution for Re-part and Im-part has been given. The influences of source field period, the conductivity, the buried depth and the length of the conductor on the transfer functions were studied. The extrema of transfer functions appear at the center, the four corners and around the edges of conductor, and move with the edges. This feature demonstrates that around the edges are best places for transfer functions' observation.

Application of 3D stereotomography to the deep-sea data acquired in the South China Sea:a tomography inversion case

A 3D stereotomography algorithm, which is derived from the 3D Cartesian coordinate, is applied for the first time to the deep-sea data acquired in the LH area, South China Sea, to invert a macro velocity model for pre-stack depth migration. The successful implementation of stereotomography is highly dependent on the correct extraction of slowness components and the proper application of regularization terms. With the help of the structure tensor algorithm, a high-quality 3D stereotomography data space is achieved in a very efficient manner. Then, considering that the horizontal slowness in cross-line direction is usually unavailable for 3D narrow-azimuth data, the regularization terms must be enhanced to guarantee a stable convergence of the presented algorithm. The inverted model serves as a good model for the 3D pre-stack depth migration. The synthetic and real data examples demonstrated the robustness and effectiveness of the presented algorithm and the related schemes.

3D Finite Elements Technique for Collapse Causes of the Pylons in Egyptian Temples: A Study of the Great Pylon of Ramesseum Temple, Luxor, Egypt

This research presents damage causes of the pylons in the ancient Egyptian temples based on 3D finite elements analysis. The main purpose of the research determines the failure causes of the first pylon of the Ramessium temple, which is situated in Upper Egypt, at Luxor “Thebes” on the west bank of the Nile River. The first pylon of Ramessium temple subjected to seismic activity effects on long term, combined with several structural damage factors such as the defects resulting from the construction technique, where the builder used the poor quality of stones in foundations of the pylon, the building materials residue was used as filler for the core of the pylon walls, and it lacked vertical joints between the courses. In addition to it founded on alluvial soil that is vulnerable to contaminated water, it is still suffering damage factors and urban trespasses at the moment. All of the former factors helped the pylon to be affected by the earthquakes loads that occurred on it. The structural behavior of the pylon under self-weight and earthquakes loads were carried out by Numerical analysis to find out the loads and stresses which caused collapsing of the pylon. Results of the study indicated that the pylon subjected to a horizontal displacement due to old earthquakes force, led to collapse of the pylon. Finally, the study represents use of modern technique to study the structural behavior of the most important architectural units in ancient Egyptian temples to identify the causes of its collapse.

Modeling 3D Ex-Filtration Process of a Soak-Away Rain Garden

This paper presents a three-dimensional (3D) model developed using COMSOL Multiphysics to understand the 3D ex-filtration process of a soak-away rain garden. With a design hyetograph of 3-month average rainfall intensities of Singapore, it is found that the average vertical ex-filtration rate that is obtained by dividing the average vertical ex-filtration (drained through bottom of the soak-away rain garden, averaged over the simulation period = 720 min, and expressed in m3) by the surface area of the soak-away rain garden and the simulation time step is almost constant regardless of increase in saturated hydraulic conductivity (K) of the in-situ soil and the surface area of the soak-away rain garden as a percentage of catchment area. However, as depth to groundwater table which is measured from bottom of the filter media increases, in between 0.5 m and 1 m of depth to groundwater table, the average vertical ex-filtration rate decreases significantly (by around 15 - 20 mm/hr) and the decrease is almost twice, compared with that between 1 m and 1.5 m of depth to groundwater table. Furthermore, this study shows that for a given K of in-situ, K of filter media, and depth to groundwater table, as the surface area of the soak-away rain garden increases, the horizontal flow coefficient which is defined as the ratio between total horizontal ex-filtration (drained through sides of the soak-away rain garden, summed over the simulation period, and expressed in m3) and total vertical ex-filtration (drained through bottom of the soak-away rain garden, summed over the simulation period, and expressed in m3) decreases. Moreover, for a given surface area of the soak-away rain garden, K of in-situ, and depth to groundwater table, the horizontal flow coefficient decreases as K of the filter media increases. However, it is found that for a given surface area of the soak-away rain garden, K of in-situ, and K of filter media, the horizontal flow coefficient increases as depth to groundwater table increases.

Development and prospect of acoustic reflection imaging logging processing and interpretation method

Acoustic reflection imaging logging technology can detect and evaluate the development of reflection anomalies,such as fractures,caves and faults,within a range of tens of meters from the wellbore,greatly expanding the application scope of well logging technology.This article reviews the development history of the technology and focuses on introducing key methods,software,and on-site applications of acoustic reflection imaging logging technology.Based on the analyses of major challenges faced by existing technologies,and in conjunction with the practical production requirements of oilfields,the further development directions of acoustic reflection imaging logging are proposed.Following the current approach that utilizes the reflection coefficients,derived from the computation of acoustic slowness and density,to perform seismic inversion constrained by well logging,the next frontier is to directly establish the forward and inverse relationships between the downhole measured reflection waves and the surface seismic reflection waves.It is essential to advance research in imaging of fractures within shale reservoirs,the assessment of hydraulic fracturing effectiveness,the study of geosteering while drilling,and the innovation in instruments of acoustic reflection imaging logging technology.

Analysis of global and local stress changes in a longwall gateroad

A numerical-model-based approach was recently developed for estimating the changes in both the horizontal and vertical loading conditions induced by an approaching longwall face.In this approach, a systematic procedure is used to estimate the model's inputs.Shearing along the bedding planes is modeled with ubiquitous joint elements and interface elements.Coal is modeled with a newly developed coal mass model.The response of the gob is calibrated with back analysis of subsidence data and the results of previously published laboratory tests on rock fragments.The model results were verified with the subsidence and stress data recently collected from a longwall mine in the eastern United States.

A NOVEL 3-D MODEL FOR THE WATER CRESTING IN HORIZONTAL WELLS

In the presence of bottom water, a drop in the reservoir pressure due to fluid production causes the aquifer water to expand and to flow into the reservoir. Therefore, hydrocarbon production from a well is limited by the critical flow rate. The main purpose of this study is to investigate the breakthrough time and the critical rate by using a novel 3-D horizontal well model. Based on the hypothesis that the horizontal well is located in any position of a circular reservoir with no-flow boundary on the top of the reservoir and constant pressure boundary at the bottom, the horizontal well has been regarded as an infinite conductivity line sink and then a 3-D steady-state flow model of the horizontal well is set up. A point sink pressure solution can be obtained with the Fourier transform. The result of the pressure distribution of the uniform flux horizontal well can be presented by means of the principle of superposition. According to the stable water cresting theory, this study confirms the stable height of water cresting and the critical rate. Meanwhile, it can re-confirm the breakthrough time at a specific rate. The output of a comparison between this 3-D model and the reservoir numerical simulator （Eclipse） shows the method presented here can be applied to investigate the behavior of a water cresting and to predict the breakthrough time at the bottom water driver reservoir.

Numerical study of power production from tidal energy in the Khuran Channel and its feedback on background hydrodynamics

This study focuses on the development of a farm of tidal turbines in the Khuran Channel.The important factors include the location of turbines and their hydrodynamic effects on the environment.A three-dimensional circulation model for the Persian Gulf is employed for the comprehensive evaluation of the tidal energy potential throughout the study area.The model is validated by using in situ observations of water level and current data.The appropriate potential points for extracting the tidal energy were identified in the Persian Gulf using the model results.The Khuran Channel,located in the north of Qeshm Island,was found to be the best place to extract tidal energy inside the Persian Gulf.By adding the term of momentum losses to the governing equations,the feedback of extracting energy on the hydrodynamic around Qeshm Island was studied.The simulation results show that the average daily power production of a tidal farm with 99 turbines for one month is approximately 1.3 MW.This tidal farm also has a significant impact on the water level inside the Khuran Channel,especially near the tidal farm where these fluctuations exceed 4 cm.The change in the current speed caused by wake reaches 0.4 m/s.Wake effects were active up to 7 km downstream of the turbines.The current velocity was also estimated to be 1.6 m/s and 2.1 m/s during the spring and ebb tides within the channel,respectively.

A STUDY ON FAULT STRUCTURE USING COHERENCE BODY TECHNOLOGY

Coherence body technology is known as the best important breakthrough in 3D seismic interpretation for 30 years.In comparison with old methods of revealment underground abnormal body,coherence body technology can clearly identify faults and stratum characters.Special calculation method of coherence body technology compares similarity of local seismic waveform in 3D data body.The point of lower coherent value is correlated with geological uncontinuity such as fault and boundary of stratum or special lithologic body.Obtained slices from coherence body can reveal faults,edge of lithologic body,unconformity and geologic phenomena,and they provide powerful proofs for studying the earth′ s structures.

The Use of Edge Enhancement Methods and Euler Deconvolution to Estimate an Ore Deposit Depth from Gravity Data

The Hercynian massif of the central Jebilet (Morocco) is characterized by the outcrop of many gossans with great economic importance. This work focuses on interpreting gravity data of Benslimane gossan, located about thirty kilometres to the North-West of Marrakech. The residual gravity map of the study area highlights several anomalies which coincide with the mining and geological contexts. Applying edge detection methods, for example, tilt angle derivative (TDR), the total horizontal derivative of the tilt angle derivative (HDR_TDR) and the 3D Euler deconvolution, allowed us to estimate the depth of the Benslimane deposit. As a result, the average depth of the ore deposit was estimated to exceed 200 m. The results are promising, and the processing methods must be applied to the other gossan in the Jebilet massif for further exploration studies.

长庆油田陇东三维水平井用PDC钻头个性化设计

长庆陇东油田因受地形地貌和整体开采方案的制约，需要采用三维水平井开发。水平井施工中由于上部地层复杂，靶前距离短，偏移距大，井眼轨迹控制难度大，对于PDC钻头的性能提出了更高的要求。针对该区块地层和定向轨迹控制特点，笔者进行了三维水平井用PDC钻头个性化设计，现场应用表明：钻头平均机械钻速和单只钻头进尺分别提高了21．29％和20．12％，较好地满足了三维水平井的优快施工。

A STUDY ON TRANSIENT FLUID FLOW OF HORIZONTAL WELLS IN DUAL-PERMEABILITY MEDIA

To adopt horizontal wells in dual media reservoirs, a good understanding of the related fluid flows is necessary. Most of the recent studies focus on dual porosity media instead of dual permeability media. In this article, through both integral transformation and sink-source superposition, a new Laplace-domain solution is obtained for the slightly-compressible fluid flow in the 3-D dual-permeability media in which the horizontal well is operating in a constant rate of production. Major asymptotic characteristics of diagnosis curves of dimensionless downhole pressure are analyzed by the limited analysis. Effects of parameters of dual-permeability media including mobility ratio k, storativity ratio ω and inter-porosity flow parameter k on the downhote pressure are studied by using the Laplace numerical inversion. The new solution obtained in this article includes and improves the previous results and then can be used as a basis for either pressure transient analysis or formation behavior evaluation for the typical reservoir with horizontal wells.

侧钻水平井开采剩余油的三维物理模拟研究

研究了水平井开采物理模拟的相似准则，设计了三维油藏相似比例模型，建立了水平井开采三级油藏物理模拟系统。该系统既能在高温高压模拟油藏条件下研究水平井开采机理，又能在常温常压下研究水平井开采机理和油藏内流体流动。在水平井开采三维油藏物理模拟系统上进行了侧钻水平井开采的实验研究，分析了侧钻水平井开采曲线变化规律，比较了侧铅水平井与直井的开采效果，研究了侧钻水平井的侧钻时机、开采速度、水平段长度等对开采效果的影响。侧钻水平井确实能提高开采效果，延长注水油藏的生产寿命，提高最终采收率。

盾构出洞水平冻结解冻温度场三维有限元分析

为揭示人工冻土解冻规律,对某地铁区间隧道盾构出洞水平冻结工程融化温度场进行了三维数值模拟分析,并研究了土体导热系数、比热容、含水率和环境温度等因素变化对人工冻土融化温度场的影响。计算结果表明:冻结帷幕解冻所需热量主要来自于与隧道管片和混凝土槽壁接触的大气;解冻过程可为负温阶段、相变阶段和正温阶段,土体温度在负温阶段上升较快,相变阶段上升速度明显变缓,进入正温区后土体温度回升速度再次增大;负温阶段受比热容的影响比较显著,含水率增大引起相变阶段明显延长,导热系数和环境温度变化对三个阶段都有显著影响。为跟踪注浆控制融沉提供了理论依据。

浅薄层超稠油油藏蒸汽吞吐后开发方式实验

应用三维相似准则设计并建立了高温高压注蒸汽三维实验模型,对影响注蒸汽采油过程的重要油藏参数进行了比例模化,研究了3种不同井网的蒸汽吞吐后注蒸汽采油接替开发方式。实验结果表明,与直井汽驱和水平井注汽直井采油相比,直井注汽水平井采油方式高产期较长,采油速率高,实验采出程度可达到70%.对于油层厚度为10~15 m的浅层超稠油油藏吞吐后期,直井注汽水平井采油是可选的接替开发方式。

双向地震作用对框架柱端弯矩增大系数的影响分析

在世界各主要多地震国家的建筑抗震设计规范中,普遍采用的柱端弯矩增强措施一般在与柱正交的两个主轴方向上的各平面框架内施行,仅新西兰NZS3101规范采用简化方法考虑了双向地震作用对柱端弯矩增大系数的影响。在OpenSees平台上,以钢筋混凝土6层三维框架为例,采用基于柔度法的纤维模型从而更加真实地模拟柱在双向弯曲和变化轴力作用下的非线性反应。对比双向、单向地震输入下柱端滞回反应的差异及其对框架塑性铰耗能机构的影响。考察双向地震作用下柱端弯矩时程在两个正交主轴方向的相关性,着重研究同一节点处两正交方向的各梁端弯矩时程相关性的定量方法。研究表明,双向地震下柱的强度退化、屈服后变形均明显比单向受力更大,双向地震下X向、Y向柱端弯矩时程,以及同一节点处两正交方向的各梁端弯矩时程的相关性皆极大地依赖于双向水平地震动的输入方式。

水平荷载作用下群桩相互作用的弹塑性数值分析

本文利用三维弹塑性有限元法对水平荷载作用下群桩基础特性进行了分析,讨论了群桩基础水平荷载作用下的承载性状和破坏机理,并探讨了桩距、桩数、桩长、桩径和土质各种因素对群桩效应的影响,指出桩距和桩数是影响群桩效应的主要因素。

双向地震作用下我国“强柱弱梁”措施的有效性评估

以往研究柱端弯矩增大系数时一般基于平面分析模型,双向水平地震作用对框架"强柱弱梁"屈服机制的影响未引起重视。严格按中国规范设计出5个不同地震烈度分区的规则空间框架,在OpenSees平台上,采用基于柔度法的纤维模型从而更加真实地模拟柱在双向弯曲和变化轴力作用下的非线性反应,对五个框架进行了罕遇地震下的非线性反应分析。结果表明,7度0.1g区三级抗震空间框架形成了柱铰为主的混合耗能机制,7度0.15g区三级抗震空间框架少量楼层发生了层侧移反应,8度0.2g区、0.3g区二级抗震空间框架均是部分楼层出现明显层侧移反应的典型柱铰机制,9度0.4g区一级抗震空间框架则形成了梁铰、柱铰均较严重的梁柱铰混合机制。五个空间框架在双向地震下的塑性铰分布特征均比相应平面框架更不利。我国不同烈度区、不同抗震等级的空间框架结构在罕遇地震下形成了不同的的塑性铰耗能机制。