3-D Fracture Propagation Simulation and Production Prediction in Coalbed

NｏｍｅｎｃｌａｔｕｒｅＡ(ｘ,ｔ)—Ｃｒｏｓｓ＿ｓｅｃｔｉｏｎａｒｅａｏｆｆｒａｃｔｕｒｅａｔｔｉｍｅｔａｎｄｓｉｔｅｘ,ｍ2 ;Ｂｇ,Ｂｗ —Ｃｏａｌｂｅｄｇａｓａｎｄｗａｔｅｒｖｏｌｕｍｅｆａｃｔｏｒ,ｄｉ ｍｅｎｓｉｏｎｌｅｓｓ;ｂ—Ｌａｎｇｍｕｉｒｆａｃｔｏｒ,(ＭＰａ) - 1 ;Ｃｇ,ＣＲ,Ｃｗ —Ｃｏａｌｂｅｄｇａｓ,ｒｏｃｋａｎｄｗａｔｅｒｃｏｍ ｐｒｅｓｓｉｂｉｌｉｔｙｃｏｅｆｆｉｃｉｅｎｔ,(ＭＰａ) - 1 ;Ｃｐ —Ｓａｎｄｒａｔｉｏ ,ｄｉｍｅｎｓｉｏｎｌｅｓｓ;Ｃｔ(ｘ ,ｔ)—Ｔｏｔａｌｆｒａｃｔｕｒｉｎ…     

A three-layer model for solid-liquid flow in horizontal pipes

A three-layer model for solid-liquid flow in horizontal pipes is proposed. This model overcomes the limitations of the two-layer model. The model predictions exhibit satisfactory agreement with the experimental data and existing correlations.     

横观各向同性油气藏水力压裂裂纹扩展规律研究

针对横观各向同性与各向同性油气藏水力压裂裂纹扩展的差异性,基于扩展有限元法建立水力压裂力学模型,通过ABAQUS子程序开发了各向同性和横观各向同性岩体的起裂判据。在各向同性岩体数值模拟结果与解析解以及现场压裂典型曲线对比吻合的基础上,得到了包含层理构造的横观各向同性岩体水力压裂过程中裂纹扩展规律。层理类岩体水力压裂的裂缝扩展方向由地应力状态、层理方向以及岩体与层理界面抗拉强度共同决定;水力压裂过程中,注水压力在裂纹尖端产生应力集中,层理面法向分量先达到界面抗拉强度时,裂纹沿层理方向开裂,反之裂纹沿垂直最小地应力的方向扩展;裂纹扩展速度随层理抗拉强度的增加而降低;由于地层的滤失,随压裂液的注入,裂纹长宽尺度增长速率降低。     

多孔线性控制套筒致裂效果影响因素分析

针对坚硬难垮落顶板弱化问题,在分析多孔线性控制套筒致裂机理的基础上,建立700mm×300mm×400mm试块。通过套筒致裂压力及钻孔孔壁周围应变变化情况,分析孔壁周围应力大小、分布及应力集中现象,研究钻孔直径、孔间距、套筒致裂压力对应力集中现象的影响,同时分析这三者对裂纹扩展方向的影响,得出套筒致裂最优法。试验结果表明:(1)套筒致裂效果受钻孔直径、孔间距和套筒压力等综合因素影响,采用大直径、大间距的布孔方式可获得较好的致裂效果;(2)多孔线性控制致裂试验的张性裂缝扩展方向主要沿着各钻孔中心连线方向;(3)钻孔直径30mm、间距300mm的试块致裂压力为18.6MPa,远大于顶板岩体抗拉强度,将套筒致裂法应用于顶板弱化是可行的。本研究对解决采空区坚硬顶板大面积悬顶具有理论意义和应用价值。     

水泥试样爆炸压裂实验及裂纹分形评价

通过室内爆炸压裂模拟实验,得到常压和20 MPa围压2种情况下的爆炸压裂效果,并对实验结果进行了对比分析,分析结果表明:围压对裂纹扩展路径、形状、弯曲度都有一定影响,与常压下的裂纹扩展情况相比,施加围压后得到的裂纹数量少、长度短、弯曲明显.在对爆炸压裂形成的裂纹进行定性描述的基础上,利用分形理论,对裂纹的分形特征进行了...     

On the Dynamic Behavior of Servo-Hydraulic Drives

A servo-hydraulic drive for position control with a flapper-nozzle type servo-valve is described by a 10th-order, non-linear system of ODEs. This system is partially singularly perturbed. The perturbation stems from the compressibility of the hydraulic fluid and the fast dynamics of some sub-systems of the valve. Center manifold theory in the version due to Fenichel is used to study the behavior of the drive system in the case of periodic motions. The insufficient differentiability properties of the system prevent the direct application of Fenichel's theorems. Thus, phase space is decomposed into sub-spaces each with sufficient differentiability properties. There, limit sets of the system can be given as the solution of the reduced problem. Approximate analytical solutions are derived for that. At the boundaries of adjacent sub-spaces transition layers occur which connect these limit set trajectories of adjacent sub-spaces. The order of magnitude of these transition layers is estimated by asymptotic expansions. Further, a comment is given on the stability properties. Stability is strongly affected by the small perturbation parameters and is most critical in the resting position of the drive. Theoretical results are compared with numerical computations and experiments.     

裂隙岩体强度试验单点法及其前景

本文在回顾裂隙岩体强度试验的基础上，用大量原位测试数据对裂隙岩体直剪破坏机理和裂隙岩体直剪破坏的基本规律及其成因进行了深入探讨；总结出一套行之有效的试验技术；给出了裂隙岩体直剪破坏时的充分必要条件并加以量化。     

深层地下地应力测量

介绍了对某水力压裂法处置中放废液工程进行的深层地下地应力测量的有关情况。利用压阻型压力传感器和压力盒相结合的办法克服压力探头敏感面小带来的测量困难 ,成功进行了地下数百米深度处地应力测量。实际测量表明系统工作可靠 ,测量数据可信。     

整体压裂裂缝导流能力与储层渗透率匹配关系研究

针对低渗透油藏存在非达西渗流的问题,建立了整体压裂三维油水两相油藏和裂缝系统的数学模型,并采用有限差分法进行求解.利用建立的数学模型,针对不同储层渗透率级别,研究裂缝导流能力对油井产能的影响.结果表明:在各级储层渗透率级别下,随着裂缝导流能力的增加,采油强度逐渐增加,但增加的幅度越来越小.在此基础上,引入采油强度变化率的概念,确定了不同储层渗透率级别下裂缝导流能力与采油强度变化率的关系,进而得到不同储层渗透率级别下的最佳裂缝导流能力.为合理、高效开发低渗透油藏提供技术支持与保障.     

Evaluating flood extent mapping of two hydraulic models, 1D HEC‐RAS and 2D LISFLOOD‐FP in comparison with aerial imagery observations in Gorgan flood plain,Iran

We compared flood mapping techniques using a one‐dimensional (1D) hydraulic model HEC‐RAS and two‐dimensional (2D) LISFLOOD‐FP for a 10‐km reach of Gorgan River in Iran. Both models were run using the same hydrologic input data. The input into the models was a steady discharge of 90 cm, corresponds to a flood peak occurred on March 25, 2012. Flood maps generated using these two models were compared with an observed flood inundation map, using F‐statistic. The roughness coefficients of the models were calibrated by maximizing the value of the F‐statistic. Based on the F‐statistic, LISFLOOD‐FP gives a slightly better result (F = 0.69) than HEC‐RAS (F = 0.67). Visual comparison of the flood extents generated by the two models showed reasonably good agreement. Validation was done using a flood event occurred on May 31, 2014. The LISFLOOD‐FP model gave a better result for validation as well. The 2D model showed more consistency in comparison with the 1D model.