页岩气储层水力裂缝网络的延伸规律

为了深入认识页岩气储层水力压裂裂缝的延伸规律及裂缝网络形成条件,通过建立页岩气储层水力裂缝延伸的二维模型,分析地应力差异系数、天然裂缝及层理面等因素对水力裂缝延伸方向的影响规律,并对页岩储层水力裂缝网络的形成机制进行研究.研究结果表明:水力裂缝在层理面内转向、分岔及沟通天然裂缝是形成裂缝网络的关键,层理面和天然裂缝逼近角和地应力差异系数需在一定临界组合条件下才形成裂缝网络,偏离该条件均形成单一裂缝;最大水平主应力方向与页岩的层理面和开度较好的天然裂缝之间的逼近角呈大角度时,更有利于形成裂缝网络.     

水平多裂缝交错扩展及其诱导应力干扰研究

QA油田X储层埋深较浅,高角度天然裂缝发育,水力压裂后形成的水力裂缝形态较为复杂,压后效果时好时坏,给压裂设计及施工带来诸多困难,急需弄清该储层水力裂缝的形态,以确定合理的压裂施工方案。首先,采用三轴岩石力学测试系统对X储层岩石力学特征进行测试,观察天然裂缝形态。其次,建立砂泥岩相间的二维平面渗流-应力-损伤耦合有限元模型,采用二次应力起裂准则作为水力裂缝是否起裂的判断依据,以幂律流来表征流体在Cohesive单元内的流动。模拟了X储层水力压裂多裂缝交错延伸的裂缝形态,探究了水力裂缝几何形态及压裂液排量、地应力、压裂液黏度对缝间应力干扰的影响,揭示了复杂多裂缝交错扩展的干扰机理,发现该储层具有形成复杂裂缝的力学和工程地质条件,为该区域的压裂改造提供理论指导。     

四川页岩压裂裂缝扩展实验及力学特性研究

采用真三轴压裂物理模拟的方法,研究了四川页岩储层压裂过程中的水力裂缝扩展行为和裂缝形态.实验结果表明,四川页岩压裂裂缝扩展模式分为主裂缝多分支裂缝和网状复杂裂缝.在水平主应力差较高的实验条件下,压力曲线波动频率高且趋势平稳,实时声发射监测结果表明,在实验的前期压裂裂缝易穿过天然节理,并形成单一主裂缝,而在实验的后期易形成多分支裂缝;在水平应力差较低条件下,压力曲线波动频率高但是不时伴有压力陡降,声发射监测结果表明,水力裂缝扩展易沿着页岩天然裂缝系统扩展,并形成复杂裂缝形态.定义了水力裂缝垂直穿过页岩层理面时的临界摩擦系数,采用实验参数和结果,揭示了在上述条件下,水平地应力差异系数和临界摩擦系数之间的相互关系,随着水平地应力差异系数的增加,临界摩擦系数显著降低.上述研究对中国的深层页岩气开发具有一定的指导意义.     

页岩储层压裂缝成网延伸的受控因素分析

压裂实践表明,页岩储层的水力裂缝呈现出非平面、多分支的复杂延伸模式,这与传统压裂理论认为的对称平面双翼裂缝从形成机理上存在本质的区别。基于室内实验、矿场压裂实践、理论分析和数值模拟等研究成果,系统分析了页岩储层压裂缝成网延伸的受控因素。研究表明:页岩储层的裂缝延伸形态受到地质因素和工程因素的双重作用,从储层地质属性上看,岩石的脆性矿物含量越高、岩石的力学弹性特征越强、水平应力差越小以及天然裂缝越发育,越有利于压裂缝的成网延伸与扩展;从压裂作业的工程条件上来说,施工净压力越高、压裂液流体黏度越低以及压裂规模越大,越有利于形成充分扩展的缝网。该研究对认识页岩储层缝网扩展机理以及提高页岩储层压裂设计的科学性具有重要的理论价值和现实意义。     

考虑毛细管力的页岩储层压裂缝网扩展研究

页岩储层中广泛发育着各种尺度的天然裂缝,这些天然裂缝小到纳米、微米量级,大到毫米甚至是工程量级,显著影响着压裂后的裂缝网络形态.同时,在页岩压裂施工过程中,压裂液会进入到这些不同尺度的天然裂缝中,在天然裂缝内部存在气-液两相流体,产生毛细管力.当天然裂缝尺度不同时,在裂缝中产生的毛细管力大小不同,尤其是当天然裂缝尺度较小时,在其内部会产生较大的毛细管力,进而显著影响天然裂缝内压裂液的流动以及压裂裂缝网络的扩展.本文建立了同时考虑天然裂缝尺度以及压裂液与储层岩石润湿特性的页岩压裂缝网扩展模型,研究了在毛细管力影响下的压裂裂缝网络的扩展特征.通过研究发现,当天然裂缝初始长度较长、缝宽较小、压力液与储层润湿性较强时,天然裂缝更容易扩展,形成较大规模的裂缝网络.当天然裂缝尺度各异时,将形成复杂的裂缝网络,该模拟结果与室内大型页岩水力压裂实验中观察到的裂缝网络扩展形态相同.     

天然裂缝群与地应力差作用下水力裂缝扩展试验

通过室内真三轴水力压裂试验,研究裂缝性储层中天然裂缝群与地应力差的组合作用对水力裂缝扩展的影响。采用内含大量随机天然裂缝的300 mm×300 mm×600 mm人工试件模拟裂缝性储层,改变地应力差、天然裂缝尺度以及压裂液排量与黏度条件,分析水力裂缝形态与地应力差、天然裂缝尺度的关系。根据水力裂缝复杂程度将其分为体积裂缝、分支裂缝和单一裂缝3类。结果表明:天然裂缝尺度越大、地应力差越小,水力裂缝形态越复杂;对含天然裂缝群的储层,当地应力差大于8 MPa时,压裂不会产生体积裂缝;当地应力差大于14 MPa时,天然裂缝群对水力裂缝形态不会产生影响,形成单一裂缝;水力裂缝的非稳态扩展易受到天然裂缝群的影响,从而有利于产生缝网结构。     

注液速率及压裂液黏度对煤层水力裂缝形态的影响

注液速率及压裂液黏度是煤层气井压裂设计中两个重要的可控参数,其不仅影响水力裂缝起裂压力及压裂施工压力,而且控制水力裂缝形态。采用鄂尔多斯盆地东南缘大宁-吉县地区天然煤岩,基于试验室物理模拟试验研究注液速率及压裂液黏度对水力裂缝形态及施工压力的影响。结果表明:注液速率及压裂液黏度较小时,主裂缝与分支缝连通形成沿最大水平主应力方向的复杂裂缝网络系统;随着注液速率及压裂液黏度的增加,水力裂缝复杂程度降低,形成平直单裂缝。提高注液速率或压裂液黏度会增大施工压力。对注液速率及压裂液黏度进行合理控制,可先在井筒附近生成平直裂缝,后在远离井筒处生成复杂裂缝网络,有利于增大煤层气单井排采体积。     

济阳拗陷页岩储层水平井裂缝扩展数值模拟

由于物理实验受到实验条件、数量的限制,难以对裂缝扩展规律开展大规模的研究。因此,在有了一定的岩石力学测试、页岩压裂破裂方式测试以及页岩压裂裂缝扩展物模试验的基础上,开展了页岩压裂裂缝起裂及扩展规律数值模拟研究。基于流固耦合Biot固结理论、Darcy渗流定律,采用最大拉伸强度准则和Mohr Coulomb准则损伤阈值进行单元损伤判断,引入全新的材料分布算法,建立了水力压裂裂缝扩展的有限元计算模型。进行了岩石样本的参数标定试验。采用有限元计算方法研究了地应力、页岩脆性指数、压裂液黏度和层理特征等关键物理参数对页岩裂缝扩展的影响。结果表明,当脆性指数较小时,水力裂缝主要沿最大主应力方向在页岩基质中扩展,难以转向形成复杂缝网。层理胶结强度较高时,水力作用即便在局部压开天然层理,也难以持续以大角度偏离,而只能形成比较单一的裂缝。地应力比、压裂液黏度越低,层理密度等特性越高时,裂纹网络越复杂。     

页岩水力裂缝网络形态及激活机制研究

针对页岩体积压裂后量化复杂裂缝网络构成及裂缝激活程度的问题,基于有限元、全局嵌入黏聚区域模型以及真实页岩露头,建立了预制结构弱面的复杂水力缝网模型。在考虑全耦合应力-流体影响下,研究了弱面逼近角、水平应力差、压裂液黏度以及排量对裂缝网络组成、几何形态以及SRV的影响,提出能够量化分析裂缝网络构成以及裂缝激活程度的裂缝相对激活程度概念。研究结果表明,页岩压后裂缝几何形态受力学性质最弱的弱面控制,分别呈轴对称与中心对称网络状分布;裂缝网络由主导游离气传输的弱面型裂缝与主导吸附气传输的基质型微裂缝共同构成;弱面逼近角、水平应力差以及压裂液黏度对SRV长轴的影响并非呈现单调性变化,逼近角的增加、水平应力差、压裂液黏度以及适当排量的降低会导致SRV短轴增加;水平应力差对裂缝相对激活程度的影响也并非呈现单调性变化,弱面逼近角、压裂液黏度以及排量的增加会引起基质型微裂缝相对激活程度、激活裂缝总长度的增加以及弱面型裂缝相对激活程度的降低。     

页岩水力压裂裂缝扩展规律实验研究

页岩气藏储层具有超低孔、超低渗的物性特征,通过体积压裂改造形成复杂人工裂缝网络,是实现页岩气有效开发的关键。试验采用大尺寸真三轴水力压裂模拟,研究水平地应力差、泵注排量,井筒数量等因素对页岩气储层压裂裂缝扩展规律的影响。通过观察压后页岩表面裂缝延伸路径,结合工业高能CT扫描确定页岩内部实际的水力裂缝形态。实验所选用页岩脆性中等,但层理特征明显,微裂隙发育,具有可压性。试验结果表明:水平应力差为3 MPa时,水力裂缝易转向,沟通近井天然裂缝或弱胶结层理面;随着水平应力差的增加,有利于横切缝的产生,沟通远处更多天然裂缝及层理;当水平应力差达到12 MPa时,仅能形成简单平面横切缝。另外,变排量压裂或双井筒同步压裂可以有效地增加裂缝密度,提高水力裂缝复杂程度;但在12 MPa的水平应力差下,双井筒同步压裂仍然仅生成2条简单的水平缝。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.