页岩储层压裂液吸收能力及其影响因素研究

研究发现：人工裂缝壁面的压裂液渗吸是导致页岩储层返排率普遍低于30%的主要原因。针对四川盆地页岩样品开展室内自发渗吸实验,并与鄂尔多斯的致密砂岩和松辽盆地致密火山岩进行对比。结果表明：页岩储层压裂液吸收的驱动力为毛细管力和粘土吸附力。页岩中压裂液的空间为孔隙空间和粘土晶格空间,富粘土页岩的粘土吸水体积会明显超过气测孔隙体积。页岩的自吸能力与粘土含量及类型有关,粘土含量越高,自吸能力越强。伊利石和伊蒙混层的存在会大大提高自吸能力。此外,阳离子表面活性剂通过改变毛细管力进而降低压裂液自吸能力,Kcl溶液通过抑制粘土膨胀进而降低压裂液自吸能力。研究页岩基质自吸能力有助于确定压裂液用量、优化返排制度以及分析低返排对页岩气产出的影响。     

一种评价页岩储层压裂液吸收的新方法

压裂液在毛细管力作用下自发吸入地层是导致页岩储层体积压裂返排率普遍低于30%的主要原因之一,有效评价页岩储层对压裂液的吸收是体积压裂优化设计、返排制度建立以及水锁伤害程度评估的基础,目前国内外尚未发现有效的评价方法。针对渝东北下寒武统鲁家坪组典型页岩和三种不同的致密储层岩石开展自发渗吸对比实验,并对比研究了3种常用的渗吸表征方法,提出了评价页岩储层压裂液吸收的方法和参数。通过实验研究发现,无因次法和Olafuyi法可用于评价页岩储层压裂液吸收能力,在表征吸收速率和规律方面尚有不足;Makhanov法可用于表征压裂液吸收速率和规律,在评价储层吸收能力方面尚有不足。新方法采用自吸能力、初期自吸速率和后期自吸速率三参数对压裂液的吸收进行定量表征,很好地反映出压裂液吸收规律。压裂液吸收可分为三个阶段:初期渗吸段、过渡段和后期渗吸段,其中初期渗吸段是压裂液吸收的主要阶段;压裂液吸收的驱动力主要为毛细管力和黏土吸附力;黏土含量越高,压裂液自吸能力越强,伊蒙混层和蒙脱石的存在可以大大提高页岩自吸能力。新方法能够评价页岩压裂液吸收的快慢、总量和规律,可以用于不同地层之间的对比评价,且直观可靠,有利于在页岩气或致密气现场推广应用。     

页岩裂缝网络水相自吸试验

水平井分段压裂形成的裂缝网络使页岩气藏经济开发,但也为压裂液大量滤失和进入页岩基块深部提供了通道和途径,削弱了压裂改造效果。开展页岩基块、单一裂缝、"T"型裂缝网络水相自吸试验,并与致密砂岩水相自吸试验进行对比分析。结果表明:与单一基块、裂缝相比,页岩裂缝网络在增大水相赋存空间的同时,也为裂缝-基块间自吸创造有利供给条件,增加了水相自吸侵入深度;致密砂岩水相自吸呈现活塞式均匀推进,且未产生新裂缝,而页岩水相自吸优先沿页理发生,因侵入流体与页岩发生水-岩作用萌生页理缝,进一步增加页岩缝网密度,扩大水相自吸范围。通过优选压裂液配方,利用滞留压裂液与页岩相互作用,发挥滞留压裂液对储层缝网的积极改造作用,可以达到改善页岩储层渗流通道、强化页岩气解吸-扩散-渗流传质能力的目的。     

页岩气储层压后返排特征及意义

为制定科学的页岩气储层压后返排策略,基于威远地区龙马溪组36口页岩气井压后返排数据,分析压后关井对产量的影响以及返排过程两相流阶段性特征,同时进行页岩气储层液相支撑验证实验。结果表明:压裂液在主压裂结束后一定时间内仍然发挥造缝作用,一定时间的关井有利于提升气井累积产气量期望值;页岩气储层压后返排气液两相流阶段出现气增液降特征点是高产气井的共同特征,根据两相流阶段特征可初步评估气井产气能力;滞留压裂液在页岩储层微细裂缝网络中具有液相支撑作用,使气相渗透率不是含水饱和度的单调函数,存在最优返排率使气相渗透率最大化;可以采用以追求气相渗透率最大化为目标,以控压、控速为原则的页岩气储层压后返排策略。     

压裂液侵入对页岩储层导流能力伤害

大规模水力分段压裂是页岩气等非常规资源高效开发的关键技术。页岩气井返排率一般较低,大量的压裂液长期滞留地层对储层岩石、支撑剂强度等造成一定的伤害,影响页岩储层压裂改造长期效果。针对该问题,通过室内试验模拟研究现场压裂前后气测导流的变化规律,对压裂液伤害程度进行表征。结果表明:压裂液侵入降低了支撑剂、页岩岩石强度,导致支撑剂破碎率、岩石嵌入程度加剧,导流能力伤害达到60%以上;使用大粒径支撑剂、较高铺砂浓度,优选破胶性能好、低残渣、防膨性强的压裂液,能有效提高导流能力,降低压裂液伤害程度。研究结果对页岩地层压裂设计,降低压裂液伤害提高产量提供参考。     

页岩储层渗吸特性的实验研究

页岩含有大量黏土矿物,遇水会导致页岩中黏土矿物水化、膨胀,为研究页岩吸水特性及探究页岩气井返排率的影响因素。开展了页岩动态渗吸及静态渗吸实验;并对实验结果进行了详细的分析。研究表明:页岩水化作用主要发生在页岩与水或水基溶液接触的表层附近,液体侵入深度十分有限;不同的液体介质下页岩的吸水能力各不相同;页岩吸水量由表面水化吸水量、渗透水化吸水量和毛管吸水量组成,而且水化吸水量基本无法排出,在一定程度上降低了页岩气井压裂液的返排率;相同的成藏条件下页岩的渗透水化吸水量及表面水化吸水量相同;页岩水化能力及压裂效果是影响返排率的主控因素。     

考虑氧化作用的富有机质页岩吸附水量

页岩气井大型水力压裂后压裂液返排率普遍较低,滞留压裂液可能诱发页岩产生裂缝,但在水力裂缝与天然裂缝中占据有效气体传输通道,影响压裂效果。选取四川盆地龙马溪组典型富有机质页岩,采用填砂管与粒状页岩模拟体积改造的页岩气层,开展了蒸馏水与氧化液体积改造后页岩气层吸附水量的对比实验,明确了氧化对压裂液渗吸分散到裂缝附近基块孔隙的作用与机理。结果表明,与蒸馏水相比,氧化作用可以增强页岩渗吸分散水相作用,降低页岩孔隙空间内的自由水量,增加页岩吸附水量;富有机质页岩氧化作用消耗有机质,分解有机黏土复合体,裂缝与孔喉壁面更多的黏土矿物接触压裂液,增加黏土矿物吸附水量,降低裂缝面及基块孔隙含水饱和度,释放渗流空间。建议根据具体工程地质特征,优选氧化性流体的加入时间及用量,充分发挥滞留氧化性压裂液的造缝能力,促进压裂液渗吸分散,实现压裂液少返排或零返排,增大气体在裂缝中有效渗流通道。     

页岩气储层的渗吸动力学特性与水锁解除潜力

大规模水力压裂是页岩气成功开发的关键技术,上万方的压裂液被注入地层,而返排率往往低于30%.根据常规油气相关理论,外来流体进入基质孔隙会引起强烈的水锁伤害.但实践中大量压裂液滞留在页岩储层中并未引起严重水锁,部分井的产能随着滞留量的增加反而升高,这说明页岩气储层具有水锁解除的能力.本文基于页岩气储层压裂液渗吸问题开展实验,分析了水与页岩相互作用以及引起的动力学效应,研究渗吸特性与储层水锁解除潜力之间的关系.压裂液通过渗吸作用进入基质产生复杂物理化学作用.页岩的渗吸能力、扩散能力、渗吸水诱发裂隙能力是影响页岩气储层水锁解除潜力的主要因素,储层能量补充、渗吸液向基质深部的扩散、水岩反应产生的微裂隙等是水锁解除的主要机理.提出了以初始含水饱和度、渗吸能力、扩散能力、吸水诱发微裂隙和黏土化学作用等为主要评价参数的水锁解除潜力评价方法,利用自发渗吸、核磁共振与脉冲渗透率测试评价水锁解除潜力.通过该方法对典型页岩气储层的水锁解除潜力进行了分级评价,该研究深入分析了页岩气储层水锁解除机理及控制因素,对页岩气储层压裂改造具有指导意义.     

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。     

临兴致密气压裂液全过程渗吸伤害规律

致密砂岩气作为重要的非常规天然气资源,需经过压裂改造才能实现有效开发。压裂施工中由于毛管力作用压裂液的渗吸现象会造成储层渗透率降低,从而降低采收率,因此开展压裂过程中压裂液渗吸伤害机理研究对储层保护和提高压后产能具有深刻意义。以临兴致密气区块为研究对象,通过室内渗吸实验模拟从压裂到返排整个过程中压裂液与储层之间的渗吸作用机理,探究了渗吸液相、压裂液黏度、岩心渗透率以及渗吸时间四种因素影响下的压裂液渗吸伤害规律,并利用灰色关联法量化分析各因素对渗吸伤害的影响程度。研究结果表明:压裂液黏度和压后焖井时间与储层伤害率呈正相关关系,与返排率呈负相关关系;岩心渗透率与伤害率呈负相关关系,与返排率呈正相关关系;压裂液渗吸对储层的伤害率较地层水大,返排率则低于地层水;各因素对致密砂岩气储层渗吸伤害的影响程度大小排序为:压裂液黏度压裂液渗吸时间岩心渗透率。研究结果为压裂施工现场的压裂液体系优选及焖井时间控制提供参考。     

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.     

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.     

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。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

A computer generator for randomly layered structures

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

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the