松辽盆地龙西地区泉四段低孔低渗砂岩性及微观孔隙结构特征研究

通过岩心观察、镜下薄片、扫描电镜和X衍射、物性和压汞等资料分析,对松辽盆地龙西地区泉四段低孔低渗砂岩的岩石学特征、储层物性及微观孔隙结构特征进行了研究。研究表明,松辽盆地龙西地区泉四段砂岩主要为长石岩屑砂岩,其次为岩屑长石砂岩,成分和结构成熟度较低,储层物性明显呈现出低孔低渗特征,孔隙类型以残余粒间孔和溶蚀孔为主,孔喉半径较小,相对小孔喉所占比率较大,孔喉分选和连通性较差,非均质性强。在总体孔喉较小的背景下,随着较大孔喉半径的增大储层物性变好,而储层物性随着孔喉集中程度的增强而变差。根据经典的孔喉分类标准,将松辽盆地龙西地区泉四段低孔低渗透储层分为4类：细孔细喉型、微孔细喉型、微孔微细喉型和微孔微喉道型。     

松辽盆地龙西地区泉四段砂岩岩石学特征及其对储层物性的影响

松辽盆地龙西地区泉四段主要为岩屑长石砂岩和长石岩屑砂岩,成份成熟度较低,粒度较细,分选中等偏差,填隙物主要为粘土矿物和方解石。研究表明,储层物性随着石英含量的增加而变好,而随着岩屑含量的增加而变差,说明成份成熟度影响岩石的抗压性,进而影响储层的物性。泉四段砂岩中的长石主要通过钾长石的溶蚀作用改善储层物性。粒度大小和均匀程度与储层物性呈正相关关系,砂岩粒度的均匀程度也是形成低孔低渗储层的内在因素之一。     

鄂尔多斯盆地华庆油田长81段储层物性影响因素

在综合大量样品测试数据与图像的基础上,研究了华庆油田长81段储层特征和物性影响因素。研究表明:砂岩岩性以中细砂岩与细砂岩岩屑长石砂岩和长石岩屑砂岩为主,储集空间以剩余原生粒间孔和长石溶孔为主。孔隙类型以中孔隙和小孔隙为主,优势孔隙具有双孔隙结构特征。储层类型为低孔特低渗-超低渗岩性油藏,储层孔喉半径与物性具有正相关的分带性。沉积作用-成岩作用共同影响着储层的发育特征,较好的物性发育在中粒岩屑长石砂岩、细-中粒岩屑长石砂岩与细粒岩屑长石砂岩的砂体中,压实作用使原生孔隙度损失21.92%,胶结作用使原生孔隙度损失8.61%,溶蚀作用使孔隙度提高了4.46%。继续研究沉积和成岩作用对储层物性特征的影响,将有利于认识和处理同类储层的勘探开发。     

孔喉半径对松辽盆地南部青一段特低-超低渗透储层质量的控制作用

针对青山口组一段特低-超低渗储层开发时,仍然存在储层认识程度低的问题.其中,明确特低-超低渗储层物性、含油性及流动性的主控因素是亟待解决的重要问题.利用常规压汞、核磁共振、孔渗测定、粒度分析和X衍射等实验方法,对松辽盆地南部青山口组一段特低-超低渗储层特征参数进行定量表征.结果表明:松辽盆地南部青山口组一段特低-超低渗透储层平均孔喉半径主要分布于0.3~1.7 μm之间.大于1.5 μm的孔喉半径对应常规低渗透储层,以细粒长石岩屑砂岩为主;0.5~1.5 μm孔喉半径对应特低渗透储层,以极细粒长石岩屑砂岩和粗粉砂岩为主,可动流体饱和度大于65%;0.1~0.5 μm孔喉半径对应超低渗透储层,以粗-细粉砂岩为主,可动流体饱和度介于50%~60%.孔喉半径决定了储层物性和流体饱和度特征,并在宏观上受控于沉积相带,应作为特低-超低渗储层评价的重要参数.      

昆北油田切12区E_3~1油藏储层孔隙结构及物性特征

为解决昆北油田切12区E13油藏在开发过程中存在的问题,综合利用岩心、薄片、扫描电镜、物性以及压汞分析等资料,对该区储层孔隙结构及物性特征进行了综合研究。结果表明:切12区E13油藏以砾岩沉积为主,粒径较大;储层岩石类型主要为岩屑长石砂岩、长石岩屑砂岩;储层孔隙类型主要为原生粒间孔隙,其次为裂缝(构造缝)以及各类次生孔隙;压汞实验表明该区孔喉半径砾岩最粗,渗透性最好,根据压汞曲线形态可将孔隙结构分为4种类型:粗喉大孔型(Ⅰ)、粗喉小孔型(Ⅱ)、细喉大孔型(Ⅲ)和细喉小孔型(Ⅳ),其中细喉大孔型(Ⅲ)、细喉小孔型(Ⅳ)在区内最发育;研究区储层物性较差,属于低孔特低渗储层,但储层孔渗相关性较好,储层物性受沉积、成岩及构造作用的多重控制。     

鄂尔多斯盆地子北油田长6储层特征研究

通过对岩芯铸体薄片、扫描电镜、物性和测井数据分析,认为研究区长6储层具有以下特征:研究区主要为长石砂岩和岩屑长石砂岩,胶结物含量较高,成分以方解石为主。长6为超低孔、超低渗储层,孔隙类型主要为粒间孔和次生溶孔,微观结构评价属于小孔—细喉型、细孔—细喉型和小孔—中细喉型储层。沉积微相、岩石学特征和成岩作用共同控制着储层的物性,研究区物性较好。     

志丹油田正356井区三叠系延长组长6储层特征研究

针对志丹油田正356井区长6油层段，对其储层岩石学、储层物性、孔隙结构及储层控制因素等进行了研究。该层段储层岩石类型主要为岩屑长石砂岩和长石砂岩，成分成熟度低，结构成熟度高；岩石物性总体较差，属低孔、低渗储层，发育粒间孔隙、溶蚀孔隙、晶间孔等孔隙类型，喉道以细喉-微喉为主；沉积作用发生后，成岩作用控制着储层孔隙结构特征及储层物性。根据岩性和物性特征，该区储集岩分为3类：Ⅰ类为好储集层，Ⅱ类为较好储集层，Ⅲ类为较差储集层。     

鄂尔多斯盆地陇东地区三叠系延长组长8储层特征

鄂尔多斯盆地陇东地区延长组长8油层段是重要的储集层之一,包括长81和长82两个砂岩组。通过储层岩石学、储层物性、孔隙结构及储层控制因素等方面对储层特征进行分析,总结并评价储层储集性能。研究结果表明,储层岩石类型主要为中细粒长石砂岩和岩屑长石砂岩,成分成熟度低,结构成熟度中—高;岩石物性总体较差,属低孔、低渗储层,发育粒间孔隙、溶蚀孔隙、晶间孔等孔隙类型,喉道以中细喉—细喉为主。储集性变化受沉积作用和成岩作用控制,沉积作用控制了储层砂体展布,进而影响其岩石学特征的表现,压实作用、胶结作用和溶蚀作用控制了储层孔隙结构特征及储层物性,根据岩性和物性分析特征可将储集岩分为4类,优质储层的勘探应以沉积作用控制的多套砂体相互叠置的水下分流河道沉积为重点。     

松辽盆地龙西地区泉四段砂岩成岩序列及孔隙演化特征

通过岩芯观察、镜下薄片、扫描电镜和X衍射分析等资料,对松辽盆地龙西地区泉四段砂岩的岩石学特征、成岩作用类型、成岩阶段划分和成岩共生序列及孔隙演化特征进行了研究。结果表明：龙西地区泉四段主要为长石质岩屑砂岩,局部为岩屑质长石砂岩;经历的主要成岩作用类型有压实作用、自生石英胶结作用、自生黏土矿物胶结作用、碳酸盐胶结作用、交代和溶蚀作用等;龙西地区泉四段砂岩为中成岩阶段A期,且细分为A1和A2亚期;随着成岩演化,压实和胶结作用使得原生孔隙减小,而溶蚀作用使得储层孔隙结构得到改善;孔隙类型由缩小粒间孔组成变为由缩小粒间孔和溶蚀粒间孔组合组成。     

北黄海东部坳陷中生界储层特征

北黄海盆地东部坳陷中生界砂岩以细砂-粉砂岩为主,夹少量砂砾岩,岩石学类型以长石砂岩、长石岩屑砂岩为主,储集空间以次生溶蚀孔及裂缝为主,孔喉结构为细小孔隙、细喉-微细喉,属于低孔低渗储层。通过对物性影响因素分析,发现裂缝、沉积相带、成岩作用是控制本区砂岩储层质量的主要因素。     

High roads and low roads

One of the joys in working as an engineering geologist on Scottish road schemes is the variety of geology that has to be dealt with, from soft silts to hard metamorphics. The properties of these materials must be assessed, cuttings and embankments designed, and site work monitored carefully to ensure safe and economic construction.     

Genesis of cristobalite and tridymite at low temperatures

It is suggested that an explanation of the observed metastable formation of cristobalite and tridymite in the stability field of quartz lies in the topology of these silica polymorphs and the resulting energies at the time of formation.     

Deformation at low and high stress-loading rates

In an extensional shear zone in the Talea Ori, Crete, quartz veins occur in high-pressure low-temperature metamorphic sediments at sites of dilation along shear band boundaries, kink band boundaries and boudin necks. Bent elongate grains grown epitactically from the host rock with abundant fluid inclusion trails parallel to the vein wall indicate vein formation by crack-seal increments during dissolutionprecipitation creep of the host rock. The presence of sutured high-angle grain boundaries and subgrains shows that temperatures were sufficiently high for recovery and strain-induced grain boundary migration, i.e. higher than 300 -350℃, close to peak metamorphic conditions. The generally low amount of strain accumulated by dislocation creep in quartz of the host rock and most veins indicates low bulk stress conditions of a few tens of MPa on a long term. The time scale of stress-loading to cause cyclic cracking and sealing is assumed to be lower than the Maxwell relaxation time of the metasediments undergoing dissolution-precipitation creep at high strain rates(10^-10 s^-1 to 10^-9 s^-1), which is on the order of hundred years. In contrast, some veins discordant or concordant to the foliation show heterogeneous quartz microstructures with micro-shear zones, sub-basal deformation lamellae, shortwavelength undulatory extinction and recrystallized grains restricted to high strain zones. These microstructures indicate dislocation glide-controlled crystal-plastic deformation(low-temperature plasticity) at transient high stresses of a few hundred MPa with subsequent recovery and strain-induced grain boundary migration at relaxing stresses and temperatures of at least 300 -350℃. High differential stresses in rocks at greenschist-facies conditions that relieve stress by creep on the long term, requires fast stress-loading rates, presumably by seismic activity in the overlying upper crust. The time scale for stress loading is controlled by the duration of the slip event along a fault, i.e. a few seconds to minutes.This study demonstrates that microstructures can distinguish between deformation at internal low stress-loading rates(to tens of MPa on a time scale of hundred years) and high(coseismic) stress-loading rates to a few hundred MPa on a time scale of minutes.     

Heat capacity and entropy of low structural state plagioclases

The heat capacity of 11 different compositions of the low structural state plagioclase binary was measured between 5 and 773 K. The results are compared to those obtained from synthetic high structural state samples investigated in a previous study and obtained from a heat-treated natural sample of this study. The heat capacity of anorthite samples with slightly different order parameters shows large differences at ~500 K, where the Ibar1-Pbar1 phase transition occurs, which affects petrological calculations. At T = 298.15 K, the vibrational entropy versus composition behaviour of the low structural state plagioclases is almost ideal, in contrast to the high structural state plagioclases with positive excess vibrational entropies. At higher temperatures, the low structural state plagioclases show a negative deviation from ideal vibrational entropy composition behaviour in the Na-rich region.     

Strain-driven disordering of low microcline to low sanidine during partial phase separation in microperthites

Microperthitic feldspar crystals containing low microcline in a braid intergrowth often have distinctive microtextures including coarse semi- to in-coherent grain-boundary pleated rims and fine coherent intracrystalline Ab- and Or-rich pleats (Lee et al. 1997). The coarser pleated rims are generally separated from the braid microtexture in the crystal interior by a coherent to semi-coherent transitional zone. Partial phase separation has occurred in the transitional zone in step with that in the Ab- and Or-rich pleats at the grain boundaries, such that Ab-rich lamellar film micro-antiperthite alternates along (010) with more Or-rich lamellar film microperthite; the microtextures and phases are those expected for the respective local bulk compositions. Lamellar microtextures contain tweed orthoclase, whereas low microcline is the only K-feldspar in the fine coherent pleats and braid microperthite. We propose that the small coherent pleats developed from the braid microtexture by interaction of the spontaneous coherency strains with discontinuities within or at the surface of the crystal, and that their initial spacing is guided by that of the braid microperthite. We infer that the transitional zone formed by straightening of the zig-zag braid microtexture above the pleat heads during coarsening and partial phase separation. We further infer that the resulting coherency shear strains induced a reversal of the K-feldspar phase transformation, involving Si, Al disordering of low microcline into low sanidine, now tweed orthoclase, although the crystal was at a T within the hydrostatic T-stability of microcline. Received: 10 June 1996 / Accepted: 12 December 1996     

Kinetics and mechanisms of the leaching of low Fe sphalerite

The surface speciation and leaching kinetics of 38- to 75-μm sphalerite (0.45 wt.% Fe) particles reacted in O₂ purged perchloric acid (at pH 1.0) at 25, 40, 60, and 85 °C over a leach period of 144 h were investigated. In all cases, an initial rapid leach rate is observed followed by a slower leach rate. These two leach regimes can each be adequately modeled using straight-line interpolation, and thus two activation energies (E_a) have been derived. E_a for the fast and slow Zn dissolution rates were 33 ± 4 kJ mol⁻¹ and 34 ± 4 kJ mol⁻¹ respectively, suggesting the same rate-determining step.     

极低级变质作用及其研究方法

近年来国际上极低级变质作用的研究进展包括综合运用了伊利石结晶度等各项指标 ,将极低级变质带划分为成岩带、近变质带和浅变质带 ,成岩带和近变质带又可进一步划分为低级成岩带、高级成岩带、低级近变质带和高级近变质带 ;研究了伸展背景、阿尔卑斯碰撞背景和增生背景下的极低级变质作用 ;进一步理解了矿物的转变过程 ,建立了变质泥质岩石的矿物反应系列。即变质泥质岩石的二八面体矿物反应系列 ,为蒙皂石—伊 /蒙混层 (I/S)—伊利石—白云母 ;对应变质镁铁质岩石的三八面体矿物反应系列 ,为蒙皂石—绿泥石 /蒙皂石混层 (C/S)—绿泥石。岩石微构造也发生同步变化 ;明确了广泛应用的伊利石结晶度的本质是雏晶大小的一种量度 ,也与晶格应变有关 ,主要受反应动力的控制 ;建立了系统的研究技术方法 ,包括野外采样方法、室内X光衍射法 (XRD)、透射电镜法 (TEM )、地质温度计、地质压力计、岩石学方法、同位素地质学方法等     

The hydrothermal synthesis of low albite

Glasses on the join NaAlSi₃O₈-Na₂Si₂O₅ were devitrified hydrothermally at pressures of 1 to 10 kb and at temperatures in the range 200 to 700° C to define more adequately the physical and chemical environments which favor crystallization of the fully ordered polymorph of albite. The presence of Na₂Si₂O₅ allows the synthesis of low albite with an obliquity of 1.140° (Cu K radiation) in runs of relatively short duration. The effect of increasing total pressure and time, and of decreasing temperature and amount of water down to critical values, is to favor the synthesis of ordered albite. Excess sodium is the chemical constituent necessary for ordering to proceed at a relatively rapid rate; this rate seems to vary with the ratio aNa⁺/aH⁺, and hence with the peralkalinity of the aqueous fluid attending recrystallization. The chemical environment of recrystallization thus seems as important as temperature in determining the ultimate degree of Si-Al order attained in albite.This paper is taken from a Ph. D. dissertation submitted to the Department of Geology, Stanford University, Stanford, California.     

Pulsations of microwave flaring emission at low and high frequencies

A wavelet analysis of the flare-intensity variations has been carried out for a solar flare observed with the Nobeyama Radioheliograph at 17 and 34 GHz and the spectrometer of Purple Mountain Observatory at 4.5–7.5 GHz. The signals contain a well-pronounced periodicity with a period of P = 14–17 s and stable, coherent behavior at frequencies higher and lower than the peak frequency. We simulated the modulation of the gyrosynchrotron emission by fast sausage magnetoacoustic oscillations for the cases of low and high plasma density in the radio source. The synchronism of the pulsations at high and low frequencies can be realized only in the case of high plasma density, when the low-frequency turnover of the microwave spectrum is due to the Razin effect, not self-absorption. Published in Russian in Astronomicheskiĭ Zhurnal, 2007, Vol. 84, No. 7, pp. 655–664. The article was translated by the authors.     

低渗砂岩储层裂缝发育及演化特征

随着石油工业的发展,低渗透油气藏所占比例越来越大,低渗透砂岩储层中的裂缝能够起到很好的储集和导流作用,对裂缝的研究具有十分重要的意义。牛庄洼陷牛35断块沙三中发育低渗透砂岩,为主要含油层系,前人对研究区低渗砂岩储层中的裂缝研究较少。运用岩心观察、镜下薄片观测及CT扫描技术对牛35块沙三中低渗致密砂岩储层裂缝的发育及演化规律进行研究,得出牛35块宏观裂缝主要发育低、高角度斜交剪切缝,长度在2～20 cm之间,分布间距大,但整体裂缝密度仅为0.27条/m,裂缝很不发育,难以构成有效的裂缝系统;微观裂缝较发育,包括粒内缝和粒间缝,改善了储层的连通性,有助于油气的储集和运移;与牛104井、河125-1井相比,牛35井岩石矿物接触关系更加不稳定,胶结程度更低,更容易在荷载作用下产生裂缝,裂缝由上到下呈辫状发育,裂缝体积随着施加荷载的增大呈线性增加。