鄂尔多斯盆地安塞油田长10优质储层特征

鄂尔多斯盆地安塞油田长10期发育以细砂岩和中砂岩为主的长石砂岩,胶结物主要有浊沸石、石英加大等硅质胶结物、绿泥石和方解石;在早成岩早期酸性地层水大量溶蚀颗粒间胶结物,压实作用强烈,在中成岩早期,湖相泥岩中生成的酸性介质溶蚀砂岩颗粒间的胶结物及长石和岩屑颗粒碎屑,形成次生溶蚀孔隙,从而形成优质储层.纵向上,在不整合面和层序界面附近,储层溶蚀作用强烈,次生孔隙发育,是优质储层发育部位,向上溶蚀作用逐渐变弱;在平面上,越靠近湖盆中心溶蚀作用越强,越远离湖盆中心溶蚀作用越弱.鄂尔多斯盆地安塞油田长10优质储层主要发育在三角洲平原高能分流河道发育带,溶蚀作用形成的浊沸石溶蚀孔隙、方解石溶蚀孔隙、长石溶蚀孔隙等次生孔隙成为优质储层形成的有利相带.     

近源湖盆砂砾岩储层次生溶孔成因探讨——以查干凹陷祥6井区为例

查干凹陷祥6井区砂砾岩储层发育蜂窝状次生溶蚀孔隙。通过对岩石薄片、阴极发光薄片及扫描电镜分析,结果表明,该孔隙主要由钙长石颗粒及碳酸盐胶结物溶蚀形成,少量长英质岩屑及石英颗粒边缘也有溶蚀迹象。荧光薄片及包裹体测温证实存在两期胶结作用,结合研究区热演化史研究结果,成岩演化规律与该湖盆主要发育的两期生烃历史、两期构造抬升剥蚀相对应。主要的成岩演化序列:压实作用为主(初次深埋)→长石颗粒大量溶蚀,少量石英次生加大,局部成藏(初次生烃)→第一期胶结(第一期构造抬升剥蚀)→第一期胶结物溶蚀,蜂窝状次生溶孔发育,局部成藏(再次深埋,二次生烃)→第二期胶结物胶结,少量石英质颗粒溶蚀(第二期构造抬升剥蚀)。     

鄂尔多斯盆地富县地区延长组成岩作用与优质储层关系研究

对鄂尔多斯盆地富县地区延长组长8、长6油层组储层砂体成岩作用研究表明,该套砂体受NE向阴山古陆物源控制,碎屑中黑云母等塑性物质含量高,压实作用强,致密程度高,油气充注于致密砂岩背景的优质储层中.富县地区储层砂体致密程度高,主要是强压实、强胶结、溶蚀作用相对较弱等原因导致.绿泥石环边发育可降低上覆地层压实作用,刚性颗粒含量高可有效降低上覆地层压力对塑性颗粒的变形作用.后期酸性水溶蚀作用的强弱与溶蚀前储层砂体物性和胶结物成份关系密切,储层砂岩溶蚀前孔隙越发育,后期溶蚀作用愈强.优质储层常发育于三角洲前缘亚相水下分流河道特别是主河道粒度较粗、刚性颗粒含量较高的砂体中.     

车镇北带古近系砂砾岩储层成岩作用特征及其对物性的影响

综合利用岩芯资料、铸体薄片、物性资料及相关分析测试资料,对车镇北带砂砾岩成岩作用特征及其对储层物性的影响进行了研究。研究表明:工区砂砾岩储层成岩作用主要有压实作用、胶结作用、溶蚀作用、灰泥重结晶作用和交代作用;成岩环境经历了中性/弱碱性→酸性→碱性→酸性→碱性的变化,相应的成岩作用序列为:压实作用→长石溶蚀/早期石英加大→碳酸盐胶结/石英溶蚀→长石溶蚀/碳酸盐胶结物溶蚀/晚期石英加大→黄铁矿胶结;区内砂砾岩储集物性较差,储集空间以次生孔缝为主;不同亚相岩相和成岩作用的差异使其储集物性有所不同,扇根主要发育颗粒支撑和杂基支撑砾岩,成岩作用以压实和灰泥重结晶为主,物性较差,发育无效储层;扇中亚相溶蚀作用较为发育,储集物性得到很好地改善,有效储层比例较高;扇缘亚相以胶结作用为主,使物性变差,局部溶蚀作用发育,可成为有效储层。     

高邮凹陷南坡真武—曹庄地区戴南组砂岩成岩作用及其对储层性质的影响

在详细岩心观察描述的基础上, 利用铸体薄片、扫描电镜、压汞分析、X-射线衍射、埋藏史-热史模拟等多种分析测试手段, 对戴南组砂岩成岩作用特征进行了详细研究, 发现砂岩储层主要经历了压实、胶结、溶蚀和交代作用, 自生胶结物主要有高岭石等粘土矿物、铁碳酸盐、石英、长石及硬石膏等, 发生溶蚀则主要为长石和岩屑, 戴南组地层现今主要处于晚成岩的A期.戴南组砂岩储层主要受压实作用、高岭石胶结、铁碳酸盐胶结、石英次生加大及溶蚀作用的影响, 发育塑性组分溶蚀成岩相和高岭石充填成岩相的储层性质往往较好, 是有利的油气储集带; 而发育压实-充填成岩相和碳酸盐胶结成岩相的储层孔渗性能很差, 多为致密储层.      

鄂尔多斯盆地华庆地区长8段成岩主控因素及其对储层的影响

利用微区原位同位素测试、流体包裹体均一化测温、X-射线衍射矿物分析和阴极发光薄片观察与统计等分析手段,系统分析了华庆地区长8段储层岩石学及物性特征,探讨了储层发育的成岩控制因素。结果表明:早期压实作用是长8段低成熟度砂岩原生孔隙降低的重要原因;两期碳酸盐胶结物的广泛发育显著降低了储集孔隙;呈薄膜发育的绿泥石未能有效保护孔隙,自生黏土矿物也是孔隙减少的因素;自生石英填充于溶蚀微孔或附着于颗粒表面,在一定程度上对储层物性产生影响;长8段储层缺乏溶蚀流体的流动空间,碎屑颗粒或前期形成的胶结物未能发生广泛溶蚀,是该区砂岩储集物性较差的另一重要原因。     

苏北盆地金湖凹陷腰滩地区古近系阜宁组储层物性特征及其影响因素

苏北盆地金湖凹陷腰滩地区古近系阜宁组储层岩石类型以岩屑长石砂岩和长石砂岩为主,其成分成熟度中等,结构 成熟度中等到好。腰滩地区储层成岩作用主要包括压实、胶结、溶蚀和交代四种类型, 目前处于晚成岩阶段A期。研究区储 层的储集物性受成岩作用和构造运动的共同影响,主要表现为对孔隙度和渗透率的影响, 其中压实和胶结作用使储层原生 孔隙迅速减少、渗透率降低、储集物性变差,而溶解作用则是导致次生孔隙发育及改善砂岩储集性能的主要因素。压实作 用主要表现为刚性颗粒发生脆性破裂、塑性颗粒挤压变形或刚性颗粒嵌入塑性颗粒中、颗粒之间呈线接触和凹凸接触、碎 屑颗粒呈明显的定向排列等; 溶蚀作用表现为碳酸盐矿物的溶解; 胶结物主要为自生黏土矿物、碳酸盐和自生石英。交代作 用主要为碳酸盐胶结物交代石英、长石及岩屑颗粒及碳酸盐胶结物之间的相互交代等。构造运动使局部的储层物性得到改 善。     

准噶尔盆地南缘西部侏罗—白垩系储层发育特征及分布

通过大量镜下薄片观察,南缘白垩系、侏罗系砂岩总体表现为低成分成熟度、低结构成熟度、较低胶结物含量和较弱溶蚀作用的"三低一弱"特征.西山窑组与八道湾组含煤系砂岩具塑性岩屑与高岭石含量较高,颗粒溶蚀压碎及成岩压实作用较强的"二高二强"特征.储层储集空间类型大致分为粒间孔、粒内孔、胶结物溶蚀及微孔隙等,以原生粒间孔为主.区域上,四棵树凹陷、霍玛吐呼背斜带是南缘侏罗—白垩系油气勘探有利区,齐古断褶带侏罗系由于断裂作用强烈,裂缝发育,对储层性质具改善作用.     

鄂尔多斯盆地陕北地区长7砂岩储层成岩相特征研究

在大量样品测试数据与野外地质调查综合分析的基础上, 对长7储层岩石学特征、物性、孔隙结构、成岩作用、成岩阶段和成岩相等进行了研究。结果表明: 研究区长7储层处于中成岩A~B期。压实作用及碳酸盐、粘土(高岭石、伊利石、伊蒙混层)矿物胶结和硅质胶结作用是造成储层原生孔隙丧失的主要原因; 绿泥石胶结抑制孔隙充填, 长石溶蚀作用使孔隙间的连通性得到改善, 储层物性得到提高。根据成岩作用类型、强度及其对储层物性的影响划分出6种成岩相, 其中压实相、碳酸盐胶结相、粘土矿物胶结相、石英加大相、浊沸石充填相不利于储层的发育, 而长石溶蚀相、绿泥石膜胶结相对储层物性改善起了重要作用。     

陕北富县地区直罗油田上三叠统延长组长6储层 成岩作用与有利成岩相带

根据物性分析、高压压汞、薄片观察、扫描电镜及X衍射资料,以及陕北直罗油田长6储层的成岩作用特征,认为该区长6储层处于晚成岩A期阶段.强烈的压实及胶结作用破坏了砂岩的原生孔隙结构,其中碳酸盐、硅质和粘土矿物胶结物是造成砂岩物性降低的重要原因,碎屑颗粒周围形成的绿泥石衬边阻止了部分石英、长石次生加大及碳酸盐胶结物的沉淀,使部分原生粒间孔隙得以保存.溶蚀作用形成次生孔隙,使储层物性得到一定程度的改善.研究区长6储层发育4种成岩相,优质储层与成岩相关系密切,其中次生孔隙成岩相物性最好,绿泥石膜相次之,它们成为储层发育的有利成岩相带.     

一种新的储层孔隙成因类型--石英溶解型次生孔隙

石英作为碎屑岩储层中的一种难溶组分,普遍认为它和次生孔隙的形成关系不十分密切。研究认为泌阳凹陷核桃园组储层中的碎屑石英颗粒存在明显的溶解现象,并形成以石英直接溶解型孔隙为主的储集空间特征。石英颗粒被溶解的部分在薄片中所占的范围为 2 %～ 7%者常见,高者达 8%以上,在总孔隙中所占的相对含量也多数在10 %～ 35 %之间,早成岩B期是其最主要形成期。石英溶解型次生孔隙的大量存在为碎屑岩储层中SiO₂ 胶结物及次生孔隙成因等问题的解释以及储层预测和评价提供了新的可能性。     

柯克亚凝析气田石英的溶解现象及其成因

储层微观特征与成岩演化等的研究表明,柯克亚凝析气田西河甫组储层中广泛存在的石英溶解现象属于石英直接溶解。石英的直接溶解是长期干旱背景下形成的储层,在较深埋藏条件下碱性地层水活动的结果。成岩过程中碱性地层水的形成和原始沉积环境中有机质含量低有关,同时也受成岩演化的制约。早成岩B期一晚成岩期的早期储层中地层水的pH值最高,是研究区储层中石英溶解最强烈的时期,同时也是石英溶解型孔隙最主要的发育期。     

Role of electrochemical reactions in pressure solution

Using a Surface Forces Apparatus we have measured changes in the electrical potential difference between quartz and mica surfaces that correlate with the changing quartz dissolution rate when surfaces are pressed together at relatively low pressures (2-3 atm) in aqueous electrolyte solutions of 30 mM CaCl₂ at 25 °C. No detectable dissolution or voltage potential difference is measured in symmetrical systems (e.g. mica-mica or quartz-quartz) or between dry surfaces subjected to similar pressures, indicating that the dissolution can not be attributed to a simple pressure effect, slow aging (creep), or plastic deformation of the quartz surface. In quartz-mica systems brought together under pressure or to close proximity in electrolyte solution, the onset of quartz dissolution is marked by a sudden, rapid decrease in the quartz thickness at initial rates in the range from 1 to 4 nm/min, which after several hours settles into a constant rate of approximately 0.01 nm/min (∼5 μm/yr). Concomitantly, the potential drops to a constant value once the dissolution rate has stabilized. The decrease in the decay rate is interpreted as being due to saturation of the confined aqueous film and/or to the buildup of a Stern layer on the quartz surface, and the constant rate as being due to the steady-state chemical dissolution and diffusion of the dissolving silica into the surrounding reservoir. The dissolution is ‘non-uniform’: the surfaces become rough as dissolution proceeds, with the appearance of pits in a manner analogous to corrosion. On occasions, the process of rapid dissolution followed by a gradual transition to steady dissolution repeats itself, suggesting that the pit structure and Stern layer are fragile and subject to collapse and/or expulsion from the gap. Preliminary experiments on the dissolution of multi-faceted milled quartz particles (∼1.0 μm diameter) compressed between two muscovite surfaces suggest an asymmetry in the dissolution rates at different crystallographic planes. The origin of the electrical potential is interpreted as arising from the overlapping of the electric double-layers of two dissimilar surfaces when they are forced into close proximity. This electrical potential difference, for as yet unknown reasons, appears to be the driving force for the dissolution, rather than pressure.     

石英溶解机理的研究进展

鉴于石英溶解对全球变化和环境影响的重要性,其机理的研究成为近来地学领域比较活跃的课题.许多学者从物理、化学,甚至生物学的角度研究了石英溶解的机理.本文从pH值、温度、离子强度和表面形态四个方面综述石英溶解机理的研究进展.前人的研究成功地解释了石英-水在不同条件下的溶解机理,成功地解决了溶解动力学相应的单个参数问题.但是,石英溶解的条件非常复杂,往往是多个因素共同作用的结果,因此只研究单个参数的影响无法真正了解矿物溶解的动力学机理.石英溶解机理需要探索实验和理论方面更深层次的问题.     

The effect of experiment geometry on the mechanism and rate of dissolution of quartz in basanite at 0.5 GPa and 1350 °C

Mineral dissolution is an important factor in many magmatic processes such as melting, assimilation and magma mixing. Since it is not possible to determine dissolution rates or mechanisms from natural samples, experimental measurements are very useful. However, the geometry of the crystal–melt system can have a large effect on the measured rate, depending on whether the contaminated melt formed during dissolution is gravitationally stable or unstable. This study examines the effects of the crystal–melt geometry on the dissolution rate and mechanism. The experiments were performed using basanite melt and cylinders and spheres prepared from a single crystal of natural quartz. All of the experiments were performed in the piston cylinder apparatus at 0.5 GPa and 1350 °C. Four crystal–melt geometries were used: (1) quartz cylinders on top of a column of melt; (2) quartz cylinders beneath a column of basanite melt; (3) quartz cylinders in the middle of column of melt; (4) quartz spheres on top of a column of basanite melt. These geometries allow an examination of non-convective, convective and mixed non-convective/convective dissolution. Sphere experiments were included, as this has been the most commonly used geometry in previous experimental studies. In all of the experiments quartz dissolves directly into the basanite without formation of cristobalite or tridymite. Quartz on top of a column of melt dissolves at a rate almost proportional to the square root of time and forms a silica-rich compositional boundary layer that is gravitationally stable. All of the samples show well-defined compositional gradients in the boundary layer; however, the melt at the interface varies in composition with time and plots of concentration as a function of distance normalized to time show that the diffusion rate of SiO₂ increases with time. These data suggest that the rate-controlling step during quartz dissolution is interface reaction rather than cation diffusion. Quartz on the bottom of a column of basanite dissolves much more quickly than in the quartz-on-top experiments and the dissolution rate is linear, due to the periodic gravitational instability and resultant convection of the boundary layer. Even though interface kinetics are the rate-controlling step in quartz dissolution, convection causes an increase in dissolution rate because it replenishes the boundary layer with new, silica-undersaturated melt, which dissolves the quartz more quickly than the contaminated melt. These data suggest that the interface reaction rate is controlled by the degree of undersaturation of the solvent melt in the dissolving component. Both quartz-in-middle and quartz sphere experiments dissolve at a rate intermediate between the two extremes and both show a power law rate. Both dissolve by a combination of convective and non-convective dissolution but the sphere experiments are affected by an additional factor. During the experiment the sphere can sink through the capsule causing forced convection which adds another complication to the interpretation of the dissolution rate data. The results of this study indicate that the choice of experiment geometry plays a major role in determining the observed dissolution rate. Mineral spheres, which have been widely used in the past, are not ideal for dissolution studies. Instead, dissolution rates and mechanisms are best determined in the absence of convection. These experiments have an additional advantage in that for diffusion-controlled dissolution, they allow determination of cation diffusivity. Received: 2 March 2000 / Accepted: 11 April 2000     

Effects of melt viscosity and silica activity on the rate and mechanism of quartz dissolution in melts of the CMAS and CAS systems

The dissolution rate of quartz in melts of the CMAS and CAS systems at 1,600°C and 1.5 GPa is a function of both the silica activity of the melt and its viscosity. In melts with low silica activity quartz dissolves more quickly than in higher aSiO₂ melts regardless of viscosity. For melts with equal aSiO₂, dissolution is faster in the low viscosity melt. Quartz dissolution is controlled by interface kinetics in three of the four melts used in this study for times much greater than predicted by the model of Zhang et al. (in Contrib Mineral Petrol 102:492–513 1989). One melt which was previously shown to adhere to the predicted behaviour at lower temperature shows a significant activation time at higher temperature. All the dissolution data indicate that there are likely to be three distinct domains of dissolution behaviour, although the details of why a particular melt falls in any one domain require further study. Although the current database is small, the relationship between quartz solubility and the dissolution constant indicate that solubility may be a useful parameter for predicting dissolution rates, particularly if silica activity and melt viscosity are also known.     

Making diagenesis obey thermodynamics and kinetics: the case of quartz cementation in sandstones from offshore mid-Norway

Calculation of the quantity and distribution of quartz cement as a function of time and temperature/depth in quartzose sandstones is performed using a coupled dissolution/diffusional–transport/precipitation model. This model is based on the assumptions that the source of the silica cement is quartz surfaces adjoining mica and/or clay grains at stylolite interfaces within the sandstones, and the quantity of silica transport into and out of the sandstone by advecting fluids is negligible. Integration of the coupled mass transfer/transport equations over geologically relevant time frames is performed using the quasi-stationary state approximation. Results of calculations performed using quartz dissolution rate constants and aqueous diffusion coefficients generated from laboratory data, are in close agreement with both the overall porosity and the distribution of quartz cement in the Middle Jurassic Garn Formation only after optimizing the product of the effective surface area and quartz precipitation rate constants with the field data. When quartz precipitation rate constants are fixed to equal corresponding dissolution rate constants, the effective surface area required to match field data depends on the choice of laboratory generated quartz rate constant algorithm and ranges from 0.008 cm⁻¹ to 0.34 cm⁻¹. In either case, these reactive surface areas are ∼2 to 4 orders of magnitude lower than that computed using geometric models.     

鄂尔多斯盆地东部下二叠统山西组山2段成岩相划分及展布

鄂尔多斯盆地东部下二叠统山西组山2段岩石类型主要为石英砂岩、岩屑质石英砂岩和岩屑砂岩,储集层经历了压实、压溶、硅质胶结、碳酸盐胶结交代、高岭石胶结、杂基蚀变以及溶蚀等多种成岩作用。在成岩作用研究的基础上,通过大量的岩心观察和薄片鉴定,结合阴极发光、探针分析等方法,将研究区划分出7种单因素成岩相,即：强压实、压溶-石英次生加大、蚀变高岭石、沉淀高岭石、杂基充填、碳酸盐胶结交代、不稳定组分溶蚀成岩相,在此基础上对其进行平面叠加,确定了利于储集层发育的优势成岩相。其中压溶-石英次生加大与杂基、假杂基溶蚀作用的综合作用（叠加和改造）决定了山西组山2段有利的成岩相带,在陕141井区、榆37井区、子洲-清涧地区山西组山2段形成了天然气优质储集层。     

Kinetics of dissolution of mechanically comminuted rock-forming oxides and silicates—I. Deformation and dissolution of quartz under laboratory conditions

The extensive evidence on the properties of ground quartz such as grain morphology and adherence and subsurface structural damage shows a consistent pattern, interpretable in terms of the competing processes of fracture and of local plastic deformation.The well-documented pattern of dissolution of ground quartz in aqueous solutions is also consistent. At large undersaturations and constant other environmental variables, the apparent dissolution rate of ground quartz decreases exponentially with the increasing thickness of the equivalent dissolved disturbed layer, and the rate of release of adherent tiny fragments shows roughly the same dependence on the latter. At small undersaturations distribution of solubilities also needs to be considered.     

塔中地区志留系海相碎屑岩储层石英溶蚀成因及影响因素分析

塔中地区志留系柯坪塔格组顶部不整合面附近沥青砂岩中发育大量因石英及次生加大边的溶蚀贡献的次生孔隙,根据薄片（铸体）观察、SEM观察显示石英溶蚀主要有3种赋存状态,其中对储层有建设性作用的溶蚀主要有石英硅质颗粒边缘的溶蚀及次生加大边的溶蚀两种,而对储层建设性作用不大的溶蚀为碳酸盐对石英及硅质的交代作用,这些SiO₂的溶蚀路径可分为碱性环境和酸性环境下的SiO₂溶解,统计表明碱性环境下的SiO₂溶蚀普遍发育,但程度较低,而在酸性环境中溶解时对有机酸的种类、数量、流体性质、溶解环境中的流体能力以及地层温度的要求更为苛刻。本次研究中的酸性流体介质条件下的石英溶解即为古油藏破坏过程中受微生物降解烃类释放出大量的草酸起主要作用,因其降低了石英颗粒表面溶解反应的活化能,并在地层水中碱金属离子的“盐效应”作用下,大大提高了SiO₂的溶解速率,溶解产物扩散到地层水中被带走,从而造成强烈的石英溶蚀现象,研究同时表明溶蚀程度强烈但具有很强的局限性。SiO₂的溶蚀（解）作用能够提供一定量的油气富集空间,改善储层的物性,对在埋藏较深、时代较老的志留系海相致密碎屑岩储层中发育孔隙度较高的优质储层具有重要意义。