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With the aim of better understanding the tight gas reservoirs in the Zizhou area of east Ordos Basin, a total of222 samples were collected from 50 wells for a series of experiments. In this study, three pore-throat combination types in sandstones were revealed and confirmed to play a controlling role in the distribution of throat size and the characteristics of gas-water relative permeability. The type-Ⅰ sandstones are dominated by intercrystalline micropores connected by cluster throats, of which the distribution curves of throat size are narrow and have a strong single peak(peak ratio 30%). The pores in the type-Ⅱ sandstones dominantly consist of secondary dissolution pores and intercrystalline micropores, and throats mainly occur as slice-shaped throats along cleavages between rigid grain margins and cluster throats in clay cement.The distribution curves of throat size for the type-Ⅱ sandstones show a bimodal distribution with a substantial low-value region between the peaks(peak ratio 15%). Primary intergranular pores and secondary intergranular pores are mainly found in type-Ⅲ samples, which are connected by various throats. The throat size distribution curves of type-Ⅲ sandstones show a nearly normal distribution with low kurtosis(peak ratio 10%), and the micro-scale throat radii(0.5 μm) constitute a large proportion. From type-Ⅰ to type-Ⅲ sandstones, the irreducible water saturation(Swo) decreased; furthermore, the slope of the curves of Krw/Krg in two-phase saturation zone decreased and the two-phase saturation zone increased,indicating that the gas relative flow ability increased. Variations of the permeability exist in sandstones with different porethroat combination types, which indicate the type-Ⅲ sandstones are better reservoirs, followed by type-Ⅱ sandstones and type-Ⅰ sandstones. As an important factor affecting the reservoir quality, the pore-throat combination type in sandstones is the cumulative expression of lithology and diagenetic modifications with strong heterogeneity. 相似文献
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核磁共振方法在致密砂岩储层孔隙结构中的应用--以鄂尔多斯大牛地气田上古生界石盒子组3段为例 总被引：7，自引：5，他引：7
采用低场核磁共振实验的方法研究了鄂尔多斯盆地大牛地气田上古生界石盒子组3段岩芯样品的核磁共振弛豫时间T2分布与由压汞毛管压力曲线所获得的孔喉半径分布之间的对应关系和转换方法,建立了T2几何平均值与毛管压力曲线孔喉结构参数之间的统计关系.研究结果表明,致密砂岩储层的核磁共振T2分布与由毛管压力曲线所获得的孔径分布之间存在密切的相关性,二者都反映了岩石的孔隙结构,利用核磁共振技术来评价致密砂岩储层的孔喉结构是有效的,同时也为利用核磁共振测井技术开展致密砂岩储层评价提供了实验基础. 相似文献
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To better understand reservoir quality and to produce accurate petrophysical interpretations, it is necessary to understand complex and heterogeneous pore throat structures in tight sands and to develop a technique to reveal the full range of pore and throat distributions. In this study, in order to characterize the features and evolutions of pore throat structures, nine samples from the Lower Cretaceous tight gas sandstone in the Songliao Basin of China are measured by nuclear magnetic resonance (NMR), rate-controlled porosimetry (RCP) and scanning electron microscopy (SEM). Throats with bifractal structures are found in these tight sands and can be divided into a backbone formation (BF) region and a percolation region using RCP data. Because (i) throats in the percolation region record treelike pore structures and are predominant in small pore spaces and (ii) a good correlation exists between NMR-derived T2 relaxation times and the RCP-derived radius of throats, the throat distribution obtained via RCP can be used to calibrate the NMR PSD and then to partition the PSD into distributions of pore bodies and throats. These data indicate that (i) throats are more common than pore bodies in pore spaces of tight sands with lower permeability, (ii) pore bodies are connected to throats from both the BF and percolation regions, in which the fluid mobility in pore bodies is mainly controlled by the pore to throat ratio (PTR), which is related to the intersection throat of these two regions, and (iii) compaction, dissolution, clay cementation and sediment properties (e.g., rock compositions) have different impacts on the evolutions of pore bodies and throats, in which larger PTR values in tight sands are mainly produced by compaction and pore-bridging clay cementation, and lower contents of pore bodies are commonly related to abundant plastic compositions and pore-bridging clay cementation. 相似文献
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Shale reservoirs of the Middle and Upper Devonian Horn River Group provide an opportunity to study the influence of rock composition on permeability and pore throat size distribution in high maturity formations. Sedimentological, geochemical and petrophysical analyses reveal relationships between rock composition, pore throat size and matrix permeability.In our sample set, measured matrix permeability ranges between 1.69 and 42.81 nanodarcies and increases with increasing porosity. Total organic carbon (TOC) content positively correlates to permeability and exerts a stronger control on permeability than inorganic composition. A positive correlation between silica content and permeability, and abundant interparticle pores between quartz crystals, suggests that quartz may be another factor enhancing the permeability. Pore throat size distributions are strongly related to TOC content. In organic rich samples, the dominant pore throat size is less than 10 nm, whereas in organic lean samples, pore throat size distribution is dominantly greater than 20 nm. SEM images suggest that in organic rich samples, organic matter pores are the dominant pore type, whereas in quartz rich samples, the dominant type is interparticle pores between quartz grains. In clay rich and carbonate rich samples, the dominant pore type is intraparticle pores, which are fewer and smaller in size.High permeability shales are associated with specific depositional facies. Massive and pyritic mudstones, rich in TOC and quartz, have comparatively high permeability. Laminated mudstone, bioturbated mudstone and carbonate facies, which are relatively enriched in clay or carbonate, have fairly low permeability. 相似文献
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全球常规油气及非常规油气资源极为丰富,其中致密油气是非常规油气资源的主要类型,是当前非常规油气勘探的重点,也是未来接替常规油气资源的重要领域。致密储层具有油气资源量大、分布面积广、成岩作用强、单井产量较低、储层非均质性强等特点。在富含油气资源的致密储层中,具有良好物性的“甜点”是提高产量的有利勘探目标,其“甜点”主要包括两类,一类为异常高孔带,另一类为裂缝发育带。目前,致密储层的研究现状主要包括致密储层划分、地质特征、形成机理和有利储层预测等。近年来,“甜点”的形成机理和预测成为当前致密储层勘探开发的重要科学问题。因此,致密储层微观孔喉结构表征、致密储层裂缝发育识别表征是目前致密储层研究的热点领域及未来主要发展方向。 相似文献
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地震动促进石油运移的一种模式及其发生边界 总被引：1，自引：0，他引：1
天然和人工地震动使地下孔隙流体瞬时产生相对于地层介质的加速运动趋势,即产生了作用于流体的瞬时冲力。在不考虑质量扩散力条件下,本文以岩石孔喉结构理想模型和充填其中的石油受力分析为基础,对水平、垂向两地震动作用方向上,促进石油运移时的油柱长度、孔隙、喉道等边界条件进行了分析,并考虑了静水常压和异常压力两种地层状态下的情况。研究表明,在无裂缝作为运移通道的条件下,地震动作用可以使油柱在岩石破裂前,突破一定岩石孔隙结构的喉道发生运移。对该地震动促进石油运移模式的边界条件分析认为,小孔喉比值、大半径孔隙和连续一定长度的油柱利于油柱突破喉道运移的发生,油柱在水平向地震动作用于静水常压地层、垂向地震动作用于静水常压地层、水平向地震动作用于低过剩压力梯度地层、垂向地震动作用于高过剩压力梯度地层等4种情况下,地震动促使运移发生的难度依次降低。 相似文献