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1.
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
2.
为分析准噶尔盆地南缘（简称准南）低煤阶煤储层可动流体、束缚流体以及孔径分布特征,对准南6个矿区6个煤样进行了高速离心和低场核磁共振实验。实验结果表明:准南低煤阶煤以吸附孔发育最优,其次为渗流孔和裂隙。建立束缚水状态的最佳离心力为1.380 MPa;结合饱和水状态和束缚水状态的核磁共振T2谱,得到可动流体孔隙度为0.45%~1.89%,平均1.29%;束缚流体孔隙度为1.03%~7.45%,平均4.18%,可动流体孔隙度与渗透率呈幂指数关系（R2=0.935 8）。根据"离心-T2C法"得到准南低阶煤孔隙半径主要分布在0.01~1 μm,平均孔隙半径为1.771 μm。 相似文献
3.
YANG Bo QU Hongjun PU Renhai TIAN Xiahe YANG Huan DONG Wenwu CHEN Yahui 《《地质学报》英文版》2020,94(2):322-336
In this study, the types of micropores in a reservoir are analyzed using casting thin section(CTS) observation and scanning electron microscopy(SEM) experiments. The high-pressure mercury injection(HPMI) and constant-rate mercury injection(CRMI) experiments are performed to study the micropore structure of the reservoir. Nuclear magnetic resonance(NMR), gas-water relative seepage, and gas-water two-phase displacement studies are performed to examine the seepage ability and parameters of the reservoir, and further analyses are done to confirm the controlling effects of reservoir micropore structures on seepage ability. The experimental results show that Benxi, Taiyuan, Shanxi, and Shihezi formations in the study area are typical ultra-low porosity and ultra-low permeability reservoirs. Owing to compaction and later diagenetic transformation, they contain few primary pores. Secondary pores are the main pore types of reservoirs in the study area. Six main types of secondary pores are: intergranular dissolved pores, intragranular dissolved pores, lithic dissolved pores, intercrystalline dissolved pores, micropores, and microfracture. The results show that reservoirs with small pore-throat radius, medium displacement pressure, and large differences in pore-throat structures are present in the study area. The four types of micropore structures observed are: lower displacement pressure and fine pores with medium-fine throats, low displacement pressure and fine micropores with fine throats, medium displacement pressure and micropores with micro-fine throats, and high displacement pressure and micropores with micro throats. The micropore structure is complex, and the reservoir seepage ability is poor in the study areas. The movable fluid saturation, range of the gas-water two-phase seepage zone, and displacement types are the three parameters that well represent the reservoir seepage ability. According to the characteristic parameters of microscopic pore structure and seepage characteristics, the reservoirs in the study area are classified into four types(Ⅰ–Ⅳ), and types Ⅰ, Ⅱ, and Ⅲ are the main types observed. From type Ⅰ to type Ⅳ, the displacement pressure increases, and the movable fluid saturation and gas-water two-phase seepage zone decrease, and the displacement type changes from the reticulation-uniform displacement to dendritic and snake like. 相似文献
4.
GUO Chen QIN Yong MA Dongmin XIA Yucheng BAO Yuan CHEN Yue LU Lingling 《《地质学报》英文版》2020,94(2):243-252
The methods of nuclear magnetic resonance(NMR)spectroscopy,mercury injection porosimetry(MIP),and gas-water relative permeability(GWRP)were used to reveal the pore structure and permeability characteristics of high-rank coal reservoirs in the Bide-Santang basin,western Guizhou,South China,to provide guidance for coalbed methane(CBM)exploration and exploitation and obtain direct insights for the development of CBM wells.The results indicate that the coal reservoirs in the study area are characterized by well-developed adsorption pores and poorly developed seepage pores.The bimodal NMR transverse relaxation time(T2)spectra and the mutation in the fractal characteristic of the MIP pore volume indicate poor connectivity between the adsorption pores and the seepage pores.As a result,the effective porosity is relatively low,with an average of 1.70%.The irreducible water saturation of the coal reservoir is relatively high,with an average of 66%,leading to a low gas relative permeability under irreducible water saturation.This is the main reason for the low recovery of high-rank CBM reservoirs,and effective enhanced CBM recovery technology urgently is needed.As a nondestructive and less time-consuming technique,the NMR is a promising method to quantitatively characterize the pores and fractures of coals. 相似文献
5.
为了研究下扬子地区二叠系大隆组页岩孔隙结构特征,联合扫描电镜、高压压汞、N2/CO2气体吸附实验手段对页岩储层孔隙结构进行了研究。结果表明,研究区二叠系大隆组页岩孔隙类型以有机质孔、粒间孔、粒内孔、溶蚀孔和微裂缝为主;孔隙结构为多峰态-多尺度孔隙并存,微孔-介孔-宏孔都有发育,各个尺度的孔隙对孔容都有所贡献,其中以0.75～1.5 nm的微孔、10～35 nm的介孔及大于100 nm的宏孔为主。通过拟合孔体积、比表面积与埋深、有机碳(TOC)、成熟度(RO)以及矿物含量的相关性发现,微孔表面积与埋深、TOC呈正相关;微介孔体积和表面积均与RO呈负相关;宏孔体积与埋深、TOC、黏土矿物含量呈负相关,与RO呈较正相关;宏孔表面积与埋深成正比,与RO成反比。研究结果说明下扬子地区大隆组页岩孔隙发育主要受控于埋深、TOC、RO、黏土矿物含量等因素。 相似文献
6.
NING Chuanxiang MA Zhongliang JIANG Zhenxue SU Siyuan LI Tingwei ZHENG Lunju WANG Guozhen LI Fengxun 《《地质学报》英文版》2020,94(2):352-363
To reveal the effect of shale reservoir characteristics on the movability of shale oil and its action mechanism in the lower third member of the Shahejie Formation(Es3l), samples with different features were selected and analyzed using N2 adsorption, high-pressure mercury injection capillary pressure(MICP), nuclear magnetic resonance(NMR), high-speed centrifugation, and displacement image techniques. The results show that shale pore structure characteristics control shale oil movability directly. Movable oil saturation has a positive relationship with pore volume for radius > 2 μm, as larger pores often have higher movable oil saturation, indicating that movable oil is present in relatively larger pores. The main reasons for this are as follows. The relatively smaller pores often have oil-wetting properties because of organic matter, which has an unfavorable effect on the flow of oil, while the relatively larger pores are often wetted by water, which is helpful to shale oil movability. The rich surface provided by the relatively smaller pores is beneficial to the adsorption of immovable oil. Meanwhile, the relatively larger pores create significant pore volume for movable oil. Moreover, the larger pores often have good pore connectivity. Pores and fractures are interconnected to form a complex fracture network, which provides a good permeability channel for shale oil flow. The smaller pores are mostly distributed separately;thus, they are not conducive to the flow of shale oil. The mineral composition and fabric macroscopically affect the movability of shale oil. Calcite plays an active role in shale oil movability by increasing the brittleness of shale and is more likely to form micro-cracks under the same stress background. Clay does not utilize shale oil flow because of its large specific surface area and its block effect. The bedding structure increases the large-scale storage space and improves the connectivity of pores at different scales, which is conducive to the movability of shale oil. 相似文献
7.
孔喉分布是控制低渗-致密砂岩储层物性的关键因素,其评价依托于各种储层微观特征测试方法,需要综合多方法各自优势进行孔喉分布定量表征。本文提出基于核磁共振标定的高压压汞孔喉分布定量评价的方法,即通过核磁共振离心前后横向弛豫时间T_2谱图对比,依据流体赋存状态重新划分三孔隙度组分百分比法的T_2值界限T_(21)和T_(22),对应将孔喉划分为束缚流体孔喉、过渡流体孔喉和可动流体孔喉,再结合T_2值与孔喉半径的关系将T_2值界限转化为孔喉半径界限r_1和r_2,最终依据高压压汞统计的不同流体赋存状态的孔喉含量S_1、S_2和S_3进行孔喉分布定量评价。该方法综合了核磁共振有效表征孔喉流体赋存状态和高压压汞有效表征孔喉大小的优势。将此方法应用于西湖凹陷花港组低渗-致密砂岩储层孔喉分布评价,建立了T_2值与孔喉半径平均转化系数C为0.0079,求取r_1和r_2为60 nm和160 nm,依据各类孔喉含量及其相互关系将孔喉分布划分为四类,从而为储层评价提供新的参数和思路。 相似文献
8.
为了探究构造煤的孔隙结构及压敏效应,采取淮北许疃矿煤样,利用扫描电子显微镜、压汞实验、含瓦斯煤热流固耦合三轴伺服渗流装置进行相关参数测试,研究构造煤的孔隙结构以及有效应力对煤样渗透率渗透系数的影响。实验结果表明:碎裂结构煤裂隙规则、平直,连通性较好;原生结构煤中主要以微孔为主,构造煤中以微孔和过渡孔占主导。韧性变形系列构造煤的有效应力与渗透率呈抛物线关系;有效应力小于4 MPa时,煤体渗透率敏感性显著,大于4 MPa时其渗透率敏感性弱。该趋势是有效应力和解吸效应共同作用的结果;由于解吸和有效围压的共同作用,渗透率存在最小值。与沁水盆地相比,许疃矿煤样部分渗透率损害系数较高。 相似文献
9.
Y. Y. Huyan T. S. Liu F. J. Jiang X. Z. Chen X. Q. Ma 《Australian Journal of Earth Sciences》2018,65(6):863-875
Residual and movable porosity are significant parameters for characterising petrophysical properties, especially in tight reservoirs. Eight tight sandstone samples from the upper Paleozoic gas-bearing strata in the Kangning area, from the eastern margin of the Ordos Basin, were analysed using nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), petrography, and porosity and permeability tests. The lithology and pore types were identified and classified using petrography and SEM. The residual and movable porosity were obtained with NMR. In addition, NMR was used to visualise pore structure and pore size distribution. The results suggest that the upper Paleozoic sandstones in the study area mainly comprise feldspathic litharenite and litharenite. The sandstone porosity and permeability are low, with means of 5.9% and 0.549 mD, respectively. Four pore types exist in the tight sandstones: residual primary pores, grain dissolution pores, micropores (clay-dominated) and microfractures. The T2 spectra under water-saturated conditions correlate with pore size and can be used to distinguish small and large pores based on the transverse relaxation time cutoff value of 10 ms, which corresponds to a pore diameter of 0.232 μm. Small pores account for 72% of the pores in the tight sandstones. The continuous bimodal T2 spectra suggest good connectivity between small and large pores, despite the low porosity and permeability. In this study, the movable porosity of the major tight sandstone gas reservoirs is higher than the residual porosity, which confirms the effective evaluation of movable porosity to tight sandstone reservoirs, based on NMR experiments. 相似文献
10.
煤层气储层孔隙结构特征决定着煤层的吸附能力。利用低温氮吸附法和汞侵入法对鄂尔多斯盆地东部地区煤样的孔隙特征进行测试,并分别对煤样的低温氮吸附孔隙特征和汞侵入孔隙特征进行分析。在此基础上,综合两种实验的测试结果,对煤样的孔隙类型进行分类。压汞实验表明:压汞曲线和退汞曲线相似性较好,两者之间的间距很小,退汞效率达65%~75%;液氮实验表明:低变质煤孔以一端封闭的孔为主,随着煤变质程度的增加,先是较大的孔变为两端开放的孔,接着较小孔变为两端开放的孔,到了无烟煤阶段微孔也变成以两端开放的孔为主。综合两种结果,认为煤样的孔隙中以微孔和过渡孔为主,并且微孔和过渡孔是构成煤样孔隙容积的主要贡献者,大孔和中孔的总孔容所占比例较小。鄂尔多斯盆地东部煤岩的孔隙特征有利于煤层中气体的吸附,是煤层气储层的良好场所。 相似文献
11.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》2000,25(2):169-174
A simple cutoff approach based on the capillary bundle model has become an industrial standard method to quickly obtain the irreducible water saturation from NMR T2 distribution. However this approach is not always valid. To overcome the shortcoming of the capillary bundle model that ignores pore-pore connectivity, we have conducted a two-phase flow simulation in a CT-based pore network. The CT -based pore network is a representation of a real rock pore structure that is described by a binary X-ray tomographic data set. Simulation on such network mimics a process of the porous plate measurement. The generated capillary curve is quite reasonable. The oil accession distributions at different water saturations plotted as a function of pore size provide an insight for the immiscible displacement process in the real rock pore structure. Water is trapped not only in dead ends but also in the well-connected pores due to a pore level by-pass mechanism. At the capillary end point pressure, a plot of the trapped water distribution as a function of pore size has the same lognormal distribution as the pore size distribution, which is much different from what the simple capillary bundle model suggests. 相似文献
12.
为了研究高煤级煤储层含水性对吸附能力的影响,对阳泉-寿阳区块8件代表性煤样开展了镜质体反射率、显微组分、孔隙度、压汞、核磁共振和甲烷等温吸附等实验,分析了煤储层孔径分布、核磁共振T2谱响应特征、核磁孔隙度以及煤岩吸附能力,同时对煤储层含水性和煤储层吸附能力的相互关系进行了分析。研究结果表明：高煤级煤储层孔隙以微孔发育为主,孔隙含水性以微小孔中的束缚水赋存状态为主,且其含水量随最大镜质体反射率(Ro,m)的增大而增加。在影响高煤级煤储层吸附能力的多种因素中,煤储层含水性对煤岩吸附能力起着决定性的作用,尤其体现在微小孔中的束缚水对吸附能力的影响,束缚水含量越高,煤岩吸附能力越差。 相似文献
13.
模拟裂隙多孔介质中变饱和渗流的广义等效连续体方法 总被引：2，自引：0，他引：2
描述了一种计算裂隙多孔介质中变饱和渗流的广义等效连续体方法。这种方法忽略裂隙的毛细作用,设定一个与某孔隙饱和度相对应的综合饱和度极限值,并假定：（1）如果裂隙多孔介质的综合饱和度小于该极限值,水只在孔隙中存在并流动,而裂隙中则没有水的流动;（2）如果综合饱和度等于或大于该极限值,水将进入裂隙,并在裂隙内运动。分析比较了等效连续体模型的不同计算方法,并给出了一个模拟裂隙岩体中变饱和渗流与传热耦合问题的应用算例。结果表明,所述方法具有一般性,可以有效地模拟裂隙多孔介质中变饱和渗流的基本特征。 相似文献
14.
An analytical solution to 1D coupled water infiltration and deformation in layered soils is derived using a Laplace transformation. Coupling between seepage and deformation, and initial conditions defined by arbitrary continuous pore‐water pressure distributions are considered. The analytical solutions describe the transient pore‐water pressure distributions during 1D, vertical infiltration toward the water table through two‐layer unsaturated soils. The nonlinear coupled formulations are first linearized and transformed into a form that is solvable using a Laplace transformation. The solutions provide a reliable means of comparing the accuracy of various numerical methods. Parameters considered in the coupled analysis include the saturated permeability (ks), desaturation coefficient (α), and saturated volumetric water content (θs) of each soil layer, and antecedent and subsequent rainfall infiltration rates. The analytical solution demonstrates that the coupling of seepage and deformation plays an important role in water infiltration in layered unsaturated soils. A smaller value of α or a smaller absolute value of the elastic modulus of the soil with respect to a change in soil suction (H) for layered unsaturated soils means more marked coupling effect. A smaller absolute value of H of the upper layer soil also tends to cause more marked coupling effect. A large difference between the saturated coefficients of permeability for the top and bottom soil layers leads to reduced rainfall infiltration into the deep soil layer. The initial conditions also play a significant role in the pore‐water pressure redistribution and coupling effect. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
15.
川东南地区龙马溪组页岩孔隙结构全孔径表征及其对含气性的控制 总被引：4，自引：0，他引：4
页岩气主要赋存于页岩孔隙中,研究页岩孔隙结构特征是深入认识页岩气富集机理的关键。通过CO2吸附、N2吸附、CH4等温吸附和高压压汞实验,对川东南地区龙马溪组页岩的孔隙结构进行了全孔径表征,并阐明了孔隙结构对页岩含气性的控制作用。页岩的微孔(＜2.0 nm)、中孔(2.0~50.0 nm)和宏孔(＞50.0 nm)都十分发育,且分布特征变化较大。在孔体积方面,中孔提供的孔体积最多,约40.8%,其次是微孔,约34.7%,宏孔的孔体积最少,只提供24.5%。在孔隙比表面积方面,微孔占有绝对优势,约提供76.87%,其次是中孔,约23.05%,宏孔只有0.07%。中孔和微孔提供了页岩中主要的孔体积,控制了游离气的含量。微孔的比表面积与CH4最大吸附量具有很好的正相关关系,且提供了页岩中主要的比表面积,控制了吸附气的含量。宏孔提供的孔体积和比表面积在页岩中不占优势,对吸附气和游离气含量的影响较弱,但可作为页岩气渗流的主要运移通道。因此,明确页岩的微孔、中孔和宏孔的分布特征,尤其是微孔对页岩中吸附气和游离气富集的贡献,对页岩气勘探与开发具有重要指导意义。 相似文献
16.
海拉尔盆地碎屑岩储层束缚水饱和度的确定 总被引：4，自引：0，他引：4
核磁测井资料确定束缚水饱和度主要是采用T2固定截止值法.随着对复杂岩性储层的勘探,近年来,在固定T2截止值方法基础上又发展了锥形T2截止值法、薄膜模型以及频谱模型.对于岩性多变、孔隙结构复杂的碎屑岩储层,常规测井方法和以T2截止值为基础的核磁测井方法确定的束缚水饱和度都难以满足测井评价的精度要求,这时需要考虑薄膜模型和频谱模型方法.这两种模型认为各种尺寸的孔隙中均含有束缚水,只是不同尺寸孔隙束缚水含量不一样.在对海拉尔盆地岩性多变、孔隙结构复杂的碎屑岩储层的实践中,对回波串数据作多指数反演拟合时采用了2的幂次方方式布点,相应地得到了核磁测井T2谱,并从中选取了9个孔隙组分,将其与反映粘土含量的中子-密度孔隙度差值结合,采用回归的方法得到了束缚水饱和度的计算公式.回归公式在海拉尔盆地取得了较好的应用效果,尤其是贝尔凹陷,预测效果提高了将近1倍,计算的束缚水饱和度与岩心分析束缚水饱和度相比,平均相对误差从15.1%减小到8.7%. 相似文献
17.
As the two important components of shale, organic matter(OM) and clay minerals are usually thought to strongly influence the hydrocarbon generation, enrichment and exploitation. The evolution process of OM and clay minerals as well as their interrelationship over a wide range of thermal maturities are not completely clear. Taking Yanchang(T_3y), Longmaxi(S_1l) and Niutitang(?_1n) shales as examples, we have studied the microstructure characteristics of OM and clay minerals in shales with different thermal maturities. The effects of clay minerals and OM on pores were reinforced through sedimentation experiments. Using a combination of field emission scanning electron microscopy(FESEM) and low-pressure N_2 adsorption, we investigated the microstructure differences among the three shales. The results showed that both OM and clay minerals have strong effects on pores, and small mesopore(2–20 nm) is the dominant pore component for all three samples. However, the differences between the three samples are embodied in the distribution of pore size and the location. For the T_3y shale, clay minerals are loosely arranged and develop large amounts of pores, and fine OM grains often fill in intergranular minerals or fractures. Widespread OM pores distribute irregularly in S_1l shale, and most of the pores are elliptical and nondirectional. The ?_1n shale is characterized by the preferred orientational OM-clay aggregates, and lots of pores in the composites are in the mesopore range, suggesting that over maturity lead to the collapse and compaction of pores under huge pressure of strata. The results of the current research imply that with increasing thermal maturity, OM pores are absent at low maturity(T_3y), are maximized at high maturity(S_1l) and are destroyed or compacted at over-mature stage(?_1n). Meanwhile, clay minerals have gone through mineral transformation and orientational evolution. The interaction of the two processes makes a significant difference to the microstructure evolution of OM and clay minerals in shale, and the findings provide scientific foundation in better understanding diagenetic evolution and hydrocarbon generation of shale. 相似文献
18.
为了有效指导储层描述、评价及产能预测,为致密砂岩油气勘探和开发提供理论依据,以鄂尔多斯盆地临兴地区致密砂岩储层为例,利用铸体薄片、X射线衍射、核磁共振、高压压汞、气水相渗及扫描电镜等实验,分析了致密砂岩中束缚水饱和度的影响因素.结果表明:研究区致密砂岩束缚水饱和度为３４．７７％~８３．７８％,平均值为６３．８６％,T２谱截止值(T２cutoff)为３．８６~６５．６０ms,平均值为２０．９６ms;致密砂岩束缚水饱和度受储层物性、润湿性、敏感性、黏土矿物类型、质量分数和粒径共同作用;致密砂岩粒径越细,黏土矿物质量分数越高,岩石亲水性越强,岩石比表面积和水膜厚度越大,则毛细管束缚水和薄膜束缚水越高;水敏和盐敏是造成致密储层渗透率改变的主要因素;致密砂岩发育残余粒间孔、粒间溶蚀孔、粒内溶蚀孔、晶间孔和微裂缝;充填于孔隙中黏土矿物的类型、形态存在差异,致使致密砂岩储层的孔隙结构复杂,微观非均质性强,束缚水饱和度变化大. 相似文献
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海陆过渡相富有机质泥页岩是页岩气勘查开发的重要领域。本文以西昌盆地上三叠统白果湾组富有机质泥页岩为研究对象,对研究区内富有机质泥页岩的沉积岩相古地理特征、微观孔隙类型、孔隙结构特征进行研究。白果湾组富有机质泥页岩段沉积相主要为湖泊相、三角洲相、河流相。发育不同类型的微孔隙,孔隙主要以小孔为主,微孔次之,平均孔径分布在5.56~56.89nm之间,比表面积平均为9.44m2/g,总孔体积平均为0.0187cm3/g。页岩气主要形成于滨浅湖亚相及半深湖亚相中,并主要吸附于富有机质泥页岩的小孔、微孔内;西昌盆地白果湾组富有机质泥页岩储集空间较好,具有良好的勘探潜力。 相似文献