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Fracability characterizes the effectiveness of hydraulic fracturing. The existing assessment methods cannot reflect the actual value of the effectiveness due to a lack of comprehensive consideration and neglect of the influences of engineering factors. This study aims to solve this problem by implementing geological static data and production dynamic data in multivariate analysis in Zhaotong shale gas demonstration zone. First, the reservoir quality index (RQI) was introduced to evaluate the exploration potential by integrating the geological parameters with gray relational analysis. Moreover, the differences in fracturing fluid types and proppant sizes were considered, and the operating parameters were normalized on the basis of the equivalence principle. Finally, the general reservoir fracability index (GRFI) was proposed based on a dimensioned processing of the various parameters. A case study was conducted to verify the accuracy and feasibility of this new approach. The results demonstrate that (1) the organic carbon and gas content are adjusted to contribute the most to the calculation of the RQI, while the effective porosity contributes the least; (2) the fracturing scale is the main operating parameter determining the fracability, which has the strongest correlation with the effectiveness of fracking; and (3) the GRFI has a positive correlation with shale gas production, and the lower limit of the GRFI of 2,000 corresponds to a daily production of 50,000 m3/d; this value is defined as the threshold value of a stripper well. The GRFI is consistent with the productivity trend of shale gas wells in the research block, which suggests that the new model is accurate and practical for well candidate selection. 相似文献
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随着常规油气资源的不断开发,其存量资源越来越少。美国非常规油气资源的开发成功,为页岩气勘探开发奠定了技术基础。储层改造技术是决定页岩气开发成败的两大关键技术之一。而页岩气储层的脆性指数是评价页岩气储层可改造（可压裂）的关键指标。本文对国内外的页岩气储层脆性评价方法进行了广泛深入的研究,总结了岩石脆性的各种力学表征方法以及矿物成分对岩石脆性的影响,为我国页岩气储层脆性评价方法的研究提供了基础性参考资料。 相似文献
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可压裂性是页岩在水力压裂中具有能够被有效压裂的能力的性质,是页岩开发中最关键的评价参数,影响因素包括页岩脆性、天然裂缝、石英含量、成岩作用及其他因素,目前常利用页岩矿物组成或岩石力学参数来表征,难以全面反映页岩在水力压裂过程中的综合性质。采用极差变换和经验赋值方法将参数标准化,使用层次分析法确定不同因数对可压裂性影响的权重,使用标准化值与权重系数加权得到可压裂系数的数学模型可对页岩可压裂性进行定量评价。可压裂系数越大,页岩可压裂性越强。采用该模型计算渝东南地区渝页1井龙马溪组页岩可压裂系数为0.485 5,Barnett页岩可压裂系数为0.484 4,总体处于同一水平;同时,使用该模型将页岩可压裂性分为3个级别,可压裂系数在0.132 0~0.282 0的页岩可压裂性低,水力压裂效果不佳;可压裂系数在0.282 0~0.456 7的页岩可压裂性中等,水力压裂能够取得较好的效果;可压裂系数在0.456 7~0.784 0的页岩可压裂性高,是优质的可压裂层。水力压裂应选择可压裂系数大于0.360 7的页岩。 相似文献
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WANG Ruyue HU Zongquan LONG Shengxiang LIU Guangxiang ZHAO Jianhu DONG Li DU Wei WANG Pengwei YIN Shuai 《《地质学报》英文版》2019,93(3):520-535
The Upper Ordovician Wufeng-Lower Silurian Longmaxi shale is widely distributed in the Sichuan Basin and its periphery, which is the key stratum for marine shale gas exploration and development(ED) in China. Based on sedimentary environment, material basis, storage space, fracability and reservoir evolution data, the reservoir characteristics of the Wufeng-Longmaxi shale and their significance for shale gas ED are systematically compared and analyzed in this paper. The results show that(1) the depocenter of the Wufeng(WF)-Longmaxi(LM) shale gradually migrates from east to west. The high-quality shale reservoirs in the eastern Sichuan Basin are mainly siliceous shales, which are primarily distributed in the graptolite shale interval of WF2-LM5. The high-quality reservoirs in the southern Sichuan Basin are mainly calcareous-siliceous and organic-rich argillaceous shales, which are distributed in the graptolite shale interval of WF2-LM7.(2) Deep shale gas(the burial depth 3500 m) in the Sichuan Basin has high-ultrahigh pressure and superior physical properties. The organic-rich siliceous, calcareous-siliceous and organic-rich argillaceous shales have suitable reservoir properties. The marginal area of the Sichuan Basin has a higher degree of pressure relief, which leads to the argillaceous and silty shales evolving into direct cap rocks with poor reservoir/good sealing capacity.(3) Combining shale gas exploration practices and impacts of lithofacies, depth, pressure coefficient and brittle-ductile transition on the reservoir properties, it is concluded that the favorable depth interval of the Wufeng-Longmaxi shale gas is 2200～4000 m under current technical conditions.(4) Aiming at the differential reservoir properties of the Wufeng-Longmaxi shale in the Sichuan Basin and its periphery, several suggestions for future research directions and ED of shale gas are formulated. 相似文献
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为系统深入研究湘西北地区下寒武统牛蹄塘组页岩储层可压裂性,以HY1井为依托,通过密集取心采样、实验测试分析、测井综合解释等多种方法手段,系统分析了牛蹄塘组页岩储层有机地球化学特征、储集物性、裂缝发育特征、脆性矿物组成、岩石力学性质,进而探讨了牛蹄塘组富有机质页岩可压裂性。结果表明:HY1井牛蹄塘组有机碳含量高(0.25%~13.3%),富有机质页岩发育于牛蹄塘组下部,厚约65 m;富有机质页岩段构造缝密度低(0.27~1.21条/m),页理缝发育;矿物脆性指数高(17.7%~86.4%)、静态杨氏模量大(37~62 GPa)、静态泊松比较低(0.14~0.26)、两相水平压力差异系数较大(0.21~0.54)。总体上,牛蹄塘组页岩脆性好,岩石强度大,有利于压裂改造,但大量页理缝的存在增加了裂缝复杂度的同时,对压裂缝产生一定不利影响,且两相水平压力差较大,易形成双翼缝。因此,压裂设计时要综合考虑页理缝可能造成的漏失和对裂缝高度及长度延伸的影响。 相似文献
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Fracability Evaluation of Shale of the Wufeng‐Longmaxi Formation in the Changning Area,Sichuan Basin
The fracturing technology for shale gas reservoir is the key to the development of shale gas industrialization. It makes much sense to study the mechanical properties and deformation characteristics of shale, due to its close relationship with the fracability of shale gas reservoir. This paper took marine shale in the Changning area, southern Sichuan Basin of China as the research object. Based on field profile and hand specimen observation, we analyzed the development of natural fractures and collected samples from Wufeng Formation and Longmaxi Formation. Combining with the indoor experiment, we investigated the macroscopic and microscopic structural features and the remarkable heterogeneity of shale samples. Then we illustrated the mechanics and deformation characteristics of shale, through uniaxial compression test and direct shear test. The shale has two types of fracture modes, which depend on the angular relation between loading direction and the bedding plane. Besides, the Wufeng shale has a higher value of brittleness index than the Longmaxi shale, which was calculated using two methods, mechanical parameters and mineral composition. Given the above results, we proposed a fracability evaluation model for shale gas reservoir using the analytic hierarchy process. Four influence factors, brittleness index, fracture toughness, natural fractures and cohesive force, are considered. Finally, under the control of normalized value and weight coefficient of each influence factor, the calculations results indicate that the fracability index of the Wufeng Formation is higher than that of the Longmaxi Formation in Changning area, southern Sichuan Basin. 相似文献
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以四川盆地南部长宁双河剖面五峰组-龙马溪组为例,通过常规标准薄片及大薄片镜下观察、X射线衍射全岩分析、TOC及物性测试等方法,对黑色页岩纹层特征及储层物性和可压裂性进行了研究。结果表明,五峰组-龙马溪组纹层具有富硅质纹层、富钙质纹层及富黏土纹层三种类型,主要呈板状、断续、平行等几何形态,以毫米级纹层为主,富硅质纹层发育大量天然微裂缝。通过组合叠置可形成硅质-黏土纹层组合和碳酸盐-黏土纹层组合,其中硅质-黏土纹层组合物性和可压裂性均优于碳酸盐-黏土纹层组合。五峰组以碳酸盐-黏土纹层组合为主,天然裂缝整体不发育,由底至顶, TOC值逐渐增加,至观音桥段TOC值下降,物性变差;龙马溪组LM1-LM5以硅质-黏土纹层组合为主,低角度裂缝发育,由底至顶,逐渐过渡为碳酸盐-黏土纹层组合, TOC值降低,物性变差。 相似文献
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靶窗的确定对海相页岩气储层增产改造具有重要意义。以川南长宁地区龙马溪组海相页岩气储层为研究对象，开展氩离子抛光扫描电镜、巴西圆盘实验和压裂施工统计，分析矿物颗粒粒径和断裂韧性、地应力对裂缝在水力压裂时能否快速穿透、稳定扩展、充分转向等方面的影响。针对现有方法未充分考虑储层压裂品质的情况，简化计算流程，分别采用声波、密度、伽马和矿物含量等建立脆延性指标，采用优化后的应力与应力差耦合模型建立应力差异指标，形成基于储层缝网可压性理论、根据测井解释曲线形态判别的靶窗预测方法。研究结果表明，脆延性指标和应力差异指标曲线呈现叠合度较高的Ⅰ类双"波谷"的层位最有利于开发，其次为Ⅱ类连续交错叠置的层位，最后为Ⅲ类不连续交错的层位。对长宁地区评价井、建产井的验证与实践表明，靶窗对应的指标多呈现双"波谷"形态，但靶窗对应的层位具有差异，区内自西向东靶窗呈现1小层—2小层—1小层的演化趋势。实现不同井区差异化靶窗的高钻遇率对单井获得较大储层改造规模、较高的测试产量和稳定的累计产量具有重要的控制作用。 相似文献
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储层可压裂性评价是储层改造方案设计的重要依据,影响致密砂岩可压裂性的主要因素有天然裂缝、砂岩脆性、水平应力差异、断裂韧性等。研究以准噶尔盆地中部1区块Z109井侏罗系致密砂岩为例,综合考虑天然裂缝、砂岩脆性、水平应力差异、断裂韧性四种影响因素,采用改进的层次分析和熵值法相结合的方法进行了致密砂岩储层可压裂性评价。研究结果表明:可压裂性指数越大,致密砂岩储层越易于压裂,压裂时越能获得较复杂的裂缝网络;可压裂性指数大于0.44,砂岩脆性高,断裂韧性小,裂缝发育程度高,水平差异系数小的储层段为Ⅰ级优质压裂层;可压裂性指数大于0.44,砂岩脆性高,断裂韧性小,裂缝发育程度低,水平差异系数大的储层段为Ⅱ级可压裂层;研究区Z109井4036~4039 m、4062~4067 m、4214~4218 m和4260~4272 m为Ⅰ级优质压裂层,4093~4108 m和4284~4313 m为Ⅱ级可压裂层。研究成果可为致密砂岩压裂改造提供科学依据。 相似文献
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