威远地区寒武系页岩储层特征及选区评价方法研究

发布时间：2018-09-17 15:11

【摘要】：随着能源供需矛盾的日益突出,油气勘探开发领域逐渐向着煤层气、页岩气等非常规油气方向发展。四川盆地长宁-威远地区发育下寒武统筇竹寺组和下志留统龙马溪组两套优质的海相烃源岩。最近几年来,在中石油长宁-威远区块针对页岩气的多个探井连续获得工业性气流,展现出了盆地南部下古生界页岩气巨大的勘探前景,而其中寒武系页岩勘探情况较低,具有进一步的勘探潜力。本论文以“威远地区寒武系页岩储层特征及选区评价方法研究”为题,采用有机地球化学、沉积学、以及储层特征研究等理论方法对威远地区寒武系页岩储层特征进行系统研究,建立页岩气勘探选区评价指标体系提出了选区评价的三种方法。通过岩心观察和测井资料综合分析,威远地区寒武系筇竹寺组发育浅海泥质深水陆棚。页岩沉积稳定,单层厚度大且分布广。筇竹寺组岩心分析:有机碳含量分布范围为1.65%~2.85%,其平均有机碳含量较高,为2.15%,属于较好烃源岩,同时也达到了有效页岩有机碳丰度下限。筇竹寺组页岩沥青折算镜质体反射率Ro在2.2%~4.4%之间,大部分地区分布在3.2%~4.4%之间。页岩的有机质热演化程度处于过成熟阶段,在平面上变化特征表现为西北低,东南高,在乐山-井研-威远一带的成熟度相对较低,Ro在2.2%~2.6%之间,东南部的宜宾地区Ro高达3.2%~4.4%。筇竹寺组页岩有机质来源于水生低等生物,干酪根碳同位素组成特征表现为Ⅰ型及Ⅱ1型。通过页岩氩离子抛光薄片环境扫描观察,页岩受到强烈压实作用和热演化作用影响,孔隙类型以无机孔为主,有机孔为辅,局部发育微裂缝。筇竹寺组页孔隙度平均2.85%,孔径主要为0.0366~0.1465um。页岩脆性矿物含量均较高,一般超过40%,有利于后期压裂改造。测、录井显示其含气性较好,而页岩气井均为工业气流,游离气和吸附气并存,微裂缝为其主要渗流通道。页岩气分布主要受页岩展布控制,具有大面积连续成藏的特征。由于页岩生烃、储集以及保存条件的差异,大面积连续分布范围内的不同地区或区块,页岩气富集程度也有所差异。针对盆地中南部海相页岩气在勘探起步阶段的地质资料情况,从页岩气成藏主控因素出发,建立页岩气勘探选区评价指标及其评价标准,提出页岩气勘探有利区块优选的综合评价方法。页岩气选区评价结果的可靠性,不仅取决于页岩有机碳含量、孔隙度以及脆性矿物含量等多种参数的认识程度,评价指标取值和指标权重的合理性也对页岩气选区评价具有重要影响,勘探有利区选择取决于页岩的生气、储气、保存及开采条件。页岩气选区评价的常规方法,如评分法等,虽然原理简单,应用方便,但是具有评价指标变化范围与评分标准之间的均质性以及评价等级之间具有突变性等显著缺点。针对页岩气选区评价诸多因素的不确定性和特殊复杂性,采用模糊相似理论计算评价区块指标值与有利区、较有利区或不利区指标值的相似程度系数。实例计算表明,模糊相似评价法克服了常规方法的不足之处,计算过程的操作性强,能够提高页岩气选区评价结果的可靠性。
[Abstract]:With the increasingly prominent contradiction between energy supply and demand, the field of oil and gas exploration and development is gradually developing towards unconventional oil and gas, such as coal-bed methane and shale gas. Several exploration wells of shale gas have continuously obtained industrial gas flow, which shows great exploration prospects of Lower Paleozoic shale gas in the southern part of the basin. The exploration situation of middle Cambrian shale is low and has further exploration potential. The characteristics of Cambrian shale reservoirs in Weiyuan area are systematically studied by the methods of geochemistry, sedimentology and reservoir characteristics study. Three methods for evaluation of shale gas exploration area selection are put forward by establishing evaluation index system. Through core observation and comprehensive analysis of logging data, shallow-sea mudstone is developed in the Cambrian Qiongzhusi Formation in Weiyuan area. Deep water shelf. Shale deposits are stable, single layer thick and widely distributed. Core analysis of the Qiongzhusi Formation shows that the organic carbon content ranges from 1.65% to 2.85%, and the average organic carbon content is 2.15%. It belongs to better source rocks and reaches the lower limit of organic carbon abundance of effective shale. The organic matter thermal evolution degree of the shale is in the overmature stage, which is low in the northwest and high in the southeast. The maturity in Leshan-Jingyan-Weiyuan area is relatively low, Ro is between 2.2% and 2.6%, and Ro is up to 3.2%-4.4% in Yibin area in the southeast. Carbon isotope compositions of kerogen are characterized by type I and type II 1. The argon ion polished shale slices show that the shale is strongly compacted and thermally evolved. The pore types are mainly inorganic pore, supplemented by organic pore, and micro-cracks are locally developed. The content of brittle minerals in shale is higher than 40%, which is favorable for later fracturing. Logging shows that the gas-bearing property is better, while the shale gas wells are industrial gas, free gas and adsorbed gas coexist, and micro-fractures are the main percolation channels. Because of the difference of shale hydrocarbon generation, reservoir and preservation conditions, the enrichment degree of shale gas varies in different areas or blocks in the large area of continuous distribution. The evaluation index and criteria of shale gas exploration area selection are put forward. The reliability of the evaluation results of shale gas exploration area selection depends not only on the understanding of shale organic carbon content, porosity and brittle mineral content, but also on the rationality of evaluation index value and index weight. The selection of favorable exploration areas depends on shale gas generation, gas storage, preservation and production conditions. Although the conventional methods of shale gas selection evaluation, such as scoring method, are simple in principle and convenient in application, they have the homogeneity between the range of evaluation indexes and the scoring criteria and the evaluation grades. In view of the uncertainty and special complexity of many factors in shale gas selection evaluation, the similarity coefficient between the index values of evaluation blocks and those of favorable areas, favorable areas and unfavorable areas is calculated by using fuzzy similarity theory. The computational process is highly operational and can improve the reliability of the results of shale gas evaluation.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.13

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