Reservoir characteristics of thick sandstone and micro-anisotropy of delta front micro-facies:A case study of Chang 6 reservoir in Wucangbu area
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摘要:
依据薄片、压汞、扫描电镜、物性分析及油水驱替实验资料, 对吴仓堡地区三角洲前缘亚相长6厚层砂岩储层的岩石学特征、孔渗特征、孔隙结构特征、成岩作用、微观渗流特征等进行深入研究, 分析影响储层储集性能的主控因素。结果表明, 受东北物源控制的长6厚层砂岩储层具有成分成熟度中等、结构成熟度较好的特点, 储集空间主要为残余粒间孔和粒间溶孔、粒内溶孔, 为典型中低孔、特低渗储集层; 储层储集性能主要受沉积微相和成岩作用控制。对储层发育影响最大的成岩期位于中成岩A期, 中等压实-粘土膜胶结残余粒间孔发育成岩相和弱压实-残余粒间孔+溶蚀孔隙发育成岩相是最有利储层发育的成岩相带。根据微观渗流特征, 可划分出4种驱油类型, 微观孔隙结构比宏观物性更能反映储层的本质特征。
Abstract:Based on data obtained from cast slice, mercury injection test, SEM, physical properties, and oil/water micro-displacement experiment, the authors made a thorough study of the petrological characteristics, porosity and permeability characteristics, pore structure characteristics, diagenesis and micro-anisotropy of Chang 6 reservoir in Wucangbu area, and analyzed the main influ-encing factors. The results show that the sedimentary environment of the Chang 6 thick sandstones reservoir is a delta front derived from the provenance in the northeast. In addition, the reservoir is characterized by medium compositional maturity and high textual maturity. The reservoir space includes residual intergranular pores, intergranular emposieu and intragranular emposieu. The sedimentary micro-facies and diagenesis constitute the main factors controlling the reservoir properties. The diagenetic period affecting reservoir development is stage A of middle diagenesis. The middle compaction, clay film cementation, residual intergranular pore diagenesis facies with weaker compaction and the secondary dissolution pore diagenesis facies are favorable diagenetic facies belts for reservoir development. Four oil displacement types are distinguished by studying reservoir microscopic heterogeneity, and the microscopic pore structures can more really reflect the reservoir's essential characteristics than the macroscopically physical properties.
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致谢: 长庆油田分公司勘探开发研究与低渗透油气田勘探开发国家工程实验室提供了大量基础资料和分析化验数据,在此表示感谢。
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表 1 吴仓堡长6段不同孔隙类型对面孔率的贡献值
Table 1 The contribution of pore types to surface porosity in Chang 6 reservoir of Wucangbu area
残余粒间孔隙/% 溶蚀粒间孔隙/% 溶蚀粒内孔隙/% 自生矿物晶间微孔隙/% 微裂隙
/%长石溶孔 岩屑溶孔 沸石溶孔 杂基溶孔 铸模孔 71.68 1.8 16.3 5.9 1.4 0.64 0.33 1.26 0.66 表 2 吴仓堡地区长6储层物性与孔喉特征分类
Table 2 Statistics of physical properties and pore-throat characteristics of Chang 6 reservoir in Wucangbu area
级別 物性特征 孔隙类型 孔隙喉道参数 孔隙度/% 渗透率/10-3pm2 门槛压力/MPa 喉道中值半径/μm 分选系数/Sp Ⅰ类
(好)> 12 > 1.0 混合孔隙型
(残余粒间孔+溶蚀孔)< 0.5 > 0.2 < 2.5 Ⅱ类
(中等)9 〜 12 0.3 〜 1.0 残余孔隙型
(残余粒间孔为主)0.5 〜 1.5 0.2 〜 0.05 2.5 〜 3 Ⅲ类
(差)< 9 < 0.3 致密孔隙型
(少量残余粒间孔、晶间微孔)> 0.5 < 0.05 > 3.0 表 3 吴仓堡地区长6段不同沉积微相砂体物性统计
Table 3 Porosity and permeability statistics for different sedimentary microfacies sandbodies of Chang 6 reservoir in Wucangbu area
沉积微相类型 孔隙度/% 渗透率/10-3pm2 样品数/个 分布范围 平均值 分布范围 平均值 水下分流河道 9.6〜15.6 12.3 0.18〜3.46 1.32 213 河口坝 7.1〜13.2 11.5 0.15〜2.78 0.85 89 远砂坝 5.9〜12.4 10.2 0.12〜0.91 0.39 73 分流间湾 2.7〜11.1 8.5 0.04〜0.34 0.12 25 -
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