首页|鄂尔多斯盆地长7段重力流砂岩长石溶蚀特征及控制因素

鄂尔多斯盆地长7段重力流砂岩长石溶蚀特征及控制因素

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基于岩心薄片、扫描电镜、能谱分析、X射线衍射全岩分析及溶蚀实验,研究鄂尔多斯盆地三叠系延长组7段(简称长7段)重力流砂岩中长石溶孔发育特征及控制因素,明确长石溶孔的形成与分布,为预测优质储集层分布提供依据.研究表明:①研究区长7段砂岩中的长石经历3类成岩作用:长石次生加大、黏土以及方解石的交代、长石碎屑的溶蚀作用.②长7段致密砂岩中的长石溶蚀主要源于有机酸溶蚀,此外还受长石类型、长石早期蚀变程度以及砂岩中云母碎屑对有机酸的缓冲作用影响.③不同长石的溶蚀程度不同,表现为钾长石较斜长石易溶蚀,钾长石中正长石较微斜长石易溶,未蚀变的长石较早期高岭土或绢云母化的长石易溶蚀.④溶蚀实验显示云母的存在会抑制长石溶蚀,相同质量的云母对有机酸的消耗能力明显强于长石.⑤在云母含量低的情况下,长7段砂岩长石溶孔较为发育,储集层物性得以改善,而云母含量较高的地区长石溶孔则明显减少.
Characteristics and control factors of feldspar dissolution in gravity flow sandstone of Chang 7 Member,Triassic Yanchang Formation,Ordos Basin,NW China
To clarify the formation and distribution of feldspar dissolution pores and predict the distribution of high-quality reservoir in gravity flow sandstone of the 7th member of Triassic Yanchang Formation(Chang 7 Member)in the Ordos Basin,thin sections,scanning electron microscopy,energy spectrum analysis,X-ray diffraction whole rock analysis,and dissolution experiments are employed in this study to investigate the growth characteristics and control factors of feldspar dissolution pores.The results show that:(1)Three types of diagenetic processes are observed in the feldspar of Chang 7 sandstone in the study area:secondary overgrowth of feldspar,replacement by clay and calcite,and dissolution of detrital feldspar.(2)The feldspar dissolution of Chang 7 tight sandstone is caused by organic acid,and is further affected by the type of feldspar,the degree of early feldspar alteration,and the buffering effect of mica debris on organic acid.(3)Feldspars have varying degrees of dissolution.Potassium feldspar is more susceptible to dissolution than plagioclase.Among potassium feldspar,orthoclase is more soluble than microcline,and unaltered feldspar is more soluble than early kaolinized or sericitized feldspar.(4)The dissolution experiment demonstrated that the presence of mica can hinder the dissolution of feldspar.Mica of the same mass has a significantly stronger capacity to consume organic acids than feldspar.(5)Dissolution pores in feldspar of Chang 7 Member are more abundant in areas with low mica content,and they improve the reservoir physical properties,while in areas with high mica content,the number of feldspar dissolution pores decreases significantly.

gravity flow sandstonedifferential feldspar dissolutionmica-feldspar dissolution experimentChang 7 Member of Triassic Yanchang FormationOrdos Basin

祝海华、张秋霞、董国栋、商斐、张釜源、赵晓明、张喜

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西南石油大学地球科学与技术学院,成都 610500

中国石油长庆油田公司勘探开发研究院,西安 710018

中国石油勘探开发研究院,北京 100083

重力流砂岩 长石差异溶蚀 云母-长石溶蚀实验 三叠系延长组长7段 鄂尔多斯盆地

国家自然科学基金中国石油-西南石油大学创新联合体科技合作项目

422021762020CX050103

2024

10.11698/PED.20230428

石油勘探与开发
中国石油天然气股份有限公司勘探开发研究院 中国石油集团科学技术研究院

石油勘探与开发

CSTPCD北大核心
影响因子：4.977
ISSN：1000-0747
年,卷(期)：2024.51(1)
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