›› 2019, Vol. 40 ›› Issue (6): 1-1.doi: 10.7657/XJPG20190603

• 论文 •    

库车坳陷东部下侏罗统煤系地层碎屑岩中长石溶蚀对储集层物性的影响

伍劲,王波,朱超,宫清顺,宋光永,王慧   

  1. (中国石油 杭州地质研究院,杭州 310023)
  • 出版日期:2019-12-01 发布日期:2019-12-01

Influences of Feldspar Dissolution on Reservoir Physical Properties of Clastics in the Lower Jurassic Coal Measures, Eastern Kuqa Depression

WU Jin, WANG Bo, ZHU Chao, GONG Qingshun, SONG Guangyong, WANG Hui   

  1. (Hangzhou Research Institute of Geology, PetroChina, Hangzhou, Zhejiang 310023, China)
  • Online:2019-12-01 Published:2019-12-01

摘要: 库车坳陷东部下侏罗统煤系地层中酸性流体对长石的溶蚀作用普遍存在,薄片显示长石和岩屑颗粒中发育大量次生溶孔。不同的成岩作用条件下,长石溶蚀作用强弱、长石溶蚀产物类型和长石溶蚀产物量不同,对储集层物性影响具有差异性。以普通薄片、铸体薄片和扫描电镜资料为基础,利用全岩分析、黏土矿物分析和流体包裹体数据,分析了储集层中长石溶蚀作用、溶蚀成岩环境和不同成岩环境中长石溶蚀产物差异性及对储集层物性的影响。研究表明,库车坳陷东部迪北地区下侏罗统储集层中,长石溶蚀作用发生在相对封闭的高温成岩环境中,高温条件下长石溶蚀速率大,而封闭成岩环境中流体流动速度慢,因此,长石溶蚀产物就近大量沉淀于粒间孔隙和粒内孔隙中。当埋深小于4 000 m(温度小于110 ℃)时,长石溶蚀产物主要是硅质和高岭石,高岭石呈分散质点式分布,未把孔隙充填满,晶间孔发育且连通性好,一定程度上改善了储集层的物性;当埋深大于4 000 m(温度大于110 ℃)时,长石溶蚀产物主要是硅质和伊利石,毛发状和片状的伊利石以孔隙搭桥式把砂岩孔隙充满,基本未剩下孔隙空间,且易形成碎片堵塞孔喉,降低了储集层的孔隙度和渗透率。吐格尔明地区下侏罗统储集层长石溶蚀发生在相对开放且埋藏较浅的成岩环境中,长石溶蚀产物能被有效带出溶蚀区,仅沉淀少量硅质和高岭石,长石溶蚀对储集层的增孔作用明显好于迪北地区,为有利的溶蚀成岩区。

Abstract: The dissolution of acid fluids to feldspar is commonly found in the Lower Jurassic coal measures in the eastern Kuqa depression and the thin section analysis shows that a large number of secondary dissolution pores are developed in feldspar and rock debris. Under different diagenesis conditions, feldspar dissolution degree, feldspar dissolution product type and feldspar dissolution product quantity are different, which result in different effects on reservoir physical properties. Based on the analysis of thin section, cast thin section and scanning electron microscope and using whole rock analysis, clay mineral analysis and fluid inclusion data, the paper analyzes feldspar dissolution, diagenetic environment, the differences of feldspar dissolution products and their effects on reservoir physical properties in different diagenetic environments. The study shows that in the Lower Jurassic reservoirs in the Dibei area of the eastern Kuqa depression, the dissolution of feldspar occurs in a relatively closed high-temperature diagenetic environment, the dissolution rate of feldspar is high under high temperature conditions, and fluids flow slowly in this closed diagenetic environment. Therefore, a large amount of feldspar dissolution products precipitate in the intergranular and intragranular pores nearby. When the burial depth is less than 4 000 m (the temperature is less than 110 °C), the products of feldspar dissolution are mainly silica and kaolinite, the kaolinite is dispersed like dots and the pores are not filled. The intercrystalline pores are developed and have good connectivity so that to some extent, the physical properties of the reservoir are improved. When the burial depth is more than 4 000 m (the temperature is higher than 110 °C), the feldspar dissolution products are mainly silica and illite, the hairy and flaky illite fills the pores in sandstone, leaving no pore spaces, and it is easy to form debris to block the pores, which reduces the porosity and permeability of the reservoir. The dissolution of feldspar in the Lower Jurassic reservoirs in the Tugerming area occurs in a relatively open and shallow diagenetic environment, the products of feldspar dissolution can be effectively brought out of the dissolution zone, and only a small amount of silica and kaolinite precipitate. The feldspar dissolution in this area has an effective pore-enhancing effect on the reservoir

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