西加拿大盆地都沃内(Duvernay)海相页岩油气富集机制研究

doi:10.13745/j.esf.sf.2023.9.36

摘要/Abstract

摘要：

西加拿大盆地上泥盆统Duvernay页岩是最大海侵期形成的一套页岩油气富集与生产层系。为明确Duvernay页岩油气富集控制因素,在Duvernay页岩地质背景分析的基础上,运用岩心、测井、薄片、扫描电镜、3D孔隙重建信息及有机地化资料,对有机质富集的沉积因素、流体分布、储层质量及影响因素进行了分析,认为Duvernay页岩油气富集主要受盆内成因的硅质页岩沉积环境、有机质热演化、页岩储层质量及稳定构造背景的共同控制。研究发现,Duvernay组为晚泥盆世的深水陆棚环境,岩性以泥灰岩、灰泥岩和泥页岩为主,可识别出10种岩石相,其中硅质页岩最为发育;Duvernay页岩中主要发育II、III型海相有机质,有机质热演化程度中等,处于凝析气-湿气阶段,因此凝析油含量高;油气主要富集在黏土级矿物形成的富含有机孔的硅质页岩中,孔隙类型以有机质孔和粒内孔为主,有效孔隙度占比高,连通孔隙非常发育且横向连续分布,并具有垂向上相互连通的特征;成岩作用改善了页岩储层物性,天然裂缝提高了页岩储层的渗透率,而稳定的构造发育特征是Duvernay页岩油能够较好地保存至今的关键。

关键词: 西加拿大盆地, Duvernay页岩, 岩石相, 有机质热演化程度, 油气富集机制

Abstract:

The Duvernay shale in the Upper Devonian is a formation of shale rich in oil and gas, created during the peak transgression period in the Western Canada Basin. This study aims to elucidate the factors influencing hydrocarbon enrichment in the Duvernay shale through the analysis of sedimentary elements, fluid distribution, reservoir quality, and drivers of organic matter enrichment. Utilizing data from cores, well logging, thin sections, scanning electron microscopy, 3D pore reconstruction, and organic geochemistry, this research examines the geological context to determine that oil and gas accumulation in the Duvernay shale is governed by the sedimentary conditions of siliceous shale, organic matter thermal maturity, reservoir quality, and stable structural settings. The Duvernay Formation, situated in a deep-water shelf environment during the Late Devonian, comprises primarily marl, mudstone, and shale lithologies. it is observed that Type II and III marine organic matters are abundant in the Duvernay shale through the identification of ten lithofacies, with siliceous shale being predominant. These organic materials exhibit moderate thermal maturity, falling within the condensate to wet gas stage, leading to a high condensate to gas ratio. Oil and gas are predominantly found in siliceous shale with organic pores created by clay-grade minerals, showcasing organic and intra-granular pore types. The shale possesses high effective porosity, with well-connected and horizontally distributed pores that display vertical connectivity characteristics. Diagenesis enhances the physical properties of the shale reservoir, while natural fractures boost permeability. Ultimately, the preservation of Duvernay shale oil is heavily dependent on a stable structural setting.

Key words: Western Canada Basin, Duvernay shale, lithofacies, thermal maturity of organic matter, hydrocarbon enrichment mechanism

中图分类号:

窦立荣, 黄文松, 孔祥文, 汪萍, 赵子斌. 西加拿大盆地都沃内(Duvernay)海相页岩油气富集机制研究[J]. 地学前缘, 2024, 31(4): 191-205.

DOU Lirong, HUANG Wensong, KONG Xiangwen, WANG Ping, ZHAO Zibin. Hydrocarbon enrichment mechanism of Duvernay marine shale in the Western Canada Basin[J]. Earth Science Frontiers, 2024, 31(4): 191-205.

图/表 12

图1 西加盆地区域地质简图与Duvernay页岩层系划分

Fig.1 Geological map of the Western Canada Basin and the subdivision scheme of the Duvernay shale

图2 西加盆地Simonette工区内岩性对比剖面图(剖面位置见图1a) 图中GR单位为gAPI,取值范围0~300;DT单位为μs/ft,取值范围100~40;DEN、RHOB、RHOZ为密度曲线,单位为g·cm-3,取值范围2.3~2.8。

Fig.2 A lithology correlation section in the Simonette block of the Western Canada Basin (The section position is shown in Fig.1a)

图3 Duvernay组不同类型页岩岩心照片 a—纹层状硅质页岩;b—富生物化石页岩;c—含生物遗迹页岩;d—含灰质砾屑页岩。

Fig.3 Core pictures of different types of Duvernay shales. a—Laminar siliceous shale; b—Biofossil rich shale; c—Shale with trace fossil; d—Calcareous gravel shale.

图4 Duvernay页岩电子扫描电镜照片 a—石英颗粒被伊利石包裹; b—伊利石和伊蒙混层; c—分散有机质包裹自生黄铁矿; d—有机质嵌在自生方解石与黏土矿物间。Q—石英;F—长石;K—干酪根;Op—有机颗粒;Ca—方解石;Py—黄铁矿;Si—自生石英;Cl—黏土矿物;Fd—铁白云石。

Fig.4 Electron scanning electron microscope photos of Duvernay shales. a—Quartz grains encased in illite; b—Intercalation of illite and illimolite; c—Dispersed organic matter enclosed in authigenic pyrite; d—Organic matter embedded between authigenic calcite and clay minerals; Q—Quartz; F—Feldspar; K—Kerogen; Op—Organic particles; Ca—Calcite; Py—Pyrite; Si—Authigenic quartz; Cl—Clay minerals; Fd—Ferroan dolomite.

图5 Simonette区各类页岩岩石相石英含量与有机碳含量(a)和密度(b)的关系

Fig.5 Correlation between quartz content and organic carbon content (a) and bulk density (b) of various lithofacies of shales in Simonette block

图6 Duvernay页岩有机质类型图

Fig.6 Organic types of Duvernay shale

图7 Duvernay页岩含油气特征图 a—西加盆地Duvernay页岩气油比分布图;b—Simonette区块Duvernay页岩凝析油含量分区;c—氢指数与凝析油含量相关关系。

Fig.7 Map of oil and gas characteristics of Duvernay shale. a—Gas-oil ratio distribution map of Duvernay shale in the Western Canada Basin; b—Zoning of condensate oil content in the Simonette block; c—Relationship between hydrogen index and condensate oil content.

图8 Duvernay页岩储层有机孔特征 a—Simontte地区,11-8井,3 822 m;b—Simontte地区,6-9井,3 427.37 m;c—Pinto地区,11-34井,3 959.03 m;d—Willesdon Green地区,11-05井,3 405 m。

Fig.8 Characteristics of organic pore of Duvernay shale reservoir. a—Well 11-8, 3822 m in the Simonette area; b—Well 6-9, 3427.37 m in the Simonette area;c—Well 11-34, 3959.03 m in the Pinto area; d—Well 11-05, 3405 m in the Willesdon Green area.

图9 Duvernay页岩储层3D FIB-SEM分析红色—孤立孔;蓝色—连通孔;绿色—有机质。 a—6-9井,3 432.59 m;b—11-8井,3 810.35 m; c—11-34井,3 945.27 m;d—13-5井,3 122.72 m。

Fig.9 3D FIB-SEM photos of Duvernay shale reservoir. red—isolated pores; blue—connected pores; green—organic matter. a—Well 6-9, 3432.59 m; b—Well 11-8, 3810.35 m; c—Well 11-34, 3945.27 m; d—Well 13-5, 3122.72 m.

图10 Duvernay页岩储层物性和含烃量

Fig.10 Correlation between physical properties and hydrocarbon content of Duvernay shale reservoir

图11 Duvernay页岩储层中不同热演化程度下的有机孔发育特征

Fig.11 Organic pore characteristics under different degrees of thermal evolution in Duvernay shale reservoirs

图12 Duvernay页岩储层不同尺度下微裂缝的发育与脆性特征 a—水平缝和高角度缝;b—微裂缝被方解石等填充;c—矿物颗粒间的微裂缝;d—取心照片;e—岩心中的正交缝(注:图d位置在图e岩心照片黑色箭头处)。

Fig.12 Development and brittleness characteristics of microfractures at different scales in Duvernay shale reservoirs

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