二连盆地洼槽区非常规油气富集模式及勘探潜力

doi:10.13745/j.esf.sf.2023.2.71

摘要/Abstract

摘要：

向湖盆中心和深层寻找油气勘探新领域已成为未来主要发展方向。二连盆地剩余油气资源量达8亿吨,主要分布于各富油凹陷洼槽区,以非常规资源形式富存,页岩油潜力巨大。本文通过对富油凹陷洼槽区非常规油气地质特征、成藏富集机理和成藏模式开展研究,总结提升断陷小湖盆洼槽区非常规油气地质理论认识。研究表明:二连盆地多个洼槽区发育互层型页岩油聚集,富集于洼槽区边缘,存在腾二期(120 Ma)未致密先成藏和赛汉期(105 Ma)边致密边成藏(先致密后成藏)两期成藏过程;高充注动力富集区,砂体规模控制页岩油富集程度,低充注动力洼槽区内甜点储层发育及规模控制页岩油富集程度;二连盆地夹层型页岩油存在两种富集机理,即“储层主控”和“生烃主控”。据此,构建了二连盆地斜坡带-洼槽区“常非共存、有序分布、满洼汇聚、差异富集”的全油藏系列成藏模式,研究成果坚定了深入湖盆内部寻找烃源灶边缘互层型页岩油及烃源灶内夹层型页岩油的勘探信心。

关键词: 页岩油, 富集模式, 洼槽区, 二连盆地, 勘探潜力

Abstract:

Oil and gas exploration nowadays is increasingly directed toward the center and deep layers of lake basins. In the Erlian Basin the remaining ~800 million tons of unconventional petroleum resources are mainly distributed in troughs of oil-rich depressions, with great shale oil potential. This paper seeks to summarize and improve the theoretical understanding of unconventional petroleum geology in oil-rich lake basins by studying the geological characteristics, accumulation and enrichment mechanism and accumulation model of unconventional oil and gas in the Erlian Basin. The accumulation of interbedded type shale oil in the basin occurs in multiple troughs-preferably at trough edges-via a two-stage process: “accumulation before tightening” (Tenger stage (120 Ma)) and “accumulation after tightening” (Saihan stage (105 Ma)). The degree of shale oil enrichment in high-charge dynamic enrichment areas is controlled by sandbody dimensions, while in low-charge areas it is controlled by “sweet-spot” reservoirs development status. And there are two enrichment mechanisms for interlayer type shale oil: “reservoir control” and “hydrocarbon generation control.” Based on these results a hydrocarbon accumulation model is constructed for the entire oil reservoir series in slope belts and troughs of the Erlian Basin, which is summarized as “conventional/unconventional oil coexistence, hydrocarbon orderly distribution, trough-wide accumulation and differential enrichment.” Results of this study boost our confidence in finding interbedded type shale oil at source-rock edges and interlayer type shale oil within source rocks in the interior of lake basins.

Key words: shale oil, enrichment model, trough, Erlian Basin, exploration potential

中图分类号:

P618.130.2

项鑫, 黄传炎, 曹兰柱, 曹强, 江涛, 张宇飞, 宋宇, 徐婕. 二连盆地洼槽区非常规油气富集模式及勘探潜力[J]. 地学前缘, 2023, 30(6): 462-472.

XIANG Xin, HUANG Chuanyan, CAO Lanzhu, CAO Qiang, JIANG Tao, ZHANG Yufei, SONG Yu, XU Jie. Enrichment model and exploration potential for unconventional oil and gas in troughs, Erlian Basin[J]. Earth Science Frontiers, 2023, 30(6): 462-472.

图/表 13

图1 二连盆地非常规油气勘探现状及地层发育图(引自文献[2])

Fig.1 Location and unconventional oil and gas exploration status (left) and stratigraphic section (right) of the Erlian Basin. Adapted from [2].

图2 二连盆地乌南与阿南洼槽区典型单井综合柱状图

Fig.2 Comprehensive column diagrams of typical wells in the Wunan (left) and A’nan troughs, Erlian Basin

图3 二连盆地洼槽区互层型页岩油储层致密化及油气成藏过程配置关系图 a—乌南洼槽区太591X井;b—阿南洼槽区哈20井。

Fig.3 Composite diagrams for wells, showing the relationship between hydrocarbon densification and accumulation in interbedded type shale oil reservoirs, Erlian Basin. (a) Well Tai 591X, Wunan trough. (b) Well 20, A’nan trough.

图4 二连盆地洼槽区典型砂砾岩储层互层型页岩油充注数值模拟图 a—样品孔隙度信息;b—模拟充注动力与含油饱和度关系。

Fig.4 Numerical simulation results for typical glutenite reservoirs in troughs, Erlian Basin. (a) Porosity profile. (b) Relationship between charging pressure and oil saturation for interbedded type shale oil.

表1 二连盆地典型砂砾岩储层油充注门槛阻力及富集阻力

Table 1 Average porosity and pressure threshold values by stimulation for typical glutenite reservoirs, Erlian Basin

储层层位	储层类型	样品数/个	模拟平均孔隙度/%	测井平均孔隙度/%	含油5%平均充注动力下限/MPa	含油50%平均富集动力下限/MPa
太591x-腾一下	致密	2	8.925	5.5	4.25	7.4
太591x-腾一下	常规	2	10.985	17.85	3.97	6.7
太60x-腾一下	致密	2	9.6	10.2	4	7.1
太60x-阿四段	致密	4	8.59	9.4	5.4	7.82

图5 二连盆地洼槽区赛汉期成藏关键时刻(105 Ma)代表测线剩余压力模拟 a—乌南洼槽区;b—阿南洼槽区。

Fig.5 Simulated residual-pressure profiles along representative survey lines in Wunan (a) and A’nan (b) troughs, Erlian Basin during critical accumulation period in the Saihan stage (105 Ma)

图6 二连盆地洼槽区富有机质页岩层系“石油超越效应指数”评价图

Fig.6 Plots of S1 vs. TOC content for organic-rich shale strata of troughs, Erlian Basin for shale oil potential evaluation

图7 乌南洼槽区太591X井腾一段-阿四段地球化学综合剖面图

Fig.7 Geochemical profiles along sections K1bt1-K1ba, well Tai 591X, Wunan trough

图8 二连盆地洼槽区腾一段-阿四段富有机质页岩扫描电镜照片 a—阿南洼槽区;b—乌南洼槽区。

Fig.8 SEM images of organic-rich shale from K1bt1-K1ba, Erlian Basin. (a) Wunan trough. (b) A’nan trough.

图9 二连盆地洼槽区腾一段-阿四段富有机质页岩压汞与氮气吸附结果图 a—乌南洼槽区;b—阿南洼槽区。

Fig.9 dV/dd vs. pore-size plots and N2 absortion-desorption isotherms for organic-rich shale from K1bt1-K1ba, Erlian Basin. (a) Wunan trough. (b) A’nan trough.

表2 乌南与阿南洼槽区夹层型页岩油富集条件综合对比表

Table 2 Comparison of interlayer type shale oil enrichment conditions between the Wunan and A’nan troughs

参数项	乌南	阿南
页岩生烃条件	中等(OSI:<100 mg/g)	好(OSI:100~200 mg/g)
页岩储集条件	好(墨水瓶状与平行狭缝状中孔为主)	中等(开放的平行狭缝状微孔、中孔为主)
页岩脆性矿物含量	好(61%~93%)	中等(57%~82%)
主控因素与有利层段	页岩生烃条件;页岩层系内高TOC含量、HI、OSI层段	页岩储集条件;页岩层系内高孔隙度、渗透率层段

图10 二连盆地代表洼槽区非常规油气成藏模式 a—乌里雅斯太凹陷南洼槽区; b—阿南凹陷善南洼槽区。

Fig.10 Unconventional oil and gas accumulation model for typical troughs, Erlian Basin. (a) South trough, Wuliyasitai sag. (b) Shannan trough, A’nan sag.

表3 二连盆地洼槽区页岩油气成藏地质特征

Table 3 Enrichment gelogical characteristics of shale oil/gas in the sag area of the Erlian Basin

类型	代表洼槽	相态	充注动阻力	输导通道	聚集特征	富集因素
互层型	乌南洼槽,赛东洼槽, 阿南善南洼槽等	中深层:原油(轻质油); 深层:天然气	动力:异常高压; 阻力:中值压力	致密砂砾岩孔吼、微裂缝	源-储一体型和源-储接触型,源内汇聚	高净动力+ 甜点控富集
夹层型	阿南善南洼槽、乌南洼槽、淖东洼槽等	中深层:原油; 深层:天然气	动力:异常流体压力	微纳米孔隙、裂缝 (微运移或无运移)	滞留成藏, 源内聚集	源储配置+ 甜点控富集

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