北京大学学报（自然科学版）2026，Vol.62Issue(2)：309-326,18.DOI:10.13209/j.0479-8023.2025.062
柴达木盆地西南缘狮子沟构造下干柴沟组上段天然流体压裂特征与超压起源
Characteristics of Natural Hydraulic Fracturing and Its Overpressure Origin in Upper Xiaganchaigou Formation of the Shizigou Structure,SW Qaidam Basin
摘要
Abstract
Two kinds of natural hydraulic fracturing were found in laminated argillaceous dolomite and homoge-neous argillaceous dolomite of the Upper Xiaganchaigou Formation in the Shizigou Structure in the southwestern Qaidam Basin(SW Qaidam Basin).To explore the geometric characteristics of networks of natural hydraulic frac-turing,the temperature-salinity conditions when hydraulic fracturing occured,the interaction between fluid in frac-tures and surrounding rocks,and controlling factors of natural hydraulic fracturing under the background of mul-tiple overpressure factors,the two kinds of multilevel fracture networks and inclusions in veins were described at the core scale and thin section scale under single polarized light,orthogonal light and cathodoluminescence.Types,distribution,and contents of minerals in veins and surrounding rocks were further characterized by TESCAN integrated mineral analyzer(TIMA).In addition,the homogenization temperature and salinity of aqueous inclusions in veins were tested.Results show that natural hydraulic fracturing in laminated argillaceous dolomite and homoge-neous argillaceous dolomite has similarities and differences.Regarding similarity,both fracture networks consist of three-level veins,including the main vein,the first-level hydraulic veins,and the second-level hydraulic veins,showing orthogonal nets in cores.In addition,anhydrite is the main filling mineral in veins.The differences are as follows.Firstly,the first-level hydraulic veins develop along the lamina directions that intersect the main vein with an angle in laminated argillaceous dolomite,while the first-level hydraulic veins are perpendicular to the main vein in homogeneous argillaceous dolomite.The thicker vein inhibits the development of thinner veins which are nearly parallel to the thicker one.Moreover,thinner first-level and second-level hydraulic veins in homogeneous argilla-ceous dolomite are mostly filled by calcite and celestite.Secondly,only low-mature heavy oil inclusions develop in the main vein in laminated argillaceous dolomite,while in homogeneous argillaceous dolomite,only aqueous inclusions develop in the main vein,and heavy oil traces exist in intergranular cleavage and secondary fissures.The average homogenization temperature of aqueous inclusions(215℃)is greater than the paleogeothermal range(35-150℃)controlled by the burial depth of the sample.Considering multiple overpressure backgrounds,the tectonic evolution history,thermal history,burial history,and hydrocarbon accumulation history,we propose that natural hydraulic fracturing in the laminated argillaceous dolomite may be attributed to the superposition of tectonic compression,gypsum-anhydrite transformation,and hydrocarbon generation.Hydraulic fracturing in homogeneous argillaceous dolomite is attributed to overpressure caused by upwelling of deep thermal fluid.During the reaction between hydrothermal solution and surrounding dolomite,celestite in thin veins is beneficial to enrichment by extracting Sr2+from surrounding dolomite.Formation process and geometrical patterns of two kinds of hydraulic fracturing have enlightening significance for enrichment of celestite deposits and the current artificial hydraulic fracturing of shale oil reservoirs in the upper Xiaganchaigou Formation in the SW Qaidam Basin.关键词
天然流体压裂/超压/盐水包裹体/烃类包裹体/天青石富集/柴达木盆地Key words
natural hydraulic fracturing/overpressure/aqueous inclusion/hydrocarbon inclusion/celestite enrich-ment/Qaidam Basin引用本文复制引用
吴嘉伟,郭召杰,张长好..柴达木盆地西南缘狮子沟构造下干柴沟组上段天然流体压裂特征与超压起源[J].北京大学学报（自然科学版）,2026,62(2):309-326,18.基金项目
国家自然科学基金(41930213)资助 （41930213）
