奈曼凹陷九佛堂组非烃流体地质意义及控制因素

Geological significance and controlling factors of nonhydrocarbon fluid of Jiufotang Formation in Naiman Sag

奈曼凹陷的非烃流体主要指CO2,H2S和N2。通过伴生气组分分析,结合区域构造发育史、非烃流体含量及碳同位素分析资料,对奈曼凹陷非烃流体成因、进入油藏时间、保存及分布的控制因素进行了深入探讨。研究认为:奈曼凹陷CO2和H2S均来自幔源成因岩浆喷发,先于烃类进入储层;CO2的富集程度与地层水中的HCO3-浓度呈正比;H2S性质不稳定,目前以痕量H2S、含硫有机化合物及黄铁矿结核的形式存在,H2S和含硫有机化合物的富集程度与SO42-浓度呈正比;N2来自大气成因,燕山晚期进入储层,浅部地层及浅层断裂附近N2富集。砂体的展布特征控制非烃流体的平面展布规律,泥岩厚度及泥岩与砂岩的配置关系控制非烃流体的保存条件。该研究成果为奈曼凹陷下一步油气勘探部署提供了一定的理论依据。

The nonhydrocarbon fluid in Naiman Sag of mainly refers to CO2, H2S and N2. Through component analysis of oil-associated gas, combining with regional tectonic history, nonhydrocarbon fluid content and carbon isotopic analysis, this paper studied the genesis, time entering into the reservoir and controlling factors of preservation and distribution of the nonhydrocarbon fluid in Naiman Sag. The result shows that CO2 and H2S in Naiman Sag come from mantle-derived magma eruption, prior to entering the reservoir of oil and gas. The enrichment degree of CO2 in formation water is directly proportional to the concentration of HCO3-. Nature of H2S is not stable, and exists in the form of trace H2S, organic sulfur compounds and pyrite nodules at present. The enrichment degree of H2S and organic sulfur compounds is proportional to the concentration of S04/2. The atmospheric N2 came into the reservoir at the late Yanshan tectonic uplift, and enriched in the vicinity of shallow strata and shallow fault. The distribution characteristics of sand bodies control the plane distribution rule of nonhydrocarbon fluid. Thickness of mudstone and configuration relation between mudstone and sandstone decided the preservation conditions of nonhydrocarbon fluid. The research results provide theoretical basis for next exploration deployment in Naiman Sag.