南襄盆地襄樊-枣阳凹陷白垩系油气资源前景初步评价

Preliminary evaluation of hydrocarbon prospects of Cretaceous strata in Xiangfan-Zaoyang sag,Nanxiang basin

通过南襄盆地内矿产地质、油气地球化学勘探等研究,发现一些襄樊-枣阳凹陷白垩系烃源岩信息:凹陷东缘盐矿井揭示的上白垩统中段烃源岩较发育、有机质丰度较高、演化程度适中,显示出一定的生烃能力;地表化探甲烷C同位素数据显示,近一半样品与中生界成熟石油伴生气有关,佐证了该区中生界生烃能力。地震勘探成果表明白垩系分布广、厚度大、沉积环境较稳定;在已投入地震勘探的900km2范围内,共解释出襄樊-枣阳凹陷可靠和比较可靠的白垩系圈闭23个,圈闭面积4～16km2,最大可达200km2。其中,枣阳凹陷的13个圈闭是20世纪90年代地震勘探解释成果,落实程度较高,总面积达189km2。利用现有的地质、物探、化探等资料,对襄樊-枣阳凹陷白垩系石油地质条件进行初步评价,资料显示,南襄盆地襄樊-枣阳凹陷白垩系范围较广,厚度大,埋藏深,烃源岩演化程度较高,综合认为白垩系是区内值得探索的勘探新层系。

Hydrocarbon resource exploration of the Cretaceous strata in Nanxiang basin has been rarely carried out. Through research on mining geology and geochemical oil and gas exploration in the study area, the authors obtained some information of Cretaceous hydrocarbon source rock in Xiangfan-Zaoyang sag： the salt wells in the eastern part of the sag show that in the middle of the upper Cretaceous strata, the hydrocarbon source rock is well developed and characterized by high abundance of organic matter and moderate evolution degree, suggesting certain hydrocarbon-generating capacity. Half of the samples are related to gases of the mature oil, as evi- dence by methane carbon isotope data from the surface geochemical exploration. The seismic exploration shows that the Cretaceous strata are characterized by wide distribution, great thickness and stable sedimentary environment. The interpretation made by the an- ! thors shows that, in an area of 900 km2 of seismic exploration, there exist 23 reliable or relatively reliable traps of the Cretaceous strata, and the area of a trap is generally 4~16km2, with the maximum trap area reaching 200km2 in Xiangfan-Zaoyang depression. Then there are 13 traps from the interpretation of seismic exploration made in the 1990s, possessing totally 189kin2 in the Zaoyang depres- sion, and with good precision. According to the data from geological, geophysical and geochemical prospecting, the authors prelimi- narily evaluated petroleum geological conditions. The data obtained show that the Cretaceous strata are characterized by wide distribu-tion, great thickness, deep burial depth and high evolution degree of the source rock. It is therefore considered that Cretaceous is a new target deserving further investigation.