辽河断陷地温、古地温特征与油气资源

为评价生油作用,据镜质体反射率等指标恢复了辽河断陷的古地温特征。结果表明,早第三纪早期古地温梯度(或古热流)高于今日,早第三纪晚期地温下降,晚第三纪又再度上升。新生代平均古地温与今日地温特点相近。综合地温、古地温资料可作如下结论:(1)早第三纪相对高的古地温对凹陷区沙河街组下部层位生油十分重要。(2)沙河街组为华北新生界主要生油层。在辽河断陷,它的生油时代在一些深凹陷可早自早第三纪晚期,至今仍持续生油与向更高成熟阶段演化。东营组生油局限于断陷南部,大量生油的时代当始于晚第三纪晚期,生油的规模与潜力亦远逊于沙河街组。新第三系可望生油区在辽东湾,陆地部分看来不可能。(3)本文给出石油大量成熟门限温度的等深线图,并对石油资源的评价与预测作了讨论。

GEOTHERMAL AND PALEOGEOTHERMAL CHARACTERISTICS OF LIAOHE GRABEN DISTRICT AND THEIR RELATIONSHIP TO OIL-GAS RESOURCES

Based on vitrinite reflectance and other index, an attempt in reconstructing paleogeotemperature pattern of Liaohe graben district has recently been conducted for evaluating the oil-generation processes. Results showed that the paleogeothermal gradient and, hence, the paleo-heat flow had been higher during earJy Eogene compared with present-day's ones and experienced a decline by the end of Eogene and rise again since Neogene. The averaged paleotemperature throughout Cz time was similar to that observed at present. Some conclusions can be made as follows: 1. The relatively high paleogeotemperature during Eogene is of great importance to the oil generation of lower strata of Sahejie group in depressions. 2. Sahejie group has been considered to be the key oil-genetic series of Cz sediments in North China Basin. In Liaohe graben district, oil-genetic epoch for Sahejie group in some deep depressions started as early as late Eogene, continuing till present day and leading to higher degree of petroleum maturation. Oil-genetic process of Dongying group is limited to the southern part of Liaohe graben. Epoch of large-scale petroleum occurrence for Dongying group must be traced back to late Neogene, the magnitude and potential of oil generation of Dongying group, however, is much more smaller than that of Sahejie group. Petroleum occurrence in Neogene strata is expected in Liaohe Gulf and seems to be impossible on land. 3. An isobath map of temperature threshold for large-scale petroleum maturation is given and its implications for predication and assessment of oil resouces are discussed.