Abstract:

The prominent feature of regional geotemperature pattern of Liaohe graben is revealed as follows:1.A lower geothermal gradient(about 25℃/km)is inherent for the Ceno-zoic sedimentary strata with a depth shallower than 1,000-1,200m;2.Deeper than that depth,a higher geothermal gradient(35-40℃/km)is observed.This is similar to that of other oil-bearing districts in North China.The intensive circulation of ground water and the structure of the Pre-Cenozoic bedrock are considered as major factores controlling geotemperature pattern in the region studied.Based on temperature measurements of more than 70 wells and hundreds geotemperature data inferred by predictive method recently developed for thisstudy,a set of isotherm maps of different depths has been completed for the whole area with the purpose of specifying the oil-genesis threshold depth,as-sessing oil-gas resources as well as prospecting oil and gas in the district.Heat flow measurements at 54 sites give a mean value of 1.52 HFU(63.6mW/m²)with prevailing value 1.4 to 1.7 HFU.The results are similar to the heat flow measurements in other oil-bearing districts in North China.Suitable geotemperature condition together with aboundant organic ma-terials in Cenozoic sediments,as well as appropriate geological settings and tectonic environment,are considered to be the main factors favorable to the existence of potential oil resources in this area.