Abstract:

The eleven oil-rich sags in mature exploration areas in eastern China,including Dongying, Zhanhua, Chezhen, Huimin, Biyang, Nanyang, Qianjiang, Gaoyou, Jinhu, and Baise basin,are rich in oil and gas resources. According to the third resource evaluation, the total oil and gas resources in these 11 sags are 9.66168 billion tons and 363.98 billion m³,respectively. The distribution of hydrocarbon resources is very unbalanced in different regions and horizons,because of differences in oil and gas accumulation conditions. Laterally,the oil resources mainly distribute in Dongying, Zhanhua, Dongpu, Huimin and Chezhen sags. Vertically the oil resources mainly distribute in the Paleogene.The total oil resources in these sags are 8.0466 billion tons,accounting for 83.28% of the total oil resources in the 11 sags. The oil resources mainly distribute in moderate and deep reservoirs(1 500～3 500 m), with oil resources of 7.40816 billion tons.Laterally,the gas resources mainly distribute in Dongpu sag, with the gas resources to be 235.5 billion m³.Vertically,the gas resources mainly distribute in the Paleogene, with gas resources of 212.98 billion m³.The gas resources mainly distribute in the moderate and deep reservoirs.Although the exploration areas in eastern China have been in mature and high-mature exploration stages after over 40-years exploration and development, the hydrocarbon resources that have been proved are still less than 50%. According to the experience in the world that 70% of oil resources might finally be proved, there will still be a prodigious amount of remaining hydrocarbon resources in these mature exploration areas. By the end of 2002, the cumulative proved oil reserves in these 11 sags is 4.88659 billion tons,i.e.an average of 50.57% of the oil resources have been proved and the remaining oil resources is 4.77509 billion tons. The cumulative proven gas reserves in these 11 sags is 99.393 billion m³, i.e.an average of 27.31% of the gas resources have been proved,and the remaining gas resources is 264.587 billion m³.The distribution of remaining hydrocarbon resources is very unbalanced because various sags, horizons and reservoir types have different degrees of hydrocarbon accumulation, prospecting and ascertainment. The exploration results,got recently,show that the remaining oil resources distribute mainly in Paleogene, with remaining oil resources of 4.33176 billion tons, accounting for 90.7% of the total remaining oil resources in these 11 sags. Laterally,the remaining oil resources distribute mainly in Dongying, Zhanhua, Chezhen, Huimin and Dongpu sags, with remaining oil resources of 3.94505 billion tons,accounting for 83.2% of the total remaining oil resources in these 11 sags.The remaining oil resources distribute mainly in subtle reservoirs, such as lithologic, complex fault-block reservoir and buried hill reservoirs. Vertically,the remaining gas resources (excluding the deep gas in Jiyang depression) mainly distribute in the Paleogene,with remaining gas resources of 262.9 billion m³,accounting for 99.3% of the total remaining gas resources in the 11 sags. Laterally,the remaining gas resources distribute mainly in Dongpu sag, with remaining gas resources of 176.77 billion m³. Analysis of hydrocarbon resource potential and exploration achievements show that the key exploration domains in the mature exploration areas in eastern China will be the Paleogene, subtle reserviors (including lithologic, complex fault-block and buried hill reservoirs) and new stratigraphic horizons in the depths.

Key words: eastern China, mature exploration area, remaining hydrocarbon resources, resources potential, exploration domains