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 m

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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 m

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.Vertically

the gas resources mainly distribute in the Paleogene

with gas resources of 212.98 billion m

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.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 m

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i.e.an average of 27.31% of the gas resources have been proved

and the remaining gas resources is 264.587 billion m

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.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 m

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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 m

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. 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.