Abstract:

This paper is composed of three parts:In the first part,the geological conditions how Daqing Oilfield was formed are summarized from six aspects such as oil generation and reservation,source-reservoir-cap assemblage,structural traps,coordinate relations between the periods of structure formation and oil generation as well as fault types and their effects. It is suggested that the combination of the large elongated bar and the favourable facies zone of the complex delta have led to a large structure controlled oilfield.In the second part,oil pool properties in Daqing Oilfield are described,Generally speaking,it is a secondary structural belt controlled oilfield. The north part are massive structural oil pools and shallow secondary oil pools,while the south are fault-complicated structural pools. In processes of paleo-tectonic evolution,it seemed that the reservoir pressure in the north had long been lower than saturation pressure,thus forming gas caps,whereas in the central and the southern parts,conditions were opposite. Crude oil is of high wax and low sulfur. The author thinks that the differences between the reservoirs are the main reason caused the oil to enrich and the reservoir types to differ so differently.The distribution and accumulation rules of oil and gas in Songliao basin in both horizontal and vertical are summed up in the third part of this article,showing that in this source area controlled oil field,most of the oil and gas migrated from relateve short distance,lake-shore transitional belts are favourable for oil accumulation,the period of structural formation fitted that of the generation and migration of oil and gas,stable regional cap-rocks constitute a nice seal for reservoir,It is pointed out that Songliao basin has variety of oilbearing beds,reservoir types as well as oil pools,thus the subtle oil pools are the main objects for future prospecting.