Daqing, a large sandstone oilfield with an oil-bearing area of nearly 1000 sq.km, is in an anticlinal structure with a long axis. The oil reservoir formations lie at depths of 800-1200m. The max. thickness of oil-bearing intervals is up to some 500m. The oil reservoir is a Lower Cretaceous nonmarine fluvial-deltaic sedimentary system. The reservoir rocks are from middle, finegrained to silt sandstones.

In a cross section, there are up to over 100 single layers with a minimum thickness of 0.2m. and a max. of 20m. or more. There are great variations in the extent of the distribution sandbodies and in inter-layer and in-layer permeabilities (1)(2).

The field was put on stream in 1960, and with the progressive extension of the productive area by 1975, the main parts of the field had already been fully developed, oil output entering a stable peak stage from a rising stage. In 1976 annual output reached more than 50 million tons and 55 million tons are expected in 1985. Since then, the field has kept a stable or slightly rising production for 10 years in succession.

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