Main factors controlling accumulation and distribution of oil-water isostrate reservoir in the Gulong Oilfield

Putaohua oil layer in the Gulong Oilfield,situated in the Central Depression of the northern Songliao Basin, had a complicated relation between oil and water, with low initial oil saturation and large proportion of oil-water layers. Applying recently precise and fine reservoir evaluation data , including drilling, oil testing, trial production and chemical analyses, the paper made a deeply study on the main accumulation controlling factors forming oil-water layers. It was be- lieved the creation of Putaohua reservoir being controlled by the structure, the sandstone size, the abnormal high pressure and the relative strengthen of formation water activity, which formed two types of oil-water isostrate layers. A model was set up for isostrate distribution pattern of Putaohua reservoir, namely, the oil layer retention in the west and oil layer differentiation in the east. The distribution regularity of oil-water isostrate layers provided a basis for submitting provendeposit and compiling development scheme of lithologic reservoir in the Gulong Oilfield.