The Study On The Distribution Law Of Chang6 Reservoirs In The Shajiagou Area Of Shanbei Slope

Be guided by the theories of structural geology, sequence stratigraphy, sedimentology, geophisics and petroleum geology, this thesis conducts a intensive study on the distributions of sand-bodies and oil-reservoirs in Chang611, Chang 612, Chang 613, Chang 621, Chang 622, Chang 631 and Chang 632 of Chang oil-bearing formation. On the basis of that, this thesis then further explores controllings from tectonics, sand-bodies distribution and reservoir-heterogeneity to the oil distribution.In the Chang6 period, the Yanchang Formation in researching area was governed by the Yan’an Delta, which mainly developed three kinds of sedimentary microfacies, including underwater distributary channel, interdistributary bay and channel mouth bar, with a NE-SW watercourse orientation. With characteristics of poor physical property, mixture of oil and water, lack of edge and bottom water and blurring of oil-water boundary, Chang6 reservoir typically belongs to the kind of lithologic reservoir.In Chang6 Formation, the oil reservoirs with a feature of thin in thickness and many in number mainly developed in the four small layers of Chang613,Chang 621,Chang 622 and Chang 612, most oil reservoirs in Chang613 are 2-3 layers, the wells with effective thickness between 4 to 10 meters are account for 62%. Chang621 generally has 2 layers and accounts for the same percentage to the Chang613 with 4-8 effective thickness. In Chang 622, 2 oil layers are common to be observed, the wells with effective thickness between 4 to 8 meters are account for 49%. Looking from plane graphs, these reservoirs changes rapidly horizontally, poor in connectivity and presents a character of lenticular distribution. The nose-shaped uplifts in Chang 61 and Chang62 are not the main controlling factors for the oil distribution, but in Chang 63 the nose-shaped uplifts make a great contribution for the oil distribution. Meanwhile, due to the controlling of sand-bodies distribution, the oil only develops limitedly and partly. In addition, because of the effect of reservoir heterogeneity, interlayers on the one hand impede interstitial flow of the oil in horizontal-vertical direction. On the other hand, however, they sometimes function as cap formation to in favor of preserving the dissipation of the oil.