Depositional Patterns of Microfacies of the S I Oil-Bearing Layer Reservoir in the Dense Well Pattern Y-Region of the Daqing Oilfield

摘要

In order to deeply understand and dissect the features of subaqueous narrow and small channel sand body such as development degrees, microfacies types and plane distribution form so on. By utilizing the high resolution sequence stratigraphy and the theory of fluvial fine sedimentology, to make systematic and elaborate study on the S I oil-bearing layer in the dense well pattern Y-region of the Daqing oilfield. The results show: a, It is finely divided 8 sedimentary time units on the S I oil-bearing layer in the Y-region. b, Predecessors thought it is deltaic external front subfacies on the S I oil-bearing layer in the studied area, mainly develop stable and unstable sheet-sandstone of deltaic external front. However, the results of fine dissection in the dense well pattern studied area, are that all of units are deltaic internal subfacies, besides S I 21 and S I 4+53, which are deltaic external subfacies. To distinguish sole, continuous, narrow and small subaqueous distributary channel sand body and a large area of sheet-sandstone, c, To summarize two depositional patterns of microfacies of deltaic front subfacies, i.e. "subaqueous distributary channel- main sheet sand body- sheet-shape sandstone- sheet inner margin- sheet outer fringes-mud stones between sand sheets" and "sheet-shape sandstone- sheet inner margin- sheet outer fringes-mudstones between sand sheets", the former is the depositional pattern of the deltaic internal front subfacies, the later is the external. It is possible that the S I oil-bearing layer of other development areas of the Daqing oilfield and similar reservoir all are the deltaic front subfacies, occur continuous small subaqueous distributary channel sand body. It possesses the potential to which pay attention to this, and strengthen exploitation. It is significant for thoroughly understanding the third class oil layers and further remaining oil development.