Reservoir Characterization And Analysis Of Sandbody In Wendong Area, Dongpu Depression

Wendong oilfield was firstly put into production in 1987. It is a typical mature oilfield in the east of Qianliyuan depression of Dongpu depression. The main production layer of this area is the third member of Shahejie formation, which was commonly composed by relatively thick halite, its effective layer was characterized by the frequently interbeded thin sandbody and the puzzled phenomenon is also typical which is higher place possess more sandbody while lower part contain less. All above problems have seriously restricted the understanding of reservoir characterization and its heterogeneity, and then decrease the means of further development of this mature oilfield.Based on the systematic investigation and research of the former papers of this area and 273 wells’profile, 853.35m core material was carefully described. According to the principle and method of sedimentology, the lithofacies association and its distribution law was explained, and also the genesis of all types of sandbody and its counterpart microfacies’types and distribution characteristics made clear, at last the puzzled problems of this area was probed. After all , this paper obtain the following conclusions:1) Through summarizing the regional data and core research, the 4 main microfacies in delta front was identified, 13 types of lithofacies was recognized, and then 6 types of lithofacies association which characterized 4 types of microfacies were summarized, through further work, CH and DC architecture correspond to subaqueous distributary channel while FM and WS characterize distributary mouth bar and distal bar respectively, sheet sand which respond to SS, is a little more complicated for the reason of difficult recognition.2) Based on the isochronal stratigraphic framework established by the former reserchers, guided by geological model and on the basis of the single well and well-tie microfacies analysis, all maps of microfacies were accomplished. Two provenances were existed. Northwest provenance dominate the early period while the microfacies was characterized by distributary channel and distributary mouth bar, the southwest one was the main provenance lately while the distal bar and sheet sand were well developed.3) Combining the regional geological setting and the analysis of lithofacies association, the phenomenon of frequently interbeded sandbody was explained based on the feature of microfacies distribution. The main reason depends on the distribution of sheet sand, which formed by lacustrine wave reconstruction in the setting of base level rise.4) Based on the distribution of sandbody and paleogeomorphology analysis, the causes of this phenomena was explored. Three causes, including faulting, flowing of halite and different compaction, have risen the sandbody to a higher place, which deposited on slope-broken zone compared around area.5)based on the characteristics of the map of sandbody and microfacies, the following places including the north area of 13-71, 13-147, and the south area of 13-192 are favorable for intersive wells, while the area around 203-51 is advantageous for new exploratory wells taking the ditribution of wells’position into consideration.