Study Of Fine Sedimentary Facies Characteristics Of Fuyu Oil Layer In Changde Area, Northern Songliao Basin

Sanzhao sag locates in the East of Daqing placanticline, it’s the important resource fields of stable production in Daqing oilfield. Based on several optimization of beneficial exploration target in Sanzhao area, we think that the Fuyu oil layer of Changde area have great exploration potent, it’ plays an important role on later dense petroleum exploration and increase reserve and production. In recent years, the characteristics of sedimentary systems and sedimentary microfacies in this area have received certain understanding, with the deepening of oil exploration, the complexity and particularity of Hydrocarbon accumulation become more obvious, in order to accelerate the exploration process of Fuyu oil layer, fine characterizing the sedimentary microfacies characteristics and spatio-temporal evolution law in high-frequency sequence stratigraphic framework get more important.In this paper, with the guidance of sedimentary theory, high resolution sequence stratigraphy and petroleum geology theory, on the basis of core data, logging/drilling data, combined with regional geology setting, fist,the sequence stratigraphy division and comparison of Fuyu oil layer(F Ⅰ and FⅡ)in Changde area is researched, then the high-frequency stratigraphy framework is built, meanwhile the sedimentary systems characteristics in high-frequency stratigraphy framework are alson detail researched. The main points are as follows:According to fine core obserbation, the litofacies and sedimentary facies types are determined, the results show that 3 categories lithofacies types develop:mudstone class, siltstone class and packstone class, and further subdivided into 5 mudstone facies,7 siltstone facies and 3 packstone facies.Based on the characteristics of lithofacies associations, combined with sedimentary structure characteristics, rock-electricity realtion, Cahngde area mainly develops shallow delta facies and lake faceis, and it further subdivided into 3kinds of sedimentary subfacies and 8kinds of microfacies. Among of them, shallow delta are more developed, it mainly consists of delta plain and delta front. Delta plain can be divided into distributary channel, flooding deposits, crevasse splay and so on, while delta front can be divided into underwater distributary channe, tributaries bay, underwater crevasse splay and so on. Lake facies mainly develop shallow lake, which can be subdivided into shallow lake mudstone, beach bar microfacies and so on.With the guidance of high-resolution sequence stratigraphy theory, according to core data,/drilling/logging data, the identification marks of high-resolution sequence boundary are summed. Through the analysis of sequence boundary identification and sequence interior structure characteristics, F Ⅰ and FⅡ can be divided into 12 five level sequence. Among of them, F Ⅰ is divided into 7 five level sequence, while FⅡ is divided into 5. In every sequence, its sedimentary cycle completely develop, most of them are asymmetric which dominated by uprising semi-cycle or subsiding semi-cycle. Meawhile symmetric sedimentary cycle occasionally developsOn the basis of heavy minerals associations and ZTR exponential distribution analysis, combined with the characteristics of sandstone distribution, the results show that Changde area mainly effected by the southern, northern and eastern provenance during the period of Fuyu oil layer, among of them, the southern and northern provenance are dominant. In high-resolution sequence framework, the provenance of different sedimentary period have divergence.In high-resolution sequence framework, the characteristics of sedimentary facies distribution and evolution law are deeply researched. The results show that Fuyu oil layer in Changde area mainly develop shallow delta-lake sedimentary systems, during the period of Q3-SSC1～Q3-SSC5, it mainly develops delta plain which is controlled by southern provenance, the channel width show a tendency to increase; during the period of Q4-SSC1～Q4-SSC2, it still mainly develops delta, while it is mainly controlled by southern and northern provenance, its channel width show a tendency to decrease; during the period of Q4-SSC3～Q4-SSC5, delta plain and delta front coexist, its sedimentary water gradually deepening, the channel width of delta front is obvious smaller than delta plain; during the period of Q4-SSC6～Q4-SSC7, delta front and shallow lake coexist, its sedimentary water further deepening, the channel width are commonly narrow.Through the sedimentary facies evolution research of Fuyu oil layer in Changde area, the results show that the sedimentary water upward undergo the gradually shallow and gradually deepen which are corresponding to a lake retreat-lake transgression deposition process. During the period of Q3-SSC5 and Q4-SSC1, its sand bodies are mostly developed. On the basis of above, sedimentary evolution models of Fuyu oil layer in Changde area is established.