Research On Diagenesis And Reservoir Evaluation Of Fuyang Oil Layers In Chaochang Area, Daqing Oilfield

Chao Chang area lies in the north Songhua River, Heilongjiang Province, trends from Sizhan Area in southern Fengle, Zhaozhou to Zhaoyuan area, in which the main deep reservoir is Fuyang (Fuyu and Yangdachengzhi) oil layers with low and super-low permeabilities. Based on the systematic research on lithologic characteristics and diagenesis, discussion on the controlling factors of reservoir’s properties, the reservoir is evaluated and categoried, also including the forecast of favorable reservoirs, which have very important meanings in the exploration and development of Fuyang oil layers in Chaochang Area.Based on the collection and analysis of the previous data, in addition with the core observation and sampling, firstly, the thin sections’identification is made to caculate the skeletal clastic content, determine the lithologic types and describe the lithological characteristics of sandstone; then the observation of thin sections and casts is used to determine the types of diagenesis and pores, paragenetic sequences, diagenetic stages and so on. According to the collected physical properties of reservoir’s porosities and permeabilities, the features of reservoir is sμmmaried, and based on the mercury injection’s data, caculate and analyse the pore and throat’s configuration, in combined with the facies, diagenesis facies and single well’s reservoir evaluation, the favorable reservoir is forecast.The main achievements and understanding are as follows,The lithology in Fuyang oil layers is primarily lithic arkose, a little arkose and feldspathic litharenite, smaller grain size, mediμm sorting, higher textural maturity, the dominate type is fine sandstone, siltstone as follows. The main pore-fill matrix is clay minerals and siliceous and carbonate cements. In general, the compositional maturity is low, which reflects the near source’s sedimentary environment.The storage volμme of Fuyang oil layers in Chaochang area is primarily three types: primary pores, mixed pores and secondary pores, in which the secondary pores are induced by the dissolution of feldspar, other unstable minerals and pore-fill materials, also including the micro-fissures formed in the tectonics.The diagenesis types in Fuyang oil layers in Chaochang area are mainly compaction and pressure solution, chemical cementation and dissolution. According to the quartz overgrowth, the diagenetic evolution of clay minerals and the contact between grains, the diagenetic stages are in late stage A1 and A2.The burial depth is one of the most important factors in controlling the physical properties of reservoir. Another one is microfacies. The favorable microfacies above-water and under-water distributary channels can deposit coarser, less mud sandstone under the sorting and winnowing of stronger hydrodynamic forces, which can form better physical properties of reservoir. The microfissures, which are formed in late stage, play an important part in reconstructing the reservoirs’properties. The Yangdachengzi oil layer near the axis of Chaoyanggou Anticline upgrowths many microfissures, which can improve the properties at large at deep burial depth with the background of stronger tectonics.