Reasearch On The Reservoir Characteristics Of Chang-6 Formation In Huachi-nanliang Region

Ordos Basin is one of important petroliferous basin in China, which has great potential to be developed. Huachi-Nanliang region located in the middle of Ordos Basin seeks urgently for new production blocks, as it has quickly and efficiently built the capacity in recent years and the follow-up to replace reserves are obviously insufficient. Chang-6 reservoir is a main oil-bearing reservoir of Mesozoic in Huachi-Nanliang region, which can be generally found in this strata. Many existing wells have obtained commercial oil flow from this reservoir and the reservoir displays a common oil bearing with a good exploration prospect.This paper will analyse more in-depth on the sedimentary characteristics and reservoir characteristics in studying areas. In this thesis, the author will analyse the sedimentary genesis of the thick sand body in Chang-6 reservoirs and then establishes sedimentary facies models, based on core observation and by preparing various plan drawings and by studying on sedimentary structure and petrology. Based on the analysis of sedimentary facies, the seepage mechanism, pore types, diagenesis and pore throat structure of the reservoir sandstones are analyzed by means of the porosity and permeability data, the relative permeability analysis, the chip identification and the mercury intrusion analysis.By analyzing the sedimentary facies, the main sedimentary facies of Chang-6 reservoir includes delta front deposits, gravity flow deposits and semi-deep lake deposits. The basic studying on petrology shows Chang-6 reservoir rock types are composed primarily of fine-grained lithic feldspathic sandstone and lithicfeldspathic sandstone. And the sandstone compositional maturity and fillings have something zonation. Chang 6 reservoir space mainly include intergranular pore, intergranular dissolved pores, intragranular dissolved pore and intergranular pore, among these intragranular pore and intergranular dissolved bore hole are main types. The analysis of phase permeability characteristics in Huachi-Nanliang area shows that Chang-6 reservoir is a hydrophilic reservoir which also has features of alkali sensitivity, acid sensitivity, weak salt sensitivity, weak velocity sensitivity and weak water sensitivity. In terms of the characteristics of reservoir heterogeneity, the heterogeneity of inner layer of Chang-6 reservoir belongs to moderately heterogeneous reservoirs- heterogeneous reservoirs, however the interlayer has a weak heterogeneity. Overall, from bottom to up the heterogeneity of adjacent layer will get stronger and stronger. The analysis of reservoir controlling factor shows that the reservoir properties of Chang-6 reservoir are mainly controlled by many kinds of factors such as sedimentary facies, rock types and diagenesis. In this case, water diversion channels and sandy debris flow sandbody will show a better reservoir physical propertie, and there will be positive correlation between the content of chlorite film and the number of intergranular pores. The early chlorite cementation and dissolution formation also has constructive effects on reservoir.