Research On The Flow Units Of Chang-8 Member Of The Yanchang Formation In Honghe Oilfield

Since well Honghe 105 which is in Chuankou area has been made a high yield of oil in2008, several rounds of the area resource assessment has also been conducted, showing the area has good development prospects. Chang-8 oil reservoir, which is the main producing formation in this block, is of low porosity, low permeability, and weak of oil and gas storage capacity. Therefore, for a further exploration and development, this article carried out a research on the flow units of Chang-8 reservoir in Honghe Oilfield based on the characters of low porosity, low permeability, complicated distribution and high heterogeneity of lacustrine delta in this area.In this paper research targets are the member Chang8 oil reservoirs of Chang8 formation in HH105 area in Honghe oil field in Ordos Basin.The geological, coring, logging and production behavior data, made full use of the principles of sequence stratigraphy, sedimentology and petroleum geology and other disciplines, the Chang8 oil group has been divided into three middle-term base-level cycles MSC1, MSC2, MSC3 and thirteen short-term base-level cycles. The research shows that:the structures in HH105 area are simple, the layers are horizontal, and that the provenance is in the WS direction. It belongs to the front braided stream delta facies sedimentation and can be divided into four microfacies, underwater distributary channel, distal bar-sheet bar, distributary mouth bar, underwater interdistributary. The reservoir sand bodies are mainly developed in the underwater distributary channels.The main types of rock in Chang8 reservoir are grained lithin and medium arkose,with particle grading poor to mediocre, psephicities are poor.And the types of pore are intergranular pores, intragranular pores, moldic pores, micropores, etc.The main types of pores are inter-partical and dissolution pores.The pore throat sorting is poor. What’s more, through researching the heterogeneity of inner layers, interlayers and horizons, it has been concluded that the Chang8 reservoir has serious heterogeneity.Using SPSS statistical software and clustering method of connection, the Chang8 reservoir has been divided into three types of flow units. They are respectively class B, class G, and class P, among which the properties of class B flow units are the best while the properties of class P are the worst. The classification results have been verified from seepage features, spatial location ratio and heterogeneity, and the division of flow units in this area has been proved to be reasonable. Division results show that the flow units of the major reservoir SSC3 short-term base-level cycles (S-cycles) mainly belong to class G and class P, with class G flow units accounting for 25%and the class P flow units accounting for 53%, class G mainly distributed in the central sand belt, with sand bodies continuous. Class P mainly distributed on the edges of channels, while class B distributed sporadically in whole district. The SSC4 S-cycles flow units mainly belong to class P with class G flow units accounting for 38%and class P flow units accounting for 52%, which are usually divided by class B, mainly distributed in the margins of the reservoir.The distribution of Class B is in a smaller range in the whole district and relatively sporadical. And the same flow units are far apart. The SSC5 S-cycles mainly belong to class G with class G flow units accounting for 63% and class P flow units accounting for 26%, mainly distributed in the central sand belt The SSC9 S-cycles flow units have a independent uncontinuous distribution form, and the main flow units are class P, and that is followed by class G, Class B hardly exist, only in a small scale in some areas.Taken together, the main factors influencing the flow units in this area are sedimentary microfacies, reservoir properties and diagenesis.The above research results can be applied to the actual production of oil field, and to redeploy and adjust the oilfield injection-production well pattern so as to achieve effective development, improve the oil recovery, and keep the oil field production stable.