Application Of High Resolution Sequence Strtigraphy Into Early Stage Of Development In Hongtai-Gedatai Oil And Gas Field, Tuha Basin

This paper is focused on the application of high-resolution sequence stratigraphy in the reservoir characterization and modeling at the early stage of development in Hongtai-Gedatai gas and oil field, Turpan Basin, northwestern China. In the application of high-resolution sequence stratigraphy, the sedimentary features and the controlling factors were analyzed in mid-term base-level cycles and in short-term base-level cycles. The mid-term base-level cycles controlled the distribution of subfacies and thus controlled the reservoir architecture; while the short-term base level cycles controlled the microfacies type of sand bodies and thus the heterogeneities inside sand bodies. Base on seismic, logging and geological data, four mid-term base-level cycles were distinguished from Middle-upper Xishanyao Formation and Sanjianfang Formation of the middle Jurassic, inside which the types, characters and evaluation pattern of sedimentary facies were analyzed. The concept of Coefficient of Sediment Volume Partitioning (CSVP) was put forward and used in the analysis of provenance. According to the research, the target formations were belonged to tow channel-controlled coarse-grain braided river deltas on the southern gentle slope of Turpan Basin. The provenance of Hongtai delta was from the southeast, Gedatai from the southwest. The evaluation of delta was divided into two stages, retrogradation and progradation, which was controlled by structure, climate and sediment supply. Owing to the gentle slope and the insufficiency of sediment supply, mouth bars were developed not very well. The main microfacies were braided distributary channels on delta plain and subaqueous distributary channel on delta front. Inside the mid-term base-level cycles, 41 short-term cycles (members) were distinguished on the basis of stack patterns and sedimentary sequences under different A/S. There were tow types of reservoir architecture, labyrinth and jig-saw puzzle. Digenesis was the main factor which caused the macroscopic variance of reservoir quality; while sedimentation was the reason for microscopic heterogeneities inside sand bodies. The change of reservoir architecture and the microscopic heterogeneities of sand bodies were correlative with the change of A/S. The decrease of sediment supply is the primary reason for the change of A/S value. Finally, isochronal facies-restrained stochastic modeling method is used to build up the 3-D reservoir model. Truncated Gaussian field simulation was used in the modeling of subfacies geologic model. Marked point process was used in the modeling of microfacies. 3-D reservoir parameter model was built up on the basis of microfacies model. This research provides an important geological basis for oilfield development management.