Study On Carboniferous Sedimentary Facies And Characteristics Of Reservoir In Southwestern Area, Tarim Basin

The southwest depression in Tarim basin covers an area of 15.15×10~4 km~2. The Bioclastic Limestone Member and Donghe sandstone interval of Carboniferous are the main sections for petroleum exploration. Previous explorative achievements and data of adjacent regions indicate prolific petroleum resources. It is important to develop petroleum geological studies in detail on the two sections.In this paper, using new theories such as sequence stratigraphy, advanced sedimentary and reservoir geology, based on coring data, well logging, outcrop analytical data and related basic geological data and combining previous research achievements, division and correlation of sequence stratigraphy of the Bioclastic Limestone Member and Donghe sandstone interval are done, the regional isochronous stratigraphic correlation framework is built. According to integrated analysis of lithology, texture and other facies indications of wells, it is conformed that platform marginal high energy bioclast-bank subfacies, restricted platform biolclastic-bank subfacies, restricted platform lagoonal subfacies, restricted platform tidal flat subfacies are developed in the Bioclastic Limestone Member. Foreshore subfacies, backshore subfacies, shoreface subfacies, barrier bar subfacies and restricted lagoonal subfacies are developed in Donghe sandstone interval. Through analysis of single well sedimentary facies and correlation section, combining paleogeographic province, seismic phase and logging facies, in the light of sequence stratigraphy theory, this paper reveal the space and transient evolution rule of Donghe sandstone depositional system in the studied area. The author first proposed that the semi-rising cycle in first high frequency cycle is the depositional environment of typical plane coast system and its semi-downing cycle changes into depositional environment of barrier island system,i.e. barrier bar is developed near Qun 6 well. Through analysis of sedimentary facies, and sedimentary system and its distribution and vertical evolution rule, sedimentary facies model is built. Through the study on reservoir lithology and physical property, reservoir development and the main controlling factors of reservoir quality are discussed. Combining distributions of sedimentary facies and characteristics of seismic section and reservoir, comprehensive evaluation and target optimization of reservoir are done to provide instruction to further petroleum exploration.