The Tectonic-Sedimentary Response Model Of Sequence Straitigraphy Of Shahejie Period, Kongnan Area In Huanghua Depression

Kongnan area is located in the southern of Huanghua depression. In the east and west sides, Cangdong fault and Xuxi fault are as the boundary respectively, north to NanDi, and south to DengMingsi. It developed Kongdian Group (Ek) Shahejie Group and Dongying Group in Paleogene Eocene and Guantao Group in Mirocene from bottom to top. With the enhanced role of fault depression since Cenozoic it developed four main faults and a NEE tectonic transfer zone. The four faults are Cangdong, Xuxi, Kongdong and Kongxi fault. As the boundary controlling faults, Cangdong fault and Xuxi fault controlled the subsidence pattern of all Kongnan area. Kongdong and Kongxi fault controlled the development of Kongdian tectonic zone. Kongnan area is devided in two different regions of subsidence pattern with Shenvsi– Wangguantun tectonic transfer zone. The study area can be divided into four major tectonic units as the boundary of these fault zones, which are Nanpi depression, Cangdong depression, Changzhuang depression and Kongdian tectonic zone.Currently it has carried out a lot of researches about Shahejie Group in tectonic and sedimentary. These studies focused on the identification of sediment type, the distribution of sand bodies and tectonic characteristics. The division and correlation of sequence stratigraphy have been done in some local areas of important exploration region. Comprehensive study of the relationship between tectonic, sedimentary and sequence stratigraphy has not undertaken yet in the study area. A model has not been established to explain the evolution and the relationship between tectonic, sedimentary and sequence stratigraphy, which model can also forecast the distribution of sand and stratigraphic-lithologic reservoir. This largely restricted the knowledge of evolution of tectonic-sediment and seriously slowed down the exploration progress of Shahejie Group in Kongnan area. The key to solve this problem is to determine the main controlling factors of the sequence development of Shahejie Group, study the tectonic setting of each sequence development stages and controlling of sedimentary facies, sand bodies and sedimentary systems for tectonic movement, and establish the tectonic-sedimentary response model of sequence stratigraphy of Shahejie Period.In this study, we start from the unique geological conditions in Kongnan area, take stratigraphy - sedimentary evolution of sequence stratigraphy as the main line, and research from three dimensions:①Establish the division scheme of sequence stratigraphy which applies to the whole region through analyse stacking pattern of single well and combine other means of numerical analysis, such as the wavelet transform and logging attribute analysis. Then, research the borehole seismic base level cycle matching and establish isochronous stratigraphy correlation framework. At last study the relationship between tectonic and sequence stratigraphy through the character analyse of sequence boundary, the composition of systems tract and profile structure.②According to drill core, borehole logging, well logging and other datum, analyse the types of sedimentary facies and the distribution of sedimentary systems and sand bodies. At last establish the relationship between tectonic and deposition.③Through the study of the tectonic evolution and the major fault activity to identify the tectonic settings of every sequence periods. Establish the tectonic-sedimentary response model of sequence stratigraphy under the controlling of different tectonic settings through the research of relationship between sequence, deposition and tectonic. At the base of research above, the final results and knowledge obtained as follows:(1) Shahejie Group can be divided into three third-order sequences and nine system tracts. Shahejie Group can be divided into 7 fourth-order sequences, 14 half-cycles of mid-term datum plane. SequenceⅠequals to the Shasan formation, SequenceⅡequals to the Shaer formation and SequenceⅢequals to the Shayi formation. The division scheme has universal applicability in the study area.(2) We identified the tectonic setting where the study area located during three sequence evolution period. Through the study of the stratum distribution, the subsidence pattern of isochronous stratigraphy correlation framework, the distribution of sand bodies and sedimentary systems, source of provenance, basic volcanism and seismic data, we concluded that the tectonic regimes are distinguishing in the different developmental stages of the sequence: SequenceⅠand sequenceⅢare formed under the system of strike-slip - extensional tectonics, However, during the sequenceⅢ, strength of tectonic activity was significantly weaker than sequenceⅠ. SequenceⅡformed under the tectonic regime which is dominated by strike-slip. (3) We identified the relationship between the tectonic and the sequence stratigraphy. By the research of the borehole seismic base level cycle matching and the different tectonic setting of the sequence period, we defined the relationship between the change of tectonic activity forms and sequence stratigraphy; the changes of tectonic activity in intensity and sequence stratigraphy. We believed that the changes of tectonic activity forms during the developmental stages of each sequence formed sequence boundary between sequences (third-order sequence boundary), meanwhile, the changes of tectonic activity strength within the sequences formed a flood plane or maximum flooding surface (fourth-order sequence boundary). This knowledge has deepened the understanding of the relationship between the tectonic and the sequence stratigraphy evolution.(4) Three kinds of sedimentary facies, seven kinds of sedimentary subfacies and fourteen kinds of sedimentary microfacies are identified. From bottom to top, sequenceⅠdeveloped fan delta+delta+shallow lake-delta+deep lake, semi-deep lake-delta+shallow lake, semi-deep lake sedimentary sequence; SequenceⅡdeveloped delta+shallow lake-delta+shllow lake, semi-deep lake sedimentary sequence; SequentⅢdeveloped shallow lake-semi-deep lake-shallow lake+delta sedimentary sequence.(5) The concept of the tectonic-sedimentary response model of sequence stratigraphy and classification system is proposed. According to the sequence boundaries which are formed because of the change of tectonic activity strength and the change of the tectonic activity forms, called typeⅠa nd typeⅡ, we divided the tectonic-sedimentary response model of sequence stratigraph into 9 types.(6) We established the tectonic-sedimentary response model of sequence stratigraphy during each development stages of sequence, pointed out the sand distribution patterns and advantageous exploration position of stratigraphic-lithologic reservoir.The innovative points in this article as follows:①We identified that the change of tectonic activity forms the tectonic sequence boundary and the change of tectonic activity strength forms the flooding plane or the maximum flooding plane. This conclusion has great significance for the theory of sequence stratigraphy, especially for development of the theory of tectonic-sequence stratigraphy in particular the construction of to the development of the theory. ②The concept of the tectonic-sedimentary response model of sequence stratigraphy and classification system are proposed and research the characters of sequence boundary (the positions and types of reflection termination phenomenon), filling model of sequence (source of provenance and the develop rules of sedimentary systems), developed rules of system tracts (the position and the stacking pattern of each system tracts).③Propose the concept of borehole seismic base level cycle matching and improve the concept of borehole seismic matching. It plays an important role in the research of sequence stratigraphy and high-resolution sequence stratigraphy comprehensive utilization of drilling and seismic data and calibrate special reflection axis on seismic profiles with sequence stratigraphy meaning using the well information.④We established the tectonic-sedimentary response model of sequence stratigraphy of Shahejie period in Kongnan area, summarize the forecasting means of distribions of sand bodies and the stratigraphic-lithologic reservoir which based on the model.