ARCHITECTURE STYLES AND SEQUENCE STRATIGRAPHIC MODELS OF NIUBAO FORMATION SLOPE BREAK BELT IN LUNPOLA BASIN, CENTRAL TIBET

Based on the theories of sedimentology, sequence stratigraphy, petroleum geology and an integrated investigation on well logging, seismic data, cores and outcrops, the Niubao formation has been subdivided into seven third order sequences from base to top, namely SQ1, SQ2, SQ3, SQ4, SQ5, SQ6, SQ7. Two types of sequence styles including faulted slope break zone and flexure slope break zone are identified on the basis of sequence framework analysis of Niubao Formation. We also documented the features of slope-breaks and their control on the spatial and temporal distribution of sedimentary systems. According to the previous integrated analysis, sedimentary models was set up, which is significant for the prediction of reservoir distribution and potential source rocks.

The results show that during LST stage large-scale low stand fans developed in the flexure slope break zone and incised channel distributing upper slope break. The flexure slope break can act as the abrupt transition boundary from shallow water to deeper water in the HST. The bottom boundary usually develops incised channel and the lower parts of the structural slope developed slope fan and sublacustrine fan in the LST of faulted slope break zone. The HST developed braided river delta in the faulted slope break zone. It was concluded that sublacustrine fan developed within LST of SQ2, SQ3, SQ4, SQ5 are the favorable reservoir sand bodies and targets for future hydrocarbon exploration.