Study On The Cretaceous-the Paleogene Sequence Stratigraphy Of FangZheng Fault Depression

Based on the sequence stratigraphy and sedimentology, this thesis has applied the knowledge of earth physics , the data of logging and drilling, and the data of analysis, then it has also summed the depositional systems of the target layer, the identifica- tion of sequence interfaces and the division signs of sequence stratigraphic units. And it has established sequence stratigraphic framework. The author divides the cretaceous into three 3-order sequences. And the author divides the Paleogene into seven 3-order sequences and 21 systems. The sequence stratigraphy interfaces and traditional lamination interfacial parallelism relation has been assured.The target layer develops 4 sequence patterns: shallow lake sequence, scalloped delta sequence, shallow lake sequence and alluvial sequence. The thesis has summed 3 sequence stratigraphy patterns: sequence stratigraphy pattern of abrupt slope belt, sequence stratigraphy pattern of deep depression area and sequence stratigraphy pattern of gentle slope belt.After extending sedimentary systems of three 3-order sequences of Cretaceous layer, and eight 3-order sequences of highstand systems tracts and lowstand systems tracts separately which is 16 equivalent time units of Tertiary layer. Statistically combining sequence stratigraphy with oil and gas bearing relationship, it shows that: sequenceâ…¢,â…£,â…¤are best oil and gas bearing sequence, lowstand systems tracts is non-structural trap, fan-delta sand body and sublacustrine fan developed during low water level period, as well as transgressive sand body and sublacustrine fan systems developed during transgression and high water level period, form lithological reservoir, over nipped reservoir or compound trap reservoir.Synthetically analycizing fundamental formative condition of petroliferous reservoir and extending of sand body , 4 favorable reservoir development zones have been forecasted.