Research On Sequence Stratigraphy And Sedimentary Facies Of Jiu Fotang Formation In Nai Manqi Depression

Fan-delta reservoir is one of important reservoirs in Meso-Cenozoic nonmarine basins China. It is significant to establish the relevant sequence stratigraphy method for evaluating and predicting fan-delta reservoirs. Naimanqi Depression has good generation and reservation conditions, owning enormous potential to be explored and developed. To speed up the process of exploring Naimanqi Depression, based on the analysis of existing data and research results, the paper further studied on its sedimentology and sequence stratigraphy, in order to find out the reservoir characteristics and Cenozoic hydrocarbon condition of Naimanqi Depression.In this paper, according to geologic features and seismic reflectance signatures of Naimanqi Depression, we carried out studies on sequence stratigraphy, sedimentology and reservoir geology by integrating drilling data, logging data, seismic data and some other data. On the above basis, we combined geophysics method to predict reservoir. Sedimentary results were used as constraint conditions for seismic inversion and were correlated with inversion results to constrain arbitrariness and to enhance rationality, and consequently, to improve effectiveness of prediction.The main contents studied in this paper contain: 1. to establish the sequence framework; 2. to study on the sedimentary environment and facies; 3. to predict the reservoir by using constraint inversion in the areas without well data; 4. to evaluate reservoirs and predict favorable areas by method of fuzzy mathematics.The main innovative points are as follows:1. It was the first time the sequence stratigraphy study had been done all across Naimanqi Depression. Jiufotang Formation of Naimanqi Depression was divided into two third-class sequences (SQ1 and SQ2) and five system tracts (SQ1 has LST, TST and HST; SQ2 has TST and HST), and in High System Tract (HST) of SQ2, two fourth-class sequences were defined (Ssq1 and Ssq2).2. According to the analysis of core and logging data, we considered that it is the delta fan facies and established the electrofacies model.3. The distribution of reservoir sand bodies had been predicted in the areas without well data by combining the methods of sequence stratigraphy and reservoir inversion. In addition, we summarized the method and process of combining geology and geophysics to predict reservoirs and we made a good prediction by applying it.4. Combining with sequence and depositional types, sandstone thicknesses and reservoir properties, based on Petrel Software platform, we used fuzzy mathematics to comprehensively evaluate reservoirs and define favorable areas. We classified the reservoirs in Naimanqi Depression into five types (Typeâ… , Typeâ…¡, Typeâ…¢, Typeâ…£and Typeâ…¤) and pointed out four favorable areas: Block Nai 1, Block of western Naican 1-Zhangjia Depression, Block Nai 6 and Block of Xinfa-Zhangjia Depression.