| Chepaizi uplift of Neogene oil and gas with the "shallow layer, high-quality, high-yield" and other features has great prospects for oil and gas exploration. However, the overall level of exploration in the area is still relatively low, the lithologic trap reservoir condition is very complex, "bright spot" mode is singly used that can not solve the problem in the area of exploration, especially for the second member of Shawan Formation lithology, its depth reaches 1600 m for "bright spots" threshold, It appears that pai 2 and pai 8 wells to get great breakthroughs In the early time, later, the pai 204 and pai 208 wells fall phenomenon. The reasons are mainly for target layer of sand distribution is unknown, the depositional system is not clear understood and the trap location of implementing is unable.In response to these problems, the paper on the basis of previous studies, drilling and seismic data is synthetically applied, firstly, by analysising the Early Miocene sequence stratigraphic structure of Shawan group to Set up sequence stratigraphic frame styles of The second member of Shawan; Then I choose S2-3 Parasequence group as the research subjects, through analysising the typical drilling profile of velocity and waveform to build sand identification; On the basis of these, I carry out S2-3 sand seismic scan interpretation, then by analyzing sand boundary to delineate sand and show S2-3 sand flat distribution; Finally, according to the profile structural characteristics of sand bodies(such as foreset), sand flat shape and comprehensive analysis of the sand body assemblages to calibrate of the flow direction, further seismic facies and sedimentary facies are analyzed, and recognizing delta-lacustrine depositional system. The main progress and understanding is summarized in the following five areas:(1) By doing Shawan group sequence stratigraphy analysis, Shawan group is divided into three sequences, I find that the three sequences are corresponding to the previous lithostratigraphic division unit(the 1st member of Shawan Formation, the 2nd member of Shawan Formation and The 3rd member of Shawan Formation).(2) The analysising of Shawan group Sequence stratigraphic architecture and phase distribution show that SQ2 developed in the super sequence of shawan group of Lake transgression, the lake basin rapid expansion, the undercompensation of sedimentary deposition caused to the open and deep water, this is the mainly reason for the S2-3 Parasequence development in meare, semi-deep lake and deep lake environment.(3) S2-3 Sand Formation sandstone scan interpretation of the results shows that the sand groups mainly develop channel sand, mouth bar, sheet sand, suprafan sand.(4) The results of waterflow system shows that the provenance is mainly from NNW, six branch channels are developed in delta, this recognition further confirms Xu Guoqiang et al concluded that early.(5) S2-3 depositional system studies indicate that Uplift zone near the northern develop delta deposits, prodelta of slope and meare environment lack sand accumulation, the undercompensation environment of the southern edge of the work area develop deep-water fan, thus form a large lake with a gentle slope Delta-deep water fan depositional system. Large lake rapid lake transgression and undercompensation sedimentary are the mainly reasons for this complex depositional system. |
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