Research Of Sedimentary Features And Distribution Of Near-source Sandstone Of The First Member Of Shawan Formation In Chepaizi Area

Chepaizi area is located in the western of Junggar basin.The Chepaizi uplift have a big supply of petroleum from the nearby depressions,named Shawan sag and four trees depression,they contain a large number of source rocks.In recent years,the exploration of the nearprovenance sand in the first member of Shawan formation has achieved a better results,and the area is expected to become a new exploration spot.The near-provenance sand has a low exploration degree,the distribution of sedimentary system and sand body are not cleared.Therefore,by analyzing the data of core,logging,seismic,analytical testing comprehensively,the characteristics of sedimentary & the distribution of sand bodies were studied in this paper,and obtained a series of results.The sand body of the first member of Shawan formation was mainly comes from the Zaire mountain which is located in the northwest of Chepaizi area,the lithology is mainly composed of pebbly fine sandstone,pebbly coarse sandstone,sandy conglomerate and conglomerate.The near-provenance sand body has the characteristics of low amplitude of SP and high GR,but the negative anomalies were not obvious,and the DEN curves shows a high values characteristic.The study results of sedimentary structure analysis,characteristics of grain size curve & C-M curve show that the near-provenance sand,mainly fan delta deposit,was deposited rapidly in the sag with strong water dynamic conditions.The lithologic assemblage types of near-provenance sand are "Mud coated sand" and "upper mudstone & lower igneous rock".The results of velocity statistics show that the type of "Mud coated sand" has the “low-high-low” speed characteristic,and the type of "upper mudstone & lower igneous rock" has the “low-high-higher” speed characteristic.Combining seismic data analysis & synthetic seismogram calibration results,forward modeling & attribute optimization methods,the description method of sand body was determined,the near-provenance sand body was described.The type of "Mud coated sand" was described by the method of Amplitude attribute,and the type of "upper mudstone & lower igneous rock" was described by the method of Extension of frequency and Slope break analysis.The near-provenance sand body was distributed near to the channels in the northwest of Chepaizi area,the thickness is between 0~12m.It is the favorable area for exploration.