Sedimentary characteristics and identification of thin sandstone reservoirs of Qingshankou Formation in Yaoyingtai Oilfield
ZHONG Hong-li1, PU Ren-hai1, WU Yu-yuan2, WU Qun2, ZHAO Hong-xu3
1 Geology Department,Key Laboratory of Continental Dynamics,Northwest University,Xi'an,Shaanxi 710069,China;
2 Design and Research Institute of East China Company,Sinopec,Yangzhou,Jiangsu 210011,China;
3 China-France Bohai Geology Services Company Limited,Tianjin 300452,China
Abstract：Based on sedimentary facies analysis,seismic attribute optimization and well logging constraint inversion,the distribution of delta sand body of Qingshankou Formation in Yaoyingtai Oilfield is indentified,and conclusions obtained in this paper are as follows: Firstly,Qingshankou Formation is thin sand-mud interbed in general.The most favourable reservoir is grained-middle delta front sandstone in lower part of the second member of Qingshankou Formation.Relatively favorable reservoirs are destroyed delta front sheet shape sand body,point bar sand body and crevasse channel sand body of the first Member of Qingshankou Formation.Secondly,because mudstone contains calcium,sandstone and mudstone has similar seismic velocity,natural gamma-ray value and resistivity value.The other log data,seismic amplitude and wave impedance attributes cannot be used to identify sandstone effectively except spontaneous potential logs.Lastly,sandstone growth index can effectively indicate the development of sandstone.The acceleration of amplitude is effectual in recognizing and predicting the sand body distribution of different sedimentary microfacies.The lower acceleration of amplitude value is in good agreement with higher sandstone growth index.Thus the ancient lake distribution of the first member of Qingshankou Formation was discriminated,and the lobe shape delta front sand body of the second member of Qingshankou Formation in west Yaoyingtai area was identified.The drilling proves that Qingshankou Formation in this area developed grained-middle mouth bar sand body and distributary channel sand body with thickness about 10 meters.An exploration well drilled in this target area gains higher commercial oil output than other areas.
