Ordovician Seismic Reservoir Prediction In Block 10 Of Tahe Oilfield

Carbonate rock is one of the important reservoir types in China,its exploration and development occupies an important position in the world petroleum industry.Globally,its oil and gas reserves account for about 40%and its oil and gas production account for 60%of the total production in the world.Among the recoverable reserves of oil and gas resources discovered in China,carbonate rock only accounts for 18%of the recoverable reserves in the current.Compared with the proportion of global carbonate reservoirs in the oil and gas resources,China still has the great potential for the exploration and development of carbonate reservoirs.The tarim rive oilfield,which is dominated by Ordovician carbonate fracture-cavity reservoirs,is the Paleozoic marine carbonate rockfield in China.In fractured-vuggy carbonate rocks,fractures and karst caves are the main migration channels and reservoir space of oil and gas,and a "string beads" seismic reflection structure is shown on the seismic section.However,due to the carbonate formation in the tarim river oil field is generally older,strongly karstified,deeply buried,and undergo the process of dissolution,re-dissolution and filling lends to the distribution of reservoir space not uniform,the size different,the heterogeneity strong,the shape diversified,and the genesis complex.It also leads to the difficulty in reservoir prediction and low success rate of drilling.Therefore,how to find some effective geophysical technologies to predict carbonate fractured-vuggy reservoirs is the key problem to be solved urgently in this area.In order to solve the technical problems above and promote the exploration and deployment of the research area,based on the research methods of fractured-vuggy reservoirs,this paper comprehensively utilizes the geological,seismic,drilling and logging data of the area,and combines with the "string beads" geological characteristics,extracts various seismic attributes to predict the reservoir.On this basis,compared with the effect on multiple attributes fusion of principal component analysis(PCA)and local linear embedding(LLE),the better algorithm is selected to carry out K-means clustering analysis so as to further improve the prediction accuracy.The main conclusions of this study are as follows:(1)By using ant attributes extracted through ant algorithm and combined with the original seismic data,the distribution of cracks and caves could be recongnised.(2)The method of wavelet transform is used to diviede frequency to obtain single frequency volume energy.By comparing the energy changes in low frequency and high frequency,it is concluded that the energy in low frequency band will be enhanced while that in high frequency band will be attenuated when reservoir contains fluid.(3)The attributes of formation absorption,seismic fluidity,high frequency attenuation gradient and low frequency enhancement gradient are extracted to detect the reservoir.(4)The effect of principal component analysis(PCA)and local linear embedding(LLE)on attribute fusion is compared and analyzed,on the basis of attribute fusion,K-means means clustering analysis technique is used to cluster the fused attribute so as to improve the accuracy of reservoir prediction.(5)Integrating the results of ant attributes and K-means clustering analysis,making full use of the advantages of each method,the prediction accuracy of favorable reservoirs is improved to the greatest extent,and the favorable exploration areas are divided to provide theoretical and practical guidance for later exploration.The results of the reservoir prediction obtained in this study area are in good agreement with the oil and gas production of the well in the study area.A set of methods for reservoir prediction of carbonate fractured-vuggy units has been formed.The comprehensive evaluation and application results are good,which provides a basis for later exploration and development.