Prediction Of Thin Reservoirs Under Coal Measure Strata In Hongtai-Gedaotai Area

Along with the continual elevation of prospecting,the Jurassic coal measure strata sandstone reservoirs have become the key areas for oil and gas exploration.However,due to the coal seam shielding effect,it is difficult to predict oil-bearing sand layer effectively.Through the investigation of domestic and foreign literatures,we can know the formation mechanism of strong energy shielding effect of coal seams and the technical methods of eliminating the strong energy of the coal seams.Employing Xishanyao Groups of Jurassic system in Hongtai-Gedatai Area as research objects,The typical reservoir model is established and the forward modeling is performed by using sedimentary reservoir features in the study area,which is used to analyze the frequency and energy response characteristics of the coal seam and the overlying thin sand layer,and the influence of the coal seam on the prediction accuracy of the thin reservoir with different thickness.Using the real seismic data,the applicability of seismic signal decomposition and reconstruction techniques to eliminate coal seams,and anticipated the thin reservoir of major goal layer.Based on the method of post-stack geostatistical inversion,the analysis of the effect of multi-wavelet decomposition and reconstruction on eliminating coal seam.Based on the reconstructed seismic data,a comparison study of wave impedance inversion and geostatistical inversion is carried out to determine the distribution characteristics of sand layers.Using drilling data to test and analyze the effect of conventional geostatistical inversion prediction.Based on this,a 3D trend-constrained geostatistical inversion study is conducted to improve the accuracy of the prediction.Finally,there are two techniques to corroborate by each other and a comprehensive analysis to determine the distribution of favorable reservoir.Research shows:(1)The formation mechanism of the strong energy shielding effect of the coal seam is that the interface between the sandstone and the coal seam forms a strong reflection interface so that the reservoirs under the coal seam are shielded,and the relevant reservoir information can not be clearly seen from the seismic profile.(2)Forward modeling shows that Multi-wavelets decomposition and reconstruction technology can effectively predict thin reservoir and improve the identification accuracy of sandstone under coal.(3)The wavelet decomposition and reconstruction based on the Ricker wavelet are batter than the method based on the matching pursuit and the method based on multi-wavelets data body.Using this technology predict the thin reservoirs in coal mines,and the strong anomalies in the northern Hongtai 16 well are effectively eliminated.(4)The method of post-stack geostatistical can improve the prediction accuracy,and post-stack geostatistical is batter than wave impedance inversion.The inversion results are consistent with the distribution of sedimentary facies bands.(5)Confirmed by the two technologies,a total of 6 favorable sand bodies and 4 remaining favorable sand bodies were predicted and analyzed by comprehensive analysis.The direction of the next lithological exploration of the block is pointed out,which provides a basis for the increase of reserves and production in this area.