Petrophysics And Seismic Response Characteristic Analysis In Bazhong Qianfoya Reservoir Area

There are abundant natural gas resources in China,nearly 1/3 of natural gas production is from the nonconventional tight sandstone reservoir.According to the existing reserves analysis,conventional natural gas will appears steep slippery trend after 5 years,so the unconventional tight sandstone natural gas reservoirs will be the main target of natural gas exploration and development.The middle and shallow layers of the Yuanba area are divided into three favorable zones,the four sections and the pearls are the main gas-bearing layers in the middle of the dam.In the recent exploration,thousands of wells drilled different degrees of gas show in Bazhong area,among them Yuanba 9 well get gas 22,000 square,oil 16.6 square in Qianfoya,which Indicating that the Qianfo Clay Group has the characteristics of enrichment and high yield.Therefore,this paper is aimed at predicting the subject of tight sandstone reservoirs in Qianfoya Formation in Pakistan and China.Based on the statistical analysis of logging response characteristics,the Zp & Zs intersection is selected as the sandstone sensitive parameter in the background of GR.In the background of porosity,Vp & VpVs are selected in the background of porosity.The rendezvous acts as a sensitive parameter for reservoir physical properties.And then extract the corresponding sensitive attribute from the seismic data body,combined with AVO response characteristics to improve the effective prediction of reservoir and fluid accuracy,then guide the next step in reservoir prediction work.The results obtained are as follows:(1)The sandstone stage is characterized by low natural gamma,high porosity and low muddy content,high density,high P-wave velocity and shear wave velocity,higher P-wave impedance and shear wave impedance.The mudstone is characterized by high natural gamma,low porosity and high muddy content,relatively low density,relatively low P-wave velocity and shear wave velocity,relatively low P-wave impedance and shear-wave impedance.The gas-bearing section is a part of the sand body,which is consistent with the response characteristics of the sand body.In addition,the longitudinal and transverse wave velocities of the gas-bearing intervals are lower than those of the other non-gas-bearing section.This is the most significant logging response characteristic of the gas bearing.(2)From the analysis of petrophysical: In the GR background,select Zp & Zs rendezvous as sandstone sensitive parameter pair;In the background of porosity,select the Vp & VpVs intersection as the reservoir property sensitivity parameter pair.(3)AVO simulation of actual well data,the gas-bearing layer is characterized by the fourth type of AVO response: Poor oil and gas layers are characterized by Type II AVO response.The influence of gas saturation,porosity and reservoir thickness on the response characteristics of AVO showed some regular characteristics: With the increase of gas saturation,the amplitude of the same phase of the gas-bearing layer decreases gradually;the P value decreases,the G value increases,and Sg changes from 0 to 20% in the process of large amplitude,AVO response in the fourth category changes;With the increase of porosity,the amplitude of the same phase of the gas-bearing layer decreases gradually;the P value decreases,the G value increases,and the amplitude of the change is gradually reduced,the AVO response changes in the fourth category;With the increase of the thickness of the gas-bearing layer,the amplitude of the same phase axis decreases with the increase of the thickness of the gas-bearing layer;the P value decreases first and then increases,and the G value increases first and then decreases,the AVO response is transformed from Class III to Type IV.(4)AVO anomaly analysis shows that the gas-sensitive properties of the target layer in this area are Poisson's ratio,fluid factor,AVO intensity and P * signG.(5)Earthquake Geological Characteristics of Qianfoya Formation: In the end of the first sections of Qianfoya at the same phase with the "complex wave" phenomenon,Indicating that the lower part of the vertical lithology,physical changes are smaller,from the lower part of the upper sand and shale distribution there is a big difference.So the sand body is widely spread,the thickness changes faster.The two sections of the Qianfoya group are approximately parallel to the same phase,and the whole is parallel or nearparallel.In the second paragraph,the upper section of the same phase with a strong amplitude,Local of them appear "complex wave" phenomenon,Indicating that the two paragraphs,the upper section of the horizontal lithology,physical changes in the larger.Which in the second paragraph of the next paragraph to identify the sand from the north east of the distribution,In the second section,the upper sub-section is from the north east to the east;The third section of Qianfoya are approximately parallel to the same phase,and are shown as parallel or near-parallel trending facies.In the lower part of the third section with a strong amplitude,Local of them appear "complex wave" phenomenon,indicating that the three vertical section,horizontal lithology,physical changes in the larger.