Research On Geophysical Prediction Method Of Shale Gas Reservoir And Its Application

The shale gas have the characteristics of low porosity and extremely low permeability,its geophysical parameters are less sensitive.The reservoir prediction of shale gas becomes very difficult owing to the multifarious accumulated modality and internal heterogeneity.The paper integratedly and systematically researched the influence factors(distribution feature on plane,reservoir feature,preservation condition et al.)for enrichment conditions aimed at the particularity of shale gas by geophysical method.Combined with multiple logging data and high precision processed seismic data,optimized the calculation method of reservoir parameters,and systematically predicted the evaluation parameters of shale reservoir.This paper includes a few aspects:(1)Further researched the correlation between the core materials and logging data,deeply excavated the superiority of ECS(Element Capture Spectroscopy)logging when calculated the shaliness to bind to the abnormal response features of organic on gamma-spectrometry log sufficiently,optimizated and formed a accurate calculating method of TOC by multi well-logging information,the limitation of prediction by single solution have been overcomed.On the basis of accurately calculated TOC and shale content,selected the optimization log interpretation method to realize the integrated process of multidimensional composite information.The calculated values are more closed to actual parameters.(2)Propsed a refraction static correction technique for multi-wave combined converted wave aimed at the difficulty.This technique achieved P-P-SV first break imaging and identification by the combination of the first break pick-up for P-P-P refraction wave and the first break stacking in CRP gather for P-P-SV refraction wave.On this basis,to solve the delay time of receiver point for P-P-SV refraction wave we combined the refraction static correction of P-P-P refraction wave with the delay time extraction of P-P-SV refraction wave.At last,according to the delay times of receiver point for P-P-SV refraction wave,the datum level statics of P-SV receiver point can be obtained.The experimental result shows that the refraction static correction technique of multi-wave combined converted wave improved the calculation accuracy of converted wave static correction and the imaging quality.Laid a good foundation for subsequent research of structural analysis and reservoir prediction based on seismic data.(3)Set up a simulated atomic transition nonlinear algorithm which have character of weak dependence on initial model applied in pre-stack elastic parameter inversion,the inversion accuracy was effectively enhanced.Then take the high precision inversion results of Poisson's ratio and Young's modulus achieved shale brittleness and gas-bearing prediction on the plane by Rickman formula.Based on detailed rock physics analysis,established the linear relationship between TOC and impedance,to obtain the TOC data by post-stack inversion,according to the results of organic content in well logging to depict the spatial distribution of TOC effectively.(4)Analyzed Fillippone and Liu Zhen method from different aspects,combined the advantage of independent compaction trend line formula and the logarithmic relationship between formation pressure and velocity,propsed a improved pressure prediction formula which contain a correction adaptive coefficient with velocity,eliminated the any factors except pressure impact on velocity,achieved accurate pressure prediction with seismic data,predict results had less errors,it provided an advantageous evidence for finding the "sweet spot" of shale reservoir.(5)Intensively researched the geophysical prediction method of shale distribution,burial depth,thickness,TOC,porosity,gas content,pore pressure,degree of fracture development,and shale brittleness etc.Referenced to the geologic evaluating standard for shale gas,established a comprehensive evaluating index of seismic,implemented the comprehensive prediction and grading evaluation of shale gas "sweet spot".Based on the previous study of logging,seismic and geology,explored and established geophysical method for prediction of shale gas reservoir of "sweet spot",initially formed a comprehensive evaluation system for marine shale gas in south Sichuan.Close integration of the current emphasis at exploration and development of shale gas in south Sichuan with application in Jingyan-Qianwei area.Provided the basis of structure description,fault description,fracture description,reservoir description,predicted spatial distribution of high quality shale,pressure prediction,"sweet spot" prediction,analysis of reserve condition,comprehensive evaluation,and well placement.During the research,I mastered the working methodology,ideas,and some skills of geophysical prediction and evaluation on the large area of seismic data,to deepen the cognition and understanding of shale gas in Sichuan,laid a solid basis of the work in the future.