Application Study On The Impedance Inversion And Seismic Facies Of The Igneous Rocks In JY Area In Tarim

Halahatang area of Tarim Basin area has formed good geological conditions forhydrocarbon accumulation, where also developed huge thick Permian igneous rocks.The volcanic eruption pattern is not very clear, and the Permian igneous rocks withvariation of lithology and velocity, affect the migration imaging and variable-velocitystructure mapping of the traps under igneous rocks. In this paper, geological data,logging data and seismic data of JY area located in south of Halahatang area, werefully used to analyze and explain the seismic facies of igneous rocks, and severalseismic inversion method were applied to study spatial distribution and establishaccurate velocity field of igneous rocks.First, in order to know the geology of JY area well, the geological data, loggingdata, and seismic data were collected and analyzed on the basis of previous research.The logging data were processed to remove outliers, and to be corrected with standardmean-variance method. Logging response characteristics and seismic response ofigneous rocks were analyzed by using geological data, and crossplots shows that theigneous rocks have lower DT value and higher GR value. At the same time, seismicfacies were divided into four kinds of facies, combining with traditional method andwaveform classification.Secondly, for the igneous rocks area, three different seismic inversion methodswere used and analyzed comprehensively.(1) In this area, CSSI, ANN inversion,logging property inversion were used with their processes were analyzed:well-seismic calibration, wavelet extraction, initial impedance model construction,and QC parameters setting, coming with P-impendence of igneous rocks.(2) The DTcurve constrain the whole process of inversion. In order to improve the ability toidentify lithology and maintain the velocity, the DT curves were reconstructed withwavelet transform.(3) In order to make fully use of useful information of differentkinds of inversion result, a new probability-data volume was generated by probabilitylaw, which truly shows the distribution of igneous rocks.(4) The P-impendence wastransformed into P-velocity, with evaluating the inversion velocity of boreholes, thevelocity error of10wells is less than4%. The inversion velocity meets therequirements of accuracy of velocity field.To sum up, on the basis of seismic facies analysis combined with the geologicaland logging data, three seismic inversion method were analyzed and used to figure outthe distribution of igneous rocks, and the accurate velocity field was established. The whole solution of velocity field in this paper provides an accurate velocity field forthe target layer’s depth data conversion in this area. All of this provide favorablesupport for the structure migration imaging and variable-velocity structure mapping ofsubsequent low amplitude construction.