Channel Sand Body Of The Ordos Basin Sulige Gas Field Identification Research

Aiming at He-8 low-permeable sandstone reservoir characteristics of thinner effective thickness, faster lateral change and more complicated geophysical character of Sulige gas field in Permian system of Ordos Basin, this paper plotted out the favorable zones of seismic facies, recognized the high energy fold-channels, forecasted the favorable gas-bearing areas and selected the development object blocks by combining seismic facies analysis, channel identification and gas-bearing reservoir predicting methods. The research results have provided important proofs for exploitation arrangement and plan programming of the gas field. The main productions and innovations in the paper are as follows:According to the refined demarcation of seismic and geological layers, and waveform characteristics classification, it is the first time to divide the seismic reflection patterns of He-8 reservoir into two main categories and ten sub-categories, and two sub-categories of them are the most favorable reflection patterns. Using the seismic facies analysis technique divided He-8 reservoir seismic facies into three categories. The seismic facies have better corresponding relation with the sandstone thickness, and sandstone thickness from the seismic facies conversion is more reliable than that from the impedance inversion. It is the first time to bring forward that arc length, effective band width and energy half-time are the most hypersensitive post-stack attributes to He-8 stratum. Their planar results reflect the distributing characters of sand bodies, the lithology changes in horizontal and vertical direction, and macroscopic heterogeneity of the reservoir, respectively.Integrating the results of seismic ancient landform restoration from layer flattening and high resolution seismic sequence analysis from Generalized S Transform, four main folded channels have been identified. Their distribution on the plane is near north-south direction, putting up frequent distributing, intercrossing and complex characteristics, and including seven intercrossing districts. The distributing and intercrossing zones of the channels are gas-bearing favorable areas. The identifying results reflect sediment and transformation characters of the channels, and delineate the macroscopically distributing patterns of the braided rivers. And the channels' configuration and distribution accord with the current geological understanding. That has some guiding roles to optimize the development project and dispose the exploitation wells.It is the first time in Sulige gas field to predict He-8 gas-bearing reservoir by combining AVO technology, seismic wavelet energy absorption analysis and pre-stack elastic parameters inversion methods. From the forecasting results, dozen gas-bearing favorable zones have been marked off. On the plane, type I, II and III gas-bearing zones distribute alternately, showing a highly fragmented distributing characteristics, and presenting strong non-homogeneous characters. Integrated forecasting results could reduce the uncertainties some extent. The results provide important proofs for the selection of the development object blocks.From the comprehensive appraisal results of seismic facies analysis, channel identification and gas-bearing reservoir prediction, five most favorable gas-bearing blocks and five more favorable gas-bearing blocks have been offered. And the five most favorable gas-bearing blocks (SulO, Su25, Su5. Sul3 and Su6) have been confirmed as the first selected blocks of development production. That shows clearly the way for development arrangement of the gas field.At present, Su6 block has become a production block, and the other four blocks have been elected as the important evaluation blocks.