Reservoir Prediction For T₁j^2-1-T₁j₁ Formation In Chishui - Qijiang Areas,Southeast Sichuan

Carbonate reservoir of Jialing formation in Chishui-Qijiang area of Sichuan Basin is the main exploring target in southeast area in Sichuan for years. Three marine gas fields, namely Wanglong, Taihe and Baoyuan have been discovered and developed successively. However, it is quite difficult to forecast T1j1~T1j2-1 carbonate reservoir since it is featured by low porosity, low permeability, small single-layer thickness (the effective thickness is commonly 1-5 m), strong transverse non-uniformity as well as invisibility and complexity. Therefore, it is hard to systematically describe and effectively forecast the thin reservoir just by geology method when forecasting the reservoir. So, geology and seismic prospecting must be effectively combined for comprehensive analysis and research so as to get a better forecasting effect.The present text starts with a research on geologic features of reservoir, then analyzes different types of seismic responses from the forming mechanisms by methods like making separate synthetic seismogram and forward models based on fine calibration of reservoir and determines seismic response characteristics of different stratal structure and different types of reservoir development conditions. And it further makes a reasonable geologic interpretation to wave impedance inversion and seismic attribute analysis under guidance of geophysical response analysis so as to develop reservoir evaluation on the entire area by comprehensively using various data. Finally, the following achievements and knowledge are obtained through said work:(1) T1j1~T1j2-1 reservoir in the research area is mainly distributed below the T1j2-2 within a range of 50 m; reservoir's lithology mainly comprise grainstone, Silty dolostone and argillaceous dolomite while the main permeable-conservative space is pore, corrosion holes and fracture and main pore types are intergranular pore, intercrystalline pore, intragranular dissolved pore, intercrystalline dissolved pore and intergranular dissolved pore; said reservoir has relatively better physical properties when the fracture develops; development of the reservoir are mainly affected by sedimentary facies, corrosion effect and tectonic movement.(2) It processes a geophysical response analysis to the study area as follows: firstly, respectively processing detailed analysis to the good reservoir and non-reservoir according to log curve of the entire area and establishing logging response characteristics of reservoir; Then, analyzing features like amplitude, frequency and wave form of the gas-bearing reservoir and dry formation by combining the well-log information and seismic data; and then, explaining and verifying forming mechanisms of corresponding seismic responses by making separate synthetic seismogram and forward models; and finally, determining seismic response features for the reservoir.(3) Based on processing detailed understanding to method and theory, classification and seismic inversion process, it develops constrained well-log inversion based on the many well and relatively better quality of seismic data, and processes inversion effect analysis and corresponding geologic interpretation;(4) Tt introduces classifications, extraction and optimization of seismic attributes and corresponding geologic meanings thereof in detail; it extracts more than 20 seismic attributes through DISCOVERY software, optimizes the extracted seismic attributes based on result of geophysical response analysis to choose a group of attributes which are the most sensitive ones to the reservoir to forecast the reservoir, and forecasts the developing condition of fracture in the study area with correlative analysis technique.(5) Comprehensively evaluating reservoir in the research area and finding out the beneficial area block for the reservoir development according to the achievements of reservoir features of T1j1~T1j2-1, seismic inversion, analysis on seismic attributes and facture forecast and the materials researched by former people. Classâ… area include Taihe and Wanglong;classâ…¡area have Baoyuan,Baixiangping,Jiaozishan,Tiantangba and Xingchang; classâ…¢area include Tucheng,Xiantan,Guandu and Gaomiao.