Abstract:

Donghe sandstone, the main reservoir of HD4 oilfield in the Tarim Basin, is the thin reservoir whose thickness is less than 1/4 seismic wavelength; therefore the top and bottom of the reservoir cannot be identified through seismic data. In order to calibrate properly the thin reservoir of HD4 oilfield with acoustic velocity, based on the theory of well-to-seismic calibration, the influence of the dominant frequency, kind and phase of the wavelet, and acoustic velocity on the synthetic traces was analyzed, moreover, the differences between interval velocity from stacking velocity and acoustic velocity were discussed. A new method using reference layer and adjusting acoustic velocity for calibrating thin reservoir was proposed. A reference layer is the thick stratum with stable sedimentary environment, and it corresponds to a high-amplitude and continuous reflector to be easily traceable in the seismic section. The results of well-to-seismic calibration are effective by selecting Permian igneous rock and Carboniferous double-peak limestone as the reference layers, adjusting appropriately acoustic velocity and choosing the most suitable wavelet.

Key words: thin reservoir, well-to-seismic calibration, wavelet, stacking velocity, acoustic velocity, reference layer, the Tarim Basin