Abstract: The deep brine type potash in western Qaidam Basin is a newly discovered sodium chloride subtype potash deposit with gravel layers as the storage media. In particular, a great deal of in-depth research has been done in the Heibei Concave (or Heibei'aodi)-Dalangtan secondary salt lake depression, where ~350 million tons of KCl resource of this subtype has been obtained. By dissecting this type of ore-forming system one can provide reference for the exploration of potash deposits in the area. The Heibei'aodi-Dalangtan area is the main distribution area of brine reservoir, a piedmont proluvial fan type pore brine reservoir in northeastern Qaidam Basin. In this study, we collected drill, logging and seismic-prospecting data according to the actual production needs. Through seismic reflection profile interpretation and attribute analysis, as well as drill data comparison revealing the reservoir lithology characteristics and distribution, we obtained the seismic response characteristics of the medium-deep pore brine reservoir in the study area. High amplitude in-phase reflections appeared at the bottom of the reservoir, with good local continuity; medium to high amplitude in-phase reflections were observed at top of the reservoir; at the lumpy middle part low amplitude reflections were recorded. The instantaneous frequencies were mainly medium to low frequencies. Larger “sweet spots” were observed at the bottom and top of the reservoir compared to the middle part with a low sweetness value. The envelope attribute was characterized by abnormal high peak values at the top and bottom and low peak values at the middle part of the reservoir. Through seismic profile and borehole data analyses, geophysical indicators for potash deposits were established, which provided a basis for predicting the distribution range of medium-deep reservoir and optimizing hydrogeological survey for borehole drilling.

Key words: gravel brine reservoir, attribute analysis, borehole drilling, Heibei Concave-Dalangtan, Qaidam Basin