摘要：Mixed sediment reservoirs, a special class of reservoirs well worth exploration, are very commonin oil-rich sag of western Qaidam basin. In recent years, a number of high-yield wells have emerged. which has become an important area for oil and gas exploration. Mixed sedimentation that prevails in mixed reservoirs brings great difficulties to reservoit interpretation and evaluation, especially by tradi- tional methods. At present, the research on marine facies and freshwater lake basins has made some progress, but there are few studies on classification and logging of mixed sediment in saline lacustrine basins at home and abroad. In such case, this paper was designed on previous studies to compare delta- shallow lake type sediment with salt lake type sedi- ment, which are continental and lacustrine mixed sediments in western Qaidam basin, in terms of lith- ologic features, controlling factors for oiliness and corresponding interpretation and evaluation meth- ods. By combining conventional method with image data, lithology identification technology was devel- oped to distinguish algal limestone from fine sand- stone in mixed sediment at delta to shallow lake and to discover dominant reservoirs; By utilizing the im- aging spectrum interpretation and evaluation system of "elemental spectrum, porosity spectrum and resis- tivity spectrum", effective reservoirs were identified and their quantitative parameters were figured out, according to the structural characteristics of mixed sediment at salt lake clarified by diplog data. The re- sults revealed that the method herein was feasible to identify the lithology of mixed sediment and evalu- ate the effectiveness of dominant reservoirs.
