Abstract:

Based on the core observation of the Western Sag of Liaohe, combined with rock slice and Xdiffraction quantitative analysis of whole rock, this study improves the lacustrine mudstone lithology classification method. According to the new classification scheme, shale can be divided into three types: clay shale, felsic shale and mixed shale. Clay shale is characterized by dense layer structure and organic layered enrichment. It is dominated by clay minerals and developed in the environment with relatively weak. Terrestrial input. The felsic shale mainly consists of mudscale quartz feldspar with unclear layered structure under microscope. It is developed in the freshwater sedimentary environment with strong terrigenous input. Mixed shale consists of clay minerals, carbonate and felsic minerals, no main composition. Organic matter is dominated by lucstrine alage. Organic laminae is interbedded with clay or carbonate laminae. It is developed in occlusion lacustrine environment with brackish water to salt water.Organic geochemical analysis and hydrocarbon generation kinetic experiments show that the organic matter of the clay shale and mixed shale (including carbonate type) developed in the semideep to deep lake with laminated structure is dominated by type ⅠⅡ1 It has strong hydrocarbon generation potential, and is followed by felsic shale and massy mudstones. Mixed shale are mainly distributed in the Du2 and Gaosheng sections of the upper 4th Member of Shahejie Fm of Pansan subsag. Clay shale are mainly distributed in the Du1 section of the upper 4th member of Shahejie Fm in the Dujiatai and Shuguang slope areas. Mixed shale area is the main direction of unconventional oil and gas exploration of the oil field.

Key words: shale classification, petrology, geochemistry characteristics, Liaohe Western Depression