Organic geochemical characteristics of the Laiyang Formation shales in Laiyang sag

The Laiyang Formtion shales in Laiyang sag,with oil and gas found,are well developed. Based on the field survey and lab analysis,the authors make a systematic study on the organic geochemical characteristics of the Laiyang Formtion shales in Laiyang sag. The source rocks of Laiyang Formation,with high total organic matters content ranging from 0. 22% to 3. 43%,mainly distribute in the Shuinan section and the Xiaoxiangzhuang section. Kerogen is composed of sapropelinite (40% -82%),vitrinite (3% -33%) and inertinite (10% -45%),and no exinite was found. Kerogen types include type Ⅱ₁,typeⅡ₂ and type Ⅲ,particularly type Ⅱ₁ and Ⅱ₂. The vitrinite reflectance ranges from 0. 50% to 2. 22%,it indicates that the shales have a high maturity of organic matter. Given the thickness of black shale,TOC,kerogen types,and vitrinite reflectance,Shuinan section of Laiyang formation is a favorable target for shale gas study in Laiyang sag.