The Effects of Kerogen On Rock Physics Properties of Tight Oil Reservoirs

This paper presents kerogen distribution characteristics of reservoir rocks and source rocks with FESEM pictures, and also analyzes the effects of the maturity of kerogen and the content of TOC on the velocity and anisotropy of rocks. The spatial distribution of kerogen in reservoir rocks, appeared as scattered blocks, is completely different from that of source rocks, which occurred in continuous strip belts. Ultrasonic velocity measurements reveal that the velocity of rocks decrease comparatively with increasing mature of kerogen at each mature evolution stage because the total porosity increase during the hydrocarbon expulsion process, however, the p-wave velocity of rocks climb slightly at three different hydrocarbon expulsion thresholds because more heavy pyrolysis products are generated and the bulk modulus of rocks rise at those points. The velocity anisotropy is mainly influenced by lamina and also increases along with the content of TOC and clay. The linear correlation model of P-wave impedance and combination of porosity and TOC provides convenience for sweet points prediction where have great reservoir capability (high porosity) and hydrocarbon producing potential (relatively high TOC).