Identification and prediction of source rocks in Carboniferous volcanic systems in Malang Sag, Santanghu Basin

The formation of volcanic reservoirs in the Malang Sag, the Santanghu Basin is obviously controlled by the distribution of hydrocarbon source rocks. As a result, the identification and prediction of source rocks in the volcanic systems are significant for petroleum exploration. Some core samples have been collected from the study area to calibrate the logging response of source rocks. The distribution of source rocks in different formations of Carboniferous is predicted through mathematical modeling based on the comparison between geologic background and actual logging data, and combined with the symbiotic relationship between source rocks and volcanic rocks. The occurrence of source rocks in the volcanic systems can be categorized into two types, and volcanic rocks coexist with source rocks in four ways, showed by distinctive logging-seismic responses. The contact relationships between source rocks and volcanic rocks in the Haerjiawu and Kalagang formations are quite different, referring to two occurrence types which should be studied with different mathematical models. The Kalagang source rocks are separate and limited in space formed in the normal sedimentation not belonging to the onshore volcanic system. The Haerjiawu source rocks are widespread, forming multiple thickness centers between volcanic vents.