AAPG ACE 2018

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Integration of Seimic-Sedimentary Modeling With Source Rock Prediction Methods to the Study of Lower Cambrian in the Tarim Basin, NW China

Abstract

Source rocks are a fundamental element of an effective petroleum system and have been identified as a key risk factor in the Tarim Basin. Understanding the seismic characteristics and distribution of known source rock intervals and identifying new intervals is key for future petroleum exploration of the Tarim Basin. The majority of the basin is underexplored with limited knowledge of vital petroleum system elements. This project is designed to investigate the distribution of known and potential Lower Cambrian source rocks within the Tarim basin through seismic-sedimentary modeling. This project is a component of a larger study to develop new strategies to predict and define source rock characteristics throughout the Tarim Basin. It focuses on the shales and carbonates of the Lower Cambrian interval, a known time for prolific source rock deposition around the globe.After a comprehensive analysis was conducted on regional geological data,it is believed that the distribution of Lower Cambrian source rocks is controlled by sea level variation,palaeostructures and sedimentary environments.As the product of rapid sea-level rise during Sinian-Early Cambrian,it is generally carbonate slope-to-basin depositional systems,with high-quality source rocks developed in the middle and lower slope facies.Besides,outcrop section and drilling data show that there is an “associated” sedimentation relationship between the Lower Cambrian and its underlying Sinian.The associated seismic reflection characteristics between them are further confirmed by drilling-seismic horizon calibration, the top and bottom of the associated sedimentary association have been tracked through plenty of 2D seismic data, and then build seismic-sedimentary model to calculating the thickness of source rock:H=A(T2V2-T1V1) ,in the formula,H is the thicknees of source rock;T1 and T2 respectively represent the reflection time of the associated sedimentary combination special seismic reflection characteristics upper and lower seismic event;V1 and V2 are the DT velocity of the associated sedimentary combination special seismic reflection characteristics of upper and lower seismic event;A is the scaling factor, that is related to sedimentary facies and palaeogeomorphology.This method of predicting the distribution of source rocks based on seismic-sedimentary model will decrease the uncertainty associated with the geological models constructed and improve the understanding of the viable petroleum systems.