Two Quantitative Evaluation Methods for Identifying the Migration Pathways in Hydrocarbon Carrier: Application and Comparison

Carrier is an important media linking source rocks and reservoirs. In the past two decades, it is the hot topic for the hydrocarbon geology researchers. Migration pathways in carrier are main space for the hydrocarbon migration. The identification of these pathways has great meaning for the hydrocarbon exploration. In this paper, we define a pathway as a macroscopical area in any shape that relatively apparent hydrocarbon migration exists in the carrier according to some research methods. The sandstone carrier of the Neogene Shawan formation and the unconformity carrier of the Cretaceous being located in the Chepaizi uplift of the Junggar Basin (NW China) are selected as research objects. We used quantitative grain fluorescence analysis (QGF) and effective migration thickness analysis (EMT) to quantitatively study these two kinds of pathways. Migration characteristics of the hydrocarbons are analyzed in single wells and in plane. Analysis results show that evaluation and prediction results from two methods are very similar. This verifies the feasibility of those methods for pathways analysis. Based on the calibration of commercial oil flow well, distribution of migration pathways in plane is obtained, which narrow down the exploration areas. Through practical application, the application process and the considerations of the two methods are discussed and compared. For sandstone carrier, the thickness can be obtained from well logging reports and well logging diagrams. Precondition that the samples collected are located in the carrier interval in QGF analysis is needed. For unconformity carrier, identification of the unconformity surfaces is an important basic work. Increasing the sampling density can reduce the analytical errors caused by the inhomogeneous distribution of oil. EMT method is simple; however, the precondition for application is that the oil in the carrier is not too light and is well preserved in geology history.