Petroleum Systems Analysis to Refine New and Existing Play Concepts: A Case Study of Mahu Sag, Junggar Basin, China
The one of important aim of petroleum systems analysis is try to establish the spatial and quantitative genetic relationship between d discovered petroleum accumulations and generated hydrocarbon from source kitchens, The scale and phase of residual petroleum resources can be inferred through the comparison of amount and phase between generated and expelled hydrocarbons from source kitchen and discovered oil accumulations, and which can be refine new and existing play concepts. Mahu Sag, located in the Northwestern area of Junggar Basin, which is the most petroliferous sag in China. Oil-source correlation confirmed these oil originated from a world class Permian lacustrine source rocks(mainly in the Fengchen Fm, P1f) Geochemical data and petroleum systems analysis indicate Permian lacustrine source rocks present high heterogeneity, including organofacies C, D/E and F, maturity of the Fengchen Fm lacustrine source rocks range from mature to highmature stage in Mahu sag, but oil in the northwestern margin play present low maturity with low GOR (mainly less than 30 m3/m3) and API, which reflect these oil generated from early phase of oil windows (0.60–0.90%VRo) of organofacies C in source kitchen, lateral migration and accumulation. Rifined petroleum systems analysis can delineate three new play, which can be related to the Permian lacustrine source kitchen evolution. Firstly, lower Triassic Baikoquan Formation alluvial fans play, charged from expelled petroleum in late phase of oil windows (0.90–1.30%VRo) of Permian lacustrine source kitchen, with relative high GOR, mainly ranging 50–200m3/m3, vertical migration and accumulation in the Mahu sag; Secondly, Permian-Carboniferous lower assemblage play with condensate and wet gas, charged from expelled petroleum from organofacies D/E and F of Permian lacustrine source kitchen in the highmature stage; Thirdly, Fengchen Formation tight oil and gas play, we delineated the sweet depth with maturity ranging 0.9–1.1% for tight oil play. The spatial orderly distribution of API, GOR, gas carbon isotope and molecular geochemical data in whole Mahu Sag denote the various front expelled hydrocarbon in different mature stages from organic facies C, D/E and F, which reflect the dynamic scenario of petroleum migration and accumulation from kitchen to the shallow accumulations, and imply possible new play for exploration.
AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015