Anatomy of Upper Cretaceous Lacustrine Source Rocks in Songliao Basin: Distribution, Depositional Model and Implications for Hydrocarbon Potential

Feiyu Wang¹, Huashen Zhen¹, Bo Wang¹, Tao Jing¹, Xue Wang², Wei Fang², and Zhihui Feng^2
1China University of Petroleum, Beijing, China
²Research Institute of Exploration and Development, Daqing, China

Lacustrine environment prevailed in Songliao basin during late Cretaceous and formed widespread organic matter-rich black mudstones of the Qingshankou(K2qn) and Nenjiang(K2n, Campanian) Formation.Routine organic geochemical and petrological screen analysis indicated that highly heterogeneity of TOC, hydrogen Index(HI) and organic maceals exist in Upper Cretaceous lacustrine mudstones.Relationship of TOC and organic matter quality parameters (represented by HI) show good positive correlation, HI appears to increase with increasing TOC, asymptotic to 700mg/gTOC for above 3 wt% TOC mudstones in immature phase. therefore it is pivotal to delineate source rock thickness with different TOC interval in geological frameworks for hydrocarbon potential assessment. According to TOC data and corresponding log responses, the thickness of four source rock members (K2qn1, K2qn2+3, K2n1 and K2n2) with different TOC intervals(0.5-1%,1-2%,2-3%,3-4%, more than 4%) were calibrated with ΔlogR algorithms for about 800 wells in whole Songliao basin, the high-resolution distribution model of upper cretaceous lacustrine source rocks were established through Trinity petroleum system analysis software integrated with stratigraphic architecture and sedimentological facies. The principal controls on the organic accumulation in the upper cretaceous source rocks can be described at the first and second stratigraphic order scale, firstly,the maximum TOC intervals correlate to the maximum flooding surface, which indicate that algae blossom may be related to the paleogeographic( transgression events) and paleoclimatic factors (higher Pco2 enhanced productivity), secondly, TOC vary inversely with terrigenous clasitc influx and positive with accommodation in source rocks members, which reflect TOC variations in profiles were controlled by the accommodation space and clasitc influx.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas