Methods for seismic sedimentology research on continental basins

Abstract

In contrast to marine deposits, continental deposits in China are characterized by diverse sedimentary types, rapid changes in sedimentary facies, complex lithology, and thin, small sand bodies. In seismic sedimentology studies on continental lacustrine basins, new thinking and more detailed and effective technical means are needed to generate lithological data cubes and conduct seismic geomorphologic analyses. Based on a series of tests and studies, this paper presents the concepts of time-equivalent seismic attributes and seismic sedimentary bodies and a ''four-step approach'' for the seismic sedimentologic study of continental basins:Step 1, build a time-equivalent stratigraphic framework based on vertical analysis and horizontal correlation of lithofacies, electrofacies, seismic facies, and paleontological combinations;Step 2, further build a sedimentary facies model based on the analysis of singlewell facies with outcrop, coring, and lab test data; Step 3, convert the seismic data into a lithological data cube reflecting different lithologies by means of seismic techniques; and Step 4, perform a time-equivalent attribute analysis and convert the planar attribute into a sedimentary facies map under the guidance of the sedimentary facies model. The whole process, highlighting the verification and calibration of geological data, is an iteration and feedback procedure of geoseismic data. The key technologies include the following: (1) a seismic data-lithology conversion technique applicable to complex lithology, which can convert the seismic reflection from interface types to rock layers; and (2) time-equivalent seismic unit analysis and a timeequivalent seismic attribute extraction technique. Finally, this paper demonstrates the validity of the approach with an example from the Qikou Sag in the Bohai Bay Basin and subsequent drilling results.

Distribution and controls of petroliferous plays in subtle traps within a Paleogene lacustrine sequence stratigraphic framework, Dongying Depression, Bohai Bay Basin, Eastern China

“…Some studies also have attempted to interpret the distribution and controls of subtle reservoirs by using (1) source rocks (Hu 2010;Jiang et al 2014), (2) sedimentary facies (Zou et al 2005), (3) the relationship between porosity and fluid potential (Li and Pang 2004), (4) normal faults and microfractures as conduit systems for hydrocarbon reservoirs of conventional and subtle traps (Losh 1998;Losh et al 1999;Li et al 2010;Lampe et al 2012), and (5) faults controlling hydrocarbon migration and accumulation in a continental rift basin (Mu 2012;Wei and Su 2015). Some progress has been made in understanding the conditions of hydrocarbon migration and accumulation in subtle traps, and the distribution and controls of subtle reservoirs within the sequence stratigraphic framework in continental rift basins, such as Dongying Depression (Li and Pang 2004;Feng et al 2005;Pang et al 2005;Guo et al 2010Guo et al , 2012Guo et al , 2014.…”