Application of 3D fine seismic interpretation technique in Dawangzhuang Area, Bohai Bay Basin, Northeast China

Abstract

One of the major problems in subsurface seismic acquisition, procession, and exploration we are facing today is the uncertainty in geologic interpretation because of the complexity of subsurface geology and the limited dimension of the subsurface data available (including drilling data, well logging, and core samples). Case studies from worldwide exploration projects indicate that an integrated, three-dimensional seismic volume visualization and interpretation workflow contributes greatly to resolving the problems we mentioned by extracting critical geologic information from within 3D seismic datasets. Over the last decade, with the increasing employment and improvement of geophysical technology and following 3D seismic data acquisition and processing, the subsurface seismic interpretation workflow is composed of four integrated stages from data selection and pre-procession, to structures, stratum, and facies characterization; to prospect prediction and evaluation; and to well-bore planning. In the data selection and pre-procession phase, the most favorable and frequently used datum is the full and limited angle and limited azimuth post-stack amplitude with significant structures, stratum, and facies enhancements. Signal-to-noise ratio, color scheme, dynamic range, bit resolution, and visual contrast all affect the visibility of features of interest. During the structures, stratum, and facies characterization phase, vertical slicing along arbitrary traverses demonstrates structure styles, stratigraphic architecture, and reservoir geometry in the cross-sectional view. Time/depth slicing defines lateral and vertical variability in the structural trend and areal extent in the map view. Stratal slicing and fault slicing suggest chronostratigraphic seismic facies, associated depositional information, and cross-stratal, along fault seismic signature. Volume flattening and structure restoration aid in unraveling paleo-structural framework, stratigraphic architecture, evolution, and filling histories. In the prospect prediction and evaluation phase, a combination of volume trimming, co-rendering, transparency, attribute analysis, and attribute body detection is instrumental in delineating volumetric extent and evaluating spatial connectivity of critical seismic features. Finally, in the well-bore planning phase, decision making relies on the integration of all the information and knowledge extracted from 3D seismic datasets. Most importantly, interpreters' geologic insights and employments of geophysical technology are crucial to optimal well-bore planning with high geologic potential and low economic risk. The structure of the study area, which is poorly understood to be primarily due to the complexity of subsurface geology and the limited dimension of the subsurface data available, and therefore, we design the integrated workflows and use some of the methods mentioned above to carry out fine seismic interpretation in an analysis of high-resolution 3D seismic data and other geological data in the study area. Finally, we finished the fine interpretation of 3D seismic data and achieved a series of success and good application results. The evolution of tectonics resulted in sub-tectonic units containing the sequences of Ek, Es, Ed, Ng, and Nm. Interpretation reveals that tectonic transition zone which controlled the evolution of the sequences because of its strength, and also, the structural pattern resulted in types of fault (such as “Y” type). The seismic interpretations provide new information on subsurface geology, including the recognition of complex structural patterns in rift lacustrine basin and the presence of a tectonic transition zone at the structural center. The interpretation of these seismic reflection profiles provides new insights into the structure, geological evolution, and petroleum potential of the study area.