Geophysical methods for quantitative resumption of paleo-structures and its application

Abstract

Paleo-structures can be resumed and the fine studies of tectonic evolution can be achieved using bedding flattening technique and paleo-stratigraphic thickness calculation based on the interpretation of seismic data. The synthetic records of stratigraphic and seismic refection characteristics of multiple wells were made so as to accurately calibrate the reflection wave group of the main target layer. The tectonic profiles of different layers were studied using bedding flattening technique. The three-dimensional seismic interpretation data of the bottom and top of the target layer was used to restore the paleo-structural morphology of the key sedimentary period, and to perform a three-dimensional display. In this way, the characteristics of structural changes in the key sedimentary period were finely depicted on the plane. The paleo-structural characteristics of the Zhenjing area in the Ordos Basin recovered by this technique reasonably explain the present law of oil and gas distribution. Before the deposition of the Jurassic, several nose-like uplifts had developed in this area, and the subsequent stratigraphic deposits have a certain degree of inheritance. The source rocks of the Upper Triassic Yanchang Formation entered the hydrocarbon generation threshold after experiencing thermal events during the late Middle Jurassic and began to expel hydrocarbons. Oil generation peak occurred in the middle and late periods of the Early Cretaceous, and some favorable hydrocarbon accumulation areas were formed. The oil produced by the main source rocks under the pressurization of hydrocarbon generation migrated into the channel sandstones of the Chang 81 and Chang 9 oil groups nearby, forming self-generating, self-storing and self-capped oil reservoirs. The understanding of the oil and gas distribution law in this area provides a technical support for the further optimization of favorable traps.

Keywords

• 3d seismic data
• bedding flattening technique
• paleo-structure restoration
• ordos basin