--> --> An Improved Approach for Structural Delineation With Multiple Reverse Faults From Borehole Image Dips in Compressional Stress Regime

2018 AAPG International Conference and Exhibition

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An Improved Approach for Structural Delineation With Multiple Reverse Faults From Borehole Image Dips in Compressional Stress Regime

Abstract

Accurate structural delineation is every difficult in complex compressional tectonic regime because of challenge of seismic processing with large scale thrust faults. The high resolution borehole image is always the first choice for the structure framework construction in such environment traditionally. However, only one fault can be handled in one structural zone in previous traditional method and the formation layering couldn’t be displayed in a consistent cross section direction. Moreover, it is very common that there are multiple faults developed in a horizontal well, and we can’t build a smooth structural model including multiple faults in one structure zone with continuous formation layers. In this paper, we propose a novel approach to build two-dimensional structural model with multiple faults from borehole image dips. Firstly, formation boundary dips are picked from high resolution wireline logging or logging while drilling (LWD) borehole image manually or automatically in vertical well; the true-dip based dip picking is applied in horizontal well for bull’s eye or parallel bedding features. Secondly, the structural zonation is automatically computed from formation boundary dip distribution; and the drilling polarity is also computed based on well trajectory and formation dips. Thirdly, the fault truncation relationship is analyzed from the true stratigraphy thickness index and potential fault throw. Lastly, a novel multiple faults modeling is applied for one or more structural zones in different structural types. A single well case study from west China was used to demonstrate this innovative approach with wireline logging high resolution borehole image. One major thrust fault was identified along with several small-scale faults in different depths. The re-constructed structural model is more matching drilling data and offset set well information comparing with structure interpreted from noise seismic. This near well structural model provides valuable information for the advanced seismic processing. We also applied this novel approach to a horizontal well with LWD image in an extension stress regime from Italy. Several different-scale normal faults were identified from image data. The reliable formation correlation was analyzed based on the true stratigraphy thickness index computed from picked formation boundary dips. The accurate two-dimensional structural model was constructed with multiple faults.