3-D Near-Wellbore Structural Modeling Based On High Resolution, Logging While Drilling Borehole Image Analysis: An Example From Sichuan Basin, China

Yang, Yu; Miller, Camron; Marza, Philippe; Zhao, Jack; Zhou, An-Fu; Yang, Yang

This paper presents how a new generation, 3-D near wellbore structural modeling software can dramatically reduce uncertainty related to structural geology, well placement and hydraulic fracture stimulation planning. The subject horizontal well is the first commercial oil well drilled into a tight carbonate reservoir in Sichuan Basin, China. The target reservoir is situated within an anticline structure and near a series of major complex faults having associated minor faults and natural fractures. Due to the relatively low resolution of seismic data and limited well control, detection and interpretation of these structural features is difficult. This presents a challenge during drilling, specifically with regards to well placement. Additional challenges arise during well completion and stimulation planning as the objective is to have induced, hydraulic fractures remain in the zone of interest. These issues were addressed by acquiring high resolution borehole micro-resistivity images while drilling and creating an advanced near-wellbore structural model.

The applications of borehole images within complex structural environments are well demonstrated. The structural interpretation includes the identification and mapping the orientation of bedding planes, natural fractures and fault planes. The specific approach was to analyze the dip sequences along the lateral wellbore and perform a structural analysis using the local curvature axis technique on a Schmidt plot. This structural zoning method enables geometric characterization of the multiple structures encountered during drilling. Furthermore, defining the drilling polarity and computing true stratigraphic thickness enables accurate correlations between various drilling sections and allows for an estimation of the magnitude of fault displacement. The result is a detailed, three-dimensional near-wellbore structural model that, when integrated with logged rock properties, provides critical information for use when designing the well completion and stimulation. This technique is being used to guide current drilling and completion practices in the area and provides input to reservoir scale modeling.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013