Advanced 3-D Structural Modeling of LWD Borehole Images for Optimized Well Placement

Azike, Ogochukwu; Wray, Andy

The accurate placement of a horizontal well in a preferred target interval is widely acknowledged by oil and gas operators as the first critical step towards delivering an effective completion and a productive well. The inability of non-azimuthal measurements to determine the orientation of the wellbore's intersection with a bed boundary and to calculate True Stratigraphic Thickness (TST) can open up significant correlation uncertainties during real-time geosteering operations. These uncertainties can knowingly or unknowingly result in sub-optimal well placement, inaccurate structural models and ultimately, poor production performance.

A Marcellus Shale operator in the Appalachian Basin, Pennsylvania, USA was faced with the challenge of geosteering within a predefined target interval. Geosteering technical challenges for the operator included: sparse offset data, potentially complex structure, lease boundary drilling requirements and no seismic coverage. Through the application of advanced structural modeling of LWD (Logging While Drilling) density images and azimuthal measurements, local structural uncertainty was significantly mitigated. A second example is provided from the Third Bone Spring (Delaware Basin, Texas, USA) and demonstrates the application of both high resolution LWD resistivity images and LWD resistivity ‘distance to bed boundary' (DTB) technologies for accurate horizontal well geosteering and advanced structural modeling.

In both case study examples, dip interpretation from LWD image data was the primary input for advanced 3-D near-wellbore structural modeling. By utilizing dip sequence analysis (DSA) processing of the images, local structural components were extracted and true stratigraphic thickness (TST) at the borehole level was computed. These attributes were then combined with structural dip projection to create more accurate isopach models. Finally, an integrated 3-D structural model was generated using key horizons and incorporating local faulting, TST variations and facies heterogeneity. In conclusion, the combination of LWD images and advanced 3-D structural modeling provides the opportunity to resolve and more accurately represent local structural complexities and reservoir architecture. It is considered that this enhanced understanding of the subsurface in turn helps to further optimize well placement and field development.

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