Horizontal well performance in shale gas plays is highly dependent on placing the well in the preferred target zone of the reservoir interval. Some operators who drill in shale plays do not have seismic data and depth structural maps. They plan their horizontal wells with only offset well data. Sometimes, their wells land outside of the preferred target because they blindly place horizontal wells by using only non-directional gamma ray (GR) log data. For optimal well planning and placement for optimized production, it is important to minimize uncertainty about reservoir structure and placement.

Usually, operators create a depth map from identified markers such as well tops correlated across available wells in the field. The generated map is limited and often leads to landing laterals outside the target zone, especially when well control is not ideal. The aim of this paper is to illustrate a method of building structural maps and 3D geologic models for drilling in shale gas reservoirs. This methodology lends itself particularly well (but not exclusively) to the pad drilling approach common in shale gas development. The use of logging-while-drilling (LWD) technology can be strategically planned from pad to pad to help mitigate structural uncertainty.

Data from 42 horizontal and 6 vertical wells in the project area allowed real-time density image and azimuthal logs to be coupled with vertical offset well information to model the structure along the drilled horizontal well trajectory. The model integrated all the well tops and real-time bedding dip information to produce modeled surfaces.

The structural model generated during this study can be used for new well landing-point planning with limited true vertical depth uncertainty and for other fieldwide reservoir characterization. If structure information becomes available from seismic data, this technique also can be used to update the structural model derived from seismic interpretation, thereby delivering enhanced structural control of the field.

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