Geo-Constrained Real Time Model Update (RTMU) While Drilling of the 3D Structural Framework Model

Jones, Serena¹, Simon Stewart², Stuart Bland³, Norman Armstrong¹, Robert Humphreys⁴, Michael Doe⁵ (1) Midland Valley, Glasgow, United Kingdom (2) BP Azerbaijan, Sunbury on Thames, United Kingdom (3) Statoil ASA, 9481 Harstad, Norway (4) BP Exploration, United Kingdom (5) Midland Valley Exploration, Golden

Geological models often contain uncertainties. During drilling, anticipated stratigraphic tops are often located higher or lower and with different orientations than the current model. These geometric modifications to the model mean that the drilling targets are likely to change in morphology and position. The integration of dynamic structural modelling tools and LWD data enables RTMU of the 3D structural framework model while drilling enhancing the well placement and steering workflow. The modelling workflow is as follows:

1) Acquisition of tops and orientation data from LWD. 2) Reshaping of the 3Dmodel, including drilling targets to honor new data. 3) Interrogation of the new model geometry providing well-steering feedback.

Structural geometric algorithms at the core of the model-reshaping tool make it possible for the 3D model to be intrinsically ‘linked' to the reshaping of a horizon. Horizons and faults carried during reshaping will retain the structural integrity and stratigraphic coherency of the model. The technique supports minor and major changes to the model geometry while the data can be as little as a single well top or a modified section line.

A case study from a compressional prospect is presented. The seismic image is obscured and unclear due to various reasons including steep dips, the structural detail of the target is therefore uncertain. Use of this workflow added significant value to the drilling program.

Geo-constrained RTMU while drilling is widely applicable. Minor and major changes to the 3D model require precise interrogation of the new target positioning and geometry for geo-steering feedback.