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ABSTRACT: Rigsite Geological Interpretation of a Deepwater Horizontal Well


In October, 1996, Shell Offshore Inc. drilled a successful deepwater horizontal development well to the Late Miocene "M2.8" sand. This paper shows the rigsite geologic interpretation methods which helped make this well a success.

The M2.8 interval is characterized as a stacked sequence of high-quality, turbidite channel sands and interbedded mudstones deposited in a lower slope setting. Pre-well interpretation indicated that the M2.8 sand had a gross true stratigraphic thickness of about 46 feet and contained 3 main channel sand members. While this was the primary stratigraphic model, other scenarios were also proposed. The development objective was to transect the entire M2.8 sand at a high angle and obtain 600 feet of productive interval for horizontal completion.

While drilling, an MWD slim-hole tool provided gamma ray, resistivity, and survey data and laptop computers were used to interpret these data. Geosteering software was used to correlate the real-time data with various stratigraphic models by projecting data along user-selected bed dips. The calculated apparent bed dips, actual well path, and projected plan were, in turn, checked using 3D seismic interpretation software.

When necessary, the well inclination was increased or dropped to optimize the location of the well within the target interval. The horizontal well drilled the base of the M2.8 sand and finished with 607 ft of productive interval, only 7 feet more than the goal.

AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana