A noticeable aspect of successful horizontal drilling applications is to keep the drill bit confined to the target window, which may be a relatively easy task if the target zone is a homogeneous sand body 100 feet or more thick. But what happens if the target reservoir is only a few feet thick? How much is not enough?

The purpose of this presentation is to illustrate that under certain geological conditions, and with current horizontal drilling technology, clastic reservoirs with a thickness of less than ten feet can be developed in both the offshore Gulf of Mexico and other basins. The risk associated with geosteering these small targets can be significantly reduced by using proper planning, measurement while drilling, predictive models, pilot holes for control points, and stratigraphic information, and practical experience.

The chosen reservoir, a bi-lobed Pleistocene sandstone, represented one of the most difficult scenarios to geosteer and model, owing to the absence of thick beds with sharp boundaries and the lack of differing resistivities among the multi-layered thin beds. Critical to the project's success would be the decision processes associated with 1) pilot hole well planning, 2) well data interpretation, 3) MWD predictive modeling, and 4) horizontal well design and stratigraphic placement. By comparing actual pilot-hole well data to pre-drill predictive MWD models, a more accurate horizontal well predictive model was produced which aided in geosteering the horizontal well while drilling.

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