The Art of Logging Horizontal Wells in the Denver Basin

Janet Marks

Relatively recently, petroleum drilling has gone horizontal into basin centered, continuous source rocks. Without preplanning of the well path, it is easy to deviate from the formation sweet spots during drilling. Seismic and wellbore control is examined prior to drilling the borehole to anticipate any faults. Using all the available data, the well site geologist helps make timely critical decisions on the borehole path when drilling fast in real time. Calling the top of formations while drilling vertically and landing the intermediate casing within the exact part of the desired formation is important. After drilling horizontally out of the intermediate casing, it is necessary to know what bed within the formation the bit is located in with respect to the target zone. The target is generally a 5-20 foot thick layer that has the greatest porosity, least gamma, and/or highest resistivity. The well site geologist uses various tools to log critical geological data during real-time drilling of wells to provide formation evaluation, monitor drilling performance and determine the location of the bit in the pay zone.

AAPG Search and Discovery Article #90156©2012 AAPG Rocky Mountain Section Meeting, Grand Junction, Colorado, 9-12 September 2012