Geo-Steering Horizontal Wells: Case Studies Demonstrate the Value of Fuzzy Logic Directional Steering Guidance
Mark, Sandra1 and Michael S. Stoner2
1Black Hills Exploration &
Production, Golden, CO
2Stoner Enginnering LLC, Golden,
CO
The success of horizontal drilling in Cretaceous reservoirs is
initiating many new development programs throughout the Rocky
Mountain basins. The productive zones are often thin, and the
ultimate performance of a well is usually dependant upon the number
of feet through which the lateral wellbore travels through the zone.
Geo-steering a horizontal well in real-time is geological
interpretation at its most stressful. The objective of geo-steering
interpretation is to describe the stratigraphic location of the wellbore
as drilling progresses. This task is complex because the known 3-
dimensional curving wellbore must be resolved with the unknown 3-
dimensional curving and often faulted reservoir. Modern geo-steering
requires depth-accurate formation evaluation measurements acquired
with Logging While Drilling (LWD) tools. The most common such
tool measurement in the Rocky Mountains is gamma ray. Modern
geo-steering involves correlating LWD signal data with a type log to
discern the stratigraphic location of the wellbore.
Software that performs the mathematics necessary for geosteering
has been available for many years, but there are new
techniques that take the interpretation to a new level. Technical Hole
Deviation (THD) is the mathematical unification of planned versus
actual directional well paths. THD quantifies how a directional well
path differs from its planned trajectory, and provides much greater
detail than is supplied by the directional company. When THD data
are combined with the geo-steering interpretation through Fuzzy
Logic processing, genuine steering guidance is provided. The benefits
of this additional insight have been recognized in several recent wells.
AAPG Search and Discovery Article #90071 © 2007 AAPG Rocky Mountain Meeting, Snowbird, Utah