American Oil and Gas Reporter - November 2015 - 80

SpecialReport: MWD/LWD Technology
Closure stress and best possible total organic content, mineralogy, and porosity distributions were calibrated to vertical pilot-hole logs and full core properties. Fracture and cluster
stages then were selected to target similar rock and the lowest closure stress along the well, while attempting to avoid initiating new
fractures into existing natural fractures, as determined from the
image log.
Fracture stage placement data, chemically traced production
flow, and a flowing temperature log were used to interpret well
flow versus the actual perforation cluster positions.
This article presents conclusions regarding both the engineering evaluation criteria used to fracture the well, and the geologic-based texture and fracture interpretation that explains the ultimate well performance. A new, automatic staging and cluster
placement software solution was employed to utilize insight gained
from the case study well to better plan future horizontal completions in the field.

tivity, and density data acquired from wireline logs run on a nearby offset vertical well, in addition to density and laterolog resistivity images obtained while drilling the horizontal well.
Figure 1 shows the correlation of the horizontal well. The top
two tracks display the images acquired using logging-while-drilling
tools, with the first track illustrating the density and the second
track illustrating the laterolog resistivity. Because this is a horizontal well, the images convey the bottom of the well in the center of the image.
From the images acquired, the dip magnitude and direction
FIGURE 1
Stratigraphic Correlation of Horizontal Well

Barnett Geology

Located in the Bend Arch-Fort Worth Basin of North Texas
and spanning an area of approximately 5,000 square miles, it has
been suggested the Barnett Shale has the largest producible reserves of any onshore natural gas field in the United States, with
an estimated 2.5 trillion cubic feet of recoverable natural gas reserves and 30.0 Tcf of natural gas in place.
Composed primarily of sedimentary rocks dating from the Mississippian period, the Barnett Shale is classified as a tight gas reservoir, and is known for being highly impermeable. The Lower Barnett Shale is located stratigraphically between the Forestburg and
the Viola limestones. The case study horizontal well was drilled
inside the Lower Barnett above the Viola Limestone (Ordovician).
As understanding of the geology of unconventional resource
plays such as the Barnett has evolved, it has become widely accepted that there is a large distribution of well productivity within the play. Development costs often are higher for unconventional resources than for conventional fields because of the need
for close well spacing, horizontal drilling, and hydraulic fracturing. In addition, production decline rates are greater, relative to
many conventional plays.
As a testing ground for new technologies, virtually all the wells
drilled in the Barnett have been hydraulically fractured, using various approaches that have evolved throughout the past two decades.
Although drilling was accomplished initially with vertical wells,
horizontal drilling and multistage hydraulic fracturing have led
to a dramatic improvement in hydrocarbon recovery-and ultimately the economics-by making it easier to extract gas from underdeveloped areas.
Horizontal drilling has become the prominent method for
drilling wells in this area. In fact, it is virtually the exclusive drilling
method used in the Barnett, with horizontal sections ranging from
1,500 to 4,500 feet. Devon Energy Corp., alone, has drilled more
than 1,450 horizontals in the Barnett.
Stratigraphic Placement

To confirm the stratigraphic placement of the horizontal casestudy well, a correlation was conducted based on gamma, resis-

80 THE AMERICAN OIL & GAS REPORTER

FIGURE 2
Borehole Imaging Software Example
From Horizontal Well Illustrating
Dip Magnitude and Direction in Second Track

American Oil and Gas Reporter - November 2015

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