6 Reason Why A Drilling Project Can Fail

Often, in spite of computers chock full of seismic data, months or years of study, and countless pre-drill techni-cal reviews by hordes of geoscientists and managers, wells still come up dry. A dry hole can be defined as a well that does not produce oil or gas in commercial quantities. There are relative degrees of dry holes, or dusters as they are often called. A hole can lack so much as a whiff of oil or gas, with no hydrocarbon shows detected by even the most sensitive gas chromatographs. Or, a well can be a near miss, with not quite enough ability to produce petroleum to make the economic cut. These latter types of dry holes are often re-visited in times of high oil and gas prices. Too, dry holes that were noncommercial
years ago can sometimes be re-entered and made into producing wells, thanks to ad-vances in completion technology.

Failures can stem from many factors:
1. Mechanical problems can force a com-pany to abandon a well. Drillpipe or drilling tools can get stuck in the hole, and some-times the well must be abandoned.
2. A hydrocarbon-bearing reservoir isn’t present in the wellbore—even though it may be a few feet away. Reservoirs can be faulted out by small structural displacements in the subsurface that can’t be detected with seis-mic data. And, rocks can change laterally; for ex-ample, a sandstone can grade into a shale in-terval.
3. The target reservoir is encountered, but the interval is too tight or too thin to produce economic quantities, or contains water in-stead of hydrocarbons.
4. A well drilled on a seismic anomaly finds conditions that are indeed anomalous, but that do not correlate to a productive reservoir. For instance, an anomaly may look like a gas-charged sandstone on seismic data,
but drilling reveals it is actually a thin, tight limestone layer.
5. The reservoir is found at a depth that is
lower than projections. Many assumptions about the acoustic velocity of the rock layers in an area are built into seismic interpreta-tions, and until wells are actually drilled esti-mates can be imprecise. Low wells are
usually wet.
6. A well intersects the reservoir at the an-ticipated depth, and has adequate porosity and permeability, but the hydrocarbons have leaked off because the seal wasn’t adequate. Or, trap, reservoir and seal are all found as predicted, but oil and gas never migrated into the area in the first place.