Last spring the U.S. Department of Energy actively solicited input from the petroleum industry on microhole technology -- and got it, when an April workshop brought in 63 representatives from industry, government and laboratories to identify the primary potential applications for microhole technology in an effort to focus new research.
Based on comments at the meeting:
- Independent producers preferred using microhole technology for shallow development drilling.
- Large producers leaned toward exploration tails.
- Service companies preferred drilling holes for data.
Attendees also identified five critical technologies necessary for microholes to be worthwhile. These are:
- Downhole drilling systems.
- Downhole logging systems.
- Completion equipment.
- Solids control.
- Coiled tubing units.
As with most technologies, industry officials indicated that microhole technology must evolve from current applications rather than seek to revolutionize the industry -- and without government assistance the technology would be slow to develop.
Workshop participants indicated that with DOE financially supporting its development, majors and independents will employ microhole technology, which will spur service companies to invest in technology development.
They also maintained that a targeted cost savings of 40 to 50 percent (compared with existing technology) would be necessary to push the use of microholes.
Workshop participants highlighted four primary drilling applications:
Shallow development wells (maximum depth of 6,000 feet).
Attendees said this was the number one application for microhole technology.
About 18,000 to 20,000 shallow development wells will be drilled in the United States this year, with only a handful using coiled tubing. Canada, on the other hand, drills 10,000 to 20,000 shallow wells each year and hundreds employ coiled tubing.
The real growth in shallow drilling in the United States in recent years has come from coalbed methane plays in Wyoming, Kansas, Oklahoma and New Mexico -- but almost every onshore U.S. basin has mature shallow oil and gas reservoirs that could benefit from this technology, according to the report.
Independent oil and gas producers were particularly interested in using microhole drilling to reduce the initial capital cost of a shallow development well.
As one independent commented, "The cost of drilling a conventional 5,000 foot well is $13 to $17 per foot in West Texas. Completed cost is $250,000 to $350,000 -- $150,000 is a really attractive price at which we'd drill wells all day long.
"If microholes would do that, great, but it must be reliable and repeatable."
Workshop attendees indicated coiled tubing operations save space, simplify logistics and can improve well performance. However, people expressed concern about the hydraulics of drilling very small diameter holes.
So what must the technology do to be applicable for shallow development drilling?
First, microhole technology must drill a very small diameter hole from surface to targeted depth quickly and cheaply with a minimum footprint in a manner that is reliable and repeatable. Producers are very comfortable with the traditional rotary drilling process and have made significant strides in lowering costs and drilling time, so for a coiled tubing-based microhole technology to be attractive the cost differential must be substantial -- about 50 percent.
The primary technical hurdles for this application beyond the hole itself are reliable tools designed for microholes.
Reservoir data monitoring holes.
These holes could be used to acquire seismic data, vertical seismic profiling, reservoir pressure and temperature data, rock samples and fluid samples.
To glean that type of information today companies must use an existing well, drill a standard-sized well or use a coring/slim hole rig to drill a small diameter hole.
Microhole technology can potentially provide an alternative for gathering data at lower costs, with a smaller footprint, with no lost production and better data through optimum well placement -- but, again, the need for this application is limited to larger companies. Small operators rarely operate a unitized field.
Producers and service company officials indicated that few data sampling wells are drilled in the United States each year, primarily due to the high cost of such operations. If the cost of constructing these holes can be substantially reduced, it is likely the number of data sampling holes will rise sharply.
Shallow re-entry wells.
About 50 to 100 re-entry wells are drilling daily in the United States, according to the report -- producers will spend at least $7.5 billion in 2003 re-entering existing wellbores, and microhole technology could significantly reduce the cost of the operation.
Coiled tubing drilling is used every day to exit cased wellbores, but none are the size of microholes. The bottomhole assemblies, logging tools and the entire drilling operation have been set up to drill conventionally sized holes.
Therefore, workshop participants indicated that all systems -- motors, measurement while drilling, logging, whipstocks, bits -- must be developed before reliable microhole drilling can be performed in the United States.
Also, completion and production equipment for new hole sizes should be studied to determine which additional equipment and services need to be developed.
Deep exploration tails.
This consists of drilling a very small diameter hole out the bottom of a conventionally drilled exploration well in order to evaluate an additional 2,000 feet of rock prior to plugging and abandoning a test hole.
The most obvious use of this technique would be in very high cost deepwater wells, where the total measured depth of the hole is around 20,000 feet.
Operators often run out of hole with the last casing run and can't investigate further. Companies would welcome an inexpensive option to drill a tiny investigative hole out the bottom of the last casing string to take samples, measure pressure and temperature and evaluate zones just below the targeted formation of interest.
The biggest concerns among workshop participants centered on the high temperature and pressure regimes in deepwater wells. (One company official said, "I can't imagine a one-inch tool that can withstand the pressure of a 15,000-foot hole. I can't believe it's feasible to develop systems and hydraulics for deep applications and high pressures.")
A secondary concern was how to transmit power to the drill bit.