There's a major effort under way aimed at slashing drilling costs while simultaneously reducing the environmental impact from drilling oil and gas wells.
The initiative is being spearheaded by the Department of Energy (DOE) via its Microhole Technology Program (MHT), which involves developing technologies associated with drilling wells less than 4.75 inches in diameter using coil tubing drilling rigs that are relatively small and easily mobilized.
The drill motor and bit are deployed on the end of tubing coiled around a spool.
According to DOE, MH technologies have the potential to lower the cost of drilling shallow to moderate depth holes for purposes of exploration, field development and long-term subsurface monitoring.
In fact, the agency estimates microhole technology conceivably could reduce the exploratory drilling costs by a third or more and chop at least 50 percent off the price of development drilling.
The DOE awarded funding for six projects in the MHT program last year and has since awarded the second round of projects, which will be managed by the DOE Office of Fossil Energy's National Energy Technology Laboratory (NETL).
This latest round of ventures includes field demonstrations and also technology development with the intent to take microhole technology closer to commercial application and widespread adoption by the domestic oil and gas industry.
The total funding for the second round of projects is close to $14.5 million, with $7.7 million coming from DOE and $6.8 from industry partners (see related story below).
Industry commitment and participation is noteworthy given the decline in industry-sponsored research and the operators' tendency to use the time-proven technologies rather than risk failure using advanced methods.
The MHT program's overall goal, according to DOE, is to develop cost effective technologies that enable:
- Development of shallow (<5,000 feet), currently uneconomic oil and gas resources.
- Acquisition of high resolution, real time reservoir imaging without interrupting production.
- Reduced environmental impact via lower volumes of drilling fluid, smaller operational footprint and pad/extended-reach drilling.
"The whole focus for microhole technology is mature fields," said Roy Long, technical manager for the oil E&P program at NETL. "After using the best drilling and production available, there will be an estimated 407 billion barrels of onshore discovered oil remaining.
"Of this, 218 billion barrels are at 5,000 feet or less, which is significant," he said, "because at 5,000 feet a lot of things become possible, like high speed drilling."
Coil tubing drilling applications using fast bottom hole assemblies are commonplace in Canada, according
"Around Calgary, they're drilling as many as three 3,000-foot holes a day, and that's a lot of footage," he said. "The key to make coil tubing drilling work is speed; there are some assemblies capable of getting more than 400 feet an hour.
"As more asset managers look at shallow gas, we're seeing coil tubing drilling beginning to migrate into the Lower 48, which is one goal of the program," Long said. "Coil tubing drilling is long past due.
"Any coil tubing rig can move onto existing well bores," he noted. "With the ability to drill quickly, operators begin to accept the higher day rates for a coil tubing rig. It allows them to get reserves they haven't tried to get before."
(New) American Frontiers
Recent successful field testing demonstrated the applicability of MH drilling technology in shallow, low margin gas fields in Kansas and Colorado. The testing is under the auspices of the Gas Technology Institute, which received funding during the recent second round of the MHT program awards.
The wells are being drilled by Rosewood Resources, Dallas.
In times of very low oil and gas prices, e.g., the 1980s, these fields were not economically viable, said Kent Perry, executive director of exploration and production research at GTI. He emphasized that the minimal environmental footprint and fast drill time using MHT, coupled with the low cost, positions this technology as a viable option to recover oil and gas from marginal fields like these.
The field testing aptly demonstrated the efficiency of microhole technology: The test crew moved in, rigged up, drilled, rigged down and moved out within a day, with minimal environmental impact, according to GRI.
The tests thus far have concentrated on Niobrara chalk reservoirs, drilling open holes as much as 4.75 inches in diameter at depths of 1,000 to 3,000 feet.
"The Niobrara represents a Tcf of gas just made economic," Long said, "and this is just one little area in Kansas and Colorado. Think of all the shallow, tight gas drilled through for years that was uneconomic."
Seeing Something More
It is noteworthy that while microhole technology is slowly but surely becoming essentially a no-brainer for shallow, tight gas, its potential value extends beyond natural gas.
It could, according to GTI, have substantial impact of the production of the vast domestic oil shale resource as well.
There's more going on here, however, than just drilling faster, cheaper boreholes.
"We see a real future for all this in imaging," Long said. "There are a lot of problems trying to see complex reservoirs, so the idea is to improve the seismic resolution we're doing using designer seismic.
"We punch a lot of holes 2.75 inches and smaller, or the minimum size to get the new technology geophone systems, accelerometers below the surface," Long said. "It's a new way to interpret seismic called vertical seismic profiling, which has been around for some time, but we're drilling a hole especially for it.
"Typically it's done in an existing hole, but it can be very expensive to shut a well in and then get data," Long noted. "And, ideally, you should have the equipment there all the time."
In fact, DOE anticipates that over the long haul, MHT applications will include drilling dedicated wells for continuous reservoir monitoring to allow:
- High resolution vertical seismic profiling and reservoir fluid movement detection using 4-D.
- Low impact, high resolution imaging of targets beneath environmentally sensitive locales.
- Passive seismic imaging to take advantage of noise associated with naturally occurring seismic events.