New drilling technology expected to unlock oil trapped in tight chalk

By Marianne Bom

Most of the oil in the Danish oil fields is trapped in tight chalk and cannot be commercially produced by existing technologies. DHRTC is developing a new Radial Jet Drilling technology that has the potential to increase production and unlock some of the resources.

Honestly, it can appear a bit frustrating. The oil and gas is there, deep down under the existing production facilities in the Danish oil fields in the North Sea, and the Danish consumers could very well need more of it to fuel their cars or heat their homes. However, most of the resources are stuck in the cavities of tight chalk created in the Cretaceous and Paleogene periods more than 60 million years ago. This chalk is characterised by very low permeability and so far, the oil industry has been able to extract only thirty to forty percent of the original in place deposits. Up to 70 percent could be left behind, and there is a need for new, innovative technologies to extract more from the existing wells.

Radial Jet Drilling (RJD) is considered part of the solution. RJD uses high-pressure water or acid jet to create numerous radial laterals in one or multiple layers from the main production wellbore. The laterals give access to oil and gas retained by the tight chalk near the existing wellbores, oil that otherwise will not be likely to be produced with current technologies. RJD can also be applied in the injection wells. “In these wells water is forced into the porous media to maintain pressure levels in the reservoir and enhance the sweeping of oil towards the production wells,” says Reservoir Engineer Paloma Alvarez Gallego, DHRTC.

“Our demonstration case is in the Halfdan Field, where we are evaluating the potential of jetting laterals from the existing wells. Preliminary computer simulations show that when it comes to oil rate we can expect up to a 10 percent increase. Furthermore, it might extend the well life as it will take longer to reach the economic minimum production rate. These two effects combined can yield a significant increase in the remaining hydrocarbons the well is expected to produce. Of course, the outcome will be extremely dependent on the well, the reservoir, the timing, the number of laterals and the area of the reservoir we are jetting into.”

The technology still has to be developed for use in an off shore environment. So far RJD has proven to be a successful tool for enhancing oil production on land in some locations, but the conditions are much more complicated at sea where operating the equipment in an off shore environment, and placing radials in the complex wells are the main challenges.

Three-step radial jet drilling procedure

Michael Pitts, Head of Applied Technology at Maersk Oil

The application potential of Radial Jet Drilling is good. We have many existing wells that we have the potential to do something with, to improve ultimate recovery. It is not economical these days to drill new wells, so we can reenter existing wells and use RJD to help us enhance production, or otherwise to improve injection, and give us a better return on the existing well stock.”
Michael Pitts, Head of Applied Technology at Maersk Oil

A great collaborative atmosphere

Paloma Alvarez Gallego has a background as a Reservoir Engineer in the oil industry. She has experience exploring for new opportunities in the Gulf of Mexico, in producing assets in the desert sand of North Africa and in the UK North Sea sector. At DHRTC her task is to combine her commercial knowledge and technical skills with the input fed by researchers, oil companies and the innovative minds that are going to develop the RJD equipment to be used offshore. The DHRTC aims to prove commercially viable technology at a prototype level and such is the case for RJD. This appears probable within the next few years with full deployment possible before 2023, if supported by the operators, the economic environment and the rest of the stakeholders.

“The collaboration has benefitted substantially from Maersk Oil’s willingness to share data and enthusiasm,” says Paloma Alvarez Gallego: “We have a great collaborative atmosphere and team spirit in the center, among Programme Managers, the Technology Maturation team, the researchers in DHRTC and DHRTC partners, as well as with the DUC partnership, and with a special mention to those at Maersk Oil.”

Next step: Test in the North Sea

The next step is to test the technology in a simple set up in a wellbore in the Danish sector of the North Sea. This will cast further light on the question whether RJD can be applied offshore without using a drilling rig, and therefore maximizing the chance of a commercial success as rigs are extremely costly. If after further development and testing, that proves to be the case there is a huge potential across the Danish North Sea for applying Radial Jet Drilling in other fields and formations, says Paloma Alvarez Gallego:

“I believe that the technology could go beyond the current developments focusing on the use of RJD in existing wells. It could enable new developments and opportunities in areas where there is no production yet, unlocking resources for Denmark.”

“Radial Jet Drilling is a topic I’m very interested in. We have a lot reservoirs in the DUC with significant potential. At the moment it is costly to develop many of these reservoirs, so any new technique that can tap oil and gas in these reservoirs really will be of benefit to the Danish Underground Consortium.” Anthony Hughes, Subsurface Manager at Chevron.