Using Innovative Drilling Technology to Ensure Long Term Access for Ageing Reservoirs
Far out in the middle of the North Sea, Total has been testing pioneering techniques to access further reserves of energy. Success means that we can now look at maximising production from and extending the life of older reservoirs. This increased level of efficiency will not only enhance the amount of energy we produce, but will also have an environmental benefit through increasing the time we can keep reservoirs productive and reducing the number of wells drilled over the course of a reservoir’s life.
Intelligent Mud Team
Total's Central Graben Hub
The crew onboard the Elgin Platform
Mud, glorious mud
Drilling at great depths in the search for new supplies of oil or gas is a highly technical and difficult task. The drill must be able to keep operating despite huge amounts of pressure, temperature and debris as the well gets deeper. An essential part of the drilling process is the use of drilling fluid, or as our engineers call it, ‘mud’. This is pumped down the drill pipe to keep the drill bit cool. The fluid also brings drilled cuttings back to the surface, where the cuttings are removed for examination and then safe disposal. The fluid is then recycled and reused – all with no harm to the environment.
High Pressure challenges
Many of the biggest energy reserves in the UK now lie in so-called High-Pressure/High-Temperature (HP/HT) reservoirs. Drilling these reservoirs is extremely challenging with reservoir pressures up to 1,100 bar and temperatures beyond 200°C. Once discovered and put into production, the pressure in the reservoir reduces as gas is removed and carried to surface. This pressure reduction in the reservoir creates a situation where the reservoir is at a pressure much lower than that of the rock formation immediately above it. The drilling mud must be kept at a density heavy enough to hold back the formation fluids but not be too heavy to fracture and damage the now depleted reservoir. Managing this balancing act successfully without fracturing the reservoir is critical to be able to drill wells on ageing HP/HT reservoirs.
Effective innovation leading to lower environmental impact
A team from Total Exploration and Production in the UK has been studying new types of drilling mud to help address the challenge of drilling wells in depleted HP/HT reservoirs. Over the last seven years experiments have been carried out to develop what we call ‘Intelligent Mud’. This mud contains microscopic solids within the fluids which creates tiny fractures and instantly seals them to reinforce and strengthen the formation.
We used the ‘Intelligent Mud’ on a new well in the North Sea. The results were very successful and allowed us to drill depleted zones of a reservoir previously thought impossible. Not only did this secure access to the reservoir on this well, it also gives confidence in what can be achieved with ‘Intelligent Mud’ in future wells. Extending the field life for HP/HT reservoirs will not only produce more energy, but also better energy as we will have to drill fewer wells over the course of a reservoir’s lifespan.