DOHA: A research project led by a Texas A&M University at Qatar’s petroleum engineering faculty member could lead to safer, more environmentally friendly wells for the oil and gas industry.
Dr Mahmood Amani (pictured), Associate Professor in the Petroleum Engineering Programme, said a new testing procedure developed by him and his colleagues could help the petroleum industry ensure the safety of their wells and make sure the wells don’t leak chemicals into groundwater.
Funded by Qatar National Research Fund’s (QNRF) National Priorities Research Programme (NPRP), the researchers investigated the integrity of concrete used in wells when subjected to cyclic loadings — repeated cycles of high temperatures or pressures.
When a new well is drilled, it must be drilled through thousands of feet of rock and dirt.
A steel pipe called a casing goes into the well to keep it open so it doesn’t collapse.
But there’s a gap between the outside of the casing and the rock and dirt surrounding the pipe. This gap must be cemented completely to fill so that there are no cracks, voids or other channels in the rock.
“We want oil or gas to come up through the casing, not the gap because we can control the fluids coming up through the pipe,” Amani said.
“If oil or gas comes up through the gap between the rock and casing, then we lose some of those resources we’re trying to bring out.
“It can also cause corrosion behind the pipe or, if it travels up to the surface, it can cause fire or a blowout, which could lead to loss of life or property, or environmental damage.”
Amani said another concern is oil or gas travelling up through the gap and making its way into groundwater.
This is a big worry for environmentalists concerned about hydraulic fracturing, or fracking, in which oil or gas is recovered from shale and other rock and sand formations.
Shale is a type of very tight rock. Oil and gas are trapped in it and do not flow freely. With hydraulic fracturing high-pressure water containing chemical polymers is pumped into a well. This fluid causes fractures in the rock, forcing oil or gas into the well.
Amani said what if pumping high-pressure fluids into the well causes cracks in the cement?
Fluctuations in temperature and pressure in the well could cause the metal casing to shrink or expand, causing minor fractures in the cement or cause the cement to separate from the casing. Repeating the cycle many times over through the life of the well can worsen the damage and cause the cracks to propagate.
The research team designed special cells in which to test cement using a high-temperature, high-pressure viscometer for drilling fluids.
These cement cells were bonded to steel, the type of metal that would be used as a well casing.
The cement and steel were subjected to pressures and temperatures in a variety of scenarios, and then the cycles were repeated. The team observed when — after how many cycles — the cracks initiated and then propagated.
The result of the experiments is a new testing procedure to ensure the safety of the wells and that groundwater is not contaminated. The team has filed a patent disclosure on the process and it’s now under review. The Peninsula
