Drilling locations belching once-ubiquitous black smoke are going into the archives, as contractors aggressively replace conventional diesel with cleaner, and often exotic, power sources.
“There’s been a real conscious effort over the last year to decarbonize land rigs,” Ashley Fernandes, vice president of drilling technology for Canada-based Precision Drilling, told an IADC Drilling Engineering Committee (DEC) virtual technology forum in November. “We realized we had to do something, even before operators came to us and asked what we had (to reduce emissions).”
Precision is far from alone, as rig owners have little choice, given that their operator clients are under increasing investor and societal pressure to slash direct and indirect greenhouse gas (GHG) emissions. That does not mean, however, that low-combustion diesel has disappeared entirely, as many drillers opted years earlier to rejigger drilling gensets to operate with a combination of diesel and field gas and, more recently, batteries.
The quarterly DEC forum took a deep dive into how the transition to a low-carbon future is driving drilling and equipment innovations that reduce both emissions and fuel costs. “There are a lot of really important technologies that will work together, as we move through the energy transition,” said Sean Halloran, CTO of NexESS Analytics of Denver, Colo., which is working with Ensign Energy Services to advance hybrid rigs that pair NexESS’s Battery Energy Storage System (BESS) with natural gas gensets.
All-inclusive strategy. Precision, for its part, is looking at the carbon output of every aspect of a drilling location, even down to wellsite traffic and lighting. The bulk of the years-long investigation, however, has centered on the fuel used to power rigs and equipment. This work has been driven largely by the fact that the average rig employs three generators, which together consume just over 396,258 gal (1.5 million l) of fuel/yr, equaling some 4,000 tons of CO2 emissions/rig/yr.
Precision was among those ahead of the curve in blending diesel with gas, and today the firm owns 56 rigs with either dual-fuel or natural gas-driven engines. In the early going, Fernandes said that while emissions came down, the richness of the combined diesel and gas mixture increased the maintenance required to sustain the efficiency of engines used at the time. “So, we went to 100% gas, pumped directly from wells. We also looked at how the dryness and richness of gas affects the generators, and you still have some emissions with gas when ramping up and ramping down,” he said.
More recently, Precision has partnered with a “couple of companies” engaged in battery capacity and storage to engineer rigs that combine clean fuel with batteries. Besides cutting emissions, the inclusion of self-charging batteries enables the select removal of fuel-consuming generators. “In tripping, for instance, you need less power, and yet, people are still using three generators. We went to only one, with all peak power delivered by the battery. When you turn off two generators and switch on one with a battery, you have a nice, steady load with no black smoke,” he said.
“Seven-year journey.” Since drilling its first commercial well using batteries and natural gas-powered gensets in 2014, Ensign Drilling Services is well-versed in the benefits and challenges of advancing hybrid rig technology. With the deployment of the NexESS Analytics BESS technology, the company is now in the second generation, where one of the primary objectives is to analytically capture data, as part of the joint development of a hybrid rig value proposition, says Tony DeSalvo, Ensign’s operations manager for drilling solutions.
Ensign quickly realized savings in emissions and fuel costs, but one of the major challenges early on was coordinating the genset controllers, which drove the engineering of an integrated smart energy management system (EMS) that automatically keeps an online engine running at a higher and more efficient load, while simultaneously charging the batteries. “We really understood, very early, the role software could play,” DeSalvo said. “With a smart plant controller or EMS, you can bring up an engine, as needed to top off your battery system and then go back to running in the most fuel-efficient and emissions-reduced state.”
He agrees that crews needlessly run extra generators as a contingency, which along with increasing emissions and fuel costs, puts wear and tear on generators that operate optimally at 80% to 90% load.
“So, you’re sitting there for hours at a time, doing these non-drilling operations and running engines at a very low load. What we’ve found with the batteries is that you can take that other generator offline, as you no longer need it for risk mitigation,” DeSalvo said. “Depending on the capacity of the battery storage system, you could run safely for several hours with just your base hotel load of say 300 to 500 Kw. However, risk mitigation is so engrained in rig personnel, so the challenge is to convince the crew, and particularly the driller, to just step on the gas and really trust the energy storage system.”
A hydrogen future? Both Precision and Ensign have joined in efforts to scale up green hydrogen fuel cell technologies. “We’re actively working on hydrogen cells, as we believe this is the future,” says Fernandes.
Ensign, meanwhile, has teamed up with Schlumberger to explore hydrogen-related technologies and the service company’s intelligent power management fuel system. “It’s a project that’s real and ongoing that will help us move to the Holy Grail, so to speak, of having zero-emission rigs,” DeSalvo said. “It’s great to be a part of this industry today and the changes that are happening.”
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