Last issue, as part of this series on “The Making of a Well,” we covered prospecting, leasing, site prep—everything that leads to the actual drilling of an oil or gas well. Now comes Part II of our primer on that great invention—actually a family of inventions—the American-made and American-perfected (and Texas and New Mexico mastered) oil well. Now we get rigged up and drill the actual well.
By Jesse Mullins
[Editor’s Note: This article, as well as our HR IQ column in this same issue, are part of a special initiative we’re undertaking in our April, May, and June issues. This initiative is our effort to “break down” the workings of the oil and gas industry for the benefit of our growing numbers of readers who—though they may be employed in oil and gas—are not field employees and may not have as much acquaintance with the mechanical, in-the-field side of the business as do hands-on employees. For these employees—mostly office workers—and for anyone else wanting a bit of a refresher, we walk through the “making of a well” in three issues. This installment covers the middle stage—the actual drilling of a well.]
It was an English professor, one Mason Cooley, who once wrote grandly that, “Courage, determination, and hard work are all very nice, but not so nice as an oil well in the back yard.”
Yes, nice. So nice, that remarkable, multifaceted device. That device known as a well. And let’s be nice to ourselves and call it a producer, a brought-in well. If it stays a well at all—if it is not plugged as a dry hole—then it is almost certainly a money-maker, a fountain of prosperity, an empowerer, a fueler of humankind’s wishes and needs and wherewithal. A transporter of everyone, even of those who think they despise oil.
This business of boring into the planet’s surface and bringing up high octane combustability is an ingenious art and a prodigious act. It merges cutting-edge science with blue collar grit, fine precision with heavy industry, deductive logic with innate savvy.
Last month we explored the earth-sciences side of the oil and gas endeavor—prospecting—as well as the research-and-negotiations side—leasing. We tracked the activity right up to the clearing of the wellsite and the arrival of the rig.
In other words, we got ourselves to the “where”—the whereabouts of the oil well. It was a deliberate, painstaking process. As Mike Cure, owner of Midland-based Cure Consulting, an oil and gas consulting firm, comments, the “where” is based on an idea, and the idea is based on science—geological science—and some geological history.
“And that ‘where’ is also based on associations with other wells and other production in the area,” Cure told PBOG. “So there’s a trend that’s associated. We know about this producing well over here, so maybe there would be production over here, which is right next door. Also, in that “where” we get a business situation. We get some financing and manage the risk by, maybe, taking some partners. There may be people around who already have acreage that they have mineral-leased, or have interest in, and they may contribute their acreage. And make some kind of partnership.
“So there are deals that are made that go with the ‘where,’ the location,” added Cure, who teaches at Midland College’s Petroleum Professional Development Center, the school whose curriculum appears in each issue of this magazine. (See this month’s course lineup on page 104.) But back to the “where.” The surveyor, we learn, actually pins down the precise “where,” and we have our point where the bore hole will go down.
Meanwhile, the operator and his key partners will have settled on what is called a “well plan.”
“Our well plan goes with that location, and the reason for a well plan is because we have about a hundred different contractors, consultants, and other organizations that have to get together and cooperate to get this construction project done,” said Cure. “And there are somewhere around a hundred of them that have to do with getting a well drilled. The other reason we have to have a well planned is because we have a regulatory overhead, so when you go to the regulators with what you’re doing, they are like the zoning commission in the city. With zoning, there are rules in the town, and rules in the neighborhood you’ll occupy. With the oil and gas regulators, there are various environmental considerations, and things you have to do to comply with those. One of those necessary things in our business is a performance bond. The operator, who is the one to handle this, bonds his performance, as required by law.”
Cure compared the act of taking out a performance bond with the act of taking out a bail bond. “The bail bond bonds a ‘performance’ that the bonded individual is going to show up for the trial,” Cure said. “Well, you have to post a bond to be responsible for getting your job done and afterwards cleaning up your mess—all of that is part of the regulatory compliance. The regulators also have environmental concerns. They want to protect the fresh water supplies and they want to protect the environment. And there are other political and regulatory reasons you have to have a well plan to show them what you plan to do and how you plan to do it.”
For drilling a conventional well, the typical drilling rig will be powered with a motor that supplies anywhere between 500 and 1,500 horsepower. To give some picture of what that looks like, Cure compared the 500 horsepower with the kind of engine that powers earthmoving equipment or large agricultural equipment. Then, accordingly, the 1,500 hp engines would be triple that size.
The location for a well typically covers about an acre to an acre-and-a-half of ground. It takes that much space to accommodate all the equipment and have room for all the drill strings and the pits and trailer houses and other large objects.
Moving and setting up a drilling rig is a feat of logistics. The masts, when erected, are anywhere between 100 and 140 feet in height. The rig is a crane in and of itself, to some extent, and one way to erect it is to push it up with hydraulic rams. For transport, the mast can be folded up on a carrier and, because of the way it is constructed, it comes fabricated with legs that stand up and are braced. It also comes with cables that are strung in such a way that the rig can actually pull against part of itself and raise the rest.
Said Cure: “So they can actually use the crane part of the rig to actually raise its own mast. And once they get up there, they just pin it in the vertical position. So part of it jackknifes over from the other part, and it’s all strung together with pulleys and cables, so that when they pull on it, it can pull itself into an erect and vertical position, typically.”
When the time comes to move the rig, it will be disassembled, because there are rules that must be followed if one is to transport something of this size down a highway. Rigs come in for the “Wide Load” treatment. The moving operation will generally take 20 to 30 truckloads just to move the rig and its drill string, and many hundreds of gallons of diesel per day.
But during set-up, there is a rig floor to construct and some heavy hardware to get in place. The working floor of the rig is 12 to 15 feet above the ground. Underneath the floor is where blowout preventers and valves are set—hardware that prevents the blow out of the well.
Once a rig is up and running, it can make 500 foot of hole a day, or more—often going down to 10,000 feet total depth in ten to 12 days. It’s a round-the-clock operation. That’s why they stand out so much at night—those lights are on because shifts are running 24/7.
The number of men is usually on the order of 16, and they usually work 8 hour shifts, so there are three crews that keep it running constantly. In a typical drilling operation, costs of drilling can be around $30,000 a day.The drilling operation itself is about half the cost of the well.
Said Cure: “In order to take the lease and build the road and drill the well and get everything cemented in there, and get ready for your completion activities, you’ve spent somewhere around half the money you’re going to spend on that well, probably over its entire life.”
That’s simply to get the hole made. That’s not including the cost of completion of the well—a formidable process in itself, and one that will be covered in Part III. But completion brings costs of its own—including well stimulation, the building of a tank battery, the installation of electrical service, setup of a pumping unit, and those sorts of things. “There’s a lot of other things that come downstream of the drilling phase,” Cure said. “By the time you get it completed and gotten all that other work done, you may have spent 75 percent of all the money you’ll spend on that well. And you haven’t yet gotten any of your money back.” He laughed. “So, once you’ve established production and started getting your money back, you’ve spent most all the money you’re going to spend. That’s why you’ve got to manage your risk and that’s why you get a number of partners.”
But we were discussing the business of drilling.
In starting, then, at the surface, the first set of pipe to be set into the ground is different from what will go further below it.
“We call that pipe at the top the ‘surface pipe,’” Cure said. There are other sections to be set below that. “We’ve got to set the long one for production, and sometimes we set one or more in between because we needed to change the drilling fluids for some reason. But that is normal.”
As the drilling delves down through the shallower beds, it is there that most of the fresh water—the usable, potable water—is encountered. Said Case: “The state [Railroad Commission] tells us what depth it is [groundwater zones] and we have to set a casing through that depth before we can proceed. Then there also are some correlative rights involved. Kind of like zoning. If you’ve built a house in a neighborhood, you’ve got to honor your neighbor’s wishes to some extent. It’s the same with the Railroad Commission. You can’t get too close to your neighbor’s lease line. That sort of thing. So there are regulatory compliance issues there, and various areas, that have their own special rules.”
Oilman Phil Kendrick, who was quoted in Part I of our series, supplied some insights into the drilling process also. Like Cure, he cited the need to protect the groundwater. “You have to cement the surface pipe into the hole, and you have to do it according to Railroad Commission rules,” said Kendrick, president of Kendrick Oil Company, Abilene, Texas. “In some places you only have to put in a hundred feet of surface pipe, and in other places you have to put in 800 feet, and in some [other] places you have to put 2,000 feet. But mostly around here [far eastern Permian] it is 200 to 400 feet. And that is to protect the groundwater. The Railroad Commission has published information on the depth of fresh groundwater in every area, and that determines how much surface pipe you’re going to put in.”
For the size of the pipe, “Generally around here you put in 8 5/8 inch,” Kendrick said. “If you are going to drill a deeper hole, then you go to 10 5/8. Then the next size up would be about 13 inches, if you’re planning on going really deep. In a case like that, you’ll then need quite a bit of surface. Because your surface pipe is going to take a pounding as you drill. And you don’t want it so small that the [drill pipe] is going to pound against your surface pipe. That drill string is just heavy steel. But it does tend to whip a little bit and so you want the surface pipe that it is wide enough that the drill pipe won’t whip against the surface pipe.
“If it starts to pound on the surface pipe, you’re going to start breaking down the cement that is behind it, and the next thing you know, you lose the bottom joint in the hole,” Kendrick said. “And when you lose that bottom joint in the hole, you are in big trouble. Because it is hard to bypass it or drill it out or get it up or anything. You are just in bad shape. If you are going to lose any part of the surface pipe, it will be the bottom joint. That happens. They’ve been in and out of the hole so much and they got in such a big rush, and they’re maybe turning the pipe at a higher RPM than maybe was safe, and getting in a hurry, and it is the bottom joint that will generally be the one that’ll break loose first. And once it breaks loose, you are in big trouble. So that is a very important part of drilling—to get the right size of surface pipe, and of course the right amount in the hole. Then after that, let the cement set. For a minimum of 12 hours, and we like to wait 24, but then you go in and you start drilling.”
Cure described the drilling process, beginning with the drill bit.
“The bit is a mechanical object that is picked up on the end of the drill string, and it has wheels with teeth on them, or really hard metal or ceramic cutters, like the special diamond cutters that are popular,” he said. “We pump a fluid down inside of that drill pipe that we push on that bit with, and that mud comes out the end and it cools the bit cutters and it flushes the cuttings up and out of the hole. Now, most of those drilling fluids are water. They are either based on fresh water or brine. And sometimes we can drill with air—we can actually blow the cuttings out of the hole in some areas. (See our related story on p. 82). And sometimes we use oil-based drilling fluids. The oil-based ones are either synthetic or mineral or even vegetable-based fluids that are used for special purposes. But out here I’d say about 90 percent of it is water, either fresh or brine. Now, we adjust those drilling fluid properties, to some extent, by putting materials in there that make them more viscous, to help seal the walls of the hole, and that sort of thing. So, really, the properties are more like thin milk up to maybe like paint—a consistency similar to that.”
That fluid is what is pumped around—it’s called circulation—to flush the cuttings out of the hole as the drilling proceeds.
While the shallower parts of the borehole can be drilled with some kind of drill other than the rotary rig itself—even in some cases by an augur—at some point the rotary rig is brought to bear, and when it is, there must be substantial weight on the drill string—transmitted down to the bit itself—for the bit to be able to bite the rock with sufficient force to “make hole.” As Kendrick noted, some of that weight has to be supplied by pipe that is in the drill string.
“When you go in with the rotary, you’ve got to have weight on top of that bit to really make any hole. You put what they call ‘collars’ in the drill string, for weight. Then on top of that you get your drill pipe. You need to stabilize that drill string. So you don’t whip as much.”
Said Cure: “The drill string is a series of pipes, and right on top of the bit we usually put some heavy pipes that are for gravity weight on the bit. And they will typically be six to eight inches on the outside diameter, and have a two-inch hole down the inside. The larger ones weigh about 4,000 pounds apiece and the smaller ones weigh about 2,500 pounds. So you’ll stack enough of those on the bit that you can run maybe 25 to 50 thousand pounds of gravity weight down against the bit. And on top of that we have drill pipes, and the drill pipes only weigh about 20 pounds a foot. And they’re just a transmission—just a shaft to transmit the torque down to the bit and to pull it out of the hole.
“You pump down inside of those pipes the various drilling fluids, which we commonly call ‘mud.’ We mix various materials in the mud. Clays and polymers. Polymers are kind of like the sugars and starches you use in your kitchen to make gravies. Drilling mud is kind of like a gravy and it helps to bring the cuttings out of the hole as we drill down,” he said.
Added Cure: “We may have to set multiple strings of casing. We set the surface casing to protect the fresh waters, and we always have to set the end, the production casing, to conduct the fluids or oil and gas to the surface. Sometimes we have to set one or more intermediate strings because we need to change the drilling fluids, typically. We’ll get below the salts and want to use a fresher fluid and so we’ll case it off. Or we’ll drill through some ‘seeper’ zones that aren’t strong enough to hold the weight of the fluids, and so we’ll case them off and we can go to heavier fluids below that point. ‘Case’ being to change the drilling fluids.
“To keep those seeper zones from seeping we put a clay-type material in the drilling fluid and it’ll actually make kind of a plaster on the wall of the hole to keep that seepage under control to some extent. Sometimes we drill into zones that are weak enough that just the density of the drilling fluids themselves will actually make the rock crack open and we’ll lose some of those fluids. And if we need to use heavier fluids in the end and we can’t get from here to there we’ll set an intermediate casing to cement off those troubles.”
Somewhere along the line, the crew must be on the lookout for the payzones that the well operator hopes to hit.
In some situations, the operator is looking for a “marker” zone that typically occurs just above the target zone. He wants to identify the marker zone so that he’ll be prepared to take a core sample that can be brought to the surface—a cylinder of rock—that can be examined more minutely for the presence of hydrocarbons.
But in other cases, as Phil Kendrick noted, the driller might just be looking for the payzone itself.
“A lot of people will wait until they will actually see the signs of the payzone,” Kendrick said. “Then they will slow everything down. Slow it to a lower RPM. They don’t want to drill it as fast. They slow everything down so that they can get the samples up. And they will stop and circulate. They’ll kind of feel their way because they want to just barely pop that sand or that limestone, or whatever zone it is where they expect to find some oil. And then they drill a foot or two and wait 20 minutes, or 30, depending on what depth they’re at. Wait for that sample to come up. They want to examine that one foot of sample before they drill another foot.
“Well, that really slows everything down,” he added. “But you have to do that if you want to get that core [core sample that the driller is going to take] in the right place. And core what is potentially your oil zone. You don’t want to be coring a bunch of barren limestone or water sand or something like that. You want to core what you think will be an oil zone. And some of them will not put the core barrel on until they see a show.
“But it takes a lot of time. You have to go a foot at a time. It takes 30 to 40 minutes for the samples to get up to the surface. So you drill a foot and you wait for that sample to get up to the surface. And you look and see what it is. Then you drill another foot. And you just drill your way, so that you’ll be sure that you get that core barrel in the right spot.”
Mike Cure cited the need to evaluate a well during the downhole process. “We are looking for geologic clues,” he said. “So typically we will have specialists who come and out and they catch the cuttings that come off the bit and they look at them under a microscope and they sample the drilling fluid as it returns from the hole, using little separators. Electrically, they ‘smell’ it. They put it in a little thing kind of like a blender or a food processor, and they have a ‘vacuum cleaner’ that sucks the fumes off and they electronically actually sniff the mud and they can sniff the presence of hydrocarbons and they can even sort them out a bit and kind of tell what kind of hydrocarbons they are.”
That work is the work of a mud logger. As Phil Kendrick said, the work of the mud logger is very important. It’s also very important to have the right mud weight at the right time.
“That’s so that if you do hit a gas pocket or an oil pocket, you’ll have enough weight that you’ll contain it,” Kendrick said, “You don’t want it too heavy, or you’ll lose circulation, especially in a good oil and gas zone, with that greater porosity. You’ll break that mud down, if you have too much weight—if the mud is too heavy. You need a mud logger who knows what he is doing and how many pounds of weight you need in the mud for that particular area and that particular depth. And you want to be sure that you have low water loss. The lowest water loss possible. It slows your drilling down. Drilling contractors don’t like the operator to require real low water loss. But with it, you’re going to have a much better hole, and much cleaner hole, and you’re not going to have washouts and not going to lose any mud into the formation.”
The water loss, if any is occurring, is occurring downhole, and that often indicates a problem going on.
But the key consideration is the mud. “You have to have the right mud,” Kendrick said. “You can’t put any old mud in there. You have the right weight in there so that everything is in balance. Also, mud seals off. It helps seal off the shale. Water doesn’t. It wants to eat into that shale. And get into the shale and then it swells. And you can get stuck. So you’re not really saving money if you don’t mud up until you get down deep.”
Cure added this:
“We’ve drilled our hole, run our logs, evaluated the logs, and if we decided to case the hole, we will run our casing down it, which is going to be our production conduit,” he said. “We will run that down and run the cement inside it and fill it with water to push the cement to the outside, between the casing and the wall of the hole, and then we let the cement set and we’ll move the drilling rig off the hole, and we are ready to start the completion.
“And that,” he said, “is a whole other subject.”
And, finally, a word from Leroy Peterson, a contract oil and gas driller who is vice president at Patriot Drilling Company in Midland. Asked what he could add to our discussion on the drilling of a well, Peterson said, “don’t forget about the people.”
“Those things don’t operate without people,” he said. “It’s a people-driven business. Out of all the resources we use, that is our make-or-break resource. Especially when it comes to the drilling rig. A lot of times even our customers forget that there are real people out there, operating 24 hours a day.”
Next issue:
Part III
Completions, Stimulation, and
Transport to Market
This hole we just made has made a good show, and now it’s time to, yes, commit a whole lot more money and turn it into a producing well. This step is called completion, but even completion is not “completion.” There’s still more steps before the oil or gas is on its way to the refinery or processing plant. So next month we’ll cover everything that follows the drilling. Don’t miss it!