Oil Well Drilling Primer

When I was dating my wife I told her I was an oil well driller and she said "Oh, you mean like that movie Armegeddon!"
Well not exactly. Tho there are some things in that movie that are pretty accurate. Like the part where they say they'll go and save the world but they have a few requests, take care of some warrants, a night at the White House and oh yeah, don't pay taxes again, ever.
I laugh everytime I see that flick. The writers knew or interviewed some real roughnecks when they wrote that. The scene in the med lab is priceless.

I am going on days off this morn. But I have a lot of pics and will continue this thread from home. Then when I get back we will be finishing up this well. I'll answer your question in a day or two T. Don't have time right now.

 

Just wanted y'all to know. I was really busy this time at home. Am back to work now and we have just TD'd (Total Depth) this well. I am going to be really busy for a couple of days, but am taking lots of pics and will try to finish up this thread in the next couple of weeks. Stay tuned.MM

 

The drill bit is screwed onto a drill collar. But, the bit has a threaded pin sticking up and the drill collars have the threaded pins down, so a double box "bit" sub is needed. The bit is screwed into the bit sub, and then the first drill collar is picked up and screwed into the bit sub.
The "tongs", which are basically big pipe wrenches, are used to tighten up the connections.

The "Kelly" is a square or octagonal pipe that is used to turn the drill string. It is screwed into the drill collar. On top of the Kelley is the "Swivel" which allows everything below it to rotate. It also has a connection for the "Kelly Hose" to attach so that the drilling mud can be pumped down the inside of the drill string. The Swivel has a loop or "Bale" on it. The traveling blocks have a hook that can be opened and hooks into the bale on the swivel. The entire drill string is lifted and lowered with this attachment.

 

On the Kelly is put a "Kelly Drive Bushing" this mounts around the square or octagonal Kelly and pins in the bottom of it fits into the rotary table. As the rotary table is turned it turns the Kelly drive bushing and this turns the Kelly and in turn the entire drill string and the bit on bottom.

 

The Driller eases off of the brake on the drum and lowers the drill string down until the bit sets on bottom. Then he engages the rotary table and with the drill string turning he lowers the string to put wieght on the bit.

 

As the bit turns it grinds up the ground and the cuttings are brought to the surface by the drilling mud. The mud flows through the conductor pipe, down the flow line to the shale shakers, where the cuttings are seperated from the mud. The cuttings slide off into a pit and the mud is returned to the mud tanks.

 

The drive bushing turns the Kelly, which turns the drill string and the bit. As the wieght drills off the driller lowers more wieght onto the bit. The kelly slides through the rollers in the drive bushing. So rotating and drilling is not stopped until the entire length of the Kelly is drilled down.

An interesting sidelight;
Originally wells were drilled with a "fishtailed" bit that was hammered into the ground. This spaded bit would dull after only a few hours and a few feet. It would have to be pulled from the well and a "tool dresser" would be waiting to sharpen it.
When Howard Hughes invented the roller rock bit in the early part of the 20th century it revolutionized the drilling industry. To turn the pipe and the new rotary bits a system of clamps were used. They would ratchet the clamps closed onto the drill pipe and it would bite into the pipe. When the wieght drilled off you had to back off the clamps, lower more wieght, and re-attach the clamps. This was time consuming and it damaged the drill pipe.
The rotary "Kelly" was invented in the 1920's to remedy this. During that time baseball was the American pastime and there was a player who was famous for stealing bases and sliding into them, much like Pete Rose. His name was "Kelly" and when he would take off to steal a base the crowd would chant "Slide Kelly slide!!".
During an oil show in Tulsa Oklahoma a group of oil men were watching a demonstration of this new invention. As the "Kelly" slid through the rotary drive bushing one of the oil men said "Slide Kelly Slide". The name stuck and to this day, in oil fields the world over, this now standard piece of equipment is known as a "Kelly".

 

How long is a kelly? (Or said another way, how long is a drill string piece?) I see the wedge clamps in one of the pics that hold the string for taking sections out. We had something similar on the raise bore operations. Obviously how often you have to add stick is strata dependent, but on average what's the time interval between adds?

 

Kelly is 40', average length of drill pipe or drill collar is 31'. the reason for the difference is so that you have room to get all of your other tools in the hole after a "connection" is made. I was going to describe that process next.

Underneath the Kelly drive bushing is a safety valve that can be closed to shut off any flow coming back up the drill string. Also the tongs "biting" into the kelly every time a joint is added would soon wear it out so a short 1-3' "Saver Sub" is used. After a couple of months of wear it can be replaced. So you have around 3-5 feet of tools underneath the kelly drive bushing that you have to have room for.

The top section of the hole is sand and soft shale formations. The collars are drilled down in a matter of minutes. Usually no mre than 5-10 minutes a joint. As you get deeper the penetration rate decreases. It is measured in feet per hour. A typical well will start out at 140-180 feet an hour, then slow to 60-80 feet in the intermediate section. Then the final section of the hole, the production section usually drills at around 20-40 feet an hour.

The wells I am drilling are an average of 9500' deep and take about 3 weeks to drill. Of course that varies significantly in different areas.

The hole has 3 sections that you drill, run a casing pipe into and cement, then go to a smaller sized bit to drill the next section. I'll get into that as we get to each section. The first section we are drilling on this hole is the "Surface" section. It is a 12 1/4" hole 1,500 feet deep. We will pull the drill pipe out and run a 9 5/8" casing into the hole and cement it into place. This will isolate and protect a ground water source in this area between 900 and 1400 feet.

As to the wedges you mentioned, you are very observant G. They are used to hold the drill string while you remove the kelly and add another joint. I will document a "Connection" in the next segment.

 

Here are some pictures showing the "slips". They are tapered and have dies on the inside that bite into the drill pipe and hold it. The rotary table bowl is tapered. The slips are put around the drill pipe and the pipe is lowered. The slips go down into the bowl of the rotary table and the tapers squeeze them together. The wieght of the drill pipe causes the slip dies to bite into the pipe. The pipe is then suspended by the slips in the rotary table. The tongs are put on the connection and it is broken. The rotary table is engaged and the pipe turns while the tongs hold the top pipe connection. The pipe is unscrewed and picked up.

 

This is a pic of the bottom of the kelly before the drive bushing is installed. The kelly slides through the bushing, but the wider tool joint won't go through it. It comes up when you pick the kelly up and it gets to the end. I will get some pics of that in a day or two.
We have already finished the well that we started when I began this thread. We are just getting ready to "Spud in" on a new one.

 

We need a pic of the downhole recovery tools for when you drop a joint, when the slips don't bite ---. (Had that happen once on a raise bore.) Somehow, I think that doesn't happen very often on your operations, and betting you don't have to wait too long for tools to show up.

Very interesting thread ---

 

No Thanks!! It happens occasionally, but it is the last thing you want to happen. Next to a blowout. Can cause a bunch of problems and takes a lot of time to get back on track.

 

Rodent Holes

Ok. We have the bit made up and the Kelly and drive bushing made up. So now we start drilling. As each joint is drilled down you pick up the string, remove the Kelly, and add another joint. This is called making a "Connection". This continues, joint by joint, until you get to TD (Total Depth), which can be casing point or the finish of the well.
But before I can show you that process I have to explain the rodent holes.

When the kelly is all put together, with the swivel and the saver sub etc., it is about 44' long. When you need to pull the pipe out of the hole. Either because of a dull bit or because you have reached TD, you have to have somewhere to store the Kelly. It wouldn't be feasable to break it all apart and lay it down. So we have what is called the "Rat Hole". It is a hole 40' deep and is pre drilled by the same company who sets the conductor pipe and digs the cellar. Also to make up a 30' joint of drill pipe onto the kelly you have to be able to have a fairly straight connection so that the threads will screw together. So we have a "Mouse Hole". The mouse hole is just in front of the conductor pipe and the rat hole is just to the side of it.

When the rig moves in there is a hole in the floor of the rig where a large diameter pipe is set through the floor of the rig and ran down into the rat Hole and another into the mouse hole.

The kelly is set into the rat hole and removed from the traveling block. The next joint of drill pipe to be added to the string is picked up with a winch and put into the mouse hole.

 

Making a Connection

We have the kelly picked up, the rotary table is turning the drive bushing, the next joint is in the mouse hole, and we are drilling. The 40+ feet of the kelly is drilled down by adding wieght to the bit until it gets to the bottom (or the top actually). Then it is time to make a connection.

The kelly is picked up. The pumps shut down, the slips set into the rotary table. The tongs are placed on the pipe and pulled on by the driller breaking the connection. The bottom tongs are removed and the top tongs hold a back-up as the driller engages the rotary table to unscrew the pipe. The kelly is picked up, pushed over to the pipe in the mouse hole and screwed into it. The tongs tighten the connection and the blocks are picked up, raising the kelly and the new joint of pipe screwed onto it. The bottom of the new pipe is "stabbed" into the joint in the rotary table. It is screwed together and tightened with the tongs. The string is picked up and the slips pulled out of the rotary table. The kelly is lowered until the drive bushing falls back into the holes on the rotary table. The pumps started, the rotary engaged, and drilling is resumed.

 

Making a connection cont.

More connection.

 

back to drilling

The connection made

 

casing

This process will continue until we drill to TD (Total Depth). Our TD on this section will be 1,500 feet. That will be our casing point. We will run a string of pipe called casing into the ground and cement it into place. We are drilling a 12 1/4" hole and will run a 9 5/8' casing into it. This will protect a ground water source in this area. Also it will alow us to raise our mud wieght higher than the softer formations would allow.

The casing is trucked to location. We lay it out on pipe racks, clean the threads and measure it. On the bottom of the first joint to be run is what we call the "Float Shoe". It is a one way check valve imbedded in cement that can be drilled out when we go back in the hole with a smaller bit. The "Float Collar" is placed either one or sometimes two joints up from the shoe.

We will pump cement down the inside of the casing, out the shoe and back to surface. The float collar lets us leave some cement inside the casing, insuring that we don't accidentally pump it all out. We calculate how much cement is required to fill the annulus between the casing and the open hole. We pump that much cement then we put a rubber "Plug" in the casing and start pumping drilling mud behind it. When the plug hits the float collar the pressure goes up on the pump and we stop pumping.

We are at TD right now on the well I am currently drilling. I will document the casing running and cementing process today.

 

sweeping the hole

Now that we have reached TD and drilling has ceased, the next step is to get all the cuttings out of the hole. We mix and pump a "Sweep".

The mud tanks are divided into compartments. One small compartment is called the "Slug Pit" or a "Pre-mix pit". It holds only 40 barrels and is used to mix something different than what is in the rest of the mud system. We will add Bentonite to increase the viscosity.

We are running a 38 second per quart vis now so we will bring the vis up in the slug pit to 80 sec/qt. This thick sweep will be pumped down the hole and will "sweep" the cuttings and bring them to the surface.

Here are some pics of the shale shakers doing their job. The mud comes to the surface, flows down the flow line, and is diverted to the shakers. The mud flows over screens on the shaker, the mud falls through and is returned to the mud tank, the cuttings are shaken by the vibration of the shaker and move out to the end and fall off into a trough that channels them down a slide and out to a catch pit.

A sidelight; all fluids in the oil business are measured in barrels. Oil, drilling mud, water. Most people think of an oil drum when they hear barrel. An oil drum holds 55 gallons, however, a barrel holds 42 gallons. Why the difference?

The first time oil was drilled for was in the 1860’s in Titusville, Pennsylvania. It was refined into kerosene and was sold for lamp oil. Whale oil was getting scarce and was very expensive. The inexpensive kerosene revolutionized 19<SUP>th century America. It was suddenly possible for anyone to afford lighting. </SUP>
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The oil at that time flowed to the surface in a slow easy seep. Not the roaring gushers seen in Texas a few years later. They channeled it from the well into earthen pits. The oil companies built refineries in Pittsburg. But how to transport the oil there?

Prior to the oil boom the main industry in Titusville was also based on a plentiful natural resource, oak trees. They provided the material to support a thriving business in wooden whiskey barrel construction. The oilmen started buying up every whiskey barrel available to transport their new product to the refinery. And how many gallons does a whiskey barrel hold? Yep, 42 gallons.

To this day all liquid measurements in the oil industry are in barrels and a barrel = 42 gallons.


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