Life of the Well 1: Location and Drilling

One way to describe my occupation is that I teach software in the energy business. The convergence of teaching, software, and petroleum puts me in contact with a wide variety of people, from the toughest of roughnecks to the skinniest of computer programmers.

Sometimes we get programmer turnover, and the new guy doesn’t benefit from any oilfield experience, frequently having been hired straight of college and whose main goal in life is to earn that coveted “Microsoft Certified Systems Engineer” certification. Most are smart enough to realize that it helps to know some basics of what’s going on in the oilfield when they write software for it.

I ran into this problem as “Product Champion” and ended up writing some basic tutorials in PowerPoint for them to read. Corporate hadn’t quite adopted a web policy yet. I don’t have the original aids, so I’ll reconstruct as best as I can here. In addition to perhaps saving some repeated explanations later on, I hope it makes the sub-point that there are a lot of decisions made that affect the final price of anything. Thomas Sowell would be proud.

Most tutorials I’ve seen cover the “Life of the Well” from inception to abandonment, and that’s not a bad way to do it. The Halliburton Energy Services Group changes its organization every couple of years or so to emphasize a group of services where it can make the most money, but the functions remain primarily the same: drilling, logging, cementing, stimulation, completion, and abandonment. Most of my experience has been in the middle two, so I expect those articles to be longer.

Dan the Geologist, as well as my co-workers, if you have something to add, please feel free as we go along here.

Life of the Well: Location and Drilling

There’s no question that the oilfield is an industry that has some vocational “calling” in a providential sense. Dick Cheney said in a speech to the Cato Institute on June 23, 1998, “The good Lord didn’t see fit to put oil and gas only where there are democratically elected regimes friendly to the United States.” Unfortunately oil and gas doesn’t exist everywhere in the U.S., either, and where it does exist, it may not be economically feasible to produce it. Since the late 90′s we’ve known coalbed methane exists near my old hometown of Kansas City, but today it doesn’t make as much money as the coalbed methane fields in Virginia and West Virginia. If the shallow wells in Ohio are deepened and they find more petroleum, I’ll be changing departments in a heartbeat.

Locating petroleum until recently has been a task of trial-and-error. Exploratory wells, called wildcats, are drilled in land leased from the government or private individuals. Wildcats have a high risk/reward: if the well doesn’t hit anything, the company has blown its money on a dry hole. If the well does hit something, the company then knows where some oil is and will secure mineral rights from the land around it. Seismic surveys have been used to reduce dry wells, but what seismic surveys really tell you is where there is a change in earth density. Today that density gives us clues as to whether oil and gas could be there, but we’re not to the point where we can use seismic as a divining rod.

Once those geologists have picked a site, the company starts drilling. The deeper one needs to go, the larger and more expensive the drilling rig. Howstuffworks has a nice article about what it takes to drill the well. Google has plenty of pictures of drilling rigs.

I’ve been on wells as shallow as 400 feet. The deepest I’ve been on has been around 23000 feet—4 1/3 miles. That dirt has to come out somehow. The key to removal is the hollow drill pipe that is used in drilling. The drilling bit at the end of the pipe drills a hole larger than the pipe. A fluid (gas or liquid) is pushed down through the drill pipe, and cuttings come up the outside of the drill pipe, between the pipe and the hole that is drilled. In order to get such long distances underground, drill pipe is joined in 30-60 foot sections as the hole get deeper.

Halliburton is primarily concerned with the fluids used in drilling, thanks to its acquisition of Baroid from the Dresser merger. The fluid used in drilling has several design parameters. Shallower wells can be drilled with air, which is cheap and doesn’t harm petroleum or the water table underground. As we drill deeper, we have to use liquids to avoid a blowout. Oil and gas locked for thousands of years under the weight of thousands of feet of rock, upon seeing a nice unobstructed way to surface, will leave. Fast. In the old movies a blowout was a good thing because you found oil; today it’s bad because of a) environmental concerns and b) the petroleum leaves the underground rock so fast that the rock collapses and can’t push more out later.

When fluids (called “drilling mud”) are used, there are generally three choices: water-based mud, oil-based mud, and synthetic-based mud. Water-based mud is less expensive and is heavier than oil; oil floats on top of water. Water-based mud has problems with certain types of rock. Underground dehydrated clay will swell when water hits it and choke off the drilled hole. In that case, oil- or synthetic-based mud has to be used. Oil-based mud is pretty nasty to work with; it doesn’t come off one’s clothes as easily as water-based mud. Synthetic-based muds are the most expensive and are usually designed for environmental considerations. Most wells I’ve been on use water-based mud.

Frequently the weight of water or oil isn’t enough to prevent the oil or gas from blowing out. Mud must often be weighted with additives; a favorite additive is barite, barium sulfate. Normal water has a density of 8.33 lbm/gal; mud can be weighted upwards of 20 lbm/gal.

During drilling a set of valves is installed over the hole, called a blow-out preventer. It is also known as a Christmas tree from its shape, big on bottom and narrow at the top.

Between sections of drilling, large metal pipe called casing is pushed into the hole, and cement is placed between the metal casing and the newly drilled earth. In the next Life of the Well post, we get into cementing the hole, something I’ve had some experience in and more importantly is not on howstuffworks.com.

Similar Posts:

• Life of the Well 2: Logging, Testing, and Cementing
• Removing the Water from Oil Wells
• Horizontal Drilling near Dallas