In most jobs, the professional actually sees what he’s working on. The carpenter sees the nail he’s hitting, the truck driver sees the road ahead, and the doctor sees the spleen he’s venting, but as drillers, we have it a little harder. Since none of us can see down there any better than Ray Charles, we must rely on other cues and evidence to tell what the bit is doing. Proper instrumentation will provide the driller with all the clues he needs to tell what the bit is doing – if he knows how to read them.

On all large rigs, the weight indicator is the most important tool for monitoring what is going on in the hole, but nearly no small rigs have them. There are several reasons for this. First is expense. Weight indicators are expensive, and require rig designs that just might not be practical.

Another factor is power: Big rigs usually have enough horsepower and drawworks to pull much more than the derrick will stand. This can lead to disaster if the driller doesn’t know exactly what he’s pulling. Smaller rigs seldom have strong enough drawworks to pull in the derrick, so they don’t worry about it. They just pull until it won’t pull any more. Even so, there are a number of ways a driller can get a feel for the weight he’s pulling. Manual clutches and brakes have a different feel when they are heavily loaded, so it’s not hard to feel the difference between light and heavy. Plus, the sound of the engine and the “squat” of the rig will tell a lot.

On smaller rigs, I consider the pump pressure gauge the most important gauge a driller can have. Not only does it tell the condition of the pump itself, it gives a direct readout on the condition of the hole. I get calls from drillers all over the world concerning various hole problems, and usually one of my questions is, “What was your standpipe pressure?” If they say they don’t know, I’ve got a good idea why, so I say, “Well, what did the gauge say?” That’s when they have to admit that either they don’t have one, or it doesn’t work. Fixing the problem usually goes downhill from there. It also gives a pretty good idea of the condition of the rest of the rig, too. These are the same drillers who tell me that they can tell the pressure just by listening to the rig. Right; when the engine stalls, or they pull a rod out of the cross-head, that’s a clue.

A good gauge will tell about your pump before you even start drilling. When you have fresh swabs and liners in a pump, make a note of the pressure with fresh water, through your mixing hopper. On one of my rigs, it would read about 80 psi on a new rebuild at idle. After the swabs had worn enough to need replacing, it might read about 60 psi, and I knew it was time. I sure couldn’t see this difference by looking at the flow, but the gauge told the story. I’ve seen pumps so worn out that you could close all the valves and engage the pump, and it would run, so much fluid was leaking around the swabs.

In the hole, a sudden pressure increase will indicate a balled-up bit or bottom hole assembly. When you first notice this is the time to fix the problem, rather than just drill on and leave a clay-balled hole. A sudden decrease in pressure and increased penetration is a pretty good indication of a sand. If you see this right after drilling a clay formation that tries to ball up and pressure up, it is a good idea to pick up and circulate the hole clean. If you plow into a weak sand with a balled-up hole, you stand a good chance of losing circulation. We call this “knocking the bottom out of it,” and, if not dealt with, it will stick pipe.

As you drill deeper, pump pressure gradually will go up as you add each joint of pipe. This is natural and to be expected. If you suddenly see a huge pressure drop, below what you might expect from a sand, it is a good sign that you have twisted off, or your string is parted somewhere. You often can feel a lot less weight, too. If so, circulate the hole clean, and ease back down. If the pressure increases to normal, you probably have backlashed the pipe off, and may be able to screw back into it. If the pressure does not change, or you are able to go deeper than you were, you probably have twisted off in the middle of a joint. Either way, the gauge will talk to you.

Another useful gauge on your pump (the heart of the rig) is a vacuum gauge on the suction side. If you use dug pits, the pump always is operating at a net, negative head. Pumps are rated at 100 percent with the net suction head at zero or above. Anything less than this causes the pump to lose efficiency, and pump less. If you use dug pits, 80 percent to 90 percent is a reasonable figure to use. If you use a restricted suction line because it’s easier to carry around, deduct a few more percent of efficiency. For instance, with a 5-in.-by-6-in. duplex pump rated at 154 gpm, it is not uncommon to see the measured rate at 125 gpm or so. The vacuum gauge will show this. It also will show when your suction line is plugged with sand and sticks and needs cleaning. A suction gauge also will show when you have a rock or a stick under a valve. It will go wild.

All these gauges help you see what is going on at the bit, which is where the action is. There are a lot of other surface indicators that help the driller see what’s going on down-hole, and I’ll try to touch on some of them in the future.