Run A Flowing Gradient To Identify Liquid Loading During Production

You may be familiar with a static pressure gradient survey, more commonly referred to as a "gradient". The process for a gradient is simple: run in the well with bottomhole pressure gauges and record the pressure at various depths downhole. From the data you can determine both the fluid depth and the fluid density in the well. Typically this is done with the well shut in, hence the term "static". While this is helpful information to know, when we talk about liquid loading, our concerns are usually related to the production of the well. Therefore liquid loading issues tend to impact us more when we are flowing the well, not when we are shut in. This is where a flowing gradient can be helpful.

As a well flows it pushes fluid up the hole, creating hydrostatic pressure. Even wells that are unable to lift fluid to surface, still lift the fluid at least part way up the hole. When the well is shut in, the fluid then falls back down to some equilibrium point. This problem is amplified in horizontal wells because the fluid tends to fall back into the lateral when the well is shut in. Tubing that was filled with fluid during flow becomes completely empty within minutes of shut-in. If you were to run a static gradient survey on a horizontal well (without a standing valve), you would likely find no fluid in the tubing. Your static gradient survey would not be a good representation of your liquid loading issues. In this situation a flowing gradient would be much more insightful.

If you have a well with liquid loading issues, consider running a flowing gradient survey rather than a static gradient. You might be surprised at what you discover about your well when it is flowing.

If you are interested in learning more about gradient surveys, click here to check out our Well Insights on this topic.

Address Liquid Loading Early

Engineering Tip: Address Liquid Loading Early and Save Yourself Headaches​
Liquid loading in a producing well is an inevitable reality for almost every well. Eventually, the stored energy in a well falls below the minimum threshold to lift fluid. This is a fairly straight-forward thing to predict with some basic critical velocity equations. It takes only 5 minutes to calculate the minimum flowrate necessary to lift fluid out of a well. With this number in mind, you can predict with surprising accuracy when a well will start to load up. If you know when to expect liquid loading, it's really easy to identify it when it starts to happen. You're gas and liquid rates will drop off quickly and you're well will appear to decline exponentially faster than it was.

As soon as you see this happen, address the issue right away.

There are many ways to address liquid loading: soap, plunger lift, submersible pumps and pump jacks are the most common methods. Regardless of which artificial lift method you choose, the key is to get on the issue quickly, before the well gets so loaded that it becomes difficult to get back. If wells are neglected and they get loaded up in a major way, it can be challenging and expensive to get the well kicked off again. I've seen wells get so loaded up that they require coil tubing and nitrogen to get them flowing again. This is expensive, much more expensive than a simple plunger lift or chemical setup.

We know that wells are going to load up. No one should be surprised by this. Have a plan in place to deal with this and don't act surprised when it happens. If you have an artificial lift plan in place, then you can quickly implement the solution as soon as the liquid loading occurs. This will save you money in the long run, and it will prevent downtime on the well.

Bonus Tip: Put Tubing In The Well Early

Once again, you know the well is going to load up. It's going to need tubing. Have you every tried to unload a well without tubing? It's like fighting with one hand tied behind your back. Just put tubing in the well and save yourself the headache. If it was up to me, every well completion would include tubing (*and all the production engineers cheered*).

Wells load up. Don't be caught with your pants down (or your well down). Have a plan, identify it quickly, and fix it. You'll thank me later.