A gas gathering system can be confusing when you consider all the different competing variables and goals. In this post, let’s look at a common question you might have when first looking at a compressor curve. On the Min Max curve below (provided in combination with a Startup Package for a specific running configuration), we can easily see that as the suction pressure (horizontal axis) increases, the maximum achievable flow rate (vertical axis) increases. For a compressor running at a constant configuration (cylinder configuration, pocket positions and running speeds constant) as flow rate is increased, the suction pressure increases:

You’ve probably heard your Engineering Account Manager or another subject matter expert like your production engineer, a mechanic, an applications engineer from the packager, or your lead operator tell you that adding clearance using spacers, fixed volume clearance pockets, or variable volume clearance pockets reduces the capacity of that cylinder. Maybe you’ve taken that at face value, but intuitively, shouldn’t more volume inside the cylinder mean that more gas gets through? I definitely struggled with wrapping my head around that until someone drew some pictures on a whiteboard and walked me through what actually happens in a cylinder during the intake stroke.

Blowby, can indicate inefficiencies due to a few different reasons, but for the scope of this blog post, in the simplest of explanations, Blowby in this context is a measure of the health of your cylinders and can be an indicator of your compressor valve and piston ring health. Here are some reasons why catching bad valves earlier than later would be advantageous and contribute to safer environment for your operations and maintenance staff:

Have you ever sat in a compressor review meeting where I’ve explained to the group that opening pockets reduces the appetite of a compressor cylinder, and then 10 minutes later, I’m telling you that opening your pockets will get your more production? If the answer is yes, I swear, I’m not an idiot and hopefully I can walk everyone through why it is possible to open up pockets and achieve a higher flow rate. One specific situation that I’ll focus in on is when you bring on a new well, and your suction control valve has to pinch back, limiting the amount of gas getting to your 1st stage.