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Ken: Hey Mahsa, I was wondering, you were saying the other day that the benefits of looking at some of the gathering networks and taking a conventional approach versus an unconventional sort of situation. Can you give me a few ideas on what you found with that?
Mahsa: So the first thing I realised is that in the conventional world, we normally get choked flow though the wells. So, we really don't care what happens with the subsurface until the subsurface pressure drops. And then we only design the surface independently from subsurface. But coal seam gas is completely different because you only produce as much gas as you have the pressure in the well.
So, we had to take an iterative approach to make sure that when we are doing the flow assurance that we make sure that we always correct the flow rates based on what is the pressure in the well.
That's why we have to talk to the Subsurface, because always the platform of the production that they give us, it doesn't necessarily work with any surface facility. So, we might have to change the well forecasting, well spacing, which well comes online. Are we going to get the wells closer to CGPF common line. Do we need a lot of compression? All of that is a lot of complex work that we have to do, make sure that we get the most out of the wells by reducing the back pressure on the wells.
Ken: You were saying to me the other day around the sort of interface or the integration between subsurface and surface, and that sort of connection between the two parties, which traditionally they sort of don't want to talk to each other. Can you expand on your approach to trying to bring those two parties together?
Mahsa: So, what we did in some similar applications or approach was that we basically model the first round of the gathering network based on the flow rates and forecasts with subsurface provider. Then we take a iterative approach, it's done within the software and some automation outside of the software. So, we basically calculate the back pressures based on the flow rates that subsurface has given us. And then we go back to subsurface and basically talk to them that now, what's the impact of this back pressure on the well production.
And it's important because we’re only working with a little bit of pressure. And this is very important at the end of the life. Start of the life, maybe the pressures are around 300 KPA, 400 KPA sometimes, we have no problem, but when it goes towards the end of the life, that's when we have to really get, the pressure drop in control as much as we can, because we can even get up to 2 million SCA’s from the wells.
Process Systems Practice Leaders, QLD – Australia
