How to set a production well with constant pressure
How to set a horizontal production well with a fixed pressure in tough + hydrate?
When setting source / sink in Gener, SS_ Type can only set a constant flow rate. Does anyone know how to fix the pressure of the horizontal production well?
Actually, TOUGH2/3 and I think TOUGH+ too, could use virtual elements (like those with infinite volume) connected to any element of the discretization grid.
The IFDM allows that, it is just a matter to add the necessary geometric parameters to ELEME and CONNE. If the meshmaker used does not allow that, the input file can be changed manually.
I think a rigorous approach would require the use of a coupled wellbore-reservoir flow solution, like that avaialable in T2Well. I'm not aware if something similar is available in TOUGH+. T2Well is required in particular if you are interested in modeling flow transients, such as those occurring at well opening and shut-in, and if you need a wellhead control of well production.
If you are interested in simulating the long term effects of well production and a constant BHP at some depth datum within the perforation interval is satisfactory, then probably you could use one of the options available in the reservoir simulator.
I would not explicitely include the wellbore elements in the 2D radial grid. Wellbore flow can easily be modeled with a Darcy's law approach in case of single phase liquid (or liquid-like) flow. You can find an example in Battistelli et al. (2011), TiPM. Probably in your case you will have two-phase brine + gas (CH4) flow and in this case the Darcy's approach would completely fail.
I would consider to use the wellbore on deliverability approach available in TOUGH2/3 (I guess in TOUGH+ too) by definining a well on deliverability over multiple layers covering the perforated interval. The BHP could be defined at some realistic value which might be supported by some separate wellbore flow modeling. The PI of different layers can be computed easily as you are using a 2D radial grid.
The DELV approach in TOUGH2 has the option to let the code computing the flowing pressure profile within the wellbore starting from the assigned BHP. The implemented agorithm is rather approximate and performs better when you have single liquid flow along the wellbore, as friction and acceleration P losses are neglected. The calculation of flowing P gradient assumes i) the liquid and gas phases are immiscible and ii) the volumetric flow rates are conserved along the well. As I guess you should have brine and CH4 flowing along the wellbore, the phases are actually almost immiscible. If the perforated interval has a limited lenght, then also the assumption of volumetric rates conservation is not so far from reality.
The DELV approach should let you assign the constant BHP at the bottom of perforated interval and to have a resonable flowing wellbore P computed for each wellbore element pertaining to the perforated interval. The code will compute the produced rate, the composition and enthalpy of produced mixture for each wellbore element. The amout of printed data, as well as the computation of total discharge parameter for the full wellbore, may depend on the code (or EOS module) used.
The drawback of DELV is that the BHP is constant, while it should probably vary depending on total mass rate, mixture composition and enthalpy to satisfy some WH constraint. In practice, if the constant BHP is not acceptable, then the coupled wellbore-reservoir flow solution is necessary. The option to couple DELV on multiple layers and the F-Type gener option (discussed in Marcolini and Battistelli, 2012, Tough Symposium) which allows a variable BHP to satisfy a WHP constraint, would work only for a constant composition mixture.
Hoping it can help.