Component groupings

There are certain restrictions on the component groupings (Section 11.2) that may be used in equation of state methods; There is in general no way to perform the inverse grouping, i.e. assigning amounts of flow components based on the equation of state components, after phase splitting. The grouping matrix is restricted to contain only pure groupings (several global $\to$ one local) and splits (on global $\to$ several local).

Thus,

  Grouping
  water  = H2O + salts ;   % pure grouping
  HCL    = C1 + C2 ;       % pure grouping
  HCM1   = CO2 + C3 + C4 ; % pure grouping
  HCM2   = C5 + C6 ;       % pure grouping
  HCH1   = 0.7 Cplus ;     % pure split of Cplus into   
  HCH2   = 0.3 Cplus ;     % HCH1 and HCH2

is allowed, while the otherwise valid

  Grouping
  water  = H2O + salts + 0.01 CO2 ; % not pure grouping
  HCL    = C1 + C2 ;                % pure grouping
  HCM1   = 0.99 CO2 + C3 + C4 ;     % not pure grouping
  HCM2   = C5 + C6 + 0.1 Cplus ;    % not pure grouping
  HCH1   = 0.6 Cplus ;              %
  HCH2   = 0.3 Cplus ;              % not pure split of Cplus

is not allowed for equation of state calculations.

In the case of pure groupings, the realtive amounts of each global component is assumed to be equal in all phases. For pure splits the amount of the global component is simply found by summing the amounts of the local components.