A method for producing one or more crude products is disclosed. Formation fluid is produced from a subsurface in situ heat treatment process. The formation fluid is separated to produce a liquid stream and a gas stream. At least a portion of the liquid stream is provided to a nanofiltration system to produce a retentate and a permeate. The retentate includes clogging compositions. The permeate is processed in one or more of processing units downstream of the nanofiltration system to form one or more crude products.
 The Government has certain rights in this invention pursuant to Agreement No. ERD-05-2516 between UT-Battelle, LLC, operating under prime contract No. DE-ACO5-000R22725 for the US Department of Energy and Shell Exploration and Production Company.