plurality of steam chambers 450 the steam chambers are separated by packers 452 which contain a valve to facilitate equalization of steam pressure in each steam chamber 450 further each chamber 450 may include a heat exchanger 454 to facilitate transfer of heat between the heat transfer fluid in the inlet string 412 and the feed feedwater the separation of the horizontal portion into a plurality of chambers 450 combined with the heat exchangers 454 improves the distribution and quality of steam in the horizontal portion thereby increasing the production of hydrocarbons from a subsurface formation for example the heat exchangers may include heat exchanger tubing similar to the tubing 302 described above with reference to fig3 referring now to fig6 a cross sectional view of a horizontal wellbore arrangement 400 a in accordance with another embodiment of the present invention is illustrated the embodiment illustrated in fig6 is similar to that illustrated in fig5 but with a single wellbore bore in this regard a single vertical wellbore bore splits into two horizontal wellbores 430 440 in this regard the concentricity of the strings includes the production line 490 as illustrated in fig6 and taken along vi vi in the illustrated embodiment the hot heat transfer fluid is.