Chap. 12] 



MISCELLANEOUS GEOPHYSICAL METHODS 



903 



produce large quantities of methane without relation to the underlying oil 

 deposit (last curve in Fig. 12-14). 



The role played by hydrogen is still somewhat obscure. It appears to 

 reach its maximum somewhere above and at the sides of an oil deposit;'^* 

 in some areas its surface distribution is conformable with that of methane 

 and the heavier gaseous paraffin hydrocarbons.^ In wells it may go some- 

 what parallel with methane. The greatest concentrations of the heavy 

 gaseous hydrocarbons and of methane may or may not coincide at the 



Sub - Surface Origin 



fJtar • Surface Origin 



Paraffin Hydrocarbons 



/norganics 



'Pseudo '■ Hijdrocarbons HydrocarAons 



ethane. 

 Propone, 

 Butane 



tti/droqtn 



Chlorides. 



Sulphaies. 



etc. 



w^^xvv I W/C ■'■<. w^W/'/?^v// ' ^l^■■'W/^^^W'-^v■vx^^v 



>/A\i/m^}"/.^y^A;y:VJ(fxv, 



1000 



2000- 



3000 



4000 



Oireet/y atom 

 \ 



info Att/o 



/ 



Uaualli/ in hahs 



Bamhm 



Fig. 12-14. Scheme showing variation of several organic and inorganic constituents 

 in the subsurface section and near the surface above an oil deposit. 



surface and may occur directly above an oil deposit. More often, however, 

 the heavier hydrocarbons and sometimes the methane have a maximum 

 in the form of a halo surrounding the deposit. Possibilities of origin of 

 such halos will be discussed below. 



The same appears to be true for some of the significant inorganic min- 

 erals, such as chlorides and sulfates, and for the four secondary products 

 of near-surface agents indicated on the right side of Fig. 12-14, namely, 

 the so-called liquid and solid pseudohydrocarbons and oxidized and poly- 



^^ Personal communication from E. E. Rosaire. 

 *" Horvitz, loc. cit. 



