[dowling] western GAS FIELDS 93 



The fields that have been studied in some detail include the 

 foothills area, the Bow Island anticline, and the terrace structure on 

 the eastern side of the basin from Battle river to Peace River landing. 



The Foothills. 



The western part of the Alberta syncline descends to probably 

 great depths, and as comparatively low beds appear in the foothills 

 the upward slope of these beds is steep. The presence of possibly 

 even a heavy oil in the bottom of the basin under very heavy pressures 

 and higher temperatures due to depth should be favourable to some 

 form of distillation or alteration. The short limb of the anticline 

 ofïers least frictional resistance to its migration, and an increased 

 impulse through steep slope, so that were the beds outcropping instead 

 of concealed by overthrust faults, leaks pf gas or oil might be looked 

 for. In the area selected for testing for gas southwest of Calgary, 

 the edge of the western limb of the syncline is overturned in anticlinal 

 form, thus forming a natural reservoir. This seems also to have 

 acted as a condensing chamber, and the oil found bears no resemblance 

 to crude oil, but is generally considered as a condensation product. 

 It contains about 60 per cent gasoline and that found in the higher 

 strata is much lighter. 



The main difficulty in finding other fields along this margin is 

 in the broken nature of the structure. The edge of the syncline is very 

 rarely bent over into arch form and is generally broken by faults and 

 concealed by a heavy covering of overthrust strata, making the physical 

 difficulty in reaching the productive measures very great. 



Bow Island Anticline. 

 The lower measures in this structure are exposed in the upthrust 

 of the Sweet Grass Hills in Montana, but the area exposed is not large 

 and the vent thus possible seems to have been sealed by dykes ra- 

 diating and surrounding the central masses. Wells at the boundary 

 line have proved the presence of very thick oil and some gas and wells 

 farther north great gas flows and sands impregnated with heavy 

 oil that resembles an asphalt. The wells supplying Calgary are near 

 the saturation line for the gas sands and may be considered as being 

 very near the northern end of the field. The gas is in sands that 

 appear to be in the Benton. The sands at the top of these shales 

 outcrop in the valley of Milk river and over a wide area provide ar- 

 tesian water. The presence of this water obtained from Milk river 

 seals the gas in the outer rim of the structure and is the supply ob- 

 tained in the first wells at Langevin, Cassils, and that now used at 

 Medicine Hat. 



