Field Tests of the Stem-induced Explosive Fracturing Technique

The explosive stem-induced fracturing technique has been field tested in over 20 producing oil wells in western Pennsylvania. The technique basically involves the placement of a primary explosive charge in an expendable rathole below the pay zone(s) to be fractured and of a solid gravel near the top of the pay zone to cause local fracturing through the dynamic reflection of the explosive gases. In the best cases, production increases realized with the technique are comparable to those obtained with conventional hydraulic fracturing in the area. A 35-mm downhole camera was developed and used to obtain photographs that show the absence of any vertical fracturing before the explosive treatments and well-developed vertical fractures in all zones designed to be fractured. This vertical fracturing is developed despite the fact that the in-situ stresses favor horizontal fracturing. The photographs also show that multiple radial fracturing, which might be expected with the high rates of the explosive loading, does not usually occur and that wellbore damage is less than predicted.