546 Subsurface Geologic Methods 



or drill pipe becomes lodged at shallow depths in deep holes. By side- 

 tracking around the "fish" and drilling back into the original hole below, 

 much valuable drilled hole has been salvaged. An example of this occurred 

 at Huntington Beach when a sharp bit was being run into a directional 

 well. Before the driller realized it, the hole had been unintentionally side- 

 tracked. A cement plug was used to bridge the hole, and a whipstock 

 faced in the same direction as the course of the lost well forced the bit to 

 break through into the original hole. 



Drilling of wells in close proximity to faults may present difficulties. 

 Figure 258 illustrates three wells drilled near a fault. Wells on the foot- 

 wall side of the fault plane at A will produce from a reservoir accumu- 

 lated against the fault zone. Well B, which originally bottomed at C, was 

 not a producer but was redrilled from a cement plug set at D to penetrate 

 the gouge zone and encounter oil on the other side. 



Holes drilled through faults should have courses as nearly normal to 

 the fault plane as possible and should enter the zone with a high drift 

 angle. Wells bordering the south side of Sunnyside Cemetery at Long 

 Beach were deflected to reach oil accumulated alongside a fault beneath 

 the cemetery, obviating the necessity of removing bodies and abandoning 

 the area as a burial ground. 



Wells have drilled into the gouge zones of faults and followed the 

 plane of the fault for the remainder of their course. Such wells have been 

 plugged back and redrilled to make producers. 



Edge wells have been converted into productive wells by directed 

 drilling. A large investment can be saved by plugging the well and de- 

 flecting the bottom portion upstructure away from edge water. Edge 

 property, partly productive and partly barren, presents this hazard. Wells 

 drilled on such a lease are directed to bottom on the productive portion 

 of the lease or are redrilled directionally to gain production and avoid 

 short-lived edge wells. 



Some operators have considered the directional drilling of wells to 

 increase the exposure of the oil-bearing formation. Any angled hole will 

 increase the amount of sand penetrated if drilled in nearly flat structures, 

 parallel to the strike, or down the dip of the structure. This increased ex- 

 posure of productive sand is true of practically all directional wells. 



Figure 261 illustrates an exploratory operation to define a horizon 

 marker. Multiple holes from one location were drilled by plugging the 

 well and deviating the hole twice after establishing the depth of the marker 

 with the original vertical well. Drilled hole and time are saved by such 

 methods. Recontouring of producing horizons from data collected in lo- 

 cating the markers by actual drilling causes many contour anomalies to 

 disappear. Consideration of the surveys of a number of wells on a lease, 

 together with the logs of these same wells, generally clarifies the subsurface 

 geologic picture. In exploring near salt domes, it sometimes is necessary 

 to plug and redrill wells that strike the salt initially in order to locate 

 productive zones. 



