The Middle Ground Shoal and Granite Point fields in the Upper Cook Inlet, Alaska, are major oil fields discovered seismically 20 years ago. Development drilling was based on a structural model of an anticlinal ridge bounded by large thrust faults intersecting at depth in a cross sectional "V" configuration. The oil-bearing zones of the Middle Ground Shoal field were originally believed to be confined to a relatively small anticlinal area near the bottom of the fault-bounded "V." Wells were deviated from offshore platforms, and in places where a well was deviated from one flank to the other, the borehole was initially normal to bedding until the axial plane of the fold was crossed and the other limb encountered. From that point, the borehole continued down the limb paralle to the bedding, and was interpreted as having intersected the fault plane.

Additional well data and a review of older well logs indicated that the faults might not exist. If this were the case, the flanks of the structure were not being drained. A similar interpretation was shown to be applicable to the Granite Point field by a well drilled to test this same hypothesis. The well was directionally drilled in the shape of an open hook, deviating 4,000 ft (1,220 m) to the west, then curving back to the east so that the west flank would be encountered normal to the bedding. The well intersected the west dipping flank, which was not faulted, and was completed for 400 bbl of oil per day. A second well is now being drilled.

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