Abstract

Preliminary geologic subsurface investigations along Sacramento basin’s Winters sand edge suggested several updip potential embayments. Proprietary seismic was subsequently shot over these leads and evaluated using “bright spot” anomaly criteria complimented by seismic stratigraphy.

At the Beaver Slough prospect a seismic anomaly was identified as a downdip wet Winters sand that gained considerable structure to the east before pinching out. The Coastal Gamble #1 was drilled to evaluate this anomaly and encountered 32′ of gas sand. An initial production rate of over 10.1 MMCFPD for the PG&E test was followed by 13 months of shutin while a pipeline was laid to the south and under Beaver Slough. First sales to PG&E commenced in September 1989 at a rate of 5 MMCFPD with neglible produced water.

Two months prior to the discovery well’s pipeline hookup, the Gamble #2 well was drilled 1800′ to the west-southwest and encountered 20′ of wet “Gamble” sand 144′ downstructure. The redrill failed to hit any “Gamble” sand on strike with the discovery well 1800′ to the northeast. Subsequent wells by Vern Jones to the east and Arkoma to the south likewise missed the producing sand.

The current depositional interpretation invokes a narrow longitudinal sand lobe perhaps a few hundred feed wide and a mile long, more a large gully than a substantial submarine fan. The reservoir exhibits classic pressure depletion with the Gamble #1 going on compressor in early 1991; the well passed the 2 BCF tally after two years of near constant production.