KUHFAL, DENNIS, and R. KAETZER, Texaco, Inc., New Orleans, LA

ABSTRACT: Bandera Tank Heavy Oil Play in South Texas

The extraction of viscous crude oils from unconsolidated sands has been studied since the 1950s. Steam flooding and fire-flooding to a lesser extent, are the primary means of recovery when viscosities are greater than 1000 centipose at reservoir conditions. One of the industry leaders in the thermal recovery field is Texaco.

A play that has resisted the economical use of presently adopted methods

of thermal recovery is the asphaltic oil of the Cretaceous San Miguel (Bandera Tank) sand situated in Zavala and Maverick Counties of south Texas. Occurring at depths ranging from near 1000' to below 2500' and underlying a 10 mile by 15 mile area of almost 100,000 acres, the reservoir may contain as much as four billion barrels of tar in place. Gravity measurements range from 5 to as low as -2 degrees API gravity and viscosities in excess of 1,000,000 centipose. In the area of interest the oil in place (assuming 50% oil saturation and 60' average thickness) is approximately 45,000,000 barrels of oil per 640 acres. Conoco's 5-acre Saner Ranch thermal pilot in the early 1970s recovered 167,000 barrels of oil from the Bandera Tank, but never followed through with a full-scale development program. Other companies involved in the area were unsuccessful in their pilots. A 1992 Texaco multi-discipline study to access the technical and economic feasibility of the Bandera Tank play is in progress. Technical hurdles to overcome include geological; prediction of recovery; selecting the thermal method (conventional steam, steam frac, fireflood, microwave); reducing the development costs; steam and co-generation facilities; and transportation. Several innovative recovery concepts are being considered including the useof ultra-short radius horizontal well bores.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.