Abstract

The completion of the Southland Royalty No. 1-A Harris in the Austin Chalk Formation on November 7, 1974, touched off a massive exploration effort by the oil and gas industry in a trend approximately 325 miles long and 20 miles wide from the Rio Grande River to Robertson County, Texas. The No. 1-A Harris was drilled in the Pearsall field, located in Frio County, Texas, and an index of the activity that followed can be seen in the fact that as of July, 1977, 754 new wells are producing in this field alone. In just less than 3 years, the production from Pearsall field has grown from 2925 BO to 831,566 BO per month. The rest of the trend has been extensively leased and has seen a substantial amount of drilling activity.

The primary objectives of this exploration program are the Austin Chalk and the Buda Formations. Both of these are dense limestones that owe their reservoir qualities to fracturing. The fracturing is due to tensional forces that developed as a result of subsidence in the Gulf Coast basin.

Drilling activity in the Trend is declining rapidly. This decline is based on unfavorable production performance by a majority of the wells drilled in the last 3 years. Fractured reservoirs are easily damaged during drilling and completion. It seems quite possible some of the current drilling and completing practices damage the reservoir and prevent the wells from producing up to their true potential. A reappraisal of the techniques is in order. The Austin Chalk and the fluids it contains have some unique characteristics that should be taken into account before designing any portion of the well program. New products and services are available that appear to have an application to the problems facing the Trend and should be tested.

The Austin Chalk - Buda Trend offers a tremendous potential oil reserve. Total reserves could easily exceed two billion barrels of oil. However, this reserve will not be realized unless our industry applies itself to the task of developing the techniques needed to produce the oil economically.