Cotton Valley Sand Play

Introduction

The Cotton Valley Sand Trend of east Texas is famous as a tite gas play where the sands need hydraulic fracture stimulation. The wells are modest producers, typically having a Cum of 875 MMCFG. The wells are expensive, because of the 8,000 to 9,000 feet depths, and the necessity to fracture-stimulate the well; but, in general the wells are economic.

The play has many followers, due to the perceived lack of risk. Dry holes are rare. Due to the interplay of high drilling and completion cost, many of the oil and gas industry's new technologies are developed on Cotton Valley Sand wells.

Mapping the fairway of the trend is not difficult and requires no seismic. It does require an understanding of the petrophysical properties governing production and what parameters to map. Good mapping begins with production EURs (Estimated Ultimate Recoveries) tied to simple log parameters. The trends must be mapped by hand in order to delineate the bidirectional trends seen in the production.

To summarize, the key features to keep in mind about this play are:

• Pushing the resistivities to lower and lower frontiers.
• Advent of sand-propped fracs and increased productivity of both old and new wells.
• The Cotton Valley Sand facies is best developed on 40 to 80 acre densities, or 8 to 16 wells per gas unit.
• The average Cotton Valley Sand well, on the east side of the basin, will ultimately yield about 1 BCFGE, making the play economic under almost any price scenario.