Exploration and Production Program for Locating and Producing Prospective Aquifers Containing Solution Gas and Free Gas- Texas Gulf Coast

This project was designed to locate and evaluate a prospective watered-out gas reservoir in the Texas Gulf Coast inland area. The prospective reservoir was to be suitable for application of enhanced gas recovery methods for producing the unconventional gas that remained in the reservoir after primary gas production ceased. A test well site would be located within a favorable prospect area.

Previous work conducted by the Bureau of Economic Geology for the U.S. Department of Energy focused on the selection of test well sites in the Frio Formation and Wilcox Group of the Texas Gulf Coast. These studies were intended to make use of thermal energy, mechanical energy, and gas dissolved in formation waters by producing large volumes of hot water from deep, highly pressured formations. In this project, funded by the Gas Research Institute, interest shifted to locating prospective reservoirs containing significant quantities of free gas in addition to the gas dissolved in the water. Abandoned watered-out reservoirs and wet zones where large amounts of water must be produced to obtain the gas by co-production were identified.

The present project, funded by the Gas Research Institute, shows their continuing interest in unconventional gas and in developing prospects that are favorable for co-production of gas and water from watered-out gas reservoirs. Guidelines used to screen gas fields along the Texas Gulf Coast resulted in the selection of the Port Arthur field, Jefferson County, Texas, as a suitable prospect for application of enhanced gas recovery methods. Several watered-out gas sandstones in this field have excellent reservoir characteristics. All 18 wells in the field have been plugged and abandoned by previous operators; hence, leasing problems should be simplified. Abundant shallow Miocene sands in the area are available for salt-water disposal.

The "C" reservoir interval, located at an average depth of 11,130 ft, received the most extensive evaluation. Predicted gas recovery by natural flow is 5.1 billion standard cubic feet as reservoir pressure declines from 6,632 to 4,309 psig. A sample economic analysis showed a net present worth of $968,000 and a payout time of 3 years. This prospect has the potential to be economically profitable in addition to being a good research and development test for evaluating co-production techniques.

It is recommended that a co-production well be drilled and tested on a site near the Meredith No. 2 Doornbos (Well 14).