Public Update – Gas Mapping and Relief Well Placement
Mitigating any potential risk posed by the presence of shallow gas is a top priority of the response. The most advanced technology available has been used to map the geology of the Mississippi River Alluvial Aquifer (MRAA) and shallower geological units.
Mapping the thickness of the gas is an important step in implementing a comprehensive relief well system to vent gas. Texas Brine is in the process of conducting Cone Penetrometer Testing (CPT) and utilizing Membrane Interface Probe-Hydraulic Profiling Tool (MiHPT) to help identify conditions in the upper 130-140ft of the subsurface.
MiHPT is being performed in conjunction with CPT in order to better define the amount, make-up and locations of gases in the MRAA and shallow subsurface. Utilizing these technologies together is less intrusive and allows for faster collection of data than any other available methods. The additional data collected by the MiHPT adds valuable information that will enhance efforts to map and vent shallow gas.
Since the program was initiated, 106 CPT pushes have been completed; grouting and interpretation issues have been addressed; MRAA high points defined; gas zones detected; and penetration into the MRAA improved. Twenty-eight MiHPT pushes have been completed; grouting issues have been addressed; methane can be detected if present; and comparison to CPT is ongoing. CPT and MiHPT will continue until the scheduled completion in mid-September.
Current data from CPT and MiHPT is already enhancing our understanding of sub-surface conditions and identifying the presence of gas. Scientists with Texas Brine, CB&I as well as officials from DNR and AP OEP have been tasked to conduct a thorough review of the data gathering process for the purposes of developing a comprehensive design and implementation plan. This effort will enhance the ability to identify the most productive locations for additional relief well placement.
Once all the data has been collected and reviewed and a scientific consensus is reached on the plan, a public briefing will be held to explain the process and plan for well placement and venting.
While this process is ongoing normal response activities will continue and existing ORW’s will be reconditioned to ensure optimum production rates are achieved from wells already in service.