Managing CBM Produced Water in a Responsible and Sustainable Manner
In this paper coal bed methane produced water management choices and a recent injection case history in the Powder River Basin, Wyoming will be discussed. There are 1.2mmbbls of CBM water produced daily. The question of what to do with the water is not straightforward, as the choices involve science, engineering, economics, environment, politics and multiple stakeholders with many different vested interest as to what happens to the water.
The current five choices for disposal of produced water are: to discharge the water into streams and rivers, create reservoirs and evaporation ponds, surface irrigation, subsurface irrigation and injection. It is important to note that the non-meteoric CBM produced water is 50 to 60 million years in age. In the injection choice produced water is extracted from coals and injected into sandstones of the same quality of water and is saved for future use.
A reservoir characterization was completed in the fall of 2008 on multiple formations and members utilizing 670 wells from CBM producers and conventional oil and gas. From the reservoir characterization a water capacity was calculated for each formation and member and retention for each formation and member was validated. Once the capacity and retention was established, it then became an economic decision as to the depth of the injection wells, number of wells required for the volume of produced water, design of gathering systems, treatment and other considerations to be presented.
Injection provides for responsible development and the long term sustainability of the prehistoric CBM produced water.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009