Re: Beneficial Re-use of Treated Sanitary Waste to Flush Class II-D Well
Ms. Shannon Donnelly
P.O. Box 66
Kenai, Alaska 99611
Dear Ms. Donnelly:
Disposal Injection Order (“DIO”) 17 approved the injection of Class II waste fluids into North Cook Inlet Well A-12, located on the Tyonek Platform. There have been three administrative approvals granted since DIO 17 was issued clarifying fluids eligible for injection into the Class II disposal well. DIO 17.003 dated May 3, 2004 authorized ConocoPhillips Alaska Inc. (“ConocoPhillips”) to beneficially re-use domestic wastewater and treated sanitary effluent for flushes of Well A-12.
The Tyonek Platform is the sole facility developing the North Cook Inlet Unit gas field. Well A12 is both a gas production well and a periodic Class II disposal injector, completed with dedicated production and injection tubing strings. An unintended bi-product of recently completed well work on the Tyonek Platform has been the increase of water production. ConocoPhillips acknowledges that there is also an emerging need to manage fine solids (sand and clay) produced with the wet gas stream. Enhancements to the produced fluid separation process have been installed on the platform, including a water injection process (water is sprayed into the produced gas stream) to aid in sand and clay removal. ConocoPhillips has requested Commission review of the proposed use of treated sanitary effluent in the solids removal process.
As noted in DIO 17.003, periodic flushing of an injection well is a well maintenance practice that is integral to the operations and necessary for injection well reliability. Likewise, removal of fine solids is necessary to minimize erosion in the fluid flow path and to ensure reliability of critical equipment such as production tubing, surface piping, and custody transfer measurement equipment. Exploration and production wastes associated with oil and gas development, including the produced solids, are exempt from the requirements of Section 3001(b)(2) of the Resource Conservation and Recovery Act (RCRA). The exemption provides for mixing a nonhazardous, non-exempt waste with an exempt waste; the resulting commingled stream is considered exempt. The use of solids-free treated sanitary effluent (non-hazardous, non-exempt) will maximize the produced solid removal process, and minimize production equipment damage likely if solids laden fluids (produced fluid, inlet water) were used in the water wash process.
Confinement of fluids to the intended injection zone in Well A-12 has been demonstrated by historical injection performance data provided by ConocoPhillips. Well integrity has been demonstrated by successful mechanical integrity testing and monitoring the well’s annular pressures. The beneficial reuse of treated sanitary effluent in the removal of solids from the produced gas stream will have no detrimental effect on the confinement of fluids. Well integrity, correlative rights, and waste will not occur from the reuse of treated sanitary effluent and eventual disposal into Well A-12.
The Commission believes ConocoPhillips’ proposed action to use non-hazardous, non-exempt treated sanitary effluent to remove solids by injecting the wastewater into the produced gas stream is consistent with the provisions of the underground injection control program and the RCRA exemption. As provided in Disposal Injection Order 17, the Commission approves the use of treated sanitary effluent in the water wash process described by ConocoPhillips and ultimate injection of the commingled waste stream (produced water, fine solids removed from produced gas, and treated sanitary effluent) into Well A-12.
DONE at Anchorage, Alaska and dated January 4, 2005.
The Alaska Oil and Gas Conservation Commission
John K. Norman
Daniel T. Seamount, Jr.