I. INTRODUCTION

The Bureau of Land Management (BLM) Vision for the Future (as stated in the 1998 annual report) is to “provide for a wide variety of public land uses without compromising the long term health and diversity of the land and without sacrificing significant natural, cultural, and historical resource values”. The Director’s letter goes on to state, “We seek close partnerships with state and local governments, Indian tribes, other Federal agencies, and all of our publics, as we embrace a process that addresses all of the physical, biological, economic, and social aspects of land and resource management…guided by…a vision that emphasizes public land health and preservation.”

The BLM San Juan Field Office is the regulatory agency responsible for preserving the health of Federal public lands in southwestern Colorado, while regulating responsible resource development and serving Southern Ute Indian Tribal mineral interests under the trust responsibility delegated by Congress. This paper focuses on the issues currently facing the San Juan Field Office that relate to Fruitland coalbed methane production and conceivably associated environmental implications. This document will be foundational for documenting historical evidence regarding CBM development in the northern San Juan Basin. It will also serve as a basis for interim decisions concerning gas well drilling on both Federal and Indian mineral leaseholds until basin hydrology and reservoir modeling provide forecasting scenarios that will facilitate development planning. It informs the public of current theories linking Fruitland Basin production to Fruitland outcrop impacts. It provides a basis for discussion and determination of the type and timing of National Environmental Policy Act (NEPA) documentation necessary to address impacts (both at current spacing and potential infill drilling). Finally, this paper documents the need to consider prudent outcrop responses including the issues of private property, off-lease impacts, possible mitigation solutions including cost, responsibility and liability.

While the Fruitland Coalbeds were known to contain significant gas reserves, the understanding and technology of producing that gas was not available to earlier gas well developers. Therefore, the stratigraphically shallower Fruitland coals had been penetrated in the early days of gas exploration in the Basin, but bypassed in preference to deeper geologic horizons offering conventional gas reservoirs that more readily yielded the natural gas resource. The development of unconventional coalbed methane in the Fruitland Formation of the Northern San Juan Basin (Basin) in Colorado began in earnest in the late 1980s. This paper presents highlights of coalbed methane development history and associated issues in the Northern San Juan Basin, Colorado. This development has been administered by the overlapping jurisdictions of the Bureau of Land Management (BLM), Bureau of Indian Affairs (BIA), Southern Ute Indian Tribe (SUIT), Colorado Oil and Gas Conservation Commission (COGCC), and to some extent La Plata County.

This paper also presents and documents recent environmental problems associated with coalbed methane production. Unlike conventional reservoirs, where methane gas is stored in the pore spaces of the formation, considerable coalbed methane is stored on (adsorbed to) the surfaces of the coal matrix and is not free to migrate until pressure is relieved. Even in the coalbeds, though, some free gas is present in pore space and may collect in typical structural traps. In general, hydrostatic head provides the pressure that keeps the majority of the coalgas adsorbed. Once coalbed gas is liberated by the withdrawal of water reducing the hydrostatic head, the methane (estimated at over 50 trillion standard cubic feet (TSCF) in the Fruitland Coalbeds) is free to migrate. Inadequately cemented conventional gas well bores and extraction of produced water from coalbed methane (CBM) wells are suspected of contributing to natural gas resource losses and to methane migration into surface soils and groundwater.

As methane production progressed, some residents noticed an apparent increase in the occurrence of methane in their domestic water wells, while others also noticed the presence of gas seeps in pastures, manifested by dead vegetation. During the next few years, other events were noticed that time-correlated with recent coalbed methane (CBM) production.

Anoxic environments created in near-surface regimes by a predominance of methane support bacterial generation of hydrogen sulfide gas and promote plant suffocation by precluding soil oxygen. Methane from soil gas vapors can accumulate in confined spaces, such as beneath domestic dwellings, and may pose potential explosion hazards. Along the Basin rim where the Fruitland coals crop out, intensified gas seepage and an associated apparent escalation in hydrogen sulfide gas has been reported at historic seep sites. Stands of stressed and dying trees were discovered aligned with coalbeds beneath. North of the Southern Ute Indian Reservation, two homes located directly above the outcrop/subcrop of the Fruitland Formation coalbeds were declared unsafe for habitation due to explosive accumulations of methane; five homes were ultimately removed from the hazardous zone.

Self-heating of near-surface coals can result from fluctuations/lowering of the water table in the coalbeds. On the Southern Ute Indian Reservation several coal fires have been identified during 1998-99. Geologic evidence indicates that pre-historic Fruitland coalbed fires existed in similar locales. The time of ignition or resurgence of current coal fires is virtually impossible to ascertain. The most disconcerting instance (due to speculation of a possible proliferation of coal bed fires) is a coal fire detected in the fall of 1998 at a location approximately eight miles north of active coal fires first noticed during the spring of 1998. These environmentally significant phenomena, which may represent warning signs of impending changes, have engaged the attention of regulatory agencies and the community.