Using produced gas can transform the possibilities and economics of unconventional exploration--and temporary prime power is the key to doing this successfully. As a case in point, produced gas is currently fuelling power generation for more than 60 coalbed methane wells in a producing field in Wyoming's Powder River Basin--all using temporary power generation services. When the field ultimately converts to utility power, the gas-fired system will be disconnected and simply moved to the next well-site by a service truck.

The move to gas-fired power generation is a growing trend in oil and gas fields; from the Rockies and the Appalachian Basin, down to south Texas. It is proving to be a viable alternative to diesel-fired generation when a reliable gas flow is readily available.

To bring production on as fast as possible, operators are leasing trailer-mounted gas-fired generator packages to provide electricity to the wellsite ahead of utility grid connection.

Instead of flaring produced gas, gas-fired generators put it to use as fuel, and reduce emissions. Long-term gas-fired power generation can even provide an economical alternative to utility power or conventional mechanical drive (wellhead) engines.

By leasing the power generation services, operators are able to manage capital expenditures, as well as reduce in-house field maintenance and service overhead.

Bridging the Gap

For the remote Powder River Basin field, interim diesel costs were a key development consideration. To reduce costs prior to connection with the power grid, the operator chose a more economical produced-gas alternative, and leased the power-generation services from Aggreko.

The field's centralized power system uses scrubbed, de-hydrated gas from local wells to fire a parallel package of three 250 kW generating systems and switchgear. Instead of having many engines and generators scattered throughout the field driving individual wells, all power is generated from a central point. Equipment is configured to operate in parallel to ensure power reliability for the 24/7 field operations.

Temporary prime power applications typically bridge periods of a few months to a year or more, however cost benefits for fuel and capital investment can be significant enough to support long-term installations.

Reducing Emissions

Gas-fired generation reduces overall emissions. In unconventional oil plays such as the Bakken in North Dakota and Montana, and the Niobrara in Wyoming and Colorado, associated natural gas production can be problematic. When a pipeline is not available to move the gas to market it must be flared.

But flaring is often limited by air quality regulations. To reduce or eliminate burning, operators use either 100% natural gas-fired generation or diesel-natural gas hybrid systems to power well pumps.

Historically, the operator would purchase a mechanical drive engine to run on the wellhead gas. These units, while reliable and effective, are not as clean burning as gas-fired power generation, and present emissions compliance issues along with ongoing maintenance for the operator. In addition, with a service company providing gas-fired power, the site operators can focus on their oil and gas business, as well as saving on capital expenses.

The traditional mechanical drive systems also force a process change when utility service arrives. Gas-fired generation allows the production facility to be built for electrical power from the start.

Flexible Solutions

Gas-fired generator packages are used in stand-alone distributed systems for one or more wells, and in centralized systems for an entire field. By customizing the power system, operators optimize field installations to meet specific needs as well as managing overhead costs and capital investment.

Using generators ranging in size from60kW to multi-megawatt installations, operators are able to easily install electricity resources ahead of the grid. Most of Aggreko's generator packages are trailer-mounted and delivered to the field location using a one-ton service truck. Multi-megawatt installations involve more logistical coordination but most can be fully operational in less than a day.

Rapid deployment brings well production on line sooner. In contrast to mechanical drive engines, the infrastructure for portable gas-fired generation is quickly and easily deployed. The gas units provide numerous options that help expedite production.

As utility power becomes available, the units are easily disconnected and trailered to the next well or centralized generation point. Gas-fired systems greatly simplify the transition compared to the crews and crane typically required to decommission a mechanical drive engine. The well-site facility is ready to accept grid power as soon as the gas-fired system is disconnected.

Flexibility through Leasing

Leased power generation as a turnkey service is a flexible option for upstream and midstream operations, with no capital outlay.

Rental redirects capital to the operator's primary business of drilling, completing and producing oil and gas. By renting temporary prime power through gas-fired generation, capital expenditures for mechanical drive engines are eliminated. Service and maintenance support in leasing arrangements for gas-fired generation also relieves operators from the manpower overhead costs of traditional mechanical drive engines.

With 24/7 support from specially trained technicians, leased power generation, paralleled systems with back-up, and remote monitoring, downtime can be minimized--and even eliminated.

Power Advantages

Gas-fired power generation i s providing operators with a new degree of flexibility for developing oil and gas assets--bringing production on line sooner, cutting fuel costs and reducing emissions. Leasing equipment and services creates new possibilities for managing capital investment and minimizing power-generation overheads. The result is a significant advance in the economic and operational options available to oil and gas operators.