Mobile electric power and microgrids offer sensible alternatives to diesel power

Recent headlines from West Texas herald the start of what’s thought to be a big trend in months and years to come: acquisitions of large independent E&P operators and lease owners by the oil majors. These headlines, however, overshadow another profound trend: the Permian’s need for reliable, cost-effective oilfield power with as few emissions as possible.

As an indication of how much power the Permian will require, the Electric Reliability Council of Texas (ERCOT) estimates that the voracious power demands of Permian E&P activities will substantially strain the state’s electrical grid’s resource capacity of around 78,000 MW. In fact, ERCOT expects the region’s growth of electricity needs through 2023 to exceed state-wide growth by 400%.

That demand growth is despite the fact that frac operations typically don’t tap the Texas grid, but instead use either direct mechanical drives or mobile generating plants, most fueled by older-generation Tier II diesel generators or, increasingly, by newer Tier-IV units. Unfortunately, this type of power generation has a lot of downsides—cost and emissions, chief among them. The good news is that these disadvantages can be remedied by advanced mobile electric power and microgrid solutions available today, which employ gas turbines.

Once wells are completed, E&P operators must address gas-flaring restrictions. Although flaring limits in Texas are less strict than other shale-play states, some producers have cut production to not exceed their permitted flaring limits. But flared gas isn’t just an emissions source; it’s a wasted resource. In 2015, alone, Permian operators flared 45.5 Bcf of natural gas.

As flaring regulations tighten, producers can address both power and environmental concerns by capturing the gas, treating it, and using it to generate power via onsite gas turbines. The power can be used for future frac operations in nearby wells, or ongoing production power needs. In effect, they are monetizing their produced gas and realizing increased margins through diesel cost-savings.

MOBILE ELECTRIFICATION OF FRACING

Reducing emissions and monetizing produced gas can certainly benefit oilfield operators, but what about their service partners? While market conditions are tough for many, and margins can be thin, oilfield service companies also can benefit substantially by switching to electric frac solutions, helping to increase their contribution margins.

By supplying power to the electric motors driving power-hungry hydraulic fracturing pumps, gas turbines can deliver a cleaner, more efficient fracturing operation that eliminates the need for diesel or dual-fuel reciprocating engines and transmissions. Importantly, electric drivetrains are highly reliable, with up to 99% uptime.

Compared to diesel units in high-pressure pumping applications, mobile electric drivetrains using gas turbines are extremely low-maintenance. Plus, since electric drivetrains provide better flow control and higher uptime, this means more stages can be pumped at less cost and with better asset utilization. A typical frac stage, for instance, can cost $9,000 in diesel fuel, while natural gas can cost $3,500—a 60% savings.

Electrifying pressure-pumping operations can mitigate operational risk, too. There is no longer a need for “hot fueling” of diesel, as both CNG and wellhead natural gas options can be fully automated with no human interaction. In addition to lower risk and improved safety, electric-frac is also a way for pressure pumping companies to differentiate themselves by offering operators long-term agreements that feature more dependable performance guarantees.

As for emissions, gas-turbine power can generate meaningful savings, compared to diesel. On average, compared to Tier-IV diesel engines, turbines can cut CO₂ emissions by 12.5% and also reduce NOX emissions. With DLE (dry low emission) turbines, comparable NOX reductions can be quite substantial.

MOBILE POWER-GENERATING OPTIONS: FLEXIBILITY, SCALABILITY & RAPID DEPLOYMENT

One challenge in shale plays is to deploy efficient, mobile power-generating capacity that can be brought online rapidly. Often the need is temporary, such as for pressure pumping operations. After a well is completed, the mobile power plant needs to be relocated quickly to a new site.

Trailer-based, power-generation plants can deliver different power block sizes to wellsites, based on specific power needs, portability, available fuel source, and other requirements. Aeroderivative gas turbines (i.e., gas turbine technology from the aerospace industry) are well-suited to deliver mobile power, due to their lightweight design features. Also, their ability to start and stop frequently is another advantage, when compared to their industrial turbine counterparts and diesel engines.

Following are three different power block examples from Siemens for different duration requirements. These solutions can be provided via flexible financing arrangements, including long-term leases and deferred payment plans that minimize or eliminate capital outlays.

Solution 1. A 5.7-MWe, fully mobile power unit (MPU), as shown in Fig. 1, is available that can rig up onsite and start generating power in as little as an hour—ideal for frac crews that move often. They can set up one MPU to drive one to three 2,500-hp electric pump trailers in unique, transformerless configurations. Larger pump sizes are also available, and this scalability can be achieved only with an all-electric approach. Once rigged up, it can ramp up to full power in one minute. No e-houses or complicated electrical setups are required, because a system can scale to meet power needs by simply adding MPUs and pump trailers.

Fig. 1. A 5.7-MWe modular, mobile power unit: rigs up and down in as little as an hr; low noise emissions, with ultra-quiet option; road- and off-road-ready, with no flag car needed, assured bridge clearances, and special shock and vibration engineering.

MPU gas turbines and generator sets are packaged inside mobile trailer units that are both road- and off-road-ready, Fig. 2. The trailers include all required balance-of-plant equipment, such as the electrical distribution switchgear. Total power output can be scaled by analyzing an oil field’s power requirements—which can change over time, as the field is developed—then selecting the required number of MPU packages.

Fig. 2. Mobile SGT-A05 power unit.

Solution 2. When an operator needs power generation to supply multiple-site loads with a large total power demand for longer periods, Siemens’ customers have opted for lower-cost, larger 44-MWe turbines. These units can be installed and commissioned in less than two weeks.

Solution 3. A third solution is a full-scale microgrid that combines multiple gas turbines of same or varying sizes, all linked together and “load shared” across one electrical house or e-house. One can then connect as many pump trailers to the e-house as one chooses, but this will require stepping down voltage levels, using a transformer to each pump trailer. This setup takes longer to set up, but it may make sense for certain longer-term frac operations.

All Siemens solutions include wireless monitoring and controls, along with sophisticated diagnostic technology. These tools give operators the ability to collect and analyze data in real time, which can provide actionable intelligence for condition monitoring, leading to less downtime and improved maintenance scheduling. Cloud-based digital services and analytics can be deployed in the field with edge analytics, so data can be gathered and analyzed across entire fracturing fleets to continually optimize operations.

WHAT TYPE OF FUEL FOR ELECTRIC FRACING?

A recent concern from oilfield service companies is the availability of natural gas in the field. The short answer to their question and concern is, yes, the fuel is available. Companies are offering competitively priced, portable CNG delivered to site, and we are seeing long-term contracts being signed. Operators are also stepping up to plan better and ensure that cheap wellhead gas is available. When using wellhead gas, it is crucial to select mobile gas turbine packages that can handle a wide range of gas quality. This fuel flexibility can enable operators to generate power with fuel savings versus diesel of 30% to 85%, depending on the alternative fuel source and job parameters.

Many service companies start frac operations with compressed natural gas (CNG) but quickly move to wellhead gas as available. In the case of wellhead gas, once enough fuel is being produced from wellheads on the pad or from nearby gathering infrastructure, there is no need to transport fuel onsite from third parties. This saves costs, and relieves road congestion.

THE ROAD AHEAD

Flexible, reliable and scalable power is a key enabler of development in shale plays, with natural gas making traditional diesel power outdated. Today, the Permian is the largest source of supply growth in the world. However, that growth is at serious risk of being hampered by infrastructure constraints and bottlenecks. As operators build out the necessary infrastructure for their oilfield operations, the need to offset rising production costs and land prices through further cost reductions and efficiency gains will become increasingly important.

To help achieve those goals, both operators and service firms should consider the significant economic and environmental advantages of powering their frac and other oilfield operations using natural gas, either compressed or wellhead, as available. They should then engage a power infrastructure solutions partner that can handle a significant portion of their supply and service scope. It is important to pick one that can supply the right equipment, such as electric motors, rugged variable speed drives, gas turbines, and accessories. The partner should be able to help model the full lifecycle of cost and emissions savings and guarantee operational results via grid studies.

Engineering the solution is one step, but following through with quality construction, commissioning, and lifetime service are also keys to success. Leveraging a single point of responsibility for a project can generate wide-ranging, quantifiable benefits through streamlined execution, shorter delivery times, and reduced technical risk. Ultimately, this will provide a better solution that results in lower CAPEX and OPEX over the life of the gas turbine power infrastructure. WO