What's new in production

In upstream oil and gas, incremental improvement is relentless. Consider today’s Point B; then compare it to a Point A of, say, 25 years ago. In the aggregate, those increments can have a remarkable result. Even so, organizations sometimes still swing for the fences. Today, we look at a couple of outside-the-box ideas that have reached the commercial stage.

It’s in your DNA.You may not have known that formations have DNA, in a literal sense. Biota Technology says they do, contained in microbes that live in fractures, faults and inter-particle pores. The company says that microbes live in abundance within typical onshore reservoirs, such as the major U.S.  shales.

Microbes certainly seem hardy. Studies show that they are capable of reproducing at temperatures greater than 250°F, in pH ranges from 0 to 13, in hypersaline solutions, and at pressures greater than 15,000 psi. The company notes that microbes are sensitive to their surrounding environment and have an extraordinary ability to adapt accordingly. This is accomplished by the use of a wide range of chemical compounds for energy sources, depending on geology and reservoir conditions.

Energy sources for microbial growth can be acquired from pathways, such as hydrocarbon oxidation, sulfate reduction, iron oxidation and reduction, methanogenesis, and nitrate reduction. Carbon for growth is either sourced from hydrocarbons, organic matter, or the carbon dioxide found in fluids and minerals.

Specific biochemical pathways depend on reservoir characteristics, such as primary depositional environment, paleo-redox conditions, and elemental concentrations. The diversity of possible metabolic pathways rooted to geologic history makes subsurface DNA a unique and powerful tool for understanding the subsurface.

How DNA describes the subsurface.The company says that geological controls—including depositional environment, lithology, diagenetic processes, and vertical/lateral heterogeneity—ultimately drive modern microbial colonization and thus subsurface DNA. Where reservoir and subsurface conditions change, these variations can be observed through alterations in microbial communities.

Subsurface DNA is obtained from reservoir fluids (oil, water, emulsions), well cuttings and/or cores. Samples are collected in the field and returned to the lab, where DNA is extracted, using techniques optimized specifically for oil field samples, and then sequenced.

Non-invasive, high-resolution data source.Unlike tracers, which need to be added to stages and require supplemental oversight, subsurface DNA requires no additional work, as it relies on naturally occurring microbes. The company notes that tracers and geochemical measurements generally result in a single data point per sample, while its subsurface DNA method returns a minimum of 5,000 sequences per sample. DNA sequencing helps operators to estimate drainage height, to optimize well placement; monitor well connectivity to improve field development; identify sweet spots for targeted stimulations; and measure production over time for engineered completions.

An electric idea for well stimulation. Well Services has deployed what it calls the world’s first fully electric, fully mobile, well stimulation system. According to the company, its fleet runs on electric power generated by 5.7-MWe natural-gas-fueled turbine generators.

The company claims its fleet reduces hazardous emissions, and points out that independent, third-party testing confirms that its fleet decreases emissions by 99%, compared to conventional diesel-powered fleets, all but eliminating environmental exposure to pollutants, such as nitrogen oxides (NOx) and carbon monoxide.

Specifically, NOx emissions measured on the turbine exhaust stacks were found to be 0.036 grams per kilowatt hour (g/kW-hr), a drastic reduction compared to the Environmental Protection Agency’s (EPA) requirements for off-highway diesel engines. This reduction is achieved by eliminating conventional diesel engines and replacing them with electric motors powered by natural gas generators. Clean Fleet technology also eliminates methane slip issues observed in dual-fuel applications.

Conventional diesel stimulation sites are extremely loud, with some locations measuring as high as 129.5 decibels, 1 ft away from the equipment.

The company employed a third party to perform a sound survey of the electric fleet and compared it to a conventional site. More than 140 monitoring locations were recorded and the result was up to a 69% reduction in the average sound pressure at the electric-fleet stimulation site.

Fuel sourcing is another advantage. While a conventional fleet must transport diesel fuel to the well site, natural gas for the turbine generator sets is delivered more efficiently, directly from a pipeline. Subsequently, the use of natural gas eliminates approximately 25 diesel truck deliveries to the well site that would be required for an average horizontal completion. This reduces traffic, and eliminates fire hazards and spills associated with refueling operations. The company says the use of produced field gas [can] reduce fuel operating costs by as much as 80%.

By replacing the engine and transmission with a VFD that controls the electric motor, which is coupled directly to the hydraulic fracturing pump, high-pressure iron vibration reduction, of up to 80% compared to diesel powered equipment, is also achieved.

Commercialization is a way station on the uncertain journey to mainstream use. While incremental steps may offer surer footing, big jumps like these can cover a lot of ground. And, they’re fun to watch.