What's New in Production

Marvin Gaye wasn’t an oil and gas technology researcher, as far as I know, but the title of his best-known album easily could be about a flyover of activity, in several intersections of that world. Ergo, its appropriation here. Put smart people in a room, add gadgets, stir, and the results can be worth singing about. But, lacking said song, you’ll have to resort to humming whatever ear-worm (Editor’s note: You may want to look up this obscure, although appropriate term.) is in your head, as we look at some projects that our white-coated colleagues are conducting, under the auspices of the National Energy Technology Laboratory (NETL).

Fracture diagnostics using Low-Frequency Electromagnetic Induction (LFEI) and electrically conductive proppants. The goal here is to develop an LFEI method, which has the potential to estimate not only the propped length, height and orientation of hydraulic fractures, but also the vertical distribution of proppant within the fracture. The proposed LFEI tool can be used to detect far-field anomalies, in the rock matrix, from a single borehole.

NETL points out that lab measurements made, for the electrical conductivity of the proppant, showed that values of the proppant conductivity were found to be 10,000 times larger than the shale conductivity. As the project team notes, we still lack an inexpensive, direct, and repeatable post-fracturing diagnostic tool to measure the dimensions, and orientation, of propped hydraulic fractures.

The team anticipates that the proposed technology will be a game-changer in fracture diagnostics, because it is inexpensive, repeatable, and fairly simple to operate. Additional benefits, such as additional recovery, and reduced costs, are also possible.

A possible environmental benefit is particularly interesting. This technology tracks the location of conductive proppant using a proposed electromagnetic logging tool. Therefore, it can be used to track fractures that are hydraulically connected to natural aquifers. This tool can be operated alongside cement bond logs, in fractured reservoirs, to ensure hydraulic isolation of oil and gas producing zones. Additionally, the inverted product of this data can be combined with other geophysical data (2D and 3D seismic and/or controlled-source electromagnetic data) to find connections with natural fractures.

Natural gas in surface process equipment replaces water as primary fracing fluid. This is about developing and field-testing the use of readily available natural gas collected at the wellhead as a primary fracturing fluid. The work proposes to develop, validate, and demonstrate affordable non-water-based and non-CO₂-based stimulation technologies, which can be used instead of, or in tandem with, water-based hydraulic fracturing fluids to reduce water usage, as well as the volume of flow-back fluids. The process will use natural gas at wellhead supply conditions, and will produce a fluid at conditions needed for injection.

We all know the problem. One of the principal drawbacks to hydraulic fracturing is its excessive water use. Each application of hydraulic fracturing consumes between 3 million and 7 million gal of water. During the fracturing process, some of the fracturing fluid is lost permanently, and the portion that is recovered is contaminated, by both fracturing chemicals and dissolved solids from the formation. The recovered water, or flow-back, represents a significant environmental challenge, because it must be treated before it can be reintroduced into the natural water system. Although there is some recycling of flow-back fluids for future fracturing, the majority of the flow-back water is hauled from the wellsite to a treatment facility, or to an injection well, for permanent underground disposal.

The team’s proposed fix sure seems like a good idea. NETL intends to develop and field-test an optimized, lightweight and modular surface process involving natural gas liquefaction, compression and injection. This will replace water as a cost-effective, environmentally-clean fracturing fluid. Using natural gas produced from the well for hydraulic fracture stimulation will result in nearly zero consumption of water. The gas, in a liquefied state, is injected as a fracturing fluid; it will mix with newly-released formation gas, and both will be extracted to the surface. This eliminates the collection, waste and treatment of large amounts of water, and reduces the environmental impact of transporting and storing the fracturing fluid.

Maximize liquid production from shale oil and gas condensate reservoirs via cyclic gas injection. Natural gas within easy reach appears to be a handy solution to another problem. The primary recovery stage for shale oil wells, drilled horizontally and stimulated with multiple transverse fractures, yields less than 10% of the oil in the reservoir, and typically recovers closer to only 5%. Because the oil recovery factor is very low, improvements in enhanced oil recovery can add significant economic and environmental benefits to ensuring adequate oil and gas supplies for the country.

This project was initiated to investigate cyclic natural gas injection, which includes both gas flooding and huff-n-puff processes. In both processes, a fraction of produced gas is cyclically injected into shale reservoirs to maximize liquid oil production. Both types of shale reservoirs—oil and gas condensate—will be investigated. Cyclic re-injection of produced natural gas reduces gas flaring and sales potential, but increases oil recovery and avoids the need for water to enhance oil and gas recovery.

These efforts bode well. I hope they are music to your ears.