The EcoWave field unit is compact, portable, and robust enough for routine oilfield use.

Production declines and well failures due to downhole deposits are a significant concern for operators of mature wells around the world. Traditional treatments stimulate production by removing damaging deposits from the near-wellbore area, perforations, and tubing. However, they can create economic, environmental, and safety challenges or even cause additional near-wellbore concerns.

A new technology uses tuned energy waves to alter molecular bonds downhole, stimulating production increases by disrupting damaging deposits and altering relative permeability in the near-wellbore area.

Damaging deposits

Mature wells suffer a variety of damage mechanisms that can greatly affect their ability to produce. Some of the damage occurs naturally as part of the well’s productive life; other damage can be caused by poorly designed or executed treatments that were intended to remediate one problem, but caused others.

For a mature well producing in the radial flow regime, the bulk of the pressure drop to the well bore occurs within 20 ft (6.1 m) of the well bore, an area that also is typically cooler than the deeper formation. The pressure and temperature changes in the near-wellbore area, perforations, and tubing affect the chemistry of produced fluids; paraffins and asphaltenes begin to be deposited from produced hydrocarbons and water. These changes also cause hydrate and salt blocks that affect production, downhole, and even surface equipment.

Produced water also can carry and create downhole problems: bacteria, fines migration, clay swelling, emulsions, and corrosion. Corrosion can then create sludging problems as well as tubing and downhole equipment damage that can require expensive workovers.

Some of the traditional solutions to these problems can — if not properly engineered — create additional problems.

One example is inexpensive hot oil and hot water treatments, which are often used in mature wells to melt waxy wellbore deposits so they can be lifted out of the well. Typically, however, these treatments affect only the upper 1,000 ft (350 m) of the tubing because the treatment fluid cools as it falls, thus losing effectiveness. They also generally affect only lighter waxes, leaving heavier, more persistent deposits in place. The heavy deposits build up over time into a significant problem that can only be resolved with a workover that can apply mechanical and chemical energy to the deposits.

If not properly treated, injected fluid can create additional depositional problems — for example, introducing bacteria or ferric iron to a downhole environment that is ripe for deposits, corrosion, or souring. Improperly selected fluid treatment systems (biocides, scale inhibitors, corrosion inhibitors, non-emulsifiers, etc.) can alter formation wettability and relative permeability, thereby inhibiting production.

Of course, well-designed batch and continuous chemical treatments can manage many downhole problems and allow steady, long-term production. But to significantly increase production, more invasive workover or stimulation treatments typically are required.

Given the wide variety of downhole problems and the potential for solutions to exacerbate one problem while treating another, a main goal of any stimulation or remediation treatment — and the focus of BJ’s BlueField services for mature fields — should be to “first, do no harm.”

Altering bonds

The latest addition to this fit-for-purpose stimulation portfolio is EcoWave technology, an environmentally friendly, chemical-free means of stimulating hydrocarbon production by removing near-wellbore damage. Instead of chemical and mechanical energy, this technology uses directed waves of energy to alter downhole fluid chemistries.

The theory behind the technology is to use tuned energy waves as a means of altering proton and electron spin states, which affects molecular bonding. Calculations related to the process of wax crystallization suggested that a low-energy system tuned to ideal wavelengths could interfere with static forces and hydrogen bonding. The result is similar to that of typical oilfield threshold inhibitors and surfactants. Potentially problematic molecules stay in solution longer, minimizing agglomeration, and relative permeability to both oil and water are affected in a way that promotes additional oil production.

To employ the technology (for which a patent has been applied) in the field, wave frequencies are chosen to optimally target specific chemical bonds. For example, the most frequent commercial application to date has used wavelengths designed to selectively alter proton spin states, simplifying damage removal from the well bore and near-wellbore area.

Using a fit-for-purpose antenna deployed on the tree or into the annulus through the wellhead, the treatment lasts from
30 minutes to two hours. Results have been demonstrated to last as long as three months.

In early field applications, sample testing before and after treatment has included gas chromatography, showing reduction in molecules with long carbon chains typical of paraffin-plagued wells.

Ultimately, the system’s greatest benefit is economic — reduced lifting costs and increased hydrocarbon production.

After extensive laboratory testing, the technology has been used in more than 60 wells in Texas, Oklahoma, New Mexico, and Utah. Applications have included both flowing and pump-assisted wells.

Technology at work

Operators have reported production increases from 20% to more than 120%, compared to slight increases in chemically treated offsets. All wells are being monitored to determine treatment longevity, with benefits continuing more than 60 days after treatment in most wells.

For example, the technology was used recently to stimulate eight wells near Levelland, Texas. Historically, the wells had been treated with hot water every 90 days to maintain production and with occasional workovers to remove deeper organic deposits. Two months after the EcoWave treatments, oil production had increased by as much as 20%, and gas chromatography results indicated a significant reduction in long-chain carbon molecules. All eight wells produced continuously with no issues for the three-month test period following the treatment.

In another example, two wells near Hobbs, N.M., were treated. Historically, these wells had been treated with hot oil every 90 days to maintain production. Fifteen days after the new treatment, oil production from Well #1 had increased
by 57% and from Well #2 by 126%. The increased production was sustained through August. An offset well that was treated only with chemicals (dispersant, solvent, and wetting agent) has recorded mostly steady production.

Finally, an operator in northeastern Utah had an emulsion and paraffin problem that was plaguing remote wells.

Produced fluid had such a high cloud point that the operator was forced to run heaters for the wellheads, flowlines, gathering lines, and tanks. This solution created issues with corrosion and safety and greatly increased lifting costs throughout the field. In an effort to eliminate the need for the heaters, the customer requested treatment for 11 wells.

Three wells were treated on the first day of the treatment series. The third well had been shut down because the pump was stuck in downhole deposits. The operator was planning to schedule a hot oil treatment to free the pump, but because the technology was in the area and available, the decision was made to try a treatment using EcoWave technology. The antenna was run into the annulus and the equipment operated for two hours. The pump was then switched on. After two struggling strokes, the pump began to run and continued to pump smoothly for the entire week that the crew was in the field treating other wells. This performance, combined with early increased production results, exceeded customer expectations.