Production

Cost-Effective Produced Water Treatment







  
The fail-safe solution for the treatment of produced water from off- and onshore oil and gas wells
August 5, 2011

Each year, oil and gas producers in the U.S. spend an average of $1 to $6 billion dollars on the disposal of produced water. For every barrel of oil, five to nine barrels of water are produced. For each MCF of natural gas produced from the ground or ocean floor, the result is 0.1 to 1 barrel of produced oily water. Cost efficiencies in oil and gas production depend on the economics of the produced water treatment and disposal.

When these barrels of oily water are produced, the oil and gas producers must find ways to treat and dispose of the water, which is expensive. In onshore operations, the produced water must be hauled to re-injection sites or disposed of in evaporation pits. Third-party haul away or disposal costs about $0.5 to $8 per barrel of water, depending on the location of disposal from the production sites. This amount can be more than $5 million each year to dispose of 5,000 barrels per day of produced water.

Discharge into evaporation ponds require no visible oil sheen or less than 10 parts per million (ppm) oil content in the water. Some reinjection disposal methods also require less than 10 ppm oil content.

This highly-regulated process is  an environmental challenge because of the trucking footprint, the toxicity of the oils and hydrocarbons and the potential damaging impact to underground water aquifers and surface wildlife. The underground reservoirs can plug or foul, which increases the pressure and reduces the ability to dispose of the produced water.

Currently, Kinetic Hydrate In-hibitors (KHI) are used widely in the production line. They can cause the emulsification of oils and hydrocarbons in the produced water and can compromise existing secondary treatment options, such as float cells or nut shell filters. How do oil and gas producers reduce the oil sheen and dissolve volatile and semi-volatile hydrocarbons in the produced water?

A clean water technology offers a complete break from obsolete filtration, operating on the principle of chemical cohesion. This technique is a clean break from other existing produced water treatment technologies, which are mostly based on mechanical separation, chemical injection or adsorbent technology. This chemical cohesion principle enables the treatment system to remove free, emulsified and dissolved oils and hydrocarbons in the water. It achieves 0 to10 ppm on total oil content including free and emulsified oils. Using this system increases the water quality and makes it amenable for surface discharge, reinjection or reuse, and it removes toxicity and hydrocarbons.

The system cuts costs and provides a quick return on investment. It offers a reduction in the environmental footprint of the producers by offering a small, compact and environmentally-friendly process for handling and disposing of produced water. After the produced water is treated, it is oil free and can be disposed of into surface water or evaporation pits, or it can be reinjected. The water is also reusable as frac water or can be fed into a desalination process to create fresh water. The system is easy to operate and maintain and can be engaged online within a few hours.

Produced Water Treatment in Greater Natural Buttes, Utah

Anadarko Petroleum Corporation is one of the world’s largest independent gas producers in Utah, with more than 17,000 gas wells. Anadarko is one of the companies benefiting from the new water treatment system onsite.

More than 10 million barrels of produced water have been treated and discharged from the system, at processing capacities of 10,000 to 25,000 barrels (bbls) per day. The treated water is discharged into evaporation ponds at less than 10 ppm oil content and no visible oil sheen. The Anadarko facilities have implemented a simple, robust and effective oily water treatment process with a small environmental impact. The treatment systems provide robust, fail-safe and efficient oil removal while ensuring a consistent and sustainable discharge water quality even when emulsified oils and dissolved hydrocarbons are present.

Anadarko treatment system in Vernal, Utah
Produced Water Treatment, Vernal, Utah

In Vernal’s Anadarko produced water treatment facilities, the treated water is put into evaporation ponds. The system allows for about 10,000 to 25,000 barrels of produced water to be successfully treated per day, removing all visible oil sheen, leaving the water with less than 10 ppm oil content (most of the time, the value is not detectable). This has reduced the environmental footprint of produced water significantly by cutting salt water trucking by at least 75 percent and has saved significant trucking and water disposal costs of $5 to $10 million each year for the operator.

Before deciding on this solution, engineering consultant MWH evaluated other possible strategies for cleaning the water—including separators, flotation cells, coalescer, backwashable nutshell filters, carbon/ clay absorbents and then this new technology. The treatment system was considered the final, fail-safe step behind the conventional treatment systems to ensure the 0 to10 ppm discharge guarantee for oil content even during process upset. This option proved to be environmentally-friendly and cost-effective. The hydrocarbon content of the water was consistently less than 5 ppm. Filtration of the water has been so thorough and reliable that disposal into large ponds has been a solid discharge solution.

The main benefits of the technology are dependability and reliability. Conventional produced water handling methods proved non-reliable for Anadarko until this system enabled them to cost effectively treat the produced salt water.