Produced Water Treatment Technology

ONE MILLION GALLON PER DAY * PRODUCED WATER TREATMENT SYSTEM

Unique four-step produced water (PW) treatment system that successfully processes up to one million gallons of day of PW removing TSS (Total Suspended Solids) and reducing TDS (Total Dissolved Solids) from 6500 milligrams per liter (mg/l) to below 50 mg/l. The automatic/continuous treatment system features: chemical conditioning, high-efficiency-large-particulate (low-profile) gravity-sand filtration, reverse osmosis (RO) pre-filtering, and, a high-capacity-single-pass RO treatment system (See photo). The unit is supported by an anti-scalant-control system and an in-place portable cleaning skid to service RO.

Designated as the HEI PW-10, the integrated system is designed, engineered and fabricated to handle a total treatment stream of 730 gpm with a total quality water stream of 365 gpm. While the feedstock (influent) and the exit flows for PW systems will vary, the HEI PW-10 will easily handle high-production PW flows that are tied to offshore oil and natural gas production. Some typical influent values and target outflows are:

PARAMETER INFLUENT VALUE PERMEATE TARGET
pH 8.8 9.8-10.2
Chloride (mg/l) 4500 45-55
Total P (mg/l) 2700 <5
Dissolved Fe (mg/l) 0.9 0.1
Total hardness (mg/l) 130 <130
Calcium (mg/l) 26 NN

HEI provides design, engineering, manufacturing, installation and operation of environmental equipment and biological treatment systems that are utilized in the oil and gas patch, process power and pipeline industries.

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Hoffland Environmental Inc. (HEI) is an acknowledged leader in the area of water and wastewater treatment and the company’s design, engineering and systems capabilities extends directly into the oil and gas patch. Here, oil and gas producers are finally beginning to recognize that they are really in the water production business, and the expense of water treatment keeps nudging the price of oil upwards. HEI provides economical system design for treating the water that comes from oil and gas wells.

In countries that use advanced drilling and production technology, the ratio of water to oil from onshore and offshore production rigs may run 5:1 to 7:1. In countries using poor completing technology or obsolete water flooding recovery methods, the Produced Water (PW) may run 15 barrels for every one barrel of oil produced—or even higher. HEI treatment systems for PW are focused on handling these large volumes while meeting strict water pollution control laws and regulations. In offshore treatment units, HEI  specifically addresses the problems of space and weight requirements.

While HEI is particularly apt in design and operation of new equipment, the company has particular expertise in addressing environmental issues of many older production properties where older PW technology was not designed to handle today’s stricter regulations. HEI also considers retrofits that consider increased water to oil ratios that can come with an aging field or one that is now undergoing Enhanced Oil Recovery (EOR) that involves flooding or hydraulic fracturing.

HEI engineers, as a result, recognize that PW treatment is becoming more complex, particularly when the PW contains Naturally Occurring Radioactive Materials (NORMs). Another complex issue faced by HEI is fine particulate removal. The latter is a common occurrence in the USA where slant or horizontal drilling takes place (for example, near Giddings Texas) in formations located on The Austin Chalk. There, the PW treatment system may have to address a complex of ultra-fine particulates, oil and gas, a myriad of drilling chemicals and muds, and varying concentrations of dissolved salts. Sometimes the issues involve 3-phase separation technology.
In respect to PW, HEI has recognized that certain chemicals and salts of metals travel in groups. For example, Column II of the periodic chart contains: Calcium,  Magnesium, Strontium, Barium and Radium……….all valence 2 metals whose treatment and removal have common denominators.

In light of the above, there are common denominator equipment considerations that HEI integrates into PW treatment systems. The first is an upflow deep bed filter that is suitable for oil and solids. For offshore use, the weight and size of these units can be a drawback.

The next generation of filters for PW service is the black walnut shell (BWS) filter. The inert nature of the shells and their specific gravity (close to that of water) plus the inherent surface tension properties of the shell make this unit suitable for mechanical cleaning.

The third category uses anthracite and garnet……and……the one drawback of this unit is that it needs clean water to backwash.

Cartridge filters are the fourth category, and HEI utilizes specially constructed high volume filters that dwarf the throughput of conventional cartridge filters.

PW systems also utilize Induced Gas Flotation (IGF), either hydraulic or mechanical. IGFs must address the problem of handling Volatile Organic Compounds (VOCs). This is a fifth type of PW treatment.

Simple skimming tanks are a sixth device, and the seventh category of PW treatment is “other.” (This last catagory includes a variety of separation equipment from centrifuges to hydrocyclones, membranes, adsorbers and absorbents, DA units and microfiltration.

In its PW process systems, Hoffland Environmental addresses both the water itself and the chemistry of the various down-hole additives. The reactions and reactivity have to be thought out because the stoichiometry of treatment demands that face the wastewater-treatment-engineer are, indeed, complex. Each oil field and its associated PW-treatment system has its own esoteric conditions. And, other factors contribute to the problem. For example poor cementing practice may lead to increased volume of PW or related complications.  Complicating PW treatment is that many PW system designers are flying blind in terms of what has actually been in the hole.

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