As “easy oil” from traditional wells becomes depleted over time, the oil and gas industry has looked toward other more aggressive methods of meeting the world's energy requirements. Production and extraction from unconventional oil sources provides new recovery opportunities—for example, 10% of estimated oil resources are in shale or tight formations, according to the U.S. Energy Information Administration—but this also results in unique field challenges. The continued development of advanced technologies and chemistries is necessary to enhance operational efficiency and capture valuable hydrocarbons while at the same time meeting economic incentives and environmental obligations.

The oil and gas production process is water-intensive. In fact, by volume water production represents about 98% of the nonenergy-related waste produced by the oil and gas industry, yielding about 77 Bbbl of water per year worldwide, according to Argonne National Laboratory. However, with the United Nations anticipating that world population will grow from 7 billion in 2011 to more than 9.5 billion by 2050, profound stress has been placed on the world’s limited water supply, not only by its burgeoning population but by other issues such as rapid urbanization, industrialization, pollution and climate change.

Limited freshwater supplies are driving the industry to seek improved solutions for reducing oil in water prior to discharge and to employ reuse schemes in water-intensive activities such as boilers and direct injection for EOR processes.

Convergence between oil and water

As oil and gas exploration continues to expand, so have water management challenges associated with onshore and offshore operations. Water management decisions within oil production fall into three primary categories: water acquisition, water utilization within operations and the disposal of wastewater from drilling and production. A typical petroleum reservoir or well is able to extract approximately 10% to 15% of oil during primary recovery in which hydrocarbons rise to the surface without employing extensive pumping. During secondary recovery, operators are able to extract additional hydrocarbons through the process of water injection, in which water is injected into the reservoir at high pressures to effectively stimulate additional oil recovery to the surface. This industry practice typically allows an additional 20% to 30% of oil to be recovered throughout the life of the well, but not without challenges.

During crude oil production, a mixture of formation water and oil is recovered. Once oil has been separated from this water mixture, produced water remains. Produced water can contain high amounts of salts, solids and organics such as benzene, toluene, ethylbenzene and xylene along with residual oil. In some cases, produced water undergoes chemical and mechanical treatment to separate contaminants and oil from the water so that crude oil can be sent for refining and treated water can be reinjected, disposed or reused. However, the removal of solids from produced water is challenging due to its widely varying characteristics, which depend on location and formation geochemistry, among other considerations.

Technology advancements promote water reuse

Oil and gas producers are looking for efficient technologies to reduce costs, increase uptime and protect downstream assets. Consequently, advanced water systems and chemistries can provide an economic advantage while addressing strict environmental regulations to meet oil and grease specifications on discharged water. Releasing even a small quantity of oil back into the environment through produced water can quickly add up, negatively impacting an operator’s bottom line and raising a red flag to environmental regulators. Water reuse is widely seen as a potential means of reducing the impact on local water resources, particularly in areas where water is relatively scarce.

Despite the quantities of water needed in oil recovery, there is no reason that the water used in oil and gas production needs to be dependent on freshwater assets. Water to support oil and gas production can come from a variety of sources, including fresh or brackish water from surface or groundwater withdrawal, treated industrial or municipal wastewaters, and recycled produced water.

While operators must take vigilant steps to ensure that specific water chemistry is compatible with any given reservoir, the trend of water reuse underscores the importance of using effective filtration technology and clarifying chemistry as a means to promote sustainable industry practices and reduce operating costs. Recycling not only supplies oil and gas operators with large amounts of water for reuse in secondary oil recovery and well drilling, among other uses, but also reduces the need for long-range trucking of makeup water to the well pad and subsequent wastewaters to remote disposal facilities. Advancements in technology allow the reduction of wastewater requiring disposal and increased recycling of water recovered from producing oil and gas wells.

Aqueous-based chemistry

Environmental concerns are clear: We must value and respect the scarcity of water as one of our most precious natural resources. Numerous technologies are available today to enable complete or tailored removal of ionic, organic and particulate contaminants from source waters for injection or produced waters for discharge.

During the primary separation step, produced water is treated with demulsifiers that aid in removing water from water-in-oil emulsions; however, a variety of solids and organics are still present. Water clarifiers are then used to further separate oil from water streams to meet regulatory discharge limits required for reinjection, disposal and reuse.

ROMAX Water Clarifiers from Dow provide a solution for separating oil from produced water and reverse (oil-in-water) emulsions, helping to protect both the environment and production equipment. These products are effective and environmentally responsible and can help treat produced water for reinjection, discharge or recycling in areas such as chemical EOR.

One of the biggest factors hindering long-term uninterrupted system operations blockage is caused by fouling generated during oil and produced water processing. For example, conventional clarifying technologies have, in some cases, been found to cause downstream issues including water-handling system fouling and the extraction of gel-like oil during the clarification step.

Consequently, it is of the utmost importance that produced water is treated with precise, reliable chemistry that not only reduces solids and contaminants but prevents pump and system fouling. By minimizing fouling, ROMAX 6000 and 9000 water clarifiers protect the chemical injection pumps used to dose the chemicals into the produced water stream. Similarly, Dow’s clarifier chemistry effectively streamlines treatment and helps increase operational efficiency, which can ultimately reduce capital costs, maintenance and handling so that produced water meets regulatory oil and grease specifications and can be reinjected, reused or discharged back into the environment.

Conventional clarifier technologies can take the form of hydrocarbon-based dispersions that require a maintenance-intensive mixer to support the inversion process prior to dosing. Dow’s aqueous-based products require no such inversion, which means they can be dosed directly. In addition, these water clarifiers eliminate the need for dilution or activation, which ultimately reduces operating expense. In fact, the series of anionic, cationic and nonionic water clarifiers are fully formulated and ready to use as soon as they arrive at the field.

For colder climates, the ROMAX 9000 series of water clarifiers are freeze-stabilized formulations for use at temperatures as low as -40 C (-40 F). This capability allows the operator to practice without issue, even in the harshest climates.

ROMAX water clarifier technologies can help lower the oil and contaminant content of injection water so that it can be safely and responsibly reused or discharged back into the environment. This is especially necessary for offshore operations, which focus on controlling the quality and subsequent impact of seawater that is either injected into the formation during secondary recovery or sent to overboard discharge. Clarifiers can help with water cleanup and have even helped reduce sheening issues in discharge water.

Residual oil in reinjection water also can adversely affect injectivity if reused in the reservoir, resulting in lost revenue and remediation costs. Clean water is necessary for peak performance as well as long-term production of a well. These products help facilitate oil levels that are low enough that water can be confidently reused and integrated back into the system. With dosage rates of 1 ppm to 100 ppm of ROMAX technologies, it is possible to reduce residual oil-in-water from more than 1,000 ppm to below 20 ppm.

In a recent case study, an oil and gas service company was able to significantly reduce pump fouling by switching to a ROMAX 9000 product. Making the switch allowed it to meet its oil and grease specification while reducing the manpower needed to maintain the chemical addition pumps in the field. Next-generation technology will continue to be researched and developed to help improve quality and the environmental integrity of a well's performance without increasing the cost of servicing the well.

As the global population continues to grow, balancing the need for clean water and energy will remain a clear focus for operators and regulators alike. By employing effective water clarifiers that reduce pump and system fouling and streamline the oil recovery process, operators can increase operational efficiency in a cost-efficient way and play an integral role in the trend toward more sustainable, environmentally conscious EOR operations.