Mechanical admixtures and oil in injection water

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Clean Water for FPM as a New Challenge in the Industry

Studies have shown that if the content of mechanical admixtures and residual oil in the injection water exceeds 50 mg/l, then the intake capacity of each injection well decreases by half in only one year, while the energy consumption required to maintain the formation pressure at the design level will increase by 100,000 kWh per year. In such a situation, OPEX and FPM system cost of ownership will increase because of the growing number of acid treatment operations and the cost of energy consumed by water injection station’s pumping sets.

In this regard, quality indicators of water injected into the formation must meet the impurity criteria subject to the porosity type of reservoirs. The content of mechanical admixtures and petroleum products in water is restricted in certain limits subjected to the reservoir porosity.


Alternative Solutions for Water Treatment Problem

Today, the use of settling tanks based on vertical stock tanks (VST) is the most widely spread alternative. The advantage of this solution is its simplicity and independence from the initial content of oil and mechanical admixtures, since there is often an uncertainty in physical and chemical properties of the medium to be pumped at the development stage. The disadvantages include high labour content and hazards when cleaning VSTs from oil sediments, risks of catching oil when draining water from VST, and, as a result, failure to meet the requirements for oil content. In addition to the above, the settling tanks are often located far away from the central gathering facilities, and the operator usually controls the process manually, which makes the operation more difficult.

However, there is a wide range of water treatment technologies available today to handle the problem of both the efficiency of treatment and the reduction of capex and cost of ownership. The Process Engineering Standards for oil fields set forth the set of available technologies.


Cyclone Technology as an Efficient Water Treatment Solution

The cyclone technologies are most efficient per totality of the treatment degree and rate characteristics for both the mechanical admixtures and the residual oil. OZNA engineers set up a target to develop a cyclone solution outperforming the main foreign counterparts. The work stages include:

  • Developing a computational model for cyclone separation of oil-water emulsions and water-sand suspensions
  • Developing and optimizing the design of water treatment devices on the basis of the computer experiment design method
  • Pilot testing
  • Verification of the computational models

The computational model for separation is a system of partial differential equations, describing the flow of liquid, which are closed with a set of algebraic equations for calculation of turbulent parameters. The device design was optimized by using a field of centrifugal forces where multiphase mixtures are separated.


Digital Simulation to Solve Real-World Problems

Based on the computational model, a series of computer experiments was carried out to optimize the working processes in hydrocyclone devices for water treatment technology. Several optimization stages were applied in the range of various parameters using the computer experiment design method. The computational model is a system of differential equations; the Navier-Stokes equations, selected as primary flow equations, were complemented with the RANS equations for stresses, equations for inter-phase momentum transfer, and the Luo equation for droplet breakup and coalescence. The differential equations were resolved with higher-accuracy finite-difference approximation methods.


Result – New Efficient Solution

Using the optimization results, we manufactured the water treatment devices and carried out the factory and pilot tests at some field facilities. The multicyclones have proved they are operable and comply with the claimed characteristics. To learn more, request information, or make the order, please, go to the Solutions page.

Fluid filtration system