High water cut


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Problem


In modern oil production environment, the water cut of oil fields can reache 80–98 %. Such high ballast water content causes significant capital expenses for production fluid gathering and field transportation facilities where water fills 80 % of their capacities which do not contribute any financial values to the project. As a result for some oil fields it is becoming non-profitable; their development stops, and the accumulated infrastructure becomes a non-demanded burden.


Alternative Solutions


To address the task of cutting down the non-productive capacities for pumping ballast water with oil, early free water knockout systems are used. Usually, a booster pump station facility with a free water knockout production facility (FWKO) is a basic decision. OZNA primary water knockout solutions can include technologies based on either bulk-capacity apparatus, such as end-of-pipeline tubular phase splitters, or standard horizontal separator samps. It helps to get rid of the ballast water and inject it into the formation even before transporting to the central oil gathering and treatment facilities, thus decreasing the capex for field and inter-field pipelines. However, the field gathering system remains highly loaded with the ballast water, which is not always advantageous; moreover, when operating wells in the salvo modes, the water treatment quality in terms of oil and mechanical admixtures content is insufficient when using such equipment.

 

Solution

The solution offered by OZNA is a distributed injection system based on FWKO with the lower-capacity for well pads, which provides preliminary knockout of free water immediately at well pads and injects it into injection wells by using modular stations with horizontal pumping units. The FWKO for well pads includes a compact horizontal separator with high-performance internals and an in-stream water treatment unit based on sorption and cyclone technologies. The distributed injection system does not need a single large modular water injection station designed for peak performance, and permits to knockout the free water and to build up the injection with modular horizontal pumping unit immediately at well pads, while distributing the capex load based on the growing water cut.


Result – New Efficient Solution


The brightest example is to reduce the water cut from 99 % to 98 %. Simple math shows that 1 % in water cut here with the same amount of oil halves the total amount of liquid, thus radically decreasing the requirements for the oil gathering and transportation system performance and saving on capex. Moreover, the distributed injection system will permit to replace centralized water gathering and injection with shorter, lower-capacity injection clusters with high pressure waterlines, thus reducing the cost of pipelines in terms of wall thickness and total length. We estimated that savings on steel only for a typical field with a peak production of 3 mln. t may exceed 500 mln. roubles, apart from considerable savings on the construction of line facilities in marshy environment.




Modular cluster pump station (MCPS)


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