Abstract

Hydrocyclone technology has been successfully applied to standard oilfield production separation in the North Cowden Deep Field of West Texas. A hydrocyclone was successfully tested as the primary means of water separation for a high water cut electric submersible pump (ESP) well, thereby eliminating the need for expanding the conventional water separation and handling facilities at the recipient battery. This hydrocyclone system was environmentally and economically preferred over conventional systems. A permanent unit has since been installed. With its feasibility proven, the hydrocyclone has countless applications to standard oilfield production separation; its proper use will substantially reduce capital investment for facilities and lower operating expenses for many oilfield leases.

Background

Many oilfields produce large quantities of water. Naturally water driven or artificially waterflooded leases often produce upwards of 90%. Therefore water separation and handling are major components of surface production facilities. Conventional onshore systems include gravity separation vessels, such as free-water knock-outs (FWKO's) and heater-treaters, followed by water tanks and transfer pumps. The investment for these facilities, and the expense required to operate them, is substantial. A less expensive means of water separation and handling is desired.

A hydrocyclone separation system is an economically attractive alternative. As per Figure 1, the hydrocyclone is a fluid separation device in which incoming fluid is directed at high speed tangentially into a vortex tube. Centrifugal forces separate component fluids by density. The heavier fluid, produced water, is spun around and down the tube wall. The lighter fluid, oil, is drawn into the lower pressure core and forced upward in a reverse axial flow. There are no moving parts, and the entire unit occupies only a small area (typically less than 30 square feet).

Hydrocyclone technology has long been proven in water cleanup systems. When the hydrocyclone was demonstrated to the ARCO Odessa office in 1990, it was presented as a water cleanup technique. The technology was impressive, but there was no recognized economic application for it locally. That is until we realized its application to standard oilfield separation.

When the waterflood response on a particular lease required expansion of the water separation and handling facilities, we remembered the hydrocyclone demonstration and considered the hydrocyclone as an alternative to the conventional system. In water clean-up operations the hydrocyclone removes residual oil from a stream that is predominantly water. Water separation in high water cut production streams is essentially the same. Subsequent contacts with hydrocyclone manufacturers confirmed the feasibility of this application. We negotiated a test installation and installed a unit at an ESP well. The well produces approximately 1500 gross bpd at 95% water. The downhole ESP served as the pump source, providing the surface hydrocyclone with a continuous stream of pressurized produced fluid. The hydrocyclone successfully separated 80% of the water and thereby eliminated the need for expanding the conventional separation and handling facilities. A permanent hydrocyclone has since been purchased and installed.

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