The Development of a No-Moving Part Choke Valve for Oil and Gas Wellhead Flow Control

Abstract

ABSTRACT A vortex choke valve is being developed to combat the erosive nature of wellhead flow. A spin off from research carried out for the British Nuclear industry, the valve uses a technology known as Power Fluidics and has no moving parts. The vortex choke valve makes use of the pressure drop generated by a spinning vortex flow to control the well fluid rather than the variable orifice found in conventional chokes. In this paper the development programme is reviewed and its implications for increased valve lifetimes and lower maintenance costs are discussed. INTRODUCTION The erosion damage suffered by conventional choke valves in wellhead flow control applications is a common problem. The basiccause is straightforward. High velocity particles of solid material impinge on the control surfaces of the valve causing degradation of control, or on downstream pipework causing qaterial loss which could lead ultimately to failure to atmosphere. Advances in choke technology have concentrated on providing hardened ceramic inserts for wear resistance and designing better flow paths for the well fluid. The rewards sought are to produce a longer choke life which in turn reduces maintenance costs and downtime. However, the fundamental method of providing the flow control and Pressure loss remains unchanged; a variable area orifice. The nuclear industry has similar pressures to those encountered in the petroleum industry. It too requires high reliability and long lifetimes from process equipment since maintenance is costly or sometimes impossible. This has led to the development of a technology known as Power Fluidics for use in nuclear processing plants. The philosophy of Power Fluidics is to provide control of liquids and gases without the use of moving parts in contact with the process fluid. This is achieved by using the properties of vortex flow, jet entrainment and other basic hydrodynamic forces to effect control. By having no moving parts and simple geometries, Power Fluidic devices are inherently reliable and maintenance free. One such device is the vortex valve. Originally developed to provide control of ventilation processes in nuclear plant, it uses the properties of vortex flow to provide a variable pressure drop. The concept of flow control is therefore radically different to conventional variable orifice techniques. This background vortex valve technology is now being developed for use as flow control chokes for the petroleum industry. The aim of the development programme is to fully explore the potential of the vortex choke valve to offer an improvement in the lifetime of chokes in erosive environments or to provide economic solutions to well control problems which cannot currently be addressed by conventional chokes, such as high pressure wells or deep water locations. This paper describes the vortex valve technology, the aims of the development programme and some of the results from the first two stages. Finally, the options for installation are discussed. First, a look at the basic vortex valve Technology.