The Offshore Technology Conference (OTC), held each year in Houston, Texas, US, is one of the world's leading upstream oil and gas events. Before OTC 2020 was cancelled due to the COVID-19 pandemic, Oilfield Technology contacted a range of key players in the upstream industry and asked for their insight on the latest technologies that were due to be showcased at this year's OTC.
In this submission, Sven Olson, Leistritz Advanced Technologies Corp., USA, describes the applications of twin-screw pumps in the upstream industry.
Multiphase pumping technology has advanced substantially in recent decades. The twin-screw pumps manufactured by Leistritz that are in use today have a larger capacity, are more gas-tolerant and designed for much higher pressures than previous versions. The automation and controls, together with packing of systems, enables unmanned operation in remote fields. Large gas volumes can be handled by pumps operating in parallel, which can remove the need for extensive bulk separators and allows the centralised processing of oil and gas.
A basic function of multiphase pumping is to lower the gathering and wellhead pressure, which enhances production and total recovery. The resulting reduced bottomhole pressure leads to improved well inflow, which in turn increases the submergence of an electric submersible pump (ESP) or sucker rod pump which can now operate safely above the bubble point pressure. Additionally, savings are realised in power consumption, and the improved reliability and service life of the downhole pumps results in fewer interventions and work overs.
Figure 1. Twin-screw pump for transfer of oil/water emulsion from a two-phase separator liquid leg.
The twin-screw pump is designed to meet challenges posed not only by a high gas/oil ratio (GOR) and liquid logged gas wells but also from pumping heavy oil, bitumen and oil/water emulsions. This feature makes the pump suitable not only for a number of applications in the upstream industry, but also in the midstream sector. The growth of pipelines as result of increased domestic oil production will result in an increased demand for pipeline pumps. While screw pumps have traditionally been applied more commonly in laterals than in trunk lines, there are now signs that positive displacement pumps such as screw pumps – rather than hydrodynamic or centrifugal pumps – will be installed. The reason for this is twofold: firstly, a screw pump can tolerate gas break out in condensates and the lighter hydrocarbons resulting from the growth in shale oil production. Secondly, the fact that a screw pump achieves higher total efficiency when pumping heavier crudes is an important factor as the world becomes increasingly conscious of the need for energy efficiency.
Further downstream, many refineries have recently increased their flexibility when it comes to the crude oil feed stock supply base. This trend is accelerating demand for positive displacement pumps, most notably screw pumps, that can handle crudes with large variations in viscosity through the use of variable speed control, and precise control flow rates. Typical examples are pumps for the loading and unloading of barges and rail tankers, transfer pumps and charge pumps. Traditionally, screw pumps are also used in asphalt and pitch transfer. For several years twin-screw pumps have also been successfully used as flare knockout (FKO) drum pumps, based on the pump’s ability to handle gas-entrained liquids. In contrast to the widely-used centrifugal can pump, which needs a well or pit for reasons related to the net positive suction head (NPSH), the screw pump is installed on grade.
Read the article online at: https://www.oilfieldtechnology.com/offshore-and-subsea/13052020/otc-technology-review-leistritz/