Application of MJPs in Oil&Gas Fields

Abstract

ENI E&P in 1993 launched an R&D project on production boosting using multiphase jet pumps. In these devices a high pressure oil or gas well can be used to enhance both the production and the total recovery from a depleted well. The multiphase ejector is characterized by a simple design, absence of moving parts and small dimensions, coupled with a high degree of reliability and low cost. The main disadvantages related to the use of multiphase ejectors are due to the lack of reliable design methods and to the sharp decrease of the performance when operative conditions change. In the last three years the ejector technology can be considered a standard for ENI resulted in several successful installations worldwide:West Africa (onshore oil wells)GOM (offshore, condensate gas)Italy and Mediterranean Sea (onshore and offshore, wet and dry gases) In the present work a status of these installations is reported, pointing out the following main items:design and installation peculiaritiespredicted and measured performancesoptimisation actions performed during the considered period The results of this review have been used to identify the new strategies on ejector design and operability, which will be also reported. In particular, new design to increase productivity and component operability life is described, together with laboratory test results. Introduction The multiphase ejector or Jet Pump, MJP, is an artificial lift method characterized by a simple structural design, absence of moving parts and small dimensions, which allows easy installation and management procedures during field operations, coupled with a high degree of reliability and low cost of installation, compared to other boosting systems. On the other hand, the ejector is a low-efficiency device: just a small fraction of the power fluid energy (approximately 20–30%) is actually transferred to the low pressure fluid. When the ejector is fed with multiphase fluids, significant modeling problems arise and no established methods are available for the design of multiphase ejectors. Design problems are increased by fluid property changes during field evolution. To cope with all these problems and extend the operative life of the ejector, an advanced multiphase ejector has been developed in order to optimize some of the main geometrical parameters and to improve the ejector performances at varying operative conditions. In this paper, the realization and the field application of this multiphase ejector are described. Multiphase Ejector Characteristics Fig. 1 shows the main components of a JP: the nozzle, the mixing chamber followed by the mixing duct and the diffuser sections. Power fluid, at an injection pressure Pd is forced through the nozzle. As the fluid accelerates because of the area reduction, its kinetic energy increases and the pressure decreases to the value Pn at the nozzle exit section. The power fluid and the produced fluids then enter the mixing chamber were the pressure reaches its minimum value, Ps. Inside the mixing chamber, mixing duct and diffuser the pressure increases and the gas-liquid mixture leaves the ejector at a pressure Pl. The main concern about actual multiphase ejectors is the limited capability of the hardware which have to be adjusted when boundary conditions change (i.e. well depletion, water cut and/or GOR variation, production profiles). To this aim, the present multiphase ejector has been designed to be adaptable in terms of:nozzle diametermixing chamber lengthmixing tube length and diameter, with the objective of improving as much as possible the performance of a conventional ejector.

An Overview of Multiphase Pumping Technology and its Potential Application for Oil Fields in the Gulf Region

“…The motive fluid can be another well fluid, separated gas or water from a water injection system [3,4]. A motive fluid is accelerated through a nozzle.…”