World population is rising at a rapid rate and the need for energy is increasing, particularly by the highly populated developing countries. Oil and gas form at present 63%of the total world primary energy demand. The proven world reserves for oil and gas, although relatively high, show that at present level of production will not last more than 41 years (oil) and 64 years (gas) on average. The proven oil reserve to production ratio (R/p) for Europe is much lower and is close to 8.2 years. There is therefore a need for this valuable source of energy for the foreseeable future. The low price of oil is causing the development of many marginal oil and gas fields to become uneconomical. The response to this challenge is to achieve cost–reduction, improve recovery from the fields and to take strategic steps to survive and improve profitability. The production and total recovery from many fields can be enhanced by using a boosting system downhole or at wellheads for production systems located subsea, offshore or onshore. The cost of some boosting systems is, however, relatively high, making them uneconomical. Factors such as fragmentation of reservoir or production from satellite fields result in some wells having high pressure, while others may have low pressure with restricted production. A team of engineers at CALTEC have developed a simple cost–effective system which uses energy from high–pressure wells to boost production and recovery from low–pressure wells. The system is patented by CALTEC and is named ‘WELLCOM’, short for well commingling system. The main advantages of the system are: increase in production and revenue; simplicity; having no moving parts; low capital cost, with the payback achieved often within a few weeks or months from the added revenue. A further benefit of the system is that it uses the energy from HP wells that is usually wasted through choke valves. This paper describes the system, the background to its development, its performance and applications. A team of engineers from CALTEC won the 1998 Royal Society's Esso Energy award for the development of the WELLCOM system.