Hydrocyclone Produced Water Treatment for Offshore Developments

Abstract

Abstract Ever increasing water production and more stringent environmental standards have driven up the cost of produced water disposal. What was once a small consideration in the design of production facilities has become a high profile and costly component of offshore production projects. The large space and weight requirement for conventional produced water treatment (PWT) systems (skim tanks, CPI's and flotation cells) could have a large negative impact on the overall economics of a deep water development. Recent advances in static hydrocyclone technology for PWT has added an attractive alternative to conventional systems. In 1985, Conoco installed a small hydrocyclone PWT system on the Murchison platform in the North Sea. The success of that first pilot system has lead to the expanded use of the technology in other locations in the North Sea and the Arabian Gulf. With the experience gained from the design, testing and extended operation of these systems, Conoco has developed a high level of confidence in defining the capabilities and limits of hydrocyclone PWT systems, and the economic benefits possible when applied to offshore projects. projects Introduction Water tends to become the dominant produced fluid as an oil field matures. produced fluid as an oil field matures. With ever increasing water cut, up to 90% or higher, the volume of produced water that a facility must process often far exceeds that of the hydrocarbons - At the same time, concern for the environment has resulted in more stringent standards for discharged water quality. Increasing awareness of the impact of oil field discharges by the industry has accelerated the cleanup efforts. In some cases, self imposed corporate guidelines are more stringent than those allowed by governmental regulations. The combined effect of larger volumes and higher level of polishing has driven up the cost of polishing has driven up the cost of produced water disposal. produced water disposal. Conventional produced water treatment (PWT) systems, consisting of a low pressure separator, CPI and flotation units, pressure separator, CPI and flotation units, are highly space and weight intensive. These system usually require costly chemicals and constant attention to be effective. For offshore operations where weight, space and manpower come at a premium, PWT facilities have become a high premium, PWT facilities have become a high profile and costly component of major profile and costly component of major projects. Furthermore, operating projects. Furthermore, operating experience has shown that conventional PWT systems do not work well on floating structures. Platform movements tend to induce excessive turbulence for good gravity settling in CPI'S, and too wave motion for effective skimming in flotation cells. So what is the alternative for cost conscious operators and the many deepwater developments currently being considered? STATIC HYDROCYCLONE TECHNOLOGY It has been said that "necessity is the mother of invention." P. 473