Abu Dhabi Company for Oil Operations (ADCO) UAE have been field testing and assessing the multiphase flow meter (MPFM) technologies as an alternative well testing tool for the past decade.
Currently, there are not any governing industry standards existing for the MPFM technology. Commercially available industrial MPFMs each apply their own unique technology and principle, which are sensitive to the fluid properties and flow regimes, which ultimately dictate the final MPFM reading. Every reservoir has its own characteristics and behavior, which changes with time and ultimately affects the MPFM measurements. Hence the selection of the MPFM suitable for its exclusive application is critical.
In order to implement and apply with confidence the MPFM technology and achieve optimal results, field trials are necessary for both the operator and the engineer. The field trials will further develop the knowledge (its limitation, potential and its behavior) of each of the MPFM's technologies available in the market.
This paper describes ADCO's experience and the methodology that was applied for the selection of MPFM and there upon its accuracy, reliability and its performance to develop confidence of the application and its usage.
MPFMs are no longer a novel technology or a myth; they are now being accepted as testing tools and are becoming common element in various well testing programs. They are being deployed gradually and the number in the fields increasing systematically. The benefits for the MPFMs are becoming transparent to the end users, however, due to its complexity and the variety of the technologies that it offers, there still exists some resentment for the use of it.
Each of the technology is unique for the detection of the multiphase flow rate and requires its unique knowledge and understanding. The application and implementation of the present generation of most MPFMs is not to "install and forget".
For reservoir management, the single most important requirement is monitoring the performance of its producing wells accurately. This provides insight to the reservoir behavior, sustaining of the production capacity, knowledge on the remaining reserves and thus enhancing the maximum recovery.
Traditionally, metering of the multiphase flow is carried out utilizing two or three phase test separators (full or partial separation) using single-phase flow meters installed on the outlets of the oil, water and gas legs. These have an acceptable accuracy limit, which depend on operator's skills and its maintenance work. This varies for oil (min. +/−5% to max. +/− 10 %), water (min. +/−5% to max. +/−60%) and gas (min. +/− 10% to max. +/−15%). These wide ranges in the measurement accuracies are depended on various factors. This approach, i.e. the use of the test separators, is practical and the accuracies acceptable during early production. However, as the fields mature and as the water cut increas es, yielding changes in the flow regime and the fluid characteristics, the test separators are less accurate in that they become non-adaptive to these changes. They also have trouble in handling slugging flows, wide variations in water cut and physical changes in the fluid properties. The latter affect the performance and the accuracy of the measurements due to the gas under carry in the liquid and liquid carryover in the gas. Multiphase flow meters, on the other hand do not rely on full separation (100%) of the fluid and operate under various conditions for the multiphase flow measurement.
Due to the changes in the reservoir behavior and characteristics, the reservoir models require regular updating and history matching. Due to the complexity of modeling in today's age, there is a requirement for a faster, accurate and reliable data, in order to adequately update, calibrate and tune. MPFMs are attractive for their fast response, fast deployment and short duration tests, which provide acceptable data for an accurate and reliable reservoir forecast. In addition, the growing need to increase productivity and field development and tie-in of satellite fields to existing processing and export facilities (to reduce the capital and operating costs) are leading major operating companies to consider the use of multiphase flow meters as a better alternative than the test separators.
This paper describes the ADCO field applications and trial methods of the MPFM technology.