Predicting problems of offshore gas-oil-condensate fields development

One of the most important problems of offshore gas-condensate field development (were an access to a well head is restricted) - is the accurate record of wells efficiency changes during continuous exploitation. In response to this problem it is necessary to do complex experimental and theoretical researches. On the basis of experimental researches it is possible to predict: gas-liquid flows parameters in vertical, inclined and horizontal pipe sections, in accordance with multiphase “gas-watercondensate” flows; parameters of oscillatory process and the wave effect in multiphase flows. The results of experimental researches make it possible to construct and specialize mathematical models, to provide them with the required accuracy and the ultimate gas recovery.
Materials and methods
The experimental unit, constructed in Gazprom VNIIGAZ LCC and designed to analyze gas-liquid flow characteristics in wells and flowlines, consists of special stands for the exploration: vertical flows; inclined and subhorizontal flows; pipe flows of complex configuration (reproducing the landscape, including seabottom, profile for offshore pipelines); methods of oilfield gas-liquid flows diagnostics; the elastic vibration speed extension in multiphase flows; the influence of different effects on the flow for the purpose of properties amplification. The article provides information about technical characteristics of experimental unit.
Results
The investigative and experimental researches of multiphase hydrodynamics in some onshore fields, that had been done by Gazprom VNIIGAZ LCC, made it possible to increase the predictive efficiency of well operation and field systems in case of availability of fluid phase in the production [3]. The analysis of the results shows that even a little amount of fluid imposes significant constraints on the range of valid operating modes, focusing attention on requirements for rational use of reservoir gas elastic energy in the development stages. In the Kovyktinskoe oil and gas-condensate field the concentration of the condensate is only 45-70 g/m3, the availability of fluid in the production leads to additional restrictions on the rate of recovery and pressures, and presses for the optimization of structures: in a well bores - diametrically and according to the inclination; in the opened-up zones - diametrically, according to the inclination of sizes and lengths; in the flowline - diametrically, according to the lengths and topography of the laying and etc.
Сonclusions
The described research process provides efficiency of the development of offshore gas and condensate fields; the application of the results is necessary during different stages of design, choosing the downhole and field arrangement, operation conditions, management algorithms, under the specific geological and technical conditions, that is able to reduce possible negative influences on the field productivity of wells, pipelines.