Fluid characterization and mapping in the Greater Burgan field was performed using an extensive database of PVT analysis reports. This enabled an enhanced understanding of the distribution of fluids, in which a lateral compositional gradient was discovered.
Summary information of 381 samples that had been acquired from 1938 to 2017 was gathered and plotted against both true vertical depth subsea (TVDSS) and spatial directions (northing and easting). Correlations of average fluid characteristics of all these samples against TVDSS and the direction in 15° north-east was determined. The API gravity, oil viscosity and solution gas to oil ratio were parameterised as a function of horizontal direction and depth. The saturation pressure was modelled using a correlation, being a function of the other variables modelled in space. Over 30 correlations published in the literature were ranked, and the best-fitting correlation was selected to predict the saturation pressure distribution spatially. All these properties were mapped by formation.
This is the first study in which the existence of this lateral gradient is fully described. This work is being used as a reservoir management tool to predict zones close to or below the saturation pressure and reduce the production offtake from those zones and to develop an appropriate sampling plan. This work has also help manage access to the heavy oil zones.