No abstract

The in-line scavenging of hydrogen sulfide is the preferred method for minimizing the corrosion and operational risks in offshore oil production. We model hydrogen sulfide removal from multiphase produced fluids prior to phase separation and processing by injection of triazine solution into their gas phase. Using a kinetic model and multiphase simulator, the flow regimes, amounts, and composition of three phases are determined along the horizontal and vertical flow path from subsea well to separator tank. The flow regimes were found to be slug flow or intermittent flow. The highly reactive triazine is destroyed on contact with water phase flowing near the wall. We have simulated the hydrogen sulfide concentration profiles for different amounts of gas injection. The results are compatible with the available field data from an offshore oil well and are useful in determining the injection rates of expensive chemical scavengers and optimal gas injection rates.

In this paper, a virtual metering system (VMS) for oil and gas monitoring based on a differential pressure transducer (orifice plate, venturi or nozzle) is presented. The model for the measuring device considers one-dimensional subsonic flow of gas, oil and water. Oil and water are considered to flow with a single velocity (homogeneous flow), while relative velocity between the gas and liquid phases is taken into account by means of a slip ratio calculated with Chisholm's correlation. Neglecting friction, mass transfer, compressibility and variations in the slip ratio along the converging portion of the flowmeter, it is possible to integrate the mass and conservation equations to obtain a generalization of the mass flow versus pressure drop relationship corresponding to a differential pressure flowmeter for multiphase flow. The total mass flow depends on a set of variables evaluated at operating condition: density and viscosity of the liquid and gas phase, mass quality, pressure drop across the flowmeter and geometry (contraction area and beta factor). The determination of the fluid variables at operating condition is made by using a black oil model and a set of variables at standard condition that characterizes fluid composition, being the most important GOR, BSW and densities of the individual phases. An experimental campaign was carried out at different wells located at Urucu field, Solimões basin (Amazonas, Brazil), using orifice plates. The total mass flow rate and the volumetric flows for each individual streams at standard condition calculated with the VMS showed an excellent agreement with the experimental data.