| Popis: |
The new generation of wireline formation testing fluid analyzer presented in this paper integrates in-situ optical fluid analysis device with a oscillating mechanical sensor providing downhole density and viscosity measurements in real-time at reservoir conditions. Fluid density is measured primarily by measuring corresponding changes in the vibrational frequency of the oscillator while viscosity is determined primarily by monitoring the decay time of the resonance. The formation testing wireline tool was utilized in combination with the new optical fluid analyzer to identify the fluid types downhole in the complex lithology reservoir drilled with an oil based mud. Focused sampling was essential to reduce mud contamination thereby enabling accurate determination of fluid compositions and properties such as density and viscosity.The in-situ optical fluid analyses provide the quantitative hydrocarbon compositions in terms of C1, C2, C3-C5, C6+, CO2 along with the water fraction in both oil based mud (OBM) and water based mud (WBM) wells. Gas Oil Ratio (GOR) or Condensate Gas Ratio (CGR) is also computed from the optical analyses. The density measurement provided by the mechanical sensor brings additional value in comparison with pressure gradient analyses and is critical to evaluating thin, tight or depleted flow units. The viscosity measurement, the first downhole measurement of its kind, is particularly important as viscosity is one of the key fluid properties that directly affect the producibility of the flow units.A field test was conducted in an onshore reservoir in the Sultanate of Oman. It was performed in a well having oil, gas and water zones. As a result of the quantitative downhole compositional analyses and fluid property measurements, single phase samples with low mud filtrate contaminations were collected. The PVT laboratory results served as a valuable comparison for the fluid composition as well as density and viscosity measurements. |
