Research has been undertaken in the development of an improved wireline formation fluid sampler and tester. Formation fluids are pumped from the formation to the well bore at surface controlled rates. The formation fluid characteristics are measured and surface monitored. When the mud filtrate has been removed a sample may be taken. The resistivity, conductivity and temperature are measured and hence the formation water salinity may be determined.

Flowing fluid density is measured and thus oil, gas and condensate may be distinguished and the API gravity estimated. There is almost no theoretical limit to the number of samples that may be taken and therefore the entire well may be tested and the salinity and pressure profiles recorded. The use of controlled flowrates to match the reservoir deliverability and the surface recording of flow pressures allows multi-rate testing, the determination of permeability and formation damage. Since the reservoir pressure may be measured after repeated small fluid volumes are taken, the problem of supercharging or depletion, that often invalidate present wireline measured pressure profiles in low permeability formations, may be avoided. An isolation valve is used to trap a known volume of hydrocarbons, taken under minimum drawdown, which is then expanded to determine the compressibility and bubble-point. These tests may be repeated to ensure accuracy.

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