Applications of wireline formation testing (WFT) and downhole fluid analysis (DFA): Reviewing the importance of this technology in reservoir evaluation

Abstract

Wireline formation testing (WFT) is an important aspect in both exploration and production phases for reservoir evaluation. WFT tools can directly measure the formation pore pressures and then the pressure profiles are used to identify the type of pore fluids, identify the fluids density, fluid contact estimation, depletion and overpressure quantification, detection of continuity and connectivity of the reservoir in both the lateral and vertical directions. WFT is mostly used to evaluate formation permeability and taking fluid sampling.

The new generation wireline formation sampling tools include a downhole fluid analyzer (DFA), which can analyze the composition of fluids in real-time and under in-situ conditions and also can measure the spectra of crude oil. So, in result, it is possible to identify fluid compositional variation and reservoir vertical compartmentalization. The analysis of fluid composition depends on the optical absorption, and the mass fraction estimation for the three groups of hydrocarbons: methane (C₁), C_2-5, and C₆ + along with CO₂ as well. Also, it provides formation fluid properties like gas oil ratio (GOR), density, viscosity, and resistivity. The DFA results are subsequently validated and modified by laboratory analysis on the fluid samples attained from the formation.

The potential advantage of early measurements demonstrates that the DFA is a good decision-making solution in early stage without waiting for the lab result for months. Also, early DFA measurements are important in completion designing and well testing, the establishment of fluid gradients in reservoirs and connectivity, identifying and validating fluid distributions and reservoir structures.