Efficient Formation Testing and Data Interpretation Using Advanced Probes and In-Situ Fluid Property Evaluation

Abstract

Deepwater environments pose significant challenges in design and execution of comprehensive yet cost effective formation testing programs. For a recent deepwater appraisal well, pre-job modeling, advanced formation testing technologies, and in-situ fluid analysis were utilized to design and execute a formation testing program which provided significant improvement in the quality of data and fluid samples acquired, as well as significantly reduced time required for testing. Multiple PVT and bulk samples were collected with an advanced focused sampling probe, providing an average pumping time of 3.5 hours per sampling depth with sample contamination as low as 1%. This compared favorably to nearly 9 hours per sample depth, double the volume of fluid pumped, and fluid contaminations of 8-14% observed in the previous appraisal well using an unfocused probe. The low contamination improved the accuracy of real time Downhole Fluid Analysis (DFA) measurements such as density and viscosity, hydrocarbon composition and GOR performed with an advanced in-situ fluid analyzer. Fluorescence and reflectance detectors within the same tool were used to evaluate fluid phase state. Another important component of the acquisition were several Interval Pressure Transient Tests (IPTT) performed to evaluate horizontal and vertical permeability. An advanced 3D radial probe was selected over a conventional Dual Packer to perform these tests. The 3D radial probe was more time-efficient, provided better quality buildup data including vertical interference data (VIT), and presented lower operational risk. Real time measurement of fluid viscosity enabled the immediate estimation of permeability. Zonal permeability and permeability anisotropy (kv/kh) for the tested intervals were interpreted from the pressure transient responses of the radial probe and observation probe