Formation Testing Strategy Based on Quick-Look Data Evaluation From a Fractured Basement Reservoir: A Case Study From Kharir Field Yemen

Abstract

This reference is for an abstract only. A full paper was not submitted for this conference. In Kharir Field (Yemen, Block 10), major hydrocarbon accumulation is hosted in fractured basement. Along drilled basement sections, only restricted intervals account for flow. Accurate identification of open flowing fractures (amid numerous planar features) is crucial to characterize and monitor non-conventional basement reservoir. At well Kharir-XX, relevant logs were acquired in single run (Resistive-Acoustic Borehole Image, Fullwave Cross-dipole Acoustic, Induction and Spectral GR). Logging program was designed to provide maximal time for flowing intervals identification before decision to perform Formation Tester Run. Acoustic image and Cross-dipole full wave data acquired RIH were sent from wellsite, QCed and processed. Interpretation focused on Acoustic Travel Time Image which is a key parameter for flowing fracture recognition. Wellsite Monopole VDL images were used for evaluation of Stoneley Wave Reflectors. High-definition Array Induction Log and Micro-resistivity Borehole Imager data were logged whilst POOH and sent at regular intervals for evaluation. From above logs, fractures that appeared large, continuous and visible on the Acoustic Travel Time (potentially open at borehole wall); with a conductive appearance on micro-resistivity images were located and oriented. These fractures were then ranked taking into account their good match with while-drilling gas shows and increased rate of penetration. From tens of candidate intervals only twelve were selected for testing. Interval Formation Tester was deployed using Dual Inflatable Packer System (1m packer spacing). Borehole images were used to accurately position packers to avoid risking damage or no/lost seal. Formation Tester was run under Aphron mud system (reversible cake). Special clean fluid carriers inflated packers, thus avoiding risk of plugging fluid lines inside the tool with congealing mud. At well Kharir-XX, 80% of selected sampling stations gave reliable formation pressures, pressure transients, fluid gradients, mobilities and representative formation fluid samples.