In a gas-condensate field in Kazakhstan, advanced production logging tools and techniques were used to assess well productivity, characterize flow profiles, and determine hydrocarbon saturation pressure at downhole well flowing conditions.
The exploration and appraisal wells produce from a complex carbonate reservoir. To assess well productivity, each well was perforated and tested across each formation separately. Intervals to perforate were selected based on petrophysical log evaluation, core analysis, and the results of selective testing with a wireline formation tester. While testing these wells, production logging data were acquired at different downhole flowing pressures and a detailed analysis of gas holdup measurements with optical probes enabled the determination of the dew-point pressure of produced gas-condensate.
Such analysis is beneficial, especially when pressure/volume/temperature (PVT) analysis of produced fluid is not yet available for exploration and appraisal wells. Further comparison of wireline-acquired PVT samples showed good agreement between measured dew-point pressure from the production logging tool and PVT laboratory analysis results.
In the field, production logging helped in understanding well behavior by locating producing intervals in wells that have more than one perforated interval or produce from only one long perforated interval that has several producing intervals. Field experience verifies that a properly planned and executed production logging operation can yield invaluable early information for key investment decisions and complement the results of the well test.