Experience of Application of Extended Logging Suite and Formation Testers for characterization of Jurassic Age Deposits of the Em-Egovsky Field

摘要

In a recent Em-Egovskoe well an extended logging suite was performed with the aim to evaluate the petrophysical properties of Jurassic and Paleozoic formations as well as to improve the structural geological model of this part of the oilfield and to do detailed characterization of the dynamic model by desired properties of formations and fluids. Apart from a standard “triple combo” logging suite the following advanced technologies were applied in the well: neutron-gamma spectroscopy, nuclear magnetic resonance, formation micro imager, formation testers in different modes of reservoir and fluid properties evaluation. Noteworthy, the zone of interest was considered to contain only oil-saturated reservoirs – no gas cap was expected. Indeed on the initial triple combo log data there were no routine gas attributes were observed. Gas-saturated reservoirs were only observed based on integrated analysis of standard and advanced log data, particularly, nuclear magnetic resonance and cross-dipole sonic measurements. Gas-saturated intervals were fully proven by formation tester using downhole fluid analysis (DFA) As a result, one of the Jurassic layers was acknowledged as gas/gas-condensate saturated down to the bottom and the rest of Jurassic intervals were found to be oil saturated. The Abalak formation was also encountered in this well and evaluated. Thin carbonate streaks were identified with the micro-imager and were tested with the dual-packer module of the wireline formation tester. The result was the first ever Abalak oil sample in this field. Furthermore, based on pressure transient analysis of the build-up from the pressure test it was suggested that these tight streaks are laterally discontinuous. Finally, we created a stress profile in the Jurassic and Paleozoic layers. Based on formation micro-imager and acoustic scanning measurements the maximum horizontal stress directions and magnitudes were estimated. Then dual-packer formation tester micro-stress measurements were made to acquire direct measurements of fracture closure pressure. These measurements were used to calibrate our stress model.