Abstract

Kuwait Oil Company is developing deep tight fractured carbonate and kerogen rich shale gas plays in northern part of Kuwait. Understanding the flow medium is important to resolve ingress of offending fluids such as water and salt during production history in the vertical/deviated wells of this play.

These unconventional reservoirs have been established to be hydrocarbon producing in several prolific vertical producer wells, without having such early water breakthrough. The tight fractured limestone reservoir is sandwiched between salt-anhydride sequence above (Gotnia cap rock) and Kerogen rich carbonate below. A dedicated casing is set at the top of limestone reservoir with the main objective of isolating the Gotnia section prior to opening the reservoir, as some sequences of anhydrites with calcite stringers in Gotnia are high pressured and prone to high water, CO2 and H2S. Based on the current understanding, main source of offending fluids is suspected to be the overlying Gotnia formation, which has limestone stringers.

Fracture studies from several conventional cores and image log data could not conclusively infer through going fractures into Gotnia, although many sub-vertical fractures of different nature have been observed and interpreted in the reservoir section in these logs.

This paper highlights the approach for detection and characterization of flow mediums, in the near well bore region (NWR) within a diameter of investigation of 3 meters or 10 feet. Results of spectral noise log (SNL), high precision temperature (HPT), pressure and natural radioactivity (GR) of a vertical well logged in shut in and flowing mode helped in understanding different flow mediums such as channel flow, fracture flow and reservoir flow. Thus the detection and characterization of different flow path systems with respect to their spatial dimension and their interactive flow contribution could be ascertained with high confidence.

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