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.

No abstract

No abstract

No abstract

The oil and gas industry drills wells in harsher conditions year after year. Besides drilling challenges, these harsh conditions make it difficult to obtain accurate and consistent petrophysical measurements, particularly sonic and density data, because of high temperature, high pressure, and high mud weight (MW) in highly deviated wells. Such conditions, in particular the high MW, attenuate sonic waves significantly, affecting the detection of sonic arrivals as well as ultrasonic caliper measurements. In addition, extremely high MW affects density data and invalidates photoelectric effect (Pe) measurements because of the high barite content. The Pe is typically used as an input to volumetric lithology interpretations in a four-mineral model. When the Pe is unreliable, sonic velocities can be applied to the interpretation workflow instead, if they are accurate. This paper discusses engineering solutions for software and hardware challenges and operational and technical aspects of acquiring the sonic log in combination with conventional triple-combo data. As a result of the introduction of a high-frequency sonic logging-while-drilling (LWD) tool and advanced processing techniques, signal coherence tripled from an initial 0.3 (30%) to almost 0.9 (90%), significantly improving the quality of the data. Additionally, ultrasonic caliper coverage quadrupled from 25 to 100% of the logging interval, compared to previous runs in offset wells. Furthermore, acoustic velocities play an important role as an input to geomechanical models, which study the stress regime and allow for estimation of rock moduli. Thus, an azimuthal acoustic tool measuring velocities 360° around the borehole provides information on formation stress anisotropy. Estimating formation rock moduli requires accurate density and acoustic properties provided by high- frequency sonic measurements. For wells with inclination greater than 60°, it becomes difficult to run wireline logging. Therefore, LWD quad combo with a high-frequency, azimuthal acoustic tool is a viable solution for this environment. Additionally, it is advantageous that formation-evaluation measurements can be acquired while in drilling mode, saving rig time and reducing well-construction costs.