Unconventional fractured Najmah-Sargelu (NJ-SR) and tight carbonates of Middle Marrat constitute Jurassic reservoirs in Minagish Field. Although NJ-SR oil was discovered in mid-eighties, reservoir development remains a challenge in this field where exploratory delineation wells have been drilled until 2002. The reservoir characterisation difficulties in this unconventional fractured reservoir include large well spacing, field compartmentalization, low resolution seismic and oil based well logs besides drilling problems. Therefore, understanding of the productivity controls is primarily based on the image logs and core data collected in vertical exploratory or Marrat development wells. Based on these data in Minagish and adjoining fields, supplemented with seismic facies analysis for identifying sub-seismic ‘fracture corridors’, a regional 3D Discrete Fracture Network model (DFN) was built for West Kuwait in 2004. It thus became feasible to place a Marrat well through NJ-SR fractured area or even to intercept a fracture corridor using a deviated well profile. Yet, since the model was largely conceptual, a quantitative validation was planned through acquisition of NJ-SR core in such wells, followed by core orientation using Goniometry technique and detailed core to image log fracture calibration to understand relationship between large and small scale features and their role in productivity.

First such deviated well was successfully drilled near a fracture corridor and cored using ‘half-moon’ core barrel technology despite repeated core jamming. Core was oriented using goniometry technique and striking parallelism was observed between the image log based and core based fractures. However, the well could not be tested in NJ-SR and was completed in Marrat based on reservoir considerations. Similar core-based fracture characterization was successfully done in second such deviated well that traversed through a deformation zone further away from a fracture corridor. The well has recently been tested and produced oil from NJ-SR reservoir fulfilling combined objectives of appraisal and development of multiple Jurassic reservoirs. Present paper provides a detailed account of these fracture characterization efforts through goniomentry and core to image log calibration for understanding the productivity controls, and discusses further well design optimization possibilities.

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