The Burgan Reservoir having vertically stacked channel sands, fault network connected to the aquifer and hydrocarbon viscosity of about 40cp has the potential for premature water breakthrough leaving behind zones of by-passed oil. Placing and completion of horizontal wells in such reservoirs is a challenge necessitating collaborative approach from petroleum geoscience, reservoir engineering and petroleum engineering. The current work scope describes placing of the horizontal wells in this kind of heterogeneous reservoir through an integrated approach involving all segments of petroleum geoscience. The workflow incorporates utilization of real-time geochemical analysis (XRF) on rock cuttings, LWD data and real-time petrophysical evaluation to geosteer the smart multi-lateral wells in zones of highest flow potential and less structural complexity. The pre job planning had two components such as:

  • building a geosteering model based on offset well logs, geological and geophysical information and

  • preparation of geochemical model based on XRF analysis of core chips from offset wells.

The later model was calibrated through logs and utilized further to predict key rock attributes such as:

  • detailed lithological variations generally beyond the resolution of LWD logs,

  • detailed mineralogy to determine the diagenetic overprint and

  • depositional environment of different Burgan sand facies.

The real-time geosteering operation was guided not only by the LWD tools but also through the continuous interpretation and integration of XRF and petrophysical analysis. Azimuthal Litho-density Images were interpreted in real-time not only to understand the formation dip but most importantly to identify cluster of fractures/faults, which was further complemented with XRF and seismic data analysis. Nature of the fractures/faults (open or healed, contribution to porosity and communication with water zone) were inferred from the several cross plots and Dipole-sonic data in real time and further validated with XRF obtained elemental markers. Several other cross plots along with quick volumetric analysis provided information on rock quality/type and fluid saturations.

The integrated approach not only has resulted in successful geosteering and placing the wells with maximum reservoir contact but also was very instrumental for (i) isolation of potential trouble zones, (ii) segmentation of horizontal sections and (iii) optimization of nozzle sizes of the ICDs and hence planning of smart completion designs.

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