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Advanced multilateral well drilling & completion requires the application of innovative technologies while drilling to place the well in sweet spots by managing all the geological uncertainties. The smart level-4 multilateral well with dual stacked lateral was drilled by integrating advanced Real-Time geo-steering formation characterization along with geochemical, advanced gas analysis and seismic data interpretation.The Burgan reservoir consists of vertically stacked channelsands associated with geological heterogeneities along with series of fault networks connected to the aquifer at the bottom. The reservoir contains ultra-high water mobility with down hole oil viscosity of about 40cp enhances water breakthrough and requires customized ICD and ICV completions to enhance dry oil production and maximize oil recovery. Real-time geo-steering performed on Multi-lateral well by utilizing advanced technologies including High resolution Geochemical Analysis has been utilized in Real-Time to identify "geochemical proxies" and allow geochemical steering, distance to boundary tool using 4 resistivity curves with deep spacing Geosignal, At-bit measurements and density image to correct well positioning and locating faulted areas. The pre job planning had two components such as: (i) building a geosteering model based on offset well logs, geological and geophysical information and (ii) 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: (a) detailed lithological variations generally beyond the resolution of LWD logs, (b) detailed mineralogy to determine the diagenetic overprint and (c) depositional environment of different Burgan sand facies. Continuous interpretation and integration of XRF and petrophysical analysis supported by LWD data was a key factor for real-time geosteering operation. Such integrated approach also resulted in successful placing the wells with maximum reservoir contact and 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.

In the Minagish field, the Shuaiba formation has very low porosity and permeability, However, the presence of shrinkage cracks, joints and fractures make it ideal disposal zones. Karsts feature south east of the Minagish structure, containing an abundance of fractures and dissolution channels, have been identified for disposal. Karsts are formed by the passage of meteoric water through the carbonate rock and dissolved the rock as it passed. In the areas with significant dissolution, the formation has collapsed due to weight of overburden, creating areas of massive fracture and faulting. The karsts area have been successfully targeted with 2 horizontal wells drilled within last three years, with disposal capacity of 30000 to 40000 bw/day per well. Seismic attributes are one of the most routine technologies applied in geosciences interpretation and analysis of 3D seismic data, contain incredibly rich information in terms of amplitudes, frequency, geometry and texture. Since seismic attributes are sensitive to spatial variations in subsurface, these can acts as guide for horizontal wells specially in complex and unpredictable area. The Coherency Cube quantifies the measurement of local waveform similarity. Since it provides spatial change in the seismic waveform hence it can be related to sub surface features like Geometry of the subsurface reflectors, Faults, Pinchouts, Unconformities, changes in lithology, Changes in pore fluid density, Changes in elastic properties as well as depositional environments. In present case study seismic attributes specially coherency along with other data was applied to identify the shale dominated area and limestone formation near collapsed feature. The horizontal well targeted fractured limestone near the edge of collapsed feature. The drilling data was correlated with seismic attributes to identify the shale dominated area and Shuiaba limestone near the collapsed feature. It was observed that Shuiaba limestone was severely eroded inside the collapsed feature and filled with overlying base Burgan shales and silts. With this information well was side tracked toward the limestone formation and completed with its objectives. By correlating the seismic attributes with real time drilling data, more accurate information about the spatial variation in the vicinity of well is available. In case of drilling complications these information are very useful to find out best possible trajectory for side track as done in this Shuaiba disposal well. Hence seismic attributes can be applied not only for identifying the location but also for providing support during horizontal drilling. Above technique can also be applied in planning the different legs of multilateral well.

The Middle Cretaceous Burgan reservoir in Minagish Field exhibits variable depositional clastic settings ranging from "Fluvial", "Fluvio-tidaT to "tidal wave sands". The sand bodies of Upper Burgan reservoir are highly heterogeneous in terms of the stratigraphic architecture implying extensive lateral facies variations, stacked sand bodies and varying petrophysical properties. Modeling the target sand channels and optimizing subsurface well trajectory with maximum reservoir contact requires "high resolution" geological and seismic data integration in order to minimize uncertainties related to correlations of timeline surfaces, channels geometries and sub-seismic fault network. Since traditional logs could not capture the textural differences characterizing the reservoir zones, Real-time formation evaluation and geosteering challenges addressed to ensure the successful drilling and completion of level-4 "Multi-lateral" producers. A combination of the latest advanced geo-steering technology used in this well including Rotary Steerable, Distance to Boundary and Sourceless petrophysical evaluation while drilling. The uncertainties in the geostatistical models were further reduced while drilling the first lateral section (LAT-0) by deploying extra deep azimuthal resistivity measurements. It has a higher precision and accuracy to consistently mapping the rise in OWC due to production operations with depth of detection up to 100 feet TVD above and below the well path and maintaining a standoff from the top of onset transgression undulating surface with poor sand facies. The resultant mapping window provided accurate guides to update the geo-models. The formation evaluation along with borehole imaging and geo-correlation assisted in identifying a fault having a great impact on well positioning of the upper lateral due to a high amount of throw fault with significant formation dip changes. This is in turn eliminating risks of geosteering in such a complex heterogeneous reservoir. The integrated approach utilizing geological, seismic, petrophysical and geosteering data provided better understanding for well positioning while drilling and achieving the MRC without exiting the sweet zones of targeted upper and lower Burgan sandstone in Minagish field and enhanced water free oil production.

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