Maximizing sustained well productivity from smart multilateral wells in heterogeneous reservoir completed with Inflow Control Device completion (ICD) and smart completion requires effective filter-cake cleanup to ensure uniform inflow contribution from entire horizontal section. The specially designed reversible invert emulsion Reservoir Drilling Fluid (RDF) along with filter-cake cleanup agent were utilized in drilling and completion of Kuwait's first Level-4 smart multilateral well in Burgan reservoir of west Kuwait. Further the reservoir is having vertically stacked thin channel sands associated with complex fault network makes drilling and completion of multilateral wells challenging and necessitated an innovative Reservoir Drilling Fluid and effective filter-cake cleanup to maximize the completion efficiency. Moreover the combination of high water mobility due to hydrocarbon viscosity ranging from 40 to 60 cP at reservoir conditions and fault network connected to aquifer causes severe premature water breakthrough. The smart multilateral wells have addressed premature water breakthrough problem and enhanced well productivity by facilitating the adequate reservoir management. The horizontal sections of smart multilateral wells were drilled with invert emulsion reservoir drilling fluid and achieved gauged hole which facilitated trouble free ICD completion installation along with large quantity swell packers. Novel filter cake cleanup agent was pumped immediately after running the ICD completion to change filter cake wettability from oil-wet to water-wet for uniform cleanup and thereby regained original reservoir permeability. This has eliminated the risk of formation impairment, ICD screen and nozzle plugging and established excellent well productivity. The well has achieved significantly increased sustained well productivity by having low wellbore skin. The paper covers the selection and design of reversible invert emulsion drilling fluid along with filter-cake cleanup system, well completion operations and long term well performance results.

The Minagish field covers an area of 90 km2, located in south-western part of Kuwait in onshore position. The studied Cretaceous Wara and Upper Burgan reservoirs, deposited in fluvio deltaic environment (clastic rocks), consist of vertically stacked sands with extensive lateral facies variation. Lower Burgan sands are more significant and blocky in nature with little variations in their properties. Reservoirs geometry, their heterogeneities and structural setting are the key issues for the development of the reservoirs. The geostatistical methodology used to simulate a high-resolution geological model representative of the reservoir heterogeneity will be described in this paper. The paper will particularly discuss the techniques used for the integration of seismic attributes to constrain the facies modeling, as well as a nested simulation workflow for a realistic representation of heterogeneities. The three dimensional structural grid was classically based on the seismic interpretation (faults and horizons) and the well correlations. Facies simulation was performed using PluriGaussian functions approach in a non-stationary frame based on vertical proportion curves (VPC) matrix. The distribution has been done separately in three zones: Wara, Upper Burgan and Lower Burgan. For Wara and Upper Burgan zones, nested simulations were used. The lithology (sand or shale) was simulated in a first step, under the constraint of proportion facies maps extracted from seismic data. In a second step, the depositional environment facies were simulated in the sand lithology. These simulations were based on two Gaussian functions to better integrate the various orientations of the different deposits, and their complex spatial relationship. For the Lower Burgan zone, because of the very low variability of the sand proportion, a stationary facies simulation was run, using a truncated Gaussian algorithm. Eventually, the paper underlines the capacity of the PluriGaussian Simulation approach to realistically mimic sedimentary bodies, and to easily incorporate seismic derived information.

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: (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. 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.

TX 75083-3836, U.S.A., fax +1-972-952-9435. AbstractThis paper describes the utilization of Real-Time geochemical analysis to support geosteering of a smart multi-lateral well, located in one of the highest flow potential areas in Kuwait. The Burgan reservoir consists of vertically stacked channel sands along with a fault network connected to the aquifer and contains highly viscous reservoir fluid. This drastically enhances the water mobility, and results in severe premature water breakthrough. Hence, leaves zones of by-passed oil. For optimum reservoir characterization, it was essential to integrate all reservoir-related data from macro to micro scale. X-ray Fluorescence elemental data collected from offset cores were used to predict key rock attributes and calibrated with standard petrophysical logs.The scope was constructing predictive models for the following properties: 1) lithological variations which cannot be captured by other LWD tools 2) detailed mineralogy to determine the diagenetic overprint 3) depositional environment of different Burgan sand facies. XRF elemental analysis while drilling was used to improve borehole positioning, and identify faults in correlation with Image logs. Nature of the fractures/faults, contributing to porosity and communicating with the aquifer, was inferred from XRF-obtained elemental markers. The integrated approach has resulted in successful geosteering and placing the well with maximum reservoir contact. Moreover, XRF elemental markers have been utilized for isolation of faulted and lower reservoir quality zones, splitting up of horizontal sections and optimization nozzle sizes of the ICDs and hence an optimized Smart completion design. X-ray fluorescence analysis on cuttings in Real-Time provides lithological information otherwise not available while drilling. It gives proxies contributing to the identification of faults and reservoir intervals in an otherwise homogeneous sequence. It helps designing the completion string, isolating sections of low quality or potentially producing water.

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.