Objective/Scope (75) Oilmen have always strived to break technological barriers to reach new heights in searching of Black Gold. In order to create an effort to do so has created world record by drilling the longest Slim Hole Horizontal section in of its deep development well in North Kuwait. The sick well lying dormant was completed as Horizontal Water Injector well through depleted Carbonate zone to augment reservoir pressure and increase oil production in producers. This re-entry well used Ultra Slim drilling technology in order to maximize oil production in the carbonate reservoir. The objective was to support the water injection campaign nearby producer wells in the eastern flank of the field. Limited slim hole logging tool without azimuthal capability and high expectation from client required extra control while drilling with precise geo-steering adjustment. Inability to transmit load during sliding due to sinusoidal buckling in long ultra slim hole, restricts penetration rate and pose challenges to maintain proper wellbore placement. Based on previous experience, we planned to drill this well in multiple runs. Methods, Procedures, Process (75-100) Geo-steering pre well modelling is required to be done prior to job execution. The application engineer also worked based on the offset well drilling data to optimize the bottom hole assembly. There was a concern regarding weight transfer, as Sinusoidal Buckling and the subsequent sliding issues are always difficult for this wellbore size. Ultra Slim Hole tool provides only gamma ray and resistivity logging while drilling tool with the current technology. Log responses incorporated with drilling dynamic and drilling parameters data in real time will be the source and justification for the wellbore placement. Results, Observations, Conclusions (100-200) Slim Hole Motor successfully drilled the long slim lateral section in one run only which otherwise required multiple runs in previous wells drilled by competitors. Despite the challenges, the logging tools allowed proper wellbore placement and wellbore was successfully maintained inside the target porous reservoir. 4.125inch Talon PDC bit endured drilling stresses and OBM helped reduce friction factor and minimize differential sticking while drilling. The well was successfully executed to total depth covered total footage of 4696 feet, making it the longest ultra slim hole horizontal well in the World. The single run job significantly reduced the drilling cost while drilling the Ultra Slim lateral section. The BHA achieved the required sliding capability to steer the well according to geological observations. The sinusoidal buckling concerns were overcome by finding the weak intervals of weight transfer in the BHA and mitigating them with continuously changing the BHA design by reshuffling the drill collars to get the required WOB. Novel/Additive Information (25-75) This will be the world longest Ultra Slim lateral section in single run with no failures.

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The field study is in northern part of Kuwait targeting heavy oil formation, known to be shallow unconventional oil reservoir. It is heterogeneous shallow sandstone reservoir (500ft TVD) with low maturity oil, has low natural pressure, and poorly consolidated. Mud losses known to be the main risk of horizontal drilling in shallow heavy oil environment and the heterogeneous including continuity of the sand are also challenging for geo-steering team in order to place the well in the optimum position. Seismic is not available, however due to high offset well density a good correlation map has been produced. We are using formation tops from offset wells to delineate the continuity of the sand and trend of the structure dipping, we called it as shooting point method, which is assuming the trend of the structure from one offset well to another nearby offset well. The resistivity contrast will be expected to give us around 9 ft depth of detection (DOD) for our Azitrak resistivity tool based on Picasso plot. We made some scenarios for exiting the reservoir and it showed us some early warning 80ft to 180 ft prior to exit the reservoir. We use Autotrak, Azitrak dan Litotrak formation evaluation and density imaging tool to geo-steer and optimally place the wellbore inside 1B sandstone. The expectation of drilling the lateral was below 1000ft MD due to wellbore stability issue. From the correlation of available offset well it is clearly seen, there are two sand bodies in heavy oil target sand. The thickness is around 30-40 ft TVD and the structure was expected to be flat or a little bit dipping down. The well was landed in the middle of 1B, based on correlation of actual landing point log data to the nearest offset wells. Distance to bed boundary (D2B) showed local conductive layer from bottom since drilling the lateral section, which was not the response of base of 1B sand. So it was recommended to go down in stratigraphy in order to place the trajectory at the bottom part of 1B sand. In order to minimize wellbore stability issue along the lateral section, Bakerhughes recommended to maintain consistent faster ROP (80-100ft/hr) and effective hole cleaning. In the middle of lateral section of well B (1750ft MD) the well trajectory was inverted for the optimum production purposes to total depth (2250ft MD). Total lateral length achieved is 1116ft MD which covers 100% of the lateral length. Shooting point method in defining the rough structure trend from one well to another well was effectively applicative in the field, where current structure after drilling the lateral section is almost flat or slightly dipping down same as predicted before.

This paper presents the first utilization of Logging While-Drilling Nuclear Magnetic Resonance (LWD NMR) and azimuthal resistivity inversion to characterize the Zubair reservoir in the North Kuwait. The Zubair formation is a complex sandstone reservoir. In general, in highly deviated wells, formation complexity causes polarization horns in the resistivity measurements. This effect is leading to both inaccurate resistivity values and related saturation calculations. Therefore, LWD NMR which is insensitive to polarization horns was used to accurately calculate saturation values. The accurate saturation calculation values in highly deviated well has been demonstrated in well-A. Subsequently, the NMR data were used to analyze the grain size distribution in the Zubair reservoir to be modelled and correlated to the lateral extension of the sand and shale bodies generated by azimuthal resistivity inversion. The LWD NMR tool was deployed in the Dual Wait Time (DWT) mode enabling to differentiate between hydrocarbon and water. The reliability of the saturation profile was later on confirmed by the production testing run in Well-A. The LWD NMR saturation was compared with production testing from one layer of the Zubair formation. Grain size analysis from the LWD NMR was evaluated using the following parameters: T2 distribution, total and effective porosity, and saturation. The LWD NMR saturation for Well-A was confirmed by the production test result. The initial production test from 1B_LCH layer in Zubair formation showed a 12% water cut, which after six months increased to 34%. The water increase was clearly observed from the LWD NMR saturation, which also showed two different saturation profiles in this 12-feet thick layer sand-body. However, this saturation differential was not clearly observed from the LWD propagation resistivity. The production test confirmation from Well-A showed that the LWD NMR saturation profile was reliable and could be used in Well-A to validate potential low-resistivity pay zones. Azimuthal resistivity inversion was performed by means of a newly developed algorithm which used the omni-directional and extra-deep LWD resistivity measurements of the Multi-Component-while-Drilling (MCWD) data. The algorithm is based on a 1D anisotropic layered model. Based on LWD NMR saturation, Well-B was found to have three potential hydrocarbon-bearing intervals with low resistivity pay zones. These intervals had a gross thickness in the range from 15ft to 25ft. The inversion result in Well-B successfully showed the lateral continuity of the sand and shale layers. Some thin layers were seen clearly from the MCWD inversion but were not shown by the standard distance-to-bed boundary inversion algorithm. Grain size analysis provides supporting geological evidence to help assess reservoir quality. LWD NMR saturation profile and grain size analysis, together with sand and shale lateral extension from azimuthal resistivity inversion, provide an integrated solution that can characterize a complex sandstone reservoir and improve the geological model.

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