Drilling Deep Horizontal Well in Highly Depleted and Thin Sandstone Reservoir:A Successful Case Study from North Kuwait

摘要

In the Asset of North Kuwait,a very productive,narrow and moderately continuous sandstone layer has been heavily exploited since 1990.Over and underlain by extensive shale barriers,this channel sand with weak lateral drive,has been developed using predominantly vertical and deviated wells.The sand body was deposited in an estuarine environment as a minor switching channel with limited lateral connectivity. With reservoir pressure currently at 3ppg MWE,horizontal completions were planned to further accelerate production in anticipation of much needed pressure support.The major challenges to overcome were i) the trajectory planning and high-angle drilling through about 300 feet of highly loss prone Dolomite,close above the target reservoir,ii)casing-off the high-pressured overlying shale,iii)restrict formation damage while drilling lateral section and iv)avoiding differential sticking using conventional over-balanced mud systems.An excellently engineered 7.6 ppg OBM(least possible mud weight)yielded rich dividends as it minimized formation damage and reduced chances of differential sticking.Pre drill modelling based on nearby well data and judicious use of Distance to Bed and Azimuthal Deep Reading Resistivity image from LWD tool suite provided excellent control that facilitated successful geosteering through thin pay. Dynamic and Contingency Planning during execution were crucial to real time decisions leading to a successful completion of the first horizontally completed well.The case study details the analytical approach and meticulous planning towards the selection of a Directional Drilling BHA,Wellbore Trajectory,Mud Weight and type,Drilling Strategy,pre-job and contingency planning that resulted in successfully drilling and completing a productive horizontal well through grossly depleted reservoir in its maiden attempt.The engineering tools and strategies outlined can be appropriated to the drilling and completion of horizontal drain holes in thin-pay,heavily depleted reservoirs that require high-angle penetration of equally depleted zones.