Improving Production in a Brownfield by Optimising the Placement of Horizontal Water Injector in Thin Clastic Reservoir:A Case Study from Malay Basin

摘要

Some of the hydrocarbon-bearing sands in ADX field,Malay basin,have been identified as minor reservoir with an average sand thickness of less than 3 m.Thus,reservoir development has become challenging.One of the effective ways to develop these reservoirs is by drilling highly deviated or horizontal wells. After long production,one of the minor reservoirs in ADX has become highly depleted and was in critical need of pressure maintenance.Based on the field study,waterflood was chosen to manage the reservoir pressure.This reservoir is distributed widely in the field,with thickness ranging from 1 to 3 m.Because of the sand thickness,the most efficient method is to place an injector well horizontally.However,placing a horizontal well in this depleted thin sand poses significant challenges for the drilling operation.These include accurately landing at the target sand,avoiding premature exit due to geological uncertainties and the thin reservoir,and managing the borehole pressure to avoid differential sticking of the bottomhole assembly.For formation evaluation,high-angle effects such as anisotropy,close vicinity to shoulder beds,and lateral property changes complicate quantitative interpretation. A full suite logging-while-drilling measurements including near-bit gamma ray,average and deep directional resistivity for boundary detection,azimuthal density,neutron porosity,and formation pressure,combined with a proactive well placement method executed by collaborative experts from subsurface,drilling,and geosteering teams were used to address these challenges.As a result,an injector well was placed optimally in the thin target reservoir for a length of 300 m,as per the objective.Modeling of the high-angle well was also conducted to extract the true formation properties and to address the high- angle effects on the measurements to improve the quantitative petrophysical evaluation.Comprehensive predrill planning,the drilling execution that included 24-hour real-time monitoring to steer the well,and post-well evaluation and modeling yielded lessons learnt,best practices,and recommendations for drilling and evaluating similar wells.