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 highangle 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.
History matching is one of the paramount steps in reservoir model validation to describe, analyze and mimic the overall behavior of reservoir performance. Performing history matching on highly faulted and multi layered reservoirs is always challenging, especially when the wells are completed with multiple zones either with single selective or dual strings. The history matching complexity is also compounded with uncertainties in production allocation, well history and downhole equipment integrity overtime. It is a common practice for deterministic history matching in reservoir numerical simulation to modify the both static and dynamic model parameters within the subsurface uncertainty window. However, for multi layered reservoirs completed with dual strings, another parameter that is most often get overlooked is the completion string’s leaking phenomenon that tremendously impacting the history matching. The objective of this paper is to introduce dual strings leaking diagnostics methodology from various disciplines’ angles. We demonstrate these dual strings leaking phenomenon impact on history matching. This paper covers dual strings leak diagnostic methodology which includes production logging tool evaluation, well’s production performance and recovery factor analysis. Possible factors that gives rise to the string’s leaks including material corrosion from high CO2 and sand production will also be discussed. We will demonstrate on how the leak phenomenon could be mimicked in the reservoir numerical model. Possible risks on future infill well identification if the leaks phenomenon is not incorporated will be also discussed. The dual strings leaks diagnosis and application in numerical simulation is illustrated on a case study of Field "D", a multilayered sandstone reservoir in Malaysia of almost 3 decades of production. This proven leak identification and reservoir model history matching methodology has been replicated for all the fault blocks across the field. It potentially unlocks more than 100 MMSTB of additional oil recovery by drilling more oil producers and water injectors in future drilling campaigns.
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