ABSTRACT

Reservoir connectivity remains one of the most significant risk factors of reservoirs; unrecognized compartmentalization is one of the most important origins of reservoir underperformance globally. Here, a multiphysics, well-log workflow is employed on a reservoir to address reservoir connectivity at the earliest stages of reservoir evaluation. Moreover, new reservoir and well-log data can be placed within this framework deep into development. The combination of borehole image logs (BHI) and downhole fluid analysis (DFA) from the discovery and early appraisal wells is used to address reservoir connectivity and other key attributes of the reservoir. High resolution BHI enable geologic interpretation of geobodies. Correspondingly, DFA data can be framed within the context of reservoir fluid geodynamics enabling a coherent evaluation of the evolution of fluids as well as their geobody containers over geologic time. There are two stacked sands that make up this reservoir, and their possible lateral and vertical connectivity are fundamentally important to assess early in the evaluation process.

From the BHI evaluations, the large-scale sedimentary system represents a sand rich basin floor fan or series of fans over the reservoir units. The basin floor fans are comprised of confined and unconfined episodes which occur in response to periodically changing axial vs off-axis positions within the governing fan. The lower sand was largely deposited in a medial, channelized sand-rich fan to channel-to-sheet transitional zone. The upper sand is interpreted as a channelized, axial lobe system. Two differently oriented channel axes define the large-scale depositional system: (i) main channel axis connecting T1 with T1ST and (ii) secondary channel axis between wells T2 and T1ST. Both these interpreted settings are consistent with isopach image analysis and bode well for potential lateral connectivity.

The DFA data indicates that the asphaltene gradients in the T1 and T1ST wells are equilibrated laterally in each sand, thus consistent with lateral connectivity. However, the offset between the asphaltene gradients in the upper and lower sand indicates limited vertical connectivity. The T2 well is in a downthrown block; when reconstructing the reservoir and asphaltene gradients prior to fault throw, it is evident that the upper and lower sands were connected across these three wells at time of charge and prior to faulting, but not in present day. Subsequent lab data on the fluids and production data confirmed all major conclusions from the early, multidiscipline analysis. This multiphysics workflow on the earliest log data available in the reservoir enables development of different scenarios which guide subsequent data acquisition and development concepts.

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