Sampling While Drilling has been successful in recent times covering numerous applications including difficult boreholes, horizontal wells, influencing drill stem test plans, cost savings in marginal fields, high sample volume collection, aid in quantifying non-hydrocarbon content for facilities design and deployment in carbonate under total losses with pressurized mud cap drilling conditions.
This case study discusses one more application, which is in weak unconsolidated sands of a field located in Tatau, Sarawak, Malaysia. The principal objective of the sampling-while-drilling run discussed in this paper was to collect representative water samples from an aquifer, the laboratory analysis of which would yield invaluable information about compatibility for future water injection. The secondary objective was to collect low contamination single-phase oil samples if the well penetrated hydrocarbon reservoir layers at virgin pressure. Determining fluid gradient was an inherent requirement as well.
This paper describes the challenges, best practices and learnings following the deployment of this technology in a deviated infill well in a mature oil field with sanding history and multiple layers of poorly consolidated sandstones with uncertainties on the pore pressure, due to production from the field and adjacent fault blocks that might have a certain level of connectivity.