Through Drillpipe Formation Testing: Unlocking Bypassed Pay, A Case Study Onshore Kuwait

Abstract

Identifying a bypassed pay is always challenging, especially for highly deviated, complex wells where well control further complicates wireline logging. This case study examines the use of a Through Drillpipe Logging (TDL) conveyed formation testing and sampling tool in addition to the conventional slim open hole logging suite. The logging program overcame the challenging well trajectory and wellbore stability complications. The resulting data provided a conclusive formation evaluation and reservoir characterization identifying bypassed oil.

The logging program targeted two formations: The primary goal was the Upper Burgan and the secondary target, a suspected bypassed pay, was the Lower Burgan. The well was highly deviated and was drilled with the oil-based mud system. In addition to the complex trajectory, a well bore stability was identified as marginal due to observed washouts. Therefore, the logging program implemented TDL for both traditional open hole logging and formation testing and sampling TDL pumps the tools down the drill pipe ID until reaching TD, where they are released into the well bore and logged back to surface. On the first acquisition run a triplecombo logging suite was run, and a complete dataset was acquired without any differential sticking. During the second run the slim formation tester was centralized to minimize sticking risk during the planned stationary acquisition of formation pressure measurements and sampling.

The TDL conveyance of slim logging tools eventually led to enhanced reservoir understanding and characterization after the data interpretation. Specifically, 22 pressure points and 2 low-contamination samples were returned to surface. The sampling series found fluid in the secondary target. The combination of pressure data, porosity, saturation, fluid mobility, and permeability data characterized the formation. This combination resulted in a deeper understanding of the storage and flow capacity of these heterogeneous reservoirs. Consequently, the well completion design was optimized by the producer.

The TDL conveyance option helped to safely log the well from TD in a complex trajectory by pumping down the slim-logging tools to avoid differential tool sticking across a major washout. Regular tool fishing operations were eliminated, and open-end drill bit usage allowed reaming during wiper trips between the logging runs. TDL significantly reduced operational risks optimizing rig utilization and minimizing overall costs in addition to reservoir and formation fluid data acquisition.

The slim formation testing of the Burgan reservoir supported completion of the primary well objectives and identified bypassed pay in the secondary objective. The field development and exploratory strategies were updated based on the logging results.