Once a niche, memory logging has expanded to become a significant part of data acquisition for formation evaluation. Openhole memory logging acquires data, by employing wireline tools with a downhole battery for power and memory for the logic and data recording. Lying between conventional wireline and logging while drilling (LWD) it seeks to capitalise on the cost-effectiveness of the former to bring operator savings, and the drillstring conveyed access to total depth (TD) shared with the latter, whilst attempting to avoid some of the disadvantages of both.

Some of the constraints may be as solid as the drillpipe dimensions or as balanced as an assessment of the risks, costs and time involved to the well (perceived, predicted and realised), versus the requirement for data. A particular example described has been overcoming the limitations of running a ‘no-go’ type landing ring through drillstrings of small internal diameter. This has opened up a further part of the memory logging market.

Drillstring conveyance for well access requires small diameter tools and novel solutions to provide the full range of measurements from challenging wells. Memory logging is a fast-growing sector, acquiring data in many previously unlogged well types.


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