An Approach to Enhance the Quality of Carbon-Oxygen Processing in Barefoot Completed Wells

摘要

Carbon-Oxygen (C/O) tools are traditionally designedfor cased hole logging environment. These tools arehowever finding application in wells with barefootcompletions. Processing and interpretation of these logsin the presence of barefoot completions are oftenassociated with problems. Some of which are due to:1. Borehole fluid re-invasion. These deep invasions,especially in highly permeable carbonate fields ofSaudi Arabia, coupled with the tools shallowdepths of investigation, makes it difficult toquantitatively use C/O tools to monitor saturations.To minimize the effects of the invading boreholefluids, barefoot completed wells are preferablylogged under flowing condition after a flow backhas been done to ensure borehole cleanup.2. Vendor's environmental correction algorithmsometimes modifies the carbon and oxygen yieldsobtained from the formation to such an extent thatthe fan charts used in building the saturation modelare no longer useful in determining the currentwater saturation.These problems are somewhat mitigated by running aProduction Logging Tool (PLT) along with the C/Otool string. The flow profiles from the PLT are used todetermine intervals of water and oil entry, andsubsequently used to ensure that the water saturationscalculated from the C/O are in conformance with therelative fluid flow from the rock.A recent effort to reduce the cost of deploying both aPLT and a C/O tool, has led to a collaborative effortwith service companies to combine just a spinner andfluid density/holdup sondes with the C/O tool.Several case study wells will be used in this paper todemonstrate that the results from a single-pass spinnerand holdup tools run in combination with a C/O toolstrings would actually give a similar two-phase flowprofile as a PLT. This provides qualitative informationthat is being used to enhance the quality of C/Oprocessing.