Cutting-Analysis
Why Cutting Analysis? Selection of the right drill bit Stratigraphic Description Configuration of the mud system Fixing the exact casing depth Final decision for a core run Petrographic Characteristics Characterisation of a reservoir Basic parameter of hydraulic systems Petrographic & mineralogical Composition Input parameter for the log interpretation (EFA Log) Cutting analysis in general Redundance and back up in case of trouble (e.g. loss of borehole measurements due to bad caliper, inclination of the hole, stuck pipe, coring)
Cost Advantage Cost relation: Complete-cored well = 1,5 2 x non-cored well
Petrographic Cuttings Description *) *) System after Mobil
The Used Cuttings Shaker > 1 mm for lithological description < 1 mm for lithological boundaries Possum Belly for structural analysis Cutting Sampler rock mechanics
Lithological Description KTB Following parameters are recorded: - The degree of contamination by drilling artifacts (strong, weak, absent) - Discrimination of the lithological components and estimation of % volume - The degree of alteration (fresh, weak, strong, complete) - Quantification of the degree of cataclasis within the cuttings - Record of mineralization
Additional Investigations Physical Parameters: Natural Gamma Spectrum Magnetic Susceptibility Porosity Thermal Conductivity Mineralogical and Geochemical Analyses: XRD XRF
Construction of a Geological Profile Qualitative and semi-quantitative methods Quantitative and semi-quantitative analytical methods Microscopic analysis Ore petrography Petropysical data Geochemical data Cuttings Preliminary cuttings profile (for daily reports) Final cuttings profile
The Name of the Lithology The allocated name for the lithology is based on the most abundant lithological component (50 vol%). At equal concentrations the logging geologist has to decide: - Alternating layers - Small discret layer - Inclusion
Cutting Profile
Geo-Tech Log
1-3 Stuck Pipe and Side Tracking The Driller wants to know: What is the best formation for side tracking? 1-3
Side Track
Cement Cutting Analysis Cement In this situation, cuttings contain the fastest and most reliable information about the success of side tracking, even the lag time may reach hours! Rock Fragments
Integration of the Logs Depth shift
Depth Shift between Log and Cuttings LD > CD LD < CD
KTB Drilling Strategy Extended Cutting Analysis Spot Coring (~ 10% of drilling) Logging Program How effective can be a cutting analysis?
Recurrence of Lithological Units From Core From Cuttings
Inflow Zones
Open Porosity? Prehnites Prehnites 3866 m 5390 m 7011 m Quartz 7776 m Quartz
Detection of Fault Zones
Cutting Log of the SE1 Reflector Franconian Line SE1
Cores from SE1 The coring interval was determined based on the cutting analysis!
Summarized Experiences Cutting analysis together with borehole measurements and spot cores can substitute complete coring to a great extent......and with significant lower costs!