Kohl, Thomas

Meixner, Jörg

Müller, Birgit

Schimschal, Stefan

Stricker, Kai Robin

Wessling, Stefan

English

KITopen

KIT – The Research University in the Helmholtz AssociationAnalysis of image and drilling logs for formation instability uncertainty analysisK. Stricker, S. Schimschal, T. Kohl, J. Meixner, B. Müller and S. Wessling kai.stricker@kit.eduInstitute of Applied GeosciencesDivision of Geothermicsagw.kit.eduMotivation Conclusion and PerspectivesInfluence of drilling processesBorehole breakouts (Tingay et al., 2008):Occurrence of breakoutswhen stresses around theborehole are higher than thestress required to generatecompressive failure of theborehole wallOrientation parallel tominimum horizontal stress σhMud weight has to beadjusted accordingly toprevent breakoutsSchematic cross sections of borehole breakouts(Hillis and Reynolds, 2000)Theoretical backgroundCircumferential stressOverview of relevant drilling processes(SOG, 2019):Pipe trips: (Partial) removal of thedrill stringConnections: Extension of the drillstring by an additional segmentMethodology and software developmentTemporal breakout evolution1• Software development in JewelSuite2• Identification and collection of useful datasets3• Analysis of image logs4• Analysis of drilling operations5• Evaluation of drilling parameters and correlation to drilling operations6• Sensitivity analysis of drilling induced pressure changes7• Investigation of time-dependent borehole instability effectsMethodologySoftware developmentBasis for development: Previously developed MATLAB prototypeProgramming language: C# (development environment: Microsoft VisualStudio)Platform: JewelSuite (BHGE 3D Reservoir Software)Major challenge: Visualization of image log data (no implementation in theJewelSuite framework available)  pixel-by-pixel realizationDesign: The main graphical user interface of the software is divided into:Left Panel: multiple user controls to manipulatethe displayed data in the plotsRight Panel: plots for image, caliper, bit andimage tool depth as well as time basedpressure and temperature dataToolbar: multiple user controls to e.g.load/save breakout data or screenshots of theviewLeftpanelRight panelToolbarSoftware prototypeReferencesSupported byClear relation between breakouts andtripping operations / flow-off events Cause for occurrence?Frequency of tripping events withinbreakout intervals one order ofmagnitude higher than outsideFlow-off events (switched-off pumps)also occur more frequently withinbreakout intervalsRelationship between drilling processes and pressure anomalies (mostly negative)Observations of increasedbreakout depth extent andopening angles by using relogimagesComparison of different imagesin the same BHA potentiallyenables the temporal analysisof breakout evolutionsFrequency of tripping and flow-off events during breakout sectionsComparison of images for the identification of drilling-related breakout developmentRelog images of the same wellbore sectionHillis, R. and Reynolds, S. (2000): The Australian stress map. Journal of the Geological Society, 157, 5: 915-921.SOG (2019): Schlumberger Oilfield Glossary. https://www.glossary.oilfield.slb.comTingay, M., Reinecker, J. and Müller, B. (2008): Borehole breakout and drilling-induced fracture analysis from image logsWessling, S., Bartetzko, A., Pei, J. and Dahl, T. (2012): Automation in Wellbore Stability Workflows. SPE Intelligent Energy International, Utrecht, The Netherlands, 27-29 March 2012.Observation of a relation between drilling processes and breakoutsNegative pressure variations may have contributed to thedevelopment of breakoutsBreakouts tend to grow both azimuthally and in their depth extentFuture research could benefit from the availability of relogs and/ormultiple image logging tools in the same wellboreAzimuthal LWD logs provide images of the borehole wall, which arewidely used for the analysis of borehole breakoutsThese breakouts develop when the circumferential stress aroundthe borehole wall exceeds the compressive strength of the rockUncertainty on how drilling processes (such as tripping) influencethe development of breakoutsPressure windowModified after Wessling et al. (2012)Angle (°) Caliper (in) Time (h)TimeDepth(m)Depth(m)Pressure(MPa) Temperature(°C)TimeTime (h)Pressure(MPa)Dpeth(m)Temperature(°C)Log resistivity (Ohmm)Angle (°C) Angle (°C)Log resistivity (Ohmm) Log density (gcm-3)Depth(m)Depth(m)Pressure(MPa)Temperature(°C)Time (h)Angle (°C) Angle (°C) Angle (°C) Angle (°C) Angle (°C)Depth(m)Depth(m)Depth(m)Depth(m)Depth(m)Original logLog resistivity(Ohmm)Relog 1Log resistivity(Ohmm)Relog 2Log resistivity(Ohmm)Relog 3Log resistivity(Ohmm)Relog 3Log resistivity(Ohmm)

Analysis of image and drilling logs for formation instability uncertainty analysis

6) Planned further development- Correction / normalization of pressure and temperature data- Determination of causal relationship between breakout intervals and viper trips- Consideration of additional drilling logs (e.g. ROP) and supplementary image logs (e.g. PE)- Observation of relog sections to investigate time-dependent changes of breakout sections- Calculation of pressure window (between collapse and fracture pressure)- Calibration of stress model around boreholes (including sensitivity analysis of pressure gradients) based on preceding results and the calculation of an initial stress field Adjustment of pressure window (crucial for correct determination of mud pressure for drilling)ANALYSIS OF IMAGE AND DRILLING LOGS FOR FORMATION INSTABILITY UNCERTAINTY ANALYSISKai Stricker, Karlsruhe Institute of Technology, GermanySTC 2018 – FREIBERGInstitute of Applied GeosciencesKarlsruhe Institute of Technologykai.stricker@kit.eduIntroductionLogging while drilling (LWD) tools are used to gather drilling and formation data during thedrilling process of a well. LWD e.g. enables to log resistivity, caliper or pressure data.Azimuthal logs provide images of the borehole wall which can be utilized to detect breakoutsections of the wellbore. One challenge with the interpretation of breakouts are theunknown borehole conditions (e.g. pressure) between a bit and an imaging sensor passinga zone of interest (“time window”). To ensure a safe and effective drilling process theborehole pressure has to be within a specified pressure window which is defined by thecollapse and fracture pressure.Objectives1. Development of a software prototype in the Baker Hughes proprietary softwareJewelSuite to display and analyze image and drilling logs.2. Analysis of wellbore stability mechanisms (e.g. borehole breakouts, drilling inducedfractures) by utilizing different image logs (e.g. resistivity, density or caliper).3. Characterization of pressure and temperature variations in the time frame until theimaging sensor reaches the drilled zone of interest Correlation to wellbore stabilityoccurrences and relevant parameters (e.g. breakout width).1) Theoretical background- Borehole breakouts (Tingay et al., 2008):- Occurrence of breakouts when stressesaround the borehole are higher than thestress required to generate compressivefailure of the borehole wall (Figure 1)- Orientation parallel to minimum horizontalstress σh- Drilling induced fractures (DIFs; Tingay et al.,2008):- Occur when stresses around a boreholeare lower than the tensile strength of theborehole wall (Figure 1)- Orientation parallel to maximumhorizontal stress σH3) Analysis of image logs- Image log types which are used: Resistivity, density and caliper- Characteristics of borehole breakouts and DIFs in image logs (Tingay et al., 2008):- Borehole breakouts (generally broad and parallel zones, separated by 180°):- Resistivity image: Lower resistivity reading due to higher conductance of mud- Density image: Lower density reading- Caliper image: Increased caliper reading- DIFs (generally narrow, sharply defined features):- Resistivity image: Lower resistivity reading due to mud invasion into fractures4) Characterization of pressure and temperature variationsAnalysis of pressure and temperature differences during the time window, pattern analysis,usage of statistical methods Analysis of drilling operation influences during time since drilled on e.g. breakout width5) Results of exemplary application- Raw pressure and temperature data are superimposed by drilling effects and parametergradients over depth (left part of Figure 4)  Correction / normalization is necessary (especiallyfor pressure data)- Occurrence of pressure spikes during downward movement of bit through already drilled depths(right part of Figure 4) pressure increase may cause/enhance DIFs- Temperature responses more slowly to breakouts and artificial influences Conclusion- Successful development of JewelSuite prototype to display and analyze image and otherdrilling logs with regards to borehole stability analysis- Investigation of pressure and temperature changes during the “time window” between bit andimage tool using an exemplary well Influence of drilling operations on especially pressure during the investigated breakoutintervalsBreakouts may be associated with drilling operations (e.g. viper trips)ReferencesM.Tingay, J. Reinecker, B. Müller (2008): Borehole breakout and drilling-induced fracture analysis from image logs, World Stress Map Project – guidelines: Image Logs, Helmholtz Vent. Potsdam, GFZ.R.R. Hillis and S.D. Reynolds (2000): The Australian Stress Map, J. Geol. Soc. London, 157, 915-921.Figure 3: Time-based relog image analysis showing increase of breakout width and length over timeFigure 2: Display of developed JewelSuite software prototype showing a picked breakout section (between green horizontal lines)(1)(2)Figure 1: Schematic cross-sections of borehole breakout and DIF (Hillis and Reynolds, 2000)- Density image: Sometimes visible asnarrow low-density axial-parallel features- Caliper image: Difficult to identify due tomissing borehole enlargement- Picking of borehole stability features usingdifferent tools of the software (first red arrow inFigure 2)  All other plots are updatedaccordingly- Relogs of image data can be used todetermine time-based changes on the boreholeinstability features (e.g. breakouts, Figure 3)- Further information of picked features can bedisplayed optionally in a separate view (secondred arrow in Figure 2)2) Software development- Basis for development: Previously developed MATLAB prototype- Programming language: C# (development environment: Microsoft Visual Studio)- Major challenge: Visualization of image log data (no implementation in the JewelSuite frameworkavailable) pixel-by-pixel realization- Design: Figure 2 shows the main graphical user interface of the software divided into:• Left Panel: multiple user controls to manipulate the displayed data in the plots• Right Panel: plots for image, caliper, bit and image tool depth as well as time based pressureand temperature data- Extras: relogs of image data, information about picked borehole instability occurrencesFigure 4: Top Left: Bitand image tool depthover timeBottom Left: Pressure& temperature data ofthe chosen breakoutinterval. Pressure andtemperature data showsuperimposition ofgradients over depthand drilling effects(black rectangles).Right: Detailed view ontwo pressure spikes(highlighted in green)which have probablybeen caused by drillingoperations.Figure 5: Number of viper trips (blue) and connections (red) during each breakout interval of the exemplary well- Pressure reductions visible in Figure 4 can not solely beexplained by hydrostatic pressure reduction due to bitmovementAdditional explanation needed- Figure 5 shows that breakout intervals of the exemplary wellalways contain viper tripsThe breakouts in the well seem to be associated with drillingoperations (at least 82 % of all viper trips of the well occurduring a breakout interval)I2 I3Induced pressure spikesI1 I2 I3 I4

https://publikationen.bibliothek.kit.edu/1000105886/95816449

Analysis of image and drilling logs for formation instability uncertainty analysis

Abstract

Similar works

Full text

Available Versions

KITopen

KITopen