1.0 Introduction to Formation Evaluation Log Analysis (1)
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1.0 Introduction Objectives of course By end of first term, for basic open hole logging suite of Mud Log, Gamma Ray, Resistivity, Density, Neutron & Sonic Logs Ability to make qualitative evaluation of a log Ability to do a quick look interpretation of logs In second term More detailed analysis Less common logs Cased hole logs Both terms Quality control Looking at practical aspects rather than lots of theory Books Openhole Log Analysis and Formation Evaluation by R.M.Bateman, 2012 Well Logging for Earth Scientists by D.V. Ellis & J.M. Singer, 2008 Well Logging and Formation Evaluation by T.Darling, 2005 Petrophysics by D.Tiab & E.C.Donaldson, 2012 The Well Logging Handbook by O.Serra, 2008 Websites especially Service Companies London Petrophysical Society (part of SPWLA) What are Formation evaluation, petrophysics and logging Formation Evaluation is designed to determine formation properties, this includes: Logging and Log Analysis Coring and Core analysis Well testing, in particular pressure transient analysis Petrophysics encompasses log analysis and core analysis A log is record with depth of some formation related parameter. Logs are split into: Mud logs – examination of cuttings and drilling parameters related to rock formation
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Transcript of 1.0 Introduction to Formation Evaluation Log Analysis (1)
1.0 Introduction
Objectives of courseBy end of first term, for basic open hole logging suite of Mud Log, Gamma Ray, Resistivity, Density, Neutron & Sonic Logs Ability to make qualitative evaluation of a log Ability to do a quick look interpretation of logsIn second term More detailed analysis Less common logs Cased hole logsBoth terms Quality controlLooking at practical aspects rather than lots of theory
BooksOpenhole Log Analysis and Formation Evaluation by R.M.Bateman, 2012Well Logging for Earth Scientists by D.V. Ellis & J.M. Singer, 2008Well Logging and Formation Evaluation by T.Darling, 2005Petrophysics by D.Tiab & E.C.Donaldson, 2012The Well Logging Handbook by O.Serra, 2008Websites especially Service CompaniesLondon Petrophysical Society (part of SPWLA)
What are Formation evaluation, petrophysics and loggingFormation Evaluation is designed to determine formation properties, this includes: Logging and Log Analysis Coring and Core analysis Well testing, in particular pressure transient analysis
Petrophysics encompasses log analysis and core analysis
A log is record with depth of some formation related parameter. Logs are split into: Mud logs examination of cuttings and drilling parameters related to rock formation Open Hole logs tools run into the well before it is cased that measure some property. Typical logs measure electrical, nuclear or acoustic properties, from which formation properties can be inferred Cased Hole logs
What properties are we trying to determine with Open Hole logging and coring?Formation tops and geological correlation (Open hole logs)Porosity (Density, Neutron and Sonic logs & Core)Oil, water & gas saturation (Resistivity for water saturation, Density & Neutron logs combined for gas)Used to determine oil or gas in place, although note sample a small volume close to wellLithology (Gamma Ray, Mud log or Geological Prognosis, also Density/Neutron/Sonic)In particular ShalinessUsed in understanding log response as well as understanding of geology (stratigraphic correlation, depositional environment, facies), response to stimulation and likely production mechanismsThickness, porosity, hydrocarbon saturation and hydrocarbon type are essential parameters to determine the oil & gas in placeOther important objectivesPressure (RFT/MDT)Used to determine (oil and) gas in place, reservoir flow rate, hydrocarbon presence and contacts, connectivity.Permeability (Core)Difficult to determine directly from logs but very important for determining production ratesPresences of faults and reservoir dip (Image logs)Important to understand geology and reservoir production behaviour.Other derived informationCasing pointsGeosteeringPerforation intervalsTie in with seismicGeomechanics (Wellbore Stability / Sand production / Youngs modulus & Poissons ratio for hydraulic fracturing)Pore Pressure prediction
Logging environmentLogs are run after holes are drilled. As the well is drilled through permeable formations mud tries to flow into the formation. As the solids are too large to enter the pores of the formation a filter cake is formed on the sides of the well. Mud filtrate, the liquid in the mud, leaks through the filter cake and displaces the fluids naturally occurring in the formation. It is the mud filtrate that most logs mainly see. As a result the type of mud used can make a big effect on the log response.
Log interpretation assumes that the borehole is the same size as the drill bit. In softer and chemically reactive formations, the borehole may become enlarged. As a result logs may see more of the wellbore contents and less of the formation.
Image logsImage logs use resisitivity or ultrasonic measurements to gain a picture of the rock on the sides of the hole. Features like dipping beds and fractures can be identified.
Cased Hole logging may have same objectives as Open hole logs but main principal purposes of Cased Hole logs are: Cement bond quality Where oil, water and/or gas is coming from in a well (Production logs) Change in oil, gas or water saturation (Pulsed Neutron logs) Condition of tubing or casing (e.g. with regard to corrosion)
Industry OrganisationMain Logging companies: Schlumberger Halliburton Weatherford Baker
MemonicsThere are abbreviations for everything, and it is not unsual for engineers to talk in these abbrieviations. It is worth learning the main ones
