Advanced Mud Logging: From Archie's Dream To Reality

Abstract

Abstract Advanced Mud Logging (AML) has been named " Archie's Dream" since AML willfulfill what must have been Archie's dream. That is: obtain high resolutionrock parameters as quickly as (wireline) logs. Up until the recent past, theidea of obtaining quantitative petrophysical parameters from mudlogging seemeda dream. However, AML is moving towards continuous, real time determination ofrock and fluid parameters from drill cuttings, drilling parameters and mud(gas) returns, in aid of well evaluation and reserves calculation. The value of (to a large extent conventional) mudlogging for hydrocarbonproductivity prediction is already significant, confirming that mud gasmeasurements, if properly analysed, provide very valuable information forproduction testing decisions. Through application of rock typing techniques and rock catalogues, amongstothers, reasonable electrical parameters, which normally require elaborate coremeasurements, can be obtained near real time from cuttings descriptions. Tests on a method for direct permeability measurement on cuttings confirmthe potential for this method for many circumstances. Micro and nano indentation techniques are being tested to provide rockmechanical properties also from drill cuttings. As the techniques to determine several of the key parameters are becomingmore firmly established, AML is entering the stage of actually providing asignificant input for a complete formation evaluation. Introduction Archie's laws and other saturation models which cater for shalyformations allow a sound quantification of hydrocarbons in place by couplingformation resistivity with some rock parameters. However, there is a majordiscrepancy between the sampling increments and timely availability of the logderived parameters on the one hand and the sparse and time consuming laboratorymeasurements which are needed to establish the required rock parameters on theother hand. This problem has hampered petrophysical interpretations in manysituations where the rock parameters are not known yet (in a new area) ordiffer from common values or vary across zones and wells (in a more maturesetting). " Archie's Dream" therefore can be said to obtain the necessaryrock parameters with a similar sampling increment and at the same time as theresistivity logs.