Pacific Section AAPG, SPE and SEPM Joint Technical Conference

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Onshore Mudlogging, Challenges & Opportunities For Improving Value

Abstract

This talk discusses challenges and opportunities to improve onshore mudlogging's value within the context of evolved drilling technology, improved wellbore geophysics and rock/reservoir characterization techniques, and greater knowledge of and ability to model and predict basin and well conditions. The talk also includes ideas for improving quality control (QC) and reliability of mud logs. Mudlogging has changed little in ∼40 years, except for the advent of reliable electronic calculations/communication (WITS, software applications, email and the web) and time freed-up because the logger no longer manually drafts logs. Today's mudlogging protocols and techniques were developed when drilling was slower, cuttings were coarser, OBMs were uncommon, basins were less understood, well-drill conditions were less predictable, and data was harder to use. Mudlogging protocols and equipment are ill-suited to the mm-size cuttings generated by PDC bits. Mudlog manuals are largely unchanged from the 1970s, and direct the mudlogger to report properties that cannot be observed in PDC-bit generated cuttings using procedures and equipment that predate now-widely used drilling technologies. Modern mudlogging rarely provides less-useful top-of-formation data than in the past. Depth-migrated seismic, more precise wireline data, geophysics-derived petrophysics, higher well density within leases, and an easily-manipulated database of digital well files enable developmental geologists to predict the depths of tops more accurately than the average onshift mudlogger can determine them. Mudlogging contract technical requirements may be unachievable when the mudlogger is working alone and ROPs are 2-15 feet per minute and/or the cuttings are fine and difficult to wash. These or other factors may incentivize the logger to use means other than examination of cuttings to ‘get the lithology on paper’ — and impacting reliability of lithologic content of logs. Ideas to improve mudlogging quality are presented. Mudlogging trends that may increase value-to-operators include: (1)geosteering ‘lite’, (2)more complex and labor-intensive GC/gas equipment, (3)catching fluid samples, (4)operation of near-real time geochemical tests (SRA, XRF, etc.), (5) analysis of pore-pressure conditions, and (6) assisting mud engineers with understanding the effects of specific formations on mud properties. This talk reflects the author's views from work in TX, ND and NM in 2012 and 2013, and not the views of his employer.