A New Optical Sensor Configuration Enables First Time Use of theMid-Infrared Optical Wavelength Region for Chemical Analysis DuringFormation Tester Logging Operations

摘要

This paper presents a new optical sensor configuration using a multivariate optical computation(MOC)platform in order to enhance chemical analysis during formation tester logging operations.The platformallows access up to the mid-infrared(λ ~ 3.5 microns)optical region,which has previously not beenaccessible for in-situ real-time chemical measurements in a petroleum well environment.The new techniquehas been used in the field for the analysis of carbon dioxide and synthetic drilling fluid components suchas olefins.MOC is a technique that uses an integrated computational sensor to perform an analog dot productregression calculation on spectroscopic data,optically,rather than by electronic digital means.Historically,a dot product regression applied to spectroscopic data requires both a spectrometer and a digital computer inorder to perform a chemical analysis.MOC sensors require neither and because the key sensor component,the multivariate optical element(MOE),is a stable temperature robust solid-state element,the techniqueis well suited for downhole petroleum environments.A new dual-core configuration using two MOEsdesigned to work in parallel enhances the sensitivity of the measurement enabling a mid-infrared analysis.Spectroscopic measurements were performed on 32 base oils that were reconstituted to reservoircompositions over a wide temperature and pressure range up to 350°F and 20,000 psi for a total of12 combinations for each base oil.Live gas compositions(i.e.reservoir conditions)were achieved byadding multiple methane,ethane,propane,and carbon dioxide charges to each base fluid.The reconstitutedpetroleum fluids were further mixed with olefin-based synthetic drilling fluid(SDF).This rigorousexperimental design data therefore allowed for solid state MOEs to be designed to operate under the samereservoir conditions.Laboratory validation showed measurement accuracy of +/-0.43 wt% for a range of0 to 16 wt% CO2 and +/-0.4% from 0 to 10 wt% SDF.A wireline formation tester optical section wasmodified with the MOC dual-core configuration to enable the mid infrared detection of both carbon dioxideand olefins.This formation tester was then deployed in five wells collecting seven samples from variouslocations.The downhole SDF and carbon dioxide measurements were subsequently found to be in good agreement with laboratory analysis with field results for valid pumpouts showing an accuracy of 0.5 wt%CO2 and 1.0 wt% olefins cross a range of 1.2 to 22 wt% CO2 and 1.4 to 9.7 wt% SDF.Carbon dioxide is an important component of petroleum whose presence and concentration affectscompletion options,surface facilities,and flow assurance,which thereby affects operational costs ofpetroleum production.Olefins are a primary component of synthetic drilling fluid(SDF),although othermid-infrared active components such as esters,ketones,alcohols,and amines also can be present.Highconcentrations of SDF in openhole formation tester samples lower the quality of laboratory phase behavioranalysis and thereby force greater monetary risk in development of assets,especially when conductingreservoir production simulations.Therefore,it is important to monitor both components during formationtester sampling operations.