US2876078A - Well logging - Google Patents

Description

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/We/ef P. J; MOORE WELL LOGGING Filed 0G12. 12. 1954 fee/ Mew/Pm@ Fee/,aar Afa/r March 3, 1959 United States Patent O WELL LOGGING Pernell J. Moore, Houston, Tex., assignor to National Lead Company, New York, N. Y., a corporation of N ew Jersey Application October 12, 1954, Serial No. 461,857

4 Claims. (Cl. 23230) This invention relates to the loggingof wells during drilling, more particularly by examination of the, mud returns, and relates to an improvement of such mudv returns logging. l

For some years, it has been common during the drilling of wells for oil and gas by the rotary process, wherein a circulating mud uid is employed to ush out the cuttings and maintain proper pressure relationships in the hole, to examine the mud return systematically, substantiallyv continuously, and by various techniques, to establish the presence of oil or gas in the returning mud. When this informtaion is coupled with information as to the depth of the formation from which hydrocarbon inclusions in the mud arose, which may be gained from a knowledge of the bit depth, rate of penetration, and mud circulation, then the necessary data are at hand to'per'mit the construction of a log of hydrocarbons, viz., oil and the terrain which has been traversed. General principles are set forth, for example, in Hayward Patent No.

One of the important hydrocarbon constituents of drilling mud which is `detected in well logging procedures of the type described is gas, which is'to say, the gaseous constituents of the drilling mud as removed therefrom, for example, by a gas trap such as shown in Wilson et al. Patent No. 2,341,169, and detected as containing combustible constituents iby a hot wire' gas detector of the known type.

The hotwire gas detector, as is well-known, operates on the principle of catalytic combustion of combustible gases in the presence of air at the surface of a heated catalytic filament which is generally of platinum. The filament is maintained at a temperature high enough to cause catalytic combustion of the gas to be determined or detected by passing an electric current through the filament. If combustion does take place, which will naturally be -at the exposed surface of the platinum filament, then the heat liberated bysuch combustion raises the temperature of the filament, and since platinum has a substantial temperature -coe'flicient of resistance, the detection of such a combustion process can be readily `accomplished by following the' change in resistance of the filament, which can bedone byY includingit in a Wheatstone bridge circuit. It has been found that methane requires av substantially higher filament 4temperature for combustion than gases' higher inthe hydrocarbon series, such as ethane, propane, butano, and so forth, and it has become common practice to getindicati'ons at two filament temperatures, generally achieved by subjecting the filaments to two different voltages, one atA a' fairly high voltage, suiiciently high to oxidi'ze 'methane, and one substantially lower, so that methane remains unoxidized, whereas the remaining hydrocarbons or other combustible constituents are oxidized in the usual fashion. By taking the difference of the two readings or'indications, a measure vof the presence of what is "ice nominally methane is obtained, which is of` importance in evaluating the nature of the strata traversed since the presence of methane may be an indication of the presence of petroleum.

yIn gas detection inl drilling mud, ofA the type which has been described hereinabove, the results obtained have often been anomalous and unexplainable in terms of the known theories applied. For example, one would normally expect ka higher indication when the filament is operated at the higher vvoltage than would be obtained vat the lower voltage, because methane combusted would always be in addition to theA other gases present. However, the 'difference is often in the opposite direction, which would normally Ibe interpreted as a negative methane content, whichfof course khas no correspondence with anything factual.v Other anomalous showings have been observed; for example,often when the alkalinity of the drilling mudwas reduced,-what appeared to be a gas show would be encountered, but it would disappear if the mud alkalinity were raised again. Again, when drilling out cement through a drillable plug, a show of 'gas has often been observed and many times under stratigraphic conditionswhich would scarcely admit of the presence of hydrocarbon gases.

An object of the present'invention is to improve they reliability of hydrocarbon detectionV in drilling mnds.

Another object of the invention is to obtain more certain indication of the presence 0f methane in a drillJ ing mud by differential indications obtained by the use of a hot wire gas detector on the gas derived therefrom. Another object of the invention is to eliminate the t d l" gas, as a functlon of depth, so as to show the nature of false show of gas generally encountered when m mg a drillable cement plug.' Another object of the invention is to make a gas showing observed substantially independent of the alkalinity or pH of the drilling mud. l

Other objects of the invention will appear as the description thereof proceeds. Y

In the drawings, Fig. 1 shows gasdetection logs against depth taken with and without the use of my invention. y

Fig. 2 shows apiece of apparatus useful in employing my invention while Fig. 3 shows a detail therein.

Fig. 4 shows across-section taken across the middle of Fig. 2.

In accordance with my invention, steps are taken to remove hydrogen from the gas taken from the drilling mud prior to its testing by means of the hot wire detection apparatus. I have found thatthis eliminates most if not all of the anomalous effects which have just been described, and permits, forv example, drilling through drillable cement plugs without the false show of gas generally obtained, and permits operating with a drilling mud at a considerably reduced alkalinity, or a pH in particular below 9, without a more or less continuous, randomly variable gas showing appearing in the indicator.

y While there are many ways of removing hydrogen from a gas, and standard texts on gas analysis may be consulted in this connection, Ivprefer t-o pass the gas mixture obtainedfrom the drilling mud through a chamber containing a catalyst of the type which oxidizes hydrogen to water, but does notoxidize saturated hydrocarbons of the methane series atthe .temperature at which the catalystis maintained. A suitable-chamber is shown in Fig. 2, wherein 10 is a brass block drilled to receive a thermostat 12 and heater 13, and also drilled and tapped to receive tubulations' 14 and 15 and a supply ofcatalyst 16.l vA detail of one of the tubulation's' is shown in Fig. 3, fromv which" it will be apparent that this l part Ahas a threaded kportion 1" I and a perforatedrportion chloride, after which the granules are driedunder a heat lamp. With the dried alumina granules still hot a stream ofhydogen is. passed over themgto reducethe palladium chloride to finely dividedlpalladium metal. Palladium catalystsoffthis type are commercially available such as Catalyst DfronrBaken andCompany, and 0.5%

palladiunronl/ inchraetivated alumina. pellets, from i Y theJ. Bishop-and CompanyvPlatinum ,Works A par ticular advantage of palladium as acatalyst is that a relatively low temperature of-about 100 C., is-suitable for oxidizing hydrogenwithoutoxidizing saturated hydrocarbons. Cupric oxide can also be used, atl a tem perature of about 300 C. lIn connection with the use of palladium, it shouldY be noted that unsaturated hydrocarbons such as ethylene or propylene may combust at low temperatures approachingthose used for hydrogen combustion. However, that isgenerally of no consequence since such unsaturated hydrocarbons do not nor mally occur in the gas fraction of natural petroleum. They may be introduced linto the mud stream artiicially, as, when light diesel oil is/usedto form an emulsion mud; but thenrof course their presence maybe readily accounted for. I i

Returning to the..device shown` in Fig. 2,l the gasfair mixture obtained from the drilling mud ispassed into tube 14, past the catalyst 1,6 maintained at a suitable temperature so that hydrogenwill be oxidized and hydrocarbons will not, through the tube 1 5 'and finally through the hot wire gas detector.

It will be understood, however, that any1 methodl of eliminating hydrogen from a gas `mixture may be used, except that it shouldnot be, of active enough nature to cause oxidation or combustion of the other constituents of the gas mixture, particularly the hydrocarbons, which as explained are the saturated hydrocarbons ofv the methane series. 'Broadly speaking,therefore, I provide a catalyst which is active enough under the conditions employed to convert hydrogen .to water withoutoxidizing or otherwise changing saturatedhydrocarbons all in the presence of air. Specific hydrogen absorbents may of course also beutilized. Y

Anexample of the great utility of myy process appears inFig. l. This is a composite log against depth of a portion of a well drilled for oil, in which the depth figures are shown in column 3 of the figure. Reference numeral i of Fig.,l shows the log of percent sand in cuttings, and reference numeral'2 indicates the curve showing `the drillingrate in feet vper hour atwhich the successive strata were drilled. Reference numeral7 shows the logof the meter reading of total gas obtained bythe use of a hot wire detector on the gas taken from the drilling mud in the` manner described, but without the use of the present invention. In other words, in obtainwere not plotted as such since, as has been pointed out, a negative quantity of methane has no physical meaning. Curve 5 of Fig. l shows the total gas reading obtained after hydrogen had been removed by means of a palla dium black catalyst operated at about 100 C. in the manner described; Curve y4 is the corresponding methane curve, obtained by operating the detecting filament at a lower temperature and subtracting the two readings.

Comparison of curves 6 and7 on the one hand,.with 4 and 5 on` the other. reveals some startling diierences. In the lirst place the total gas curve 7 has several times the absolute magnitude of the total gas curve Sthroughout the entire gas portion log. The reason for this, of course, is that hydrogen was present in the mud during the period shown, and contributed heavily, and in fact overwhelmingly, to the gas detector filament reading. However, this curve is practically meaningless for the purposes lat-hand, since the well wasrdrilled in searchof hydrocarbons instead of hydrogen, in which the latter undoubtedly arose adventitiouslyv from corrosion of steel during the drilling operations or the like. The second observation which'may-be made is that the large amount ot'.` hydrogen present masked the methane completely except where themethane content was very high. Curve 6 shows only the high peaks of curve 4, and all of the highly signicantdetails for strata indicating medium and low amountsrofv methane is missing from curve 6. On the other-hand, curves 4 and 5. are diagnostic of the strata penetrated, andthe slight difference'between curves 4 and 5 at alldepths indicates that the gas present was largely, methane, which is exactly opposite to the conf clusionwhich would be erroneously drawn from a comv ing the curve .7, the detecting filament was operated ata I temperature high enough tol combust all of the hydrocarbons including methane and therefore high enough to combust hydrogen gas. The curve indicated by 6 is the difference curve correspondingto methane, obtained by operating the filament at thefloiver temperaturedescribedv hereinabove, so that all` hydrocarbons and hydrogen,.if any, except methane would becombusted. In'those por-v tions of curve 6 where the indicated reading is zero,:.for. the most part a-negative difference was obtained, which resulted from. the Presence Qghydtgeen' as described; hereinabove, although the negative reading differences parison:of.curves 6. and 7. Theadvantages of the invention, therefore, inpresenting an accurate and useful picture'of the hydrocarbons present are immediately apparent 'from the above.

It will ,be noted from the descriptionand examples given of the invention that new and highly useful results are obtained thereby. It is therefore to be understood that the invention is a broadone and although specific embodimentshave been described, such modifications as may be made by the broad scope of the invention and the claims appended hereto are intended to be included herein.

What I-claim is:

l. The methodof logging a well drilled with the aid of circulated drilling mud fluid for the determination of certain hydrocarbon content which may include saturated hydrocarbons, wherein a portion of any gas entrained in the mud uid issuing from the well is continuously removed, admixed with a substantial quantity of air, tested for the presence ofsaturated hydrocarbons by burning in contact with an electrically heated catalytic wire wherein measured changes of resistance of said wire are an indication ofthe quantity of hydrocarbon burned, the step of eliminating inaccuracy of indication by removing the hydrogen prior to the said catalytic burning by passing the gas-air mixture over a catalyst consisting essentially of palladium on an inert carrier, and maintaining saidcatalyst at a temperature high enough to combust hydrogen buttoolow to combust saturated hydrocarbons.

2. The method of logging a well drilled with the aid of circulated drilling mud uid for the determination of the contentof certain saturated hydrocarbons, wherein at least a portionof any gas entrained in the mud Huid issuing fromthe well is continuously removed, admixed with suicient quantity of air to support the combustion of any iniiammable. gases in the mixture, tested forquantity of saturated hydrocarbons by burning said hydrocarbons by andin contact with an electrically heated catalytic wire wherein measured changes of resistance of said wire arean indication of .the relative quantity of hydrocarbonsrburned, the step of eliminating erroneous indications resultingy from the presenceof hydrogen in the gasmixtureby removing the Vhydrogen prior to said ca ta.- lyti burning by passing the whole portion of the air-gas 5 mixture over a catalyst consisting essentially ofl palladium on an inert carrier, and maintaining said catalyst at a temperature high enough to combust hydrogen and unsaturated hydrocarbons present but too low to combust saturated hydrocarbons.

3. The method of logging a well drilled with the aid of circulated drilling mud uid for the determination of the content of certain saturated hydrocarbons of the methane series, wherein at least a portion of any gas entrained in the mud Huid issuing from the well is continuously removed, admixed with a suicient quantity of air to support the combustion of any inammable gases in the mixture, passed over a catalytic wire heated at one time to a temperature to burn all but the methane and at another to a temperature to burn all hydrocarbons therein, wherein measured changes of resistance of said wire are an indication of the relative quantity of hydrocarbon burned at each time and difference in quantities is representative of the methane content, the step of eliminating erroneous hydrocarbon quantity indication resulting from the presence of hydrogen in the gas mixture by removing the hydrogen prior to said catalytic burnings.

4. The method dened in claim 3 in which the said step includes the removal of unsaturated hydrocarbons along with the hydrogen.

References Cited in the file of this patent UNITED STATES PATENTS 2,489,180 Hayward Nov. 22, 1949 2,591,808 Guild Apr. 8, 1952 2,694,923 Carpenter v Nov. 23, 1954 OTHER REFERENCES Dennis et al.:` Gas Analysis, The MacMillan Co., revised ed. (1929), pages 155-170 (QD-121-D4 1929).

Claims (1)

1. THE METHOD OF LOGGING A WELL DRILLED WITH THE AID OF CIRCULATED DRILLING MUD FLUID FOR THE DETERMINATION OF CERTAIN HYDROCARBON CONTENT WHIC MAY INCLUDE SATURATED HYDROCARBONS, WHEREIN A PORTION OF ANY GAS ENTRAINED IN THE MUD FLUID ISSUING FROM THE WELL IS CONTINUOUSLY REMOVED, ADMIXED WITH A SUBSTANTIAL QUANTITY OF AIR, TESTED FOR THE PRESENCE OF SATURATED HYDROCARBONS BY BURINING IN CONTACT WITH AN ELECTRICALL HEATED CATALYTIC WIRE WHEREIN MEASURED CHANGES OF RESISTANCE OF SAID WIRE ARE IN INDICATION OF THE QUANTITY OF HYDROCARBON BURNED, THE STEP OF ELIMINATING INACCURACY OF INDICATIN BY REMOVING THE HYDROGEN PRIOR TO THE SAID CATALYTIC BURNING BY PASSING THE GAS-AIR MIXTURE OVER A CATALYST CONSISTING ESSENTIALLY OF PALLADIUM ON AN INERT CARRIER, AND MAINTAINING SAID CATALYST AT A TEMPERATURE HIGH ENOUGH TO CONBUST HYDROGEN BUT TOO LOW TO COMBUST SATURATED HYROCARBONS.

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