Pdf total and spectral natural gammaray logs of core. Total and spectral natural gammaray logs of core samples article pdf available in arabian journal for science and engineering 311 january 2006 with 1,566 reads how we measure reads. Spectral gammaray and palynological characterization of. Pdf on jan 1, 2016, jolanta klaja and others published geological interpretation of spectral gamma ray sgr logging in selected boreholes. The spectral gammaray log is a measure of the natural radiation in rocks. Data from ammonoidbearing marine horizons provide a set of criteria which are.
Common applications of the spectral gamma ray log are in the estimation of clay mineral volumes and types, and the recognition of fractures that have had uranium salts precipitated in them by groundwater systems. The on e or more gamma ray detectors are disposed at the periphery of the. Gamma ray log records the total natural gamma radi ation in the borehole. Halliburton s csng tool measures the entire gamma ray spectrum see illustration from 0 to 3,000 kev, and uses special borehole compensation techniques to create accurate logs of k, u, and th concentrations. The amplitude of the signal from the gamma ray tool, which is just a sensor with no active source, is proportional to the energy of the gamma ray photons it encounters.
This is because the radioactive elements tend to concentrate in clays and shales. The one or more gamma ray detectors are disposed at the periphery of the. The main issues affecting the quality of the logs are tool calibration and drilling mud composition. Us7253401b2 spectral gamma ray loggingwhiledrilling. Geological interpretation of spectral gamma ray sgr logging in selected boreholes.
This gamma radiation originates from potassium40 and the isotopes of the uraniumradium and thorium series. Spectral gamma logging evaluate shale organic content and well placement with azimuthal borehole coverage the spectralwave spectralazimuthal gamma ray sensor provides azimuthal gamma ray borehole images, precise total gamma ray, and realtime potassium, uranium, and thorium k, u, th data. The gammaray log is a measurement of the natural radioactivity of the formation. Gamma ray logs used for source rock studies must be corrected for borehole size. Citeseerx document details isaac councill, lee giles, pradeep teregowda. The total gamma ray spectra measured is resolved into the three most common components of naturally occurring radiation in sands and shalespotassium, thorium, and uranium k, th, and u, respectively.
The relative contributions of these elements to the total gamma ray gr log pro. Its measure the intensity of natural radioactivity of rocks. The amplitude of the signal from the gammaray tool, which is just a sensor with no active source, is proportional to the energy of the gammaray photons it encounters. A gamma ray well log is a recording of the natural gamma radiation of the formation around the well bore and is almost always run in conjunction with other well logs. Gamma ray log 1 records radioactivity of a formation 2 shales have high gamma radioactive response 3 gamma ray logs are most commonly used logs for sequence stratigraphic analysis. The gamma ray log is widely used to interpret grain size profiles in sedimentary. The sgr tool measures the naturally occurring radioactivity of the formation surrounding the tool and outputs the results as a gross gamma ray curve. A total gammaray well log is a recording of the total natural gamma radiation of the formation around the well bore, whereas the spectral gammaray well log is a recording of the relative amounts of the three main constituents that are the sources of the natural radiation potassium, uranium, and thorium. Spectral gammaray grs logging is a powerful tool in cyclo and sequence stratigraphy of carbonate depositional systems. Spectral gamma ray tool baker hughes, a ge company. By analysing the energy levels of the incoming gamma rays in a 256channel spectrum, the tool provides the amount of potassium, uranium, and thorium contributing to the total gamma ray count. The halliburton logiq spectral density log sdl tool provides superior measurements of the bulk density.
It is a wireline logging method used in mining, mineral exploration, waterwell drilling, for formation evaluation in oil and gas well drilling and for other related purposes. The hagr tool contains a ring of geigermuller tube detectors that acquire azimuthal gamma ray data in both rotating and sliding drilling modes. Waterbearing zones water saturation sw geopressure detection depth of invasion stratigraphic correlation the borehole environment r resistivity ohms. Ca2497355a1 spectral gamma ray loggingwhiledrilling. Spectral gamma ray characteristics the gamma ray is an important tool for the petroleum geologist as it measures the natural radioactivity of rocks and can be used both on the surface and in the subsurface to distinguish lithology and formation contacts. Spectral gammaray characteristics of the succession spectral gammaray units good quality gammaray logs were recorded for about 65% of the drilled intervals on leg 150 figs. This starts out exactly the same as the standard gross gamma ray count log.
Note high resistivity upper and lower shales, which are the source rock for the oil in the sand. The use of spectral natural gammaray analysis in reservoir. Output curves spectral neutron logshydrogen chlorine natural gamma ray neutroninduced gamma ray casing collar locator benefits of the spectral neutron tool cost effectiveexcellent results at reduced costs. Spectral gr the spectral gamma ray sgr log records not only the number of gamma rays emitted, but also the energy of each processing that information gives curves for the presence of th, k and u in the formation high k, high gr response may indicate a feldspathic, glauconitic or micaceous sst. The sgr740 gamma ray core logger measures the energy level and quantity of the radiation emitted from a core sample and calculates the quantity of each of the elements. A spectral gammaray well log is a recording of the relative amounts of the three main elements that create the natural radiation potassium, uranium, and thorium. Before you can start interpreting spectral gamma ray logs or, indeed, any kind of data, you need to ask about quality. Spectral gamma ray distinguishes the different sources of gamma rays clay content organic content resistivity log applications determination of hydrocarbonbearing vs. Gamma spectral logs will discriminate multiple radioactive species. For standard gamma ray logs, the measured value of gamma ray radiation is calculated from concentration of uranium in ppm, thorium in ppm, and potassium in weight percent. Pdf use of spectral gamma ray as a lithology guide for.
A log of natural gamma ray spectroscopy is usually presented as a total gamma ray log and the weight fraction of potassium %, thorium and uranium ppm. The gamma ray log is a measurement of the natural radioactivity of the formation. In this study the log runs through casing or in bad holes hole 903c have not been used. Purchase of an open document does not constitute license for republication in any form, nor does it allow web posting without prior written permission.
Natural gamma ray spectroscopy logs were introduced in the early 1970s, although. By appropriate filtering, the total gamma ray flux can be separated into the three components. In siliciclastic systems with low chemical maturity, the multicomponent character of sediment complicates the interpretation of such logs. Total and spectral gamma natural radioactivity from potassium 40k, uranium 238u and thorium 232th of core samples from a local well were determined in the laboratory. In the analysis of spectral gamma ray data, use is commonly made of the ratios of the abundances of the main radioactive sources. Whereas the spectral gamma ray log is able to differentiate between the different radioactive elements k. Wellog has developed a basic six channel spectral gamma logging system for logging applications. These are real shales with gamma ray readings between 250 and 500 api units. A highresolution spectral gammaray sgr log is compared to elemental whole rock geochemical data in a reservoir scale outcrop analogue, the otter sandstone formation sherwood sandstone group, east. The spectral gammaray log geological log interpretation. Investigation by spectral gammaray sgr and inductively coupled plasmamass spectrometry icpms geochemical analyses of the upper jurassic arabd reservoir analogue central saudi arabia revealed a strong correlation between the sgr response of. The ofite sgr740 gamma ray core logger measures the energy level.
The geological interpretation of well logs 07 gamma. Gamma ray log shamshad ppt materials chemical substances. A case study from the wenchuan earthquake fault scientific drilling project borehole 4 wfsd4. Spectral gamma ray logging is used to quantify the clay type, volume and mineralogy within the host reservoir rock through the discrimination of natural radionuclides of potassium, uranium and thorium.
Example of a spectral gamma ray log track 1 on a resistivity log on low resistivity, radioactive bakken sand 4 ohmm in best sand. Gain of the gamm a ray detector is controlled automatically through analysis of the spectra. The counts recorded on a standard gamma ray log are the sum of all gamma rays, most of which are emitted by potassium40 and. Gamma ray logging is a method of measuring naturally occurring gamma radiation to characterize the rock or sediment in a borehole or drill hole. Clean formations usually have very low level of radioactivity 3. Detailed sedimentological, spectral gammaray and palynological sampling of three sections through the kinderscoutian r1c ammonoid biozone in a northsouth transect across the pennine basin allows the recognition of features which are diagnostic of maximum flooding surfaces in diverse depositional settings. The cesium7 source, tungsten shielding, and two highefficiency. Lithologic analysis log input spectral gamma ray tools spectral gamma ray tools provide insight into the mineral composition of formations.
By running a spectral gammaray log, shales moderate potassium and thorium contents, but low uranium could be differentiated from. Because the gamma ray log does not change with well treatment or production, it can be used to correlate the depths of the other well. Being able to differentiate between photons of differe. In sedimentary formations the log normally reflects the shale content of the formations. Naitl detector and an electronic setup coupled to a pcbased data acquisition. Now that we know how the tools work, we are ready to discuss how gamma ray logs are used in log analysis. Gamma rays have longer penetrations than either alpha or beta rays, and can be measured by simple counter devices, such as a geiger counter. The spectral gamma ray log is a measure of the natural radiation in rocks. Spectral gamma ray characteristics of the succession spectral gamma ray units good quality gamma ray logs were recorded for about 65% of the drilled intervals on leg 150 figs. A common gamma ray log records the total radiation and cannot distinguish between the radioactive elements, while a spectral gamma ray log see below can. Spectral gamma ray logs geological society, london. Crains petrophysical handbook natural and spectral gamma. Use of spectral gamma ray as a lithology guide for fault rocks. A method for determining concentrations of naturally occurring radioacti ve elements in earth formation by analysis of gamma ray energy spectra measured by at least one gamma ray detector while the borehole is being drilled.
Pdf spectral gammaray logs and palaeoclimate change. The stateoftheart tool design enables the sdl tool to achieve high gammaray count rates with minimal borehole sensitivity. The spectral gamma activity trends were deduced by analyzing the spectra. Gammaray logging has evolved from a qualitative estimation of the variation of natural radioactivity with depth in a borehole, using a geigermuller detector, to a sophisticated quantitative logging technique which yields information on the identification and amount of the radioelements present, as well as data on the likely geologic history of mobilisation of these radioelements in. The spectral gamma ray sgr tool measures the quantity of naturally occurring potassium k, uranium u, and thorium th with a scintillation detector. While the gamma ray log traditionally has been used primarily for welltowell correlation, it also plays a role in quantitative log analysis.
Comparison between outcropspectral gamma ray logging and. The latest variant on the gamma ray log is the spectral gamma ray log. High resolution spectral gamma ray log search and discovery. The result is a log of various energy gamma rays called a gamma spectral log. A total gamma ray well log is a recording of the total natural gamma radiation of the formation around the wellbore. The stateoftheart tool design enables the sdl tool to achieve. Crains petrophysical handbook natural and spectral. Pdf petrophysics msc course notes spectral gamma ray log. The hagr hostile azimuthal gamma ray tool is a rugged sensor, providing an accurate total gamma ray log, as well as realtime and recorded azimuthal gamma ray images. What is commonly known as the gamma log, is actually differentiated into the 1 gamma ray log, and 2 the spectral gamma ray log.
A highresolution spectral gamma ray sgr log is compared to elemental whole rock geochemical data in a reservoir scale outcrop analogue, the otter sandstone formation sherwood sandstone group, east devon. Using the spectral gamma ray log, zones of high uranium radiation can be detected figure 7,25, and other logs may be used to confirm the hypothesis, sourcerock evaluation the relationship between organic matter and uranium, is the basis for being able to. Before you can start interpreting spectral gammaray logs or, indeed, any kind of data, you need to ask about quality. Pdf total and spectral natural gammaray logs of core samples. Gain of the gamma ray detector is controlled automatically through analysis of the spectra. The radioactive particles like uranium, potassium, thorium are very fine grains. This spectral gamma tool can log through steel, pvc and other types of casing. Natural gammaray borehole logging is a recognized technique for evaluating uranium deposits and providing lithographic data. Crains petrophysical handbook basic physics natural. A method for determining concentrations of naturally occurring radioactive elements in earth formation by analysis of gamma ray energy spectra measured by at least one gamma ray detector while the borehole is being drilled. Schlumberger 1982 has described two types of gammaray logs. Gamma ray spectral log in gamma ray spectral logging, the three main gamma ray contributors, potassium k, thorium th, and uranium u, give gamma rays of different energy levels. A spectral gamma ray well log is a recording of the relative amounts of the three main elements that create the natural radiation potassium, uranium, and thorium.
Gamma rays from the formation are counted in a detector system. The spectral stripping algorithm supports up to three isotopes maximum. Petrophysics msc course notes spectral gamma ray log. Different types of rock emit different amounts and different spectra of. Multifunction workhorse helps characterize reservoirs compensated spectral natural gamma ray csngsm service helps you thoroughly characterize reservoirs and confidently estimate net pay. The 1460 kev gamma energy of 40k, 1765 of 214bi for uranium and 2615 kev of 208tl for thorium were analyzed. The potassiumthorium crossplot is useful for the recognition of clay minerals and distinction of micas and kfeldspars. Gamma rays are emitted by at least 24 of the 37 common natural radiaisotope of the dtu6un and uranium series and potassium. Data from 902d are used with caution because hole conditions above 500. Integration of spectral gammaray and geochemical analyses. However, there is an added level of sophistication.
Composite spectral gamma ray log of the goodland formation. The service can detect producible zones by distinguishing clean reservoir rock or radioactive pay zones from shales. These handheld gammaray measurements can sometimes be useful in matching the recovered core to the borehole logs, providing better depth positioning of the core pieces. The primary standards for the weight fractions are formations with known quantities of the three isotopes. The natural gamma radiation of rocks is the composite of emissions produced by isotopes of potassium k, thorium th, and uranium u dypvik and eriksen, 1983. A better indicator of increased organic matter content with increasing gamma ray signal can be obtained using only the uranium signal derived from spectral gamma ray logs fertl and rieke, 1980. Gamma ray log shamshad ppt free download as powerpoint presentation.
Pdf geological interpretation of spectral gamma ray sgr. The gamma ray log is the simpler of the two and only measures the total radioactive count rate in api units. Radioactive isotopes of elements continuously decay to more stable forms and emit radiation of several types. Note that even at v0 there is a gradual change from the gamma ray count in one formation and that in the next.
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