In geology, bulk density is a function of the density of the minerals forming a rock i. Lithology from well log data of nahr umr formation in luhais oil field. Litho density tool different materials have different abilities to photoabsorb gamma rays. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Lithology and mineralogy in well log analysis, the terms lithology and mineralogy are used with some ambiguity. The paper presents a numerical algorithm that performs accurate lithology. Lithology and porosity determination the measurements of the neutron, density, and sonic logs depend not only. It s also useful in the detection of gasbearing formations and in the recognition of evaporites. Pdf lithology and soil relationships for soil modelling and. It is conceptually the easiest of the porosity logs to interpret because, if ever a tool obeyed a linear bulk mixing law, it is the density logs. The density log measures the bulk density of the coal reservoir and associated rocks figure 7. Common toc from density logs methods are highly susceptible to borehole effects i.
Interpretation of porosity and fluid constituents from well. Tied to lithology, porosity, and fluid content density log dphi % porosity rhob bulk density gcm3 porosity. Bear creek valley and adjacent ridges are log interpretation by patrick tucci, both of the underlain by rocks of cambrian age fig. A combination of these logs gives good indications for lithology and more accurate estimates of porosity. Porosity logging the porosity of a zone can be estimated either from a single porosity log sonic, density, neutron, or magnetic resonance log or a combination of porosity logs, in order to correct for variable lithology effects in complex reservoirs. Formation lithology explorer flex service baker hughes, a.
If there is already a lithology pattern or lithology description column in the current log design to which youll be linking the data, you can use the data update data file from log design tool to insert a new lithology datasheet in the current data file. If ngs logging data are available, we determine the type of clay. Chapter 6 lithology and porosity determination flashcards. The collection of wireline log data includes sonic log, density log, resistivity log, calliper log, porosity log, shale volumetric log and gamma ray log as shown in table 1 and figures 1 to 8. Density log introduction the density log belongs to the group of active nuclear tools, which contains a radioactive source and two detectors. You can use the pick intervals tool to interactively pick lithology intervals from a geophysical or other crosssection. Pdf a newtonraphson approach for geophysical well logs. The natural gamma ray spectra, pe, density, and neutron expanded response equations can be combined to solve for porosity and to estimate volumes of calcite, quartz, dolomite, clay, feldspar, anhydrite, and salt.
Porosity determination using most of the logging devices presented in earlier chapters relies on a knowledge of the parameters related to the type of rock being investigated. In the standard sequential interpretation process, the analyst determines porosity directly from the density log. Neutron porosity and density logging weatherford international. The baker hughes rockview interpretation system combines geochemical data measured by the flex and bhge spectralog devices for accurate insitu mineralogical characterization. In the carbonates, mineral mixtures are primarily drawn from calcite, dolomite, and. Pdf reservoir characterization and identification of formation. Litho density tool this is called photoelectric absorption, and is a completely different process from compton scattering. Density apparent porosity the bulk density measurement, b, principally responds to formation electron density such that, 1 1. The log displayed counts per second, which was transformed to density by a semilogarithmic transform. Bishop b, john r wilford c a office of environment and heritage, po box 644, parramatta, new. Density logging is a well logging tool that can provide a continuous record of a formations bulk density along the length of a borehole. Lithology is also determined from the logs, because each main reservoir lithology has characteristic responses.
And for mixed fluid saturation, average bulk modulus and density of the effective fluid is estimated by using the following relations domenico, 1971. Density logs first appeared in 1957, based on the principle of gamma ray absorption by compton scattering. The formation density tools are induced radiation tools. The zone of interest is typically a sandshalesand sequence. Frequently, lithologies are derived by pattern recognition of the gr, density, and neutron log responses. Additionally, the interactive matrix scale method is applied to field examples of varying geology and lithology, namely, carbonate, sil. This effect can be used to provide a parameter which is dependent upon the atomic number of the formation, and therefore immensely useful in lithological. Geological survey, strike approximately north 55 degrees east. When the neutron and bulk density measurements are displayed together, either the density porosity or the bulk density can. The effects of components of the matrix on neutron porosity and bulk density are proportional to their. Pdf lithology and soil relationships for soil modelling. If the lithology is known, the neutron log can be used to calculate porosity. Log corrections locate mud cake determine salinity. Identify fractures correlation seismic data fluid saturation.
This means that if you do not initially know the regional stratigraphy, and cannot define discrete layering, you can still plot observed lithology in logs and log based crosssections. The dip of the rock varies from 30 to 70 degrees to the southeast, but the average dip is about 45 degrees well construction fig. Sonic log correlate seismic data in time to well data in depth density log tool emits gamma rays detects returning scattered gamma rays gamma ray absorption is proportional to rock density measures density. A logging tool that could measure lithology and produce a lithology log would be a valuable tool. Bulk density typical well log responses lithology fluid gamma ray caliper sp density neutron. Lithology indicators logs can be used to interpret lithology. The available well logs such as sonic, density, neutron, gamma ray, sp, and.
The density tool or gamma density tool utilizes a gamma ray source placed a distance from the gamma ray detector, which measures gamma ray count that is an inverse function of the density of the coal or. Start studying chapter 6 lithology and porosity determination. The spectral gamma ray log is helpful in sandstones containing potassium feldspars or thoriumbearing clays. Density logging is another application of gamma rays in gathering data. Each individual log records an apparent porosity that is only true when the zone lithology matches that used by the logging engineer to scale the log. Some subsequent delineation wells are likely to be cored over the entire of the reservoir interval. The combination of density and neutron logs is now used commonly as a means to determine porosity that is largely free of lithology effects. Its main use is to derive a value for the total porosity of the formation. Cross plotting of rock properties for fluid and lithology. Identify rocks shale volume correlation bed boundaries porosity. Where, rhob density log, rho s clay density and rho k kerogen density. Early tools were called gamma gamma density logs because they emitted and recorded gamma rays. Rpt analysis of well logs for lithology and fluid classification 3 reuss average, 1 i r ii f m m.
Lithology and soil relationships for soil modelling and mapping jonathan m. When software is applied to multiple logs in a well defined area, methods have been demonstrated that give lithological representations. A deterministic lithology model for the green riverupper. The bhge formation lithology explorer flex elemental spectroscopy wireline logging tool reduces uncertainties when gathering insitu mineralogical data. Generally, the neutron and density logs are run together. In the case of the density tool, the density of the rock matrix must be known. The pe photoelectric log may also be run to further improve the lithology description. One tool that is considered by many to measure lithology is the photoelectric density tool. The matrix travel time is used in interpreting the compressional wave interval transit time. When porosities from two measurements are displayed in the same log track, the porosity values are always displayed on the same scale, and are referenced to the same lithology. Lithology gr density neutron acoustic resistivity peanhydrite.
Lithology is often used to describe the solid matrix portion of the rock, generally in the context of a description of the primary mineralogy of the rock e. Rock physics template rpt analysis of well logs for. The ability of the pef log to accurately indicate lithology is not impaired in gasbearing zones, where the combination of the formation density and neutron logs may have difficulty distinguishing between lithologies. Reading lithology from a neutron density porosity log overlay. Type of porosity logs sonic log density log neutron log none of these logs measure porosity directly the density and neutron logs are nuclear measurements the sonic log use acoustic measurements a combination of these logs gives good indications for lithology and more accurate estimates of porosity. The result is that gamma rays attaining energies less than 0. In the last lesson we saw how it is now common practice to display both the density and neutron porosity curves, as a means to correct for the effect of different lithologies. The program will know how to name the datasheet tab based on the log design information. Ultrahpht neutron porosity and density logging determine neutron porosity and formation density in extreme conditions the heatwave extreme density service provides realtime measurements in highpressure, hightemperature hpht environments up to 30,000 psi 206. Lithology gr density neutron acoustic resistivity peanhydrite dolomitebackup compiled by geoff page and simon miller, graphic design by wendymclachlan baker atlas formation evaluation inteq 0. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Condition method log matrix lithology is known and the two log curves separate density porosity is less than neutron porosity if density porosity is less than neutron porosity, such as in a sandstone with shaleclay content, the density log provides a reasonable approximation of formation porosity.