hb paper was praaantad at ma 551rIAnnual Fall TOChnrCal C4nfefence and ExhMcm of the SocIeIY of ?elroleum Engmeara of AIME, held in Dallaa, Texaa, Serwmw 21.24, 19S0, ha materialISaubjw! 10corrwtkm by the author. Pernvas!on 10WY la resmclad 10an abatracI of not me Ihan 300 Words Wrte: 6200 N. Central EXPWY.,Dallas. Texaa 752W. q ABSTRACT Z = atomic numberThe calibration and recording of the compensated A = atomic weight Density Log using a digital logging system is discussed. The mathematical definition of the spine and ribs k and explained. A log example is calculated using the count rates in the calibration blocks and count rates at a point pa= 1.0704 Pe -1883 ,,, ,, .,.,, ,,, ,., . (2) on the log to obtain bulk density (Pb) and the amount of correction (Ap), where CALIBRATION STANDARDS pa= apparent bulk density as read by the tool. (112]
American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract The Direct Digital Logging System, first introduced in 1975 as a new concept in well logging, has proven the feasibility of digital systems for recording logs. The surface equipment necessary to produce logs includes a mini-computer and laser recorder, along with other input/output devices and is well sected for wellsite formation analysis. Log signals are sampled four times per foot and are recorded in engineering units on per foot and are recorded in engineering units on magnetic tape cartridges. Depth shifting required to match subsequent logs to the base log is performed through a calculator type keyboard, with the data interpolated between the depth shift points. Interpolation is possible because of the three inch depth increments. The advantage of interpolation in depth shifting is that no data is lost or created at the depth shift points. Environmental corrections are applied to the log trace data to remove borehole effects. Computer performed corrections such as borehole correction to the performed corrections such as borehole correction to the Induction Log and mud cake correction to the Sidewall Neutron Porosity Log removes the need for departure charts and hand calculations. With the digital system, wellsite quick look calculations are performed after the logs are recorded and environmentally corrected, all the data is studied, appropriate parameters are selected, and the program is executed. The digital system is an improvement over existing analog systems because the digital system does not require parameter selection before the logs are run, and the computing is not performed as the well is logged. Digital quick look techniques presently available are logarithmic F overlays and R with porosity. More detailed evaluation can be performed at wellsite, going beyond the quick look methods. For example, the Induction Electrical Log (IEL) and the Compensated Density Log (CDL) can be combined and solve for volume of shale, shale corrected porosity, and water saturation. Also the Sidewall Neutron Porosity Log (SNP) and the Compensated Density Log (CDL) combination will resolve cross-plot porosity and apparent matrix density, which combined with resistivity often provide good results in complex lithology. provide good results in complex lithology. The new concept of wellsite Direct Digital Logging and computed formation analysis opens a new era in log evaluation. The opportunity to obtain computed logs has been moved to the wellsite, and the applications are just being realized.
SPE c Copyr!ghl 1977. American Insolule 01 Mmrg. Metal lufglcal. and P&rOIWm Engineers. Inc Th,s paper was presented at the 52nd Annual Fall Techmcal Conference dnd Exhlbmon of the SOC!ely of Pelroleum Engineers of AlME. held m Denver Colorado. OCI 9.12. 977 The material IS subjecl to correchon by thP author PermK.s,ofl to copy IS restricted to an abstract of nOl more than 300 words Wfile 6200 N Central Ex.py. Dallas. Texas 75206 ABSTRACT Hand held progmmmable calcul:,tors have solved a portion of this problem by aiding the analyst in the tedious calculations(2). A wellsite computer program is described which solvas forThis approach is a vast improvement over hand calculations, but Wrosity and water saturation in formations that hava complex as a practical matter, there is time for only selected intervals to iithologies. The reconnaissance portion of the technique combines be analyzed. The technique is time consuming because log data ;he"responsesof a neutron, density, and sonic to identify Iithology must be manually entered for each level of calculaticm. and formation characteristics. The reconnaissance program can also be utilized as a quick look interpretative technique and as an Second, if the logs are processed at a remote computer aid in the selection of parameters for the advanced computation. complex, the time required to receive the results can be quite lengthy and can incur additional costs because of the waiting The advanced technique employs Iithology models determined involved. by the responsesof the neutron, density and sonic logs,Total porosity is computed from the neutrondensit y combination basedon the Previous methods have been used to solve for complex correct Iithology model, and is checked against the sonic Ic.g for Iithology interpretation( 3'4'5). These techniques use a neutronthe presence of secondary porosity. Water saturation is then density crossplot approach for Iithology and porosity determinacomputed and the resultsare printed graphically on a laser recorder. tiers with high level logic to handle the effec!s of shale and residual When gas is encountered, the residual hydrocarbon saturation
The recent evolution of equipment capable of measuring the relative dielectric constant of a formation has stimulated new approaches to the evaluation of water saturation. In many oil productive reservoirs, the formation water resistivities are either unknown or are very high; thus complicating conventional resistivity dependent solutions for water saturation.By determining the relative dielectric constant of the formation and through application of the Lichtnecker and Rother equation for the dielectric constant of mixtures, the analyst may identify the presence of hydrocarbons and in many cases, quantify reserves. Additionally, a quick look overlay technique for qualitative evaluation can be utilized. These procedures can be of great help in both exploration and development environments where conventional methods have led to confusion.
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