Pak Nyoto, terima kasih pak file Pdf-nya Saya sendiri juga baru tahu kalau log GR jaman dulu satuaannya bukan API tetapi masih CPS...
Praw ----- Original Message ---- From: nyoto - ke-el <[EMAIL PROTECTED]> To: iagi-net@iagi.or.id Sent: Thursday, September 11, 2008 12:13:37 PM Subject: Re: [iagi-net-l] Tanya mengenai unit Log Pak Prawoto, Bisa coba dilihat di link dibawah ini (dari Schlumberger Log Principles Textbook) : http://www.slb.com/content/services/resources/books/lipa.asp?rky=552&; Disitu ada file2 pdf-nya yg bisa di-copy langsung, didalam buku2 tsb ada teori mengenai log GR & Density serta log2 lainnya, bagaimana cara pengukurannya & kalibrasinya ke angka2 porosity dll. Saya akan coba attach-kan salah satu textbooknya yg ada teori log GR & density, tapi ke japri aja ya, soalnya filenya besar2. Dibawah (warna biru) ini saya coba juga copykan sedikit "teori"nya. Semoga membantu. wass, nyoto DENSITY LOGS Density logs arc primarily used as porosity logs. Other uses include identification of minerals in evaporite deposits, detection of gas, determination of hydrocarbon density, evaluation of shaly sands and complex lithologies, determinations of oil-shale yield, calculation of overburden pressure and rock mechanical properties. Principle A radioactive source, applied to the borehole wall in a shielded sidewall skid, emits medium-energy gamma rays into the formations. These gamma rays may be thought of as high-velocity particles that collide with the electrons in the formation. At each collision a gamma ray loses some, but not all, of its energy to the electron, and then continues with diminished energy. This type of interaction is known as Compton scattering. The scattered gamma rays reaching the detector, at a fixed distance from the source, are counted as an indication of formation density. The number of Compton-scattering collisions is related directly to the number of electrons in the formation. Consequently, the response of the density tool is determined essentially by the electron density (number of electrons per cubic centimeter) of the formation. Electron density is related to the true bulk density, eb, which, in turn, depends on the density of the rock matrix material, the formation porosity, and the density of the fluids filling the pores. Equipment To minimize the influence of the mud column, the skidmounted source and detector are shielded. The openings of the shields are applied against the wall of the borehole by an eccentering arm. The force exerted by the arm, and the plow-shaped design of the skid, allow it to cut through soft mudcakes. Any mudcake or mud remaining between the tool and the formation is "seen" as part of the formation and must be accounted for. A correction is needed when the contact between the skid and the formations is not perfect (mudcake or irregularities in the borehole wall). In unfavorable cases this correction can be fairly large. If only one detector is used, the correction is not easy to determine because it depends on the thickness, the weight, and even the composition of the mudcake or mud interposed between the skid and the formations. In the FDC* compensated formation density tool, two detectors of differing spacing and depth of investigation are used, as shown on Fig. 5-12. The chart of Fig. S-13 is a plot of long-spacing versus short-spacing count rates. Points for a given value of eb and various mudcake conditions fall on or very close to an average curve. Using Fig. B-12-Schematic drawing of the dual spacing Formation Density Logging Device (FDC). (Ref. 16) Fig. 5-13-"Spine-and-ribs" plot, showing response of FDC counting rates to mudcake. (Ref. 16) these average curves it is possible to enter the chart with the two count rates and determine the corrected eb from the plot without any explicit measurement of mudcake density or thickness. This measurement technique is referred to as "spine and ribs." The correction is made automatically and the corrected ~b curve and Ae (the correction made) are recorded directly on the log (Fig. S-14). The distance between the face of the skid and the extremity of the eccentering arm is recorded as a caliper log, which helps to assess the quality of contact between the skid and the formation. 2008/9/11 prawoto syuhada <[EMAIL PROTECTED]> > > > Bapak dan ibu sekalian, ada pertanyaan dari seorang mahasiswa, apakah ada > yang bisa bantu???? > Pertanyaan lengkapnya: > > Perkenalkan nama saya Hidayat Saputra > Saya seorang mahasiswa Teknik Geofisika yang sedang melaksanakan Tugas > Akhir (TA). > Saya ingin bertanya pak..... > > 1. Bagaimana prinsip dasar pengukuran log GR dan log density > sehingga bisa di dapat satuan Counts Per Second (CPS). atau API dan > Gramm/Cc > 2. Bagaimana cara mengkonversi log Gamma Ray dari CPS ke pada API. > 3. Bagaimana cara mengkonversi log Density dari Counts Per Second (CPS) ke > Gram/ CC > > Adakah Rumus yang bisa digunakan untuk mengkonversi satuan > tersebut. Bagaimana cara perhitungannya? Adakah buku atau paper yang > dapat saya baca untuk penjelasan diatas? > Bantuan dan penjelasan dari Bapak sangat saya harapkan > > Atas perhatiannya saya ucapkan terima kasih. > Jawabannya di tunggu ya...... > > Hormat saya > Hidayat S. > > >
