PMC

Field results from the SX-108 core, including stratigraphy, counts of ¹³⁷Cs from down-hole spectral gamma logging, in situ temperature, and moisture content from down-hole neutron logging and laboratory measurements. High counts of ¹³⁷Cs were observed immediately after samples were passed through the backfill surrounding the tank (see Fig. ). Blow counts refers to the number of hammer strikes required to advance the borehole a given distance by cable tool drilling. SGLS, spectral gamma logging system. (Reprinted from reference with permission of the publisher.)

Average values of various characteristics of gas bearing mudstones in Shanxi formation of four wells. Response characteristics from logging data (a). Mineral characteristics (b), geophysical and geochemical characteristics (c) from core measurements. Where GR is the natural gamma ray, RT is the deep lateral resistivity, AC is the acoustic transit time, DEN is the density, CNL is the neutron, K is the potassium, TH is the thorium, U is the uranium, H is the thickness, TOC is the total organic carbon content, and Ro is the vitrinite reflectance.

Average values of various characteristics of gas bearing mudstones in Shanxi formation of four wells. Response characteristics from logging data (a). Mineral characteristics (b), geophysical and geochemical characteristics (c) from core measurements. Where GR is the natural gamma ray, RT is the deep lateral resistivity, AC is the acoustic transit time, DEN is the density, CNL is the neutron, K is the potassium, TH is the thorium, U is the uranium, H is the thickness, TOC is the total organic carbon content, and Ro is the vitrinite reflectance.

A field example of correcting the invasion of oil-based mud to field NMR logging in well B. In the first track, the displayed curves are gamma-ray (GR), borehole diameter (CAL), and bit diameter (BIT). The second track is the depth. The third is resistivity curve. The acoustic transit time log (AC), the density log (DEN), compensated neutron log (CNL) are shown in the fourth track. The fifth track is the initial measured T₂ spectrum of NMR logging before correction (Initial T₂ spectrum). The T₂ spectrum of nuclear magnetic resonance logging (Corrected T₂ spectrum) under the condition of water-based mud corrected by the method proposed in this study is displayed in the sixth track. The NMR calculated porosity (NMR-por) and core analysis porosity (Core-por) are shown in the seventh track and have good consistency. The Corrected SDR permeability is calculated permeability from the corrected T₂ spectrum by using Schlumberger-doll-Research (SDR) model, and the Initial SDR permeability is estimated permeability from the Initial T₂ spectrum by using the SDR model, the Core-permeability is derived permeability from core analysis. The ninth track is the permeability calculated by using the traditional porosity-permeability relationship (Fitted permeability). Good consistency of estimated permeability from the Corrected T₂ spectrum with core derived permeability illustrates the reliability of the proposed method.