Abstract:

A new baseline expression (named as ΔlgR’_base) of ΔlgR for non-source shale was introduced to automate ΔlgR-based TOC interpretation and improve both the accuracy and the repeatability of the result. The improved ΔlgR method was then applied in the Songliao basin and the result is showed as follows: ΔlgR’_base varies little with the average at 2.4 in the Qingshankou Formation(K₂qn), which is supported by the quiet lacustrine deposition environment in that period; the coefficient (expressed as a) of w(TOC) and ΔlgR is not rigorously correlated to maturity (vitrinite R_o%) and the relationship of w(TOC) and ΔlgR can be generously expressed as w(TOC)=5ΔlgR＋0.3 for the low-mature to mature source rock in the K₂qn, indicating that the coefficient “a” is constant, i.e a=5; organic-rich source-rocks were mainly deposited in the K₂qn¹  and the lower part of K₂qn²⁺³ , and the thickness of these organic-rich source-rocks decreases from south-east to north-west in horizontal.

Key words: well logging, source rock, organic carbon, ΔlgR, Songliao basin