The Geochemical Characteristics Of The Shale Of Niutitang Formation In Wenshui Village,Guizhou Province,China

The shale of Niutitang Formation outcropped in Wenshui village. Baihuahu Town, Qingzhen city, Guizhou province was researched. Experiments for organic matter abundance, organic matter type, maturity and rock porosity were taken to discuss the nature and and evolution characteristics of this profile, in addition to preliminarily evaluate the gas potential of shale in the studied area. There isn’t any vitrinite in Niutitang Formation, Lower Palaeozoic,, so the maturity can’t be evaluated by vitrinite reflectance. However, the importance of maturity of source rocks can’t be overstated for the potential evaluation of shale gas potential of the formation evaluation. Severalratios., such as bitumen reflectance, reflectance of vitrinite-like maceral, index of double-adamantane, laser-raman spectrumcan be used to valuate the maturity of Lower Palaeozoic. But most of these methods have some limitation related to practice and application. In this paper, research on the applicability, feasibility of maturity indicators such as reflectance of vitrinite like maceral, index of double-adamantane, laser-raman spectrum were studied by hydrous pyrolysis. Moreover, all these indicators were compared by distribution in real geological section to optimize the applicance in Niutitang Formation in Wenshui village, Guizhou province.The following results are obtained through a series of experiments:1. Two groups of shale sample (GY and DPS) and one coal sample with low maturity (KSL-M and M) are selected out to be analysedThey are divided into two groups to conduct hydrous pyrolysis experiment (DPS&KSL-M, GY&M). The results show that: ①the reflectance of vitrinite like maceral, index of double-adamantane, laser-raman spectrum correlated to vitrinite reflectance (Ro) well, which can be expressed as: Ro=0.040X3-0.138X2+0.540X+1.268; Ro=0.853e2-87XMD; and Ro=0.097d(G-D)-19.743. ② The reflectance of vitrinite-like maceralis not influenced by regional differences and consist with previous research results, being a good indicator of the maturity of the Lower Palaeozoic. ③Index of double-adamantane, laser-raman spectrum are greatly impacted by regional differences or experimental methods, which should be used carefully; especially the index of double-adamantane, which can be used widely afterstandardization of the pre-treatment methods, data analysis method, and the integral method.2. In the shale samples of Niutitang Formation in Wenshui village, Guizhou province, the TOC average was 2.49%, and more than 91% samples with TOC> 0.5%, more than 59% samples with TOC> 2.0%, reaching the standard of "very good" potential of shale gas generation. Equivalent vitrinite reflectance (Ro) of vitrinite like maceral is 2.62% -3.38%. with average as 2.9%, suitable for gas generation and storage. The organic matter types mainly belong to type I, which is helpful for shale gas generation and absorption, the porosity mainly comes from the contribution of nanoscale organic hole, range of 3.27%-14.73%, with average as 11.09%, reaching a high level of porosity. In a word, the potential of the Niutitang shale in Wenshui village, Guizhou province is high for shale gas.