Effective Exploitation Potential of Shale Gas from Lower Cambrian Niutitang Formation, Northwestern Hunan, China

Abstract

The marine shale in the Lower Cambrian Niutitang Formation is the dominant shale-gas reservoir in northwestern Hunan, which accounts for more than 70% of unconventional energy in Hunan province. Accurately evaluating the shale-gas exploitation potential is a key to determining whether commercial exploitation standards can be met. In the literature, most existing studies have focused on evaluating the shale-gas exploitation potential based on either accumulation conditions or the shale fracability, which will lead to a gap between the real production and proven gas reserves due to the characteristics of the shale’s low permeability and low porosity. Therefore, further studies are needed to evaluate the effective shale-gas exploitation potential. To address this need, the outcrop shale samples in the Niutitang Formation were collected from the target regions, and the geological characteristics, mechanics behavior, and microstructure performance were discussed via both field data and laboratory tests. The results revealed that the shale-gas exploitation potential in the Niutitang Formation was indicated to be comparable to that of five validated shale-gas exploitation regions in the United States. To further illustrate the effective shale-gas exploitation potential, this study suggested using a comprehensive evaluation framework for this purpose, in which both accumulation condition and the shale fracability are simultaneously considered. Therefore, the shale gas reservoir in the Niutitang Formation has highly effective shale-gas exploitation potential by considering both the accumulation conditions and the shale fracability.

Experimental Gas Generation of Organic-Rich Shales at Different Oil Expulsion Efficiencies: Implications for Shale Gas Evaluation

“…Regarding overmature shale, it is of little significance to evaluate the residual gas generation potential via laboratory pyrolysis, instead concentrating on recovering its original gas generation potential . The residual gas generation potential of the kerogen in the Lower Cambrian Niutitang shale in South China should be insignificant because of the high maturity. , However, a significant amount of gas might originate from the retained oil during the following geological history. , Therefore, assessing the gas generation potential of the retained oil in the shale is key for understanding shale as a geosystem in time and space.…”

“…The Anhua 1 and Jishou 1 wells are located in northwest Hunan Province. Here, the organic geochemical characteristics of the Niutitang shale have been studied in detail. ,, It has been proposed that the R o values of the Niutitang shale in the Anhua 1 and Jishou 1 wells are approximately 2.5% and 2.9%, respectively. ,,− The measured R o can be transformed into EasyRo by the following equations where R o is vitrinite reflectance, %; R Easy is converted reflectance corresponding to EasyRo simulation, %; and L vc is conversion coefficient.…”

Research on Cuttings Carrying Principle of New Aluminum Alloy Drill Pipe and Numerical Simulation Analysis

“…As clean unconventional fossil energy, shale gas has gradually drawn people's attention due to its long exploitation life and low pollution degree [1]. It has been proved that the shale gas reserves in the Sichuan-Chongqing area have reached 100 billion cubic meters [2,3] due to the emergence of new geological equipment such as aluminum alloy drill pipe [4] (after calculation, the drilling depth can reach 50,000 m).…”

Application of Dipole Array Acoustic Logging in the Evaluation of Shale Gas Reservoirs

“…Unconventional oil and gas resources, including shale gas, are very richly concentrated around the world [1]. In recent years, the production of shale oil and gas in North America has increased rapidly, which has made the exploration and development of shale gas around the world, including in China, more popular [2][3][4]. Because of the "in-situ" hydrocarbon pooling pattern of shale gas reservoirs [5][6][7], the identification of conventional reservoirs, inclusive of sandstone reservoirs, fluid property identification methods, and evaluation criteria are not fully applicable to shale gas reservoir evaluation.…”