Standards Development

Scope

The proposed international standard specifies a method for determining desorbed shale gas content at drilling sites. The principle of this method is to heat the core after being extracted from the drilling site to the temperature of the formation fluid and the bottom of the well, obtain the desorbed gas volume using a measuring device, regress the loss gas volume of the core from the bottom of the well to the wellhead through the relationship curve between desorption gas volume and time, then crush the sample to obtain the residual gas volume at the bottom of the well temperature, and finally add up the loss gas volume, desorption gas volume, and residual gas volume to obtain the shale gas content of the reservoir.

Purpose

The development of shale gas resources is experiencing rapid growth worldwide, particularly in regions such as North America, Central Asia, China, Latin America, the Middle East, North Africa, and Russia, which are all rich in shale gas reserves. Global shale gas resources are estimated at approximately 456 trillion cubic meters, about twice the volume of coalbed methane or tight sandstone gas. As a key parameter for evaluating the potential of shale gas reservoirs, the total gas content directly affects resource estimation, economic viability assessments, and the selection of favorable target zones. Therefore, accurate measurement of shale gas content is essential for efficient exploration, development, and value assessment.

Extensive and systematic studies have been conducted by academic and industrial communities worldwide on shale gas content determination methods, including the USBM method, direct measurement method, desorption method, and volumetric-based techniques. For example, Waechter in the United States applied the USBM method under ambient conditions to determine the natural desorption gas content of coal seams, and compared results from different coring techniques using samples from the Green River Basin in Wyoming. Kissell analyzed samples from the Pittsburgh and Pocahontas No. 3 coal seams via desorption tests, demonstrating the applicability of the direct method for gas content measurement of vertical borehole cores. In the Western Canadian Sedimentary Basin (WCSB), researchers used desorption methods to measure the gas content of Devonian, bitumen-rich, dark shales, finding a total gas content range of 0.76–2.95 m³/t, with an average of 1.81 m³/t— significantly higher than other reservoirs with similar thermal maturity. As a core parameter for evaluating the development potential of shale gas reservoirs, gas content directly determines whether a target area is viable for production. Argentina’s Neuquen Basin and three other major basins are rich in shale gas, especially the Jurassic Vaca Muerta Formation, which holds recoverable reserves of 583 Tcf. In such regions, volumetric-based methods are commonly used for resource evaluation. Similarly, in the Santa Terezinha coalfield of Brazil, desorption tests on 12 coal seams and carbonaceous shale samples showed gas contents ranging from 0.32 to 2.18 cm³/g. In Ecuador’s Oriente Basin, the largest hydrocarbon-producing foreland basin in the South Andes, researchers predicted shale gas potential using gas content measurements and conducted comparative analysis with mature U.S. shale plays. Currently, there is no unified international standard for determining shale gas content. Although institutions in countries such as the United States, Canada, and Brazil have developed various testing methods, significant differences in test conditions, application scenarios, and operational procedures make it difficult to compare results across laboratories or achieve global data interoperability. This lack of standardization limits the consistency of data acquisition and impedes the effective global assessment of shale gas resources. Therefore, there is an urgent need to develop an international standard for shale gas content measurement to enable reliable inter-laboratory data comparison, enhance data accuracy, and promote mutual recognition of results globally. Such a standard would support the safe, rational, and efficient development of shale oil and gas resources both domestically and internationally.

In recent years, a series of experimental studies have been carried out through collaboration with industrial partners such as Sichuan Keyuan Engineering Testing Technology Center and academic institutions including Southwest Petroleum University, aiming to validate the reliability of shale gas content measurement methods. Multiple comparative tests have confirmed the method's effectiveness and accuracy. Based on these results, the method has been widely applied in field testing operations, and in 2020, it was formalized in the Chinese petroleum and natural gas industry standard SY/T 6940- 2020 “Determination of Shale Gas Content.” This standard defines clear technical requirements for key stages including sample acquisition, sealing and preservation, desorption testing, residual gas correction, and adsorbed gas calculation, thereby significantly improving the accuracy and consistency of measurement results. Moreover, the research outcomes have been published in several academic papers, providing a strong theoretical and practical foundation for the development of an ISO international standard.