Full Length Article Measurement of total porosity for gas shales by gas injection porosimetry (GIP) method Jianmeng Sun a , Xu Dong a,b,⇑ , Jinjie Wang c , Douglas R. Schmitt b , Chunlu Xu a , Tariq Mohammed b , Dewen Chen a a School of Geoscience, China University of Petroleum, Qingdao 266580, China b Department of Physics, University of Alberta, Edmonton T6G2R3, Canada c Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China highlights  Total porosity measurement for gas shales with gas injection method is investigated.  Effects of pressure, particle size and crushing level are investigated.  ESH pyrolysis evaluation technique of hydrocarbon cleaning effect is proposed. article info Article history: Received 19 May 2016 Received in revised form 9 August 2016 Accepted 3 September 2016 Available online 12 September 2016 Keywords: Gas shale Porosity Gas injection porosimetry (GIP) Gas injection pressure Size effect ESH pyrogram abstract Porosity is considered one of the most important rock physics parameter when evaluating a gas shale reservoir’s production potential. The measurement of total porosity by the gas injection porosimetry (GIP) method in these low permeability rocks with complex mineralogy has usually proven to be chal- lenging. It is not rare for results to vary from different laboratories but the reasons behind these incon- sistencies are not fully understood. These differences are commonly attributed to apparatus (different performances of porosimeter), core cleaning (lacking of cleaning effect evaluation criteria and arbitrary drying) and measurement (insufficient gas injection pressure and inconsistent crushing level). In this study, systematic experimental investigations are conducted to study the impact of these factors in deter- mining gas shale’s total porosity using the GIP method. We propose a modified porosimeter design to meet the particular needs of gas shales. Helium is used to minimize adsorption via the molecular sieve effect that can occur during gas shale porosity measurements. ESH (extended slow heating) pyrolysis and TGA (thermal gravimetric analysis, 200 °C) techniques are also adapted to evaluate core cleaning effects ensuring that only integrated matrix is left in the sample. The experimental results indicate that the ESH pyrolysis technique produces more reasonable results than the Rock-Eval II pyrolysis in free hydrocarbon cleaning effect and solid organic matter integrity evaluation when experimenting on gas shale and other organic-rich rocks. Besides, the effects of gas injection pressure and particle size on porosities measured with plug samples and crushed samples are studied. Results show that the gas injec- tion pressures play an important role in both crushed and uncrushed samples’ porosity measurements. It is proven through this series of experiments that both the plug and GIP methods can effectively measure the total porosity of gas shales. The plug sample requires a higher minimum injection pressure and more total diffusion time in the total porosity estimation with respect to crushed sample, because these two parameters are greatly decreased by crushing. Note that the lower crushing level should be controlled not to alter the integrity of grain size composition. The porosity resulted by GIP method is interpreted as total gas accessible porosity. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Gas shale refers to an unconventional hydrocarbon resource and has become a major target of energy resource development in recent years. In order to improve the formation evaluation and http://dx.doi.org/10.1016/j.fuel.2016.09.010 0016-2361/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: China University of Petroleum, Qingdao 266580, China. E-mail address: dongxu985@gmail.com (X. Dong). Fuel 186 (2016) 694–707 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel