Abstract
The enormous unconventional gas resources can make an effective contribution to the world's economy as conventional hydrocarbon reserves are depleting rapidly. Oil-producing countries can produce from unconventional gas resources in order to fulfill their local demands and export most of the oil produced. However, for production at economical flow rates, the reservoir volume needs to be increased after stimulation treatment, which is a big challenge for the industry.
This study aims to provide a new stimulation technique after the hydraulic fracturing stimulation to increase the stimulated reservoir volume by creating localized fractures and connecting the existing fractures using thermochemical reagents. Thermochemical reagents generate heat and pressure that cause microscale fractures in tight reservoir formations, thus increasing the fracture complexity. Microscale fractures, in turn, increase the porosity and permeability, causing sweet spot creation near the fracture zone.
A set of thermochemical reagents was used for flooding the samples under pressure and heat until an exothermic reaction took place. An integrated methodology was implemented to investigate the role of thermochemical stimulation on different rock types, including Scioto sandstone, Indiana limestone, and Berea sandstone, through routine core analysis and advanced spectroscopic analytical techniques, such as porosity, permeability, microcomputed tomographic (MCT) imaging, capillary pressures, and nuclear magnetic resonance (NMR). In addition, ultrasonic velocity (compressional- and shear-wave) measurements were performed, and dynamic elastic parameters (Poisson's ratio and Young's modulus) were determined.
The monitoring techniques exhibited significant changes in petrophysical, strength, and other mechanical properties in rock samples as a result of the exothermic reaction inside the core samples. The MCT images revealed microfractures in the core sample generated as a result of the thermochemical treatment. Post-treatment measurements exhibited a substantial increase in porosity and permeability. A reduction in capillary pressure was observed after the treatment.
The consequence of this study is to introduce a new, economical, and practical approach to increase the stimulated reservoir volume. This new stimulation technique will assist in meeting the difficult challenges related to producing unconventional reservoirs. Thermochemical stimulation may create multidirectional microfractures within the reservoir that better enhance the effective permeability around the wellbore as compared to hydraulic fracturing stimulation. This new thermochemical stimulation is a promising technique for the Middle East, where water scarcity is a big problem. A huge amount of water currently being used for hydraulic fracturing treatment could be redirected for other purposes. The outcome will result in a tremendous enhancement to unconventional gas production.