Advances in Cryogenic Fracturing of Coalbed Methane Reservoirs with LN2

Abstract

Coalbed methane (CBM) is a significant unconventional natural gas resource existing in matrix pores and fractures of coal seams and is a cleaner energy resource compared to coal and crude oil. To produce CBM, stimulation operations are required, given that the coal permeability is generally too low. Hydraulic fracturing is the most widely used technology for reservoir stimulation; however, there are a few challenging issues associated with it, e.g., huge water consumption. In the past decade, the use of liquid nitrogen (LN2) as a fracturing fluid has been intensively studied for stimulating CBM reservoirs, achieving considerable progress in understanding fracturing mechanisms and optimizing fracturing techniques. This paper presents a thorough review of experimental design and observations, modeling procedures and results, field applications, and published patents. Existing studies are divided into five different groups for discussion and comparison, including immersion tests, injection tests, jet drilling tests, numerical modeling, and field applications. Based on the comprehensive evaluation of the outcomes, it is obvious that cryogenic fracturing using LN2 is a promising eco-friendly fracturing technique that can effectively enhance coal rock permeability to increase the production of CBM.

The Time-Varying Variation Characteristics of Methane during Nitrogen Injection Process: An Experimental Study on Bituminous Coals

“…The N 2 would diffuse into the coal surface with the increase of injection [13]. Thus, the N 2 molecules would collide with the empty adsorption sites which had not yet adsorbed CH 4 molecules [27]. Then, the N 2 molecules would occupy the empty adsorption sites.…”

“…There have been several theoretical and experimental studies on gas injection technology. Longinos et al examined the efficacy of liquid nitrogen in the coal fracturing process in coalbed methane reservoirs [27][28][29]. Wu [31].…”

Cryogenic fracturing using liquid nitrogen on granite at elevated temperatures: a case study for enhanced geothermal systems in Kazakhstan

“…EGS by hydraulic fracturing (mainly multi-zone) commonly outperforms other methods 18 , 23 , 24 . However, hydraulic fracturing creates concerns over extensive water use, formation damage, contingent surface or groundwater contamination, and the cost of chemical additives 25 – 27 .…”

Analysis of the Causes of Altered Coal Seam Permeability Based on On‐Site Directional Long‐Drill Hydraulic Fracturing Tests

“…Hossain [ 35 ] studied how the change of fracturing perforation angle affects the size of fracturing force and the direction of fracture initiation. And with the progress of science and technology Longinos S.N et al [ 36,37 ] proposed LN2 hydraulic fracturing, which is a new type of fracturing method without zero water consumption and pollution. And the effects of four different cryo‐fracturing liquid nitrogen (LN2) treatment processes on coal production increase were compared, especially for the study of the microstructure and permeability evolution law of coal after LN2 treatment, which elucidated the environmental protection behaviour of cryo‐fracturing compared with traditional hydraulic fracturing.…”