Application of Pin-Point Sand Jet Perforating Annular Fracturing in Multiple Coal Seams Unleashing Clean Energy in Southwest China

Abstract

AbstractGuizhou Province which located in the southwest China is one of China's least developed but fastest growing provinces, has large reserve potential for Coal Bed Methane (CBM) but yet, the natural gas utilization is among the lowest in China. The exploitation of CBM resources in the province started since early 90's, but no substantial breakthrough has been achieved. Among all the challenges encountered in the attempt to develop the resources, one key challenge is on how to frac stimulate the coal seams effectively. The high coal-rank CBM reservoirs commonly contain low permeability multiple thin coal seams that require frac stimulation to flow. However, conventional blanket-type frac treatment via pumping down casing at high rate has been shown to leave some coal seams untreated and not contributing.Pin-point fracturing using coiled-tubing allows multiple precisely targeted coal seams to be treated, which can increase gas flow rate and reserve, and significantly shorten time cycle as compare to conventional casing frac method. Three CBM wells in the north-west Guizhou province in China have been pin-point stimulated using coiled-tubing producing gas at an encouraging rate compared with conventional method.This paper discusses how the pin-point fracturing technique been introduced for the very first time to Guizhou CBM wells, the details of the concept, fracturing process, operational methods, treatment outcome of the field trial, and how the technology could shape the future of CBM exploitation strategy in Guizhou Province.