What We Have Learned on Shale Gas Fracturing During the Past Five Years in China

摘要

Scale development of shale gas in North America has greatly stimulated the enthusiasm of China. Since July 30, 2010 the first shale gas well fracturing, more than 300 wells have been fractured in the past five years in China, an average post-frac production is more than 6E4m3 /d for one well. Technology include pre-frac evaluation, the methods of fracturing design, fracturing materials, tools and equipment, gas factory workflow and quality control system has formed. Basis on the study following recognition can be drawn: ①natural fracture distribution、stress difference and fluid viscosity are the key factors to create the complex fracture; ②geological engineering integration concept has been implemented and application successful; ③formulated the principle to improve SRV+3C (complexity, connective, conductivity), design method of shale gas reservoir stimulation has formed; ④formed including of transverse fracture to the horizontal wellbore set, PNP multi-stage fracturing, "the 3 big 2 low 1 small" (Large amount of liquid, proppant, high injection rate. Low fluid viscosity, sand concentration. Small diameter particle combination proppant) design, real-time quality control techniques, and multi-well simulfrac/zipperfrac technology, gas factory workflow, etc.; ⑤ construction capacity and parameters have reached the normal level of North America. Horizontal lateral up to 1000-2000m, single stage 60-100m, single well stages up to 25; For one stage fluid volume is generally 1600-2200 m~3 , proppant is normally 60-170t/stage, pumping rate is 8 -16 m~3 / min; Usually for zipper-frac 2-4 stages can be finished in daytime, and 6 stages for simul-frac, post-frac production is from 6 to 55 (E4 m~3 /d) for a single well. In this paper, not only successful experience on shale gas well fracturing are presented, but also some challenges, such as casing deformation, frature discription, water shortage etc.