Trabajo presentado en el 24 WGC. Disponible en CD en la biblioteca. Solicite este trabajo por email a biblio@iapg.org.ar

Since the year of 2000, the gas production in China has been increasing dramatically as a result of the large-scale application of the advanced practicable fracturing and acidizing technology, of which the annual averaged increment being more than 16%. In view of the complexity of natural gas fields in China, such as low-permeability sandstone, carbonate, fissured volcano and ultra-high temperature and in-situ stress, etc, the main fracturing and acidizing technologies and their countermeasures corresponding to above mentioned formation types are put forward in the paper. Normally, the characteristics of low-permeability sandstone gas field are summarized as low-porosity(<10%), low-permeability(<0.1×10-3 µm2), low-bearing(Sg<50%), thin-multilayer and complex “Five Sensitivities”, etc. The key difficulty is how to maintain effective long-term fracture conductivity and how to get an uniform profile stimulated vertically in case of multilayers. And the main technologies formed include fracturing and acidizing technology to enhance the period of stable production and separate layer fracturing and acidizing technology, of which, the former consists of low-damage fracturing material(ultra-low concentration CMHPG, alcohol super grade guar fracturing fluid, emulsified fracturing fluid, etc.), experimental study of long-term fracture conductivity and the control method of the relative factors, dimensionless proppant coefficient optimization and design method and “artificial fracture network “ fracturing method, etc. The latter consists of anti-sand-seize multistage packer separate layer fracturing and selectively separate layer fracturing with the seal balls put in pad fluid, etc. On the other hand, the characteristics of carbonate gas field are summarized as complex storage types, strong anisotropy, high Young’s modulus, etc. The key difficulty is how to get a deep penetration fracture length. And the main technologies include surface cross-linked acid deep acid fracturing, gelled acid or emulsified acid with multi-stage injection sealed by fracture closure acidizing technology and hydraulic sand fracturing technology. Nowadays, Surface cross-linked acid fracturing combined with proppant fracturing technology is under pilot experiment. Thirdly, the characteristics of volcanic gas field are summarized as poor physical property of matrix(K<0.02x10-3 µm2, porosity<4.0%), densely distributed natural fractures, high in-situ stress, high Young’s modulus and thick pay layers, etc. The key difficulty is how to create the artificial major fracture in order to connect the different microfissure systems. And the main technologies include large-scale proppant fracturing technology, consisting of mini fracturing before main frac, physical modeling technology of artificial fracture creation and extension in naturally fractured reservoir, small particle size proppant technology, spiral mode or slug mode of proppant pumping schedule and real-time control of net pressure technology, etc. While the abnormal high temperature and high in-situ stress gas fields are mostly encountered in low permeability sandstone gas filed, carbonate gas filed and volcano gas filed, and the key difficulty of fracturing and acidizing lies in the fact that how to improve rheology characteristics of high temperature fracturing fluids and how to effectively reduce acid-rock reaction velocity so as to get a highly penetrated fracture length. In addition, how to effectively reduce well head treating pressure is another difficulty encountered most frequently. Correspondingly, the main technique formed is the heavier fracturing fluid and acid fluid technique which can withstand high temperature. What’s more, Several countermeasures on site are developed in order to improve the effectiveness of stimulation treatments corresponding to above mentioned formation types, such as field quality control technique, “three variance” fracturing fluid, proppant slug technique, comprehensive loss control technique, comprehensive fracture height control technique, simplified mini-fracture technique and risk management as well. It has a great significance not only ensures treatment success but also maximal post-stimulation performance. An excellent result is expected after applications of above mentioned stimulation technologies in targeted gas fields, with the corresponding daily gas rate and reserves increasing significantly, which improves the pace of gas exploration and development, now it is just at the peak time in China. And the future development tendencies are mainly focused on coil tubing fracturing and acidizing technique, horizontal well and multiple well bore fracturing and acidizing technique and fracture diagnostic technique under the condition of multiple fractures,etc. Key words: complex gas field; sandstone gas reservoir; carbonate gas reservoir; volcanic gas reservoir; abnormal HPHT; post-frac stable effective period; zonal fracturing; depth acid fracturing; proppant fracturing for carbonate reservoir; control of principal fracture; heavier fracturing and acidizing fluid system