The study and application of hydraulic fracturing and acidizing in exploration wells in China

The characteristics of exploration zones in China in recent years are summarized as: 1) Special lithology such as volcano and clay-carbonate, etc. 2) low porosity and ultra-low permeability; 3) Complex storage types and fluid flow mechanics as a result of natural fractures distributed stochastically; 4) Special in-situ stress and loss characteristics; 5) complex rock mechanics and elastic-plastic traits; 6) Undetermined fracture height growth; 7) complex stress sensitivity. Therefore, a systematic technologies are put forward in the paper, the highlights are: 1) Systematic formation fine evaluation which contains Nuclear Magnetic Resonance, Constant Rate Mercury Injection and so on; 2) Low damage fracturing fluids such as super grade Guar fracturing fluid and its combination with liquid nitrogen, low cost VES(less than 300 RMB below 90 °C), low polymer concentration fracturing fluid and linear gel, and variable viscosity is utilized in different treatment stage; 3) Different type and diameter proppants are used in one treatment job, and the combined ratio is optimized; 4) A new method of multiple stage optimization is put forward to ensure not only the success of stimulation treatment but also the maximal post-treatment performance; 5) Counter measures are applied systematically such as two combinations of pumping rate and viscosity to control loss and multiple fractures, fracture height control, systematic quality control and post-treatment management, etc. What's more, above technologies have been put in to field applications in more than 39 wells in the year of 2005, and the result is satisfied with the newly increased oil reserves being greater than 1 × 10 8 t, gas reserves greater than 800 × 10 8 m 3. Consequently, it has a great significance in China's main exploration zones, in the mean time, it also has a great benefit of economy and hydraulic fracturing and acidizing themselves. Copyright 2006, Society of Petroleum Engineers.