North Ordos Gas Field Too 2 Gas Reservoir Hydraulic Fracturing Compound Acidification Technical Research,

Since hydraulic fracturing technology has developed for more than fifty years, it has done an indelible contribution on increasing output of oil well and advancing exploitation level of oil field. However, not all fracturing measure could achieve expected purpose, many wells have little or no effect after fracturing, and one of the important reasons is that fracturing measure injured the reservoir. So it' s necessary to study the damage in the fracture during hydraulic fracturing and find out corresponding method.Hydraulic fracturing design is an important component of hydraulic fracturing, it' s the foundation of fracturing practice. Considering the fracture temperature field, we calculated physical dimension of the fracture using PKN model, estimated the distribution of full-suspended fracturing fluid in the fracture and the conductivity of sand-packed fracture. Because the damage in fracture has grave impact on production response, we induced a model to calculate production response of hydraulic fracturing on the basis of considering damage in the fracture.The damage during hydraulic fracturing mainly included clay swelling and grain migration, built up created by mechanical impurities, the damage of fracture conductivity and so on. Experimental study shows that the damage rate of fracturing fluid to fracture surface is between 31. 84% and 36. 28%; the damage rate to propping agent layer is between 29. 27% and 30. 04%. So, in order to improve post fracture response, we could improve on the post fracture conductivity and advance reservoir permeability nearby the fracture, this is the gist of hydraulic fracturing compounding acidification technique.Reasonable acid system is the key factor of eliminating the fracturing fluid damage to fracture surface and proppant, and also the key factor of making the hydraulic fracturing compounding acidifying technology successful. In this paper, we have done the broken-down effect experiment of fracturing fluid damageusing some kind of available acid, screen out the most reasonable acid composition, and evaluate the effect of the acid. Analyses and contrast shows that, the acid selected by experiment could improve the permeability nearby fracture surface and the fracture conductivity preferably. Through the dispose of acid, if fracturing fluid flow-back drastically, the fracture conductivity could revert back to initial conductivity of the fracture.We calculated production response of hydraulic fracturing and hydraulic fracturing compounding acidification technical, compared of them and analyzes the factor of effecting production response. Comparison of production response of the two methods shows that, on the same reservoir conditions and execution conditions, the production response of hydraulic fracturing compounding acidification is better than that of hydraulic fracturing. For hydraulic fracturing, the damage to fracture surface is ever severe, the permeability of damage zone is ever low, and the production response of hydraulic fracturing is ever junior; for hydraulic fracturing compounding acidification technology, because acid released the damage, the permeability of damage zone would be recovered. The better the acid broke down fracture surface, the higher the permeability of fracture surface recovered, and the more evident the production response is.