Study and field test of low damage massive hydraulic fracturing techniques in tight gas reservoirs in the south of Songliao Basin

Deep tight gas reservoirs in the south of Songliao Basin feature in complicated lithology, low porosity, ultra-low permeability, ultra depth, high Yang’s modulus, high pressure and high temperature. The key difficulties encountered include small proppant volume, low proppant concentration and early screen-out so that it is very difficult to get a satisfied post-fracturing effect. So a low damage massive hydraulic fracturing technique is put forward in this paper with the key object being low damage, longer penetration, and high fracture conductivity. To sum up, the highlights include fine formation evaluation before hydraulic fracturing, low damage fracturing fluid which can withstand high temperature and high shear rate, combination of different diameter of high strength proppants with smaller one being the main body, multiple stage optimization of fracturing design, spiral or slugging mode of proppant pumping schedule, new corresponding measures etc. By conducting nine well tests in two years, the hydraulic fracturing success ratio and effective percentage has been improved a lot than ever before （from 50% to 80% above）, with the proppant volume and proppant concentration breaking through history records continuously （such the maximal proppant volume is 90 m3 compared with 30 m3 below in the past mostly）, which provides technical support for tight gas exploration and development in the south of Songliao Basin.