The Application of Refracturing Technique in Horizontal Wells of Daqing Oilfield

Abstract Aiming to the development of the tight reservoirs with low permeability in Daqing Oilfield, the horizontal well fracturing technique has achieved good results. However, the output gradually decreases later. The initial average daily oil production per well is 17.0t and drops to 2.6t after some time. Also, the wells with the production lower than 2t constitute more than 50%. Thus, to realize the economic and effective exploitation, the refracturing technique is needed to improve the production. According to the geological and producing conditions, two optimization methods have been formed, including the chart method and the dynamic method. Based on cement quality and wellbore integrity of horizontal wells, 2 kinds of refracturing pipe strings including the double-packer isolation refracturing one and the single-packer isolation refracturing one have been formed. Besides, based on the initial fracturing parameters and completions, 4 refracturing modes are formed aiming to 4 scenarios including inadequately fractured stages, new fractures supplement, diverter refracturing within the fractures and multi-stage diverter refracturing, and are carried out for field tests. (1) Small-scale initially fractured wells can be treated by the massive in-situ refracturing and 15 wells field tests are carried out. Compared with the initial fracturing, the sand amount and fracturing fluid are increased by 58% and 145% respectively and the daily oil production increases from 0.4t to 4.2t after refracturing. (2) The wells having sparse initial fractures can be treated by refracturing to infill new fractures and 13 wells field tests are carried out. Compared with the initial fracturing, the gaps among fractures are reduced by 54.7%, and the daily oil production is increased from 1.7t to the 4.6t after refracturing. (3) The wells with small angles formed by two directions between initial artificial fractures and wellbore can be treated by the diverter refracturing and 3 wells are treated by this to increase the production from 1.63t to 5.33t. (4) 2 wells having not been sectionally fractured in light of their poor cement quality have been treated by the diverter refracturing within the scope of the whole wellbore, with the production increased from 1.5t to 4.5t. In general, the daily oil production of 33 wells is averagely increased from 1.1t to 4.5t, which reaches 70.4% of the production after the initial fracturing.