Study and Application of Refracturing Technique in Horizontal Wells in Low Permeability and Thin Reservoir

With the increasing of fracturing ratio of horizontal wells in T reservoir, the production decline of horizontal wells is accelerated during the middle and high water cut stage, and effective refracturing technology should be explored to solve this problem. In this paper, we started with the selection of horizontal wells for repeated fracturing. The selection principle of wells and layers is optimized, and the technical limit of re-fracturing for high water cut horizontal wells and the stimulation model of different permeability ratios with different injection-production well spacing are established, so we can know the refracturing potential of horizontal wells. Through the design optimization of refracturing, a variety of measures are applied to tap the potential of horizontal wells, such as supplementary fracturing, cross-layer fracturing, diverting fracturing and energy-increasing fracturing. In order to further improve the technology of re-fracturing in horizontal wells, it is necessary to optimize the semi-length of fractures, the height of fractures, the construction scale, the sand-adding procedure and the technology of measures, etc. At last we achieved geological-engineering integration and accurated tapping potential, the completion of horizontal wells secondary high-yield. 14 horizontal wells were repeatedly fractured in these three years, and the average daily oil production increased 4.1 t at the initial stage, and at present, the cumulative oil increase of a single well is 1248t, so the measures we taken are good.