Oil & Gas Geology ›› 2015, Vol. 36 ›› Issue (5): 842-847.doi: 10.11743/ogg20150517

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Opening mechanism of dynamic fractures caused by water injection and effective adjustments in low permeability reservoirs, Daqing oilfield in Songliao Basin

Wang Wenhuan1, Peng Huanhuan1, Li Guangquan2, Lyu Wenfeng1, Wei Chenji1, Qin Yong1   

  1. 1. Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, China;
    2. Oilfield Service Corporation, SINOPEC, Beijing 100020, China
  • Received:2015-04-10 Revised:2015-06-20 Online:2015-10-28 Published:2015-10-23

Abstract: The performance of water flooding in low permeability reservoirs of Daqing oilfield is not satisfied due to the dynamic induced fractures.Understanding of the opening mechanisms of the dynamic induced fractures and optimization of development adjustment schemes are critical to improving water flooding recovery.Geomechanics, reservoir engineering and numerical simulation methods were utilized to establish a new method to calculate the fracture opening pressure and reveal propagation mechanism.Corresponding adjustment measures are proposed for different fracture opening scenarios.Results indicate that when injection pressure exceeds the current minimum horizontal principle stress, dynamic fractures will open first in the direction of the maximum horizontal principle stress.Then, they may open in the direction of line connecting injector and producer that has the smallest included angle with current maximum principle stress along with the rising injection pressure.Based on calculation methods of fracture opening pressure and in combination with the conditions of A reservoir in the periphery of Daqing oilfield, a critical injection pressure of 9 MPa is determined for fracture opening.Actually the injection pressure of A oilfield is up to 12~14 MPa.When the line of injection wells is in parallel with the current maximum horizontal principle stress, fractures only open in the direction of the maximum horizontal principle stress, and remaining oil are distributed along the fractures on both sides.Otherwise, fractures open in multiple directions, and the remaining oil distribute irregularly.Based on the remaining oil distribution under different well patterns, a new concept is proposed that 'controlling the opening of multi-directional dynamic fractures through limiting injection pressure and line flooding along the dynamic fracture in parallel with the maximum horizontal principle stress and lateral matrix displacement'.Water injection pressure limits and well pattern adjustment strategies are proposed under the gui-dance of this concept, and their field application is very successfully.

Key words: water flooding dynamic fracture, well pattern infilling adjustment, low permeability reservoir, Daqing oilfield

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