Petroleum Reservoir Evaluation and Development ›› 2021, Vol. 11 ›› Issue (5): 782-792.doi: 10.13809/j.cnki.cn32-1825/te.2021.05.017

• Comprehensive Research • Previous Articles    

Analysis of fracture geometry for refractured vertical wells in tight conglomerate reservoir

LEI Yangyang1(),WANG Hui2,WU Xin2,YANG Li3,SHI Le2,WANG Shuai2   

  1. 1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China
    2. The Second Oil Production Plant of Xinjiang Oilfield Branch, Karamay, Xinjiang 834000, China
    3. Sichuan Changning Natural Gas Development Co., Ltd., Yibin, Sichuan 644000, China
  • Received:2021-04-16 Online:2021-10-26 Published:2021-10-12

Abstract:

Refracturing is currently one of the most used methods to rejuvenate productivity of existing wells in low-permeability reservoirs in China. Different refracturing strategies have been conducted for vertical wells in a tight conglomerate reservoir in the Xinjiang. However, the underlying mechanisms are still unclear. By establishing the geomechanical model, the mechanism model of pore pressure inducing stress change based on the finite element method and the numerical model of unstructured reservoir, the researches on the fracture geometry of refracturing and the effect of different refracturing methods have been carried out. The results are as follows. Compared with the initial fracturing and conventional refracturing, the fracture geometry changes significantly after the volume refracturing. The azimuth of the in-situ stress before and after production does not change significantly, but the changes in pore pressure and in-situ stresses have a great impact on the geometry of hydraulic fractures. For the layers that have been perforated and produced, due to the strong energy loss, the propagation of fracture is more difficult, resulting in short fracture length and wide fracture width. In the case of adding new perforation in un-developed layers, as the formation can provide enough energy, it is easier to propagate fractures. The wells which are at the higher place of the new perforation layers have better productivity after the volume refracturing. The timing of refracturing also has a significant impact on oil production. A proper choice of refracturing time can effectively improve the well productivity.

Key words: refracturing, fracture geometry, numerical simulation, stress field, hydraulic-mechanical coupling, tight conglomerate reservoir

CLC Number: 

  • TE357