Dizhi lixue xuebao (Feb 2021)

Distribution characteristics of the present-day in-situ stress in the Chang 6 tight sandstone reservoirs of the Yanchang Formation in the Heshui Area, Ordos Basin, China and suggestions for development

  • LIU Jian,
  • HUI Chen,
  • FAN Jianming,
  • LYU Wenya,
  • WANG Jiwei,
  • YIN Chen,
  • WANG Haonan

DOI
https://doi.org/10.12090/j.issn.1006-6616.2021.27.01.004
Journal volume & issue
Vol. 27, no. 1
pp. 31 – 39

Abstract

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Tight reservoirs feature poor physical properties and strong heterogeneity. The distribution of present-day in-situ stress affects tight reservoirs in the drilling operation, well pattern deployment, fracturing transformation and water injection management. The microseismic monitoring method and the hydraulic fracturing data were used respectively to analyze the direction of present in-situ stress of single well in the Chang 6 reservoirs and the magnitude of present-day in-situ stress of single well in the study area. Combining the analysis with the characteristics of structure, sedimentation and lithofacies in the study area, we built a three-dimensional heterogeneous geological model. Based on the triaxial rock mechanics test and operation data, we identified the physical parameters of different facies, and built a three-dimensional mechanical model. Also the Ansys finite element numerical simulation was applied to build a three-dimensional present-day in-situ stress distribution model of the Chang 6 reservoirs. The simulation results showed that the maximum horizontal principal stress ranged from 34 MPa to 42 MPa, the minimum from 25 MPa to 36 MPa, and the horizontal differential stress from 3 MPa to 10 MPa. The simulation results of the wellpoint stress had a less than 10% margin of error compared with the actual measurement, proving the simulation results are reliable. It was inferred from the simulation results that the present-day in-situ stress distribution in the study area was mainly affected by the difference in rock physical and mechanical properties, but less by the tectonic framework. On the basis of the result analysis, it is suggested that natural fracture should also be considered as an influencing factor when wells are deployed in the study area. Meanwhile, in order to reduce development cost as much as possible, industrial wells should be generally deployed in the place with low stress as for the area with equal differential stress.

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