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Home All issues Volume 74 (2019) Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles, 74 (2019) 57 Full HTML
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Table 1

Flow state division and model comparison.

Sequence number Flow period Curve characteristics of the Darcy model Model comparison
1 Pure wellbore storage stage Curves of pseudo-pressure and derivative coincide and exhibit an upward line with a slope of “1”. The models keep consistent.
2 Skin effect transition stage The pressure derivative curve exhibits like a “hump”.

  • Nonlinear model is consistent with Darcy model.

  • The pressure derivative curves of the fractal model and fractal nonlinear model are lower than the other two models.
3 Early radial flow The pressure curve continues to rise and the pressure derivative curve is shown as a level straight line, whose value is related to L D . The results of model comparison are the same as the second flow stage.
4 Early linear flow The pressure derivative curve manifests as a straight line with a slope of “0.5”, reflecting linear flow characteristics around the reaction fracture.

  • Nonlinear model is consistent with Darcy model.

  • The slope of the pressure derivative curves of the fractal model and fractal nonlinear model are slightly larger than the other two models.
5 Mid-term radial flow  The pressure derivative curve behaves as a horizontal line with the value of “0.5”, indicating the oil stored in the fracture system flows radially to the horizontal well.

  • Nonlinear model is consistent with Darcy model.

  • The pressure derivative curves of the fractal model and nonlinear model still rise slowly, and the height of the derivative curves begin to exceed the other models.
6 Cross flow stage of cave system to fracture system The pressure derivative curve is characterized by a concave, which is the typical response of the oil transfers from cave system to fracture system.

  • Nonlinear model is almost consistent with Darcy model.

  • The pressure and derivative curves of the fractal model turn upward, but the width and depth of the concave of the derivative curve do not change.

  • Fractal nonlinear model is similar to fractal model except that the concave of the derivative curve becomes narrower and shallower.
7 Pseudo radial flow of cave system and fracture system The pressure derivative curve shows a “0.5” level line without considering the stress sensitivity.

  • Nonlinear model is consistent with Darcy model.

  • The pressure and derivative curves of fractal model turn upward.

  • The pressure curve of the fractal nonlinear model is similar to fractal model except that its derivative curve shows a more obvious upwarping.
8 Cross flow stage of matrix system to fracture system The flow stage is similar to the sixth stage, except that the cross flow coefficient of matrix system to fracture system is smaller and the concave section of derivative curve appears later. The results of model comparison are similar to the sixth flow stage except that the concave of nonlinear model becomes narrower and shallower.
9 Late radial flow The pressure derivative curve shows as a horizontal line with the value of “0.5” without considering the stress sensitivity. It means that the production has gone up to a unified state of dynamic balance.

  • Nonlinear model is consistent with Darcy model.

  • The pressure and derivative curves of fractal model and fractal nonlinear model turn upward sharply.

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