Abstract
Considering the rheological properties of fluid, reservoir heterogeneity, and eccentricity factor, the productivity formula of horizontal well for the power-law fluid heavy oil reservoir is derived by transforming the three-dimensional seepage problem into a two-dimensional seepage problem. The heavy oil production calculated by this formula is in good agreement with the actual production in the offshore oil field. Then, the influencing factors of production are analyzed, and the results show that the power-law index has the greatest influence on production. When the power-law index is less than 0.8, the production increases slowly with the power-law index and when it is greater than 0.8, the production increases faster. The power-law index has a greater impact on production for higher production pressure differential and longer horizontal well. Anisotropy has significant influence on the production. When the value of Kh/Kv is less than 10, the production decreases rapidly with the Kh/Kv; after the value of Kh/Kv is greater than 10, the production decreases slower. Eccentricity has trivial impact on the production.
Highlights
Heavy oil reservoirs are widely spread all over the world and has huge reserves in China, which provides an important guarantee for the security of Chinese energy supply (Li et al, 2016; Wu et al, 2016; Jiang et al, 2019; Jiang et al, 2021)
Compared to the thermal recovery method, the heavy oil reservoir cold recovery method has the benefits of lower energy consumption and better economic advantages
The productivity formula of the inner zone is given by the following equation: FIGURE 2 | Influence of power law index on production under different horizontal well lengths
Summary
Heavy oil reservoirs are widely spread all over the world and has huge reserves in China, which provides an important guarantee for the security of Chinese energy supply (Li et al, 2016; Wu et al, 2016; Jiang et al, 2019; Jiang et al, 2021). It is shown that the partial heavy oil is a power-law fluid and exhibits non-Newtonian fluid characteristics during the flow. Cold production means that the heavy oil is developed by the natural reservoir energy. The productivity formula of horizontal well for the power-law fluid heavy oil reservoir is derived, considering heavy oil rheological characteristics, reservoir asymmetry, and eccentric factors and is verified by the actual production of an offshore oilfield. Where v is the seepage velocity, m/s; K is the porous medium permeability, μm; μb is the apparent viscosity of heavy oil, mPa s; n is the power-law index; Φ is the porosity of porous media; H is the consistency coefficient, mPa Sn and; μeffis the bed factor of the formation. The inner zone is the radial flow on the plane perpendicular to the horizontal well axis, and the outer zone is the flow of the fluid far away from the horizontal well, and can be approximated to the flow on the horizontal plane with an oval drainage area
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