Study On Vertical Wells Steam Stimulation Parameters Optimization With Considering Heat Loss In The Wellbore

With the exploration and development of petroleum, as well as the soaring worldwide demand for oil, the exploitation of heavy oil reservoir becomes more and more important .The heavy oil resources is abundant in the world, rational and effective development of heavy oil is of significant importance to alleviate the energy crisis. At present the main thermal production method is steam soak. Because of its complicated in technique, high investment and economy risk, before the development, various parameters of steam soak must be compared and analyzed, optimizating the thermal systems. In this article , based on lots of investigation and analysis of the internal and overseas heavy oil reservoirs steam injection technology, influencing factors of steam injection of heavy oil reservoir by utilizing a vertical well are studied with numerical simulation method (e.g, wellbore heat transfer effect, geological parameters, injection-production parameters).This article studies steam injection system in order to increase bottom hole steam quality and improve energy utilization ratio of steam injection system. Based on the theories of mass conservation, momentum conservation, energy conservation, and the transfer of heat in the radial directions of wellbore, the comprehensive mathematical model for predicting wellbore steam quality , temperature and pressure distributions is established. In this model, the steam temperature, pressure and dry degree are regarded as variables, considering heat tube structure;the theory of two-phase flow is adopted in the calculation of the pressure drop; the equations are expressed by separable functiong, solving with iterative method and LongGe coulthard method, and the VB language is used to write the calculation program. After obtaing wellbore temperature and the pressure under some formation conditions, this article discussed the the influence of wellhead steam injection parameters (e.g, steam injection rate , steam injection dryness and steam injection time) variation on bottome hole steam parameters (e.g, pressure, temperature, dry degree) , and may offer some reference for subsequent research.Considering wellbore heat transfer, this article studies the effect of geological and fluid parameters on steam soak in details, analyses sensitiveness of various parameters and optimizes steam injection parameters to decrease production decline, play to its maximum potential. Production forecasts of 5 cycles by the best solution, it shows that considering wellbore heat losses, the recovery obtained by using cumulative oil production as optimization index is 11.05%, which is 0.15% larger than that without considering wellbore heat losses; considering wellbore heat losses, the recovery obtained by using producing gas-oil ratio as optimization index is 22.87%, which is 2.83% larger than that without considering wellbore heat losses. The study results provide theoretical basis for better understanding of the effects of various geological, fluid and steam injection parameters and evaluation of the steam stimulation of heavy oil reservoirs, and have great significance to the efficient development of such reservoirs.