Abstract: In order to solve the problem of low thermal efficiency caused by uneven steam injection of steam stimulation in horizontal wells in heavy oil reservoirs, numerical simulation methods were used to study the steam injection law of horizontal wells in heterogeneous reservoirs, the impact of steam injection screen pipe position on the steam injection law in horizontal wells was analyzed, the temperature variation coefficient was introduced to compare the degrees of uneven steam injection in horizontal sections in multiple stages, the method for optimizing the position adjustment occasion of the steam injection screen pipe was proposed, and the impact of the position adjustment of the steam injection screen pipe at different stages of the curve on the steam stimulation oil production was compared according to the "V"-shaped law of the temperature variation coefficient firstly decreasing and then increasing. The results showed that the temperature variation coefficient was decreased continuously in the initial stage of steam stimulation; according to the principle of thermodynamic additivity, the specific heat capacity of reservoirs with better steam injection at this stage was increased, proving that the water cut was increased continually, the remaining oil was produced in large amounts, and the adjustment could not fully utilize the remaining oil in the high-permeability reservoir at this moment; if the position of the screen pipe was adjusted in the late stage of steam stimulation, the steam was injected and accumulated in the high-permeability area with low oil content after a large amount of oil was recovered from the high-permeability area until the screen pipe was adjusted, resulting in low heat utilization efficiency; when the temperature variation coefficient reached the minimum value, indicating that the specific heat capacity of the high-permeability reservoir system raised to a higher value, with high water saturation and less remaining oil, the adjustment of screen pipe position at this moment could improve the uneven development of heterogeneous reservoir. Therefore, the earlier the temperature variation coefficient reached the minimum value, the better the effect of the screen pipe position adjustment. The study results were applied to Lean Oilfield. After selecting the occasion to adjust the screen pipe position according to the temperature variation coefficient method, the steam injection profile was more balanced, and the average daily oil production was increased from 0.5 t/d in the previous cycle to 3.4 t/d. The study results have no guidance for improving the uneven steam injection in steam stimulation.

Key words: steam stimulation, horizontal well, steam injection screen pipe, numerical simulation, uneven steam injection, development degree, Lean Oilfield