As a development method to replace steam stimulation of heavy oil, in situ combustion often faces many problems in thick reservoir, such as low vertical sweep efficiency and channeling combustion. According to the characteristics and development history of this kind of reservoir, a method of changing plane fire flooding to gravity fire flooding is proposed by using the existing steam stimulation development well pattern and sidetracking horizontal section of vertical production wells. The influence of different factors on sidetracking gravity fire flooding production effect is analyzed from the aspects of reservoir geology and development engineering. The internal stimulation mechanism of this method is further studied, and the evaluation model between recovery factor and main control factor is established by using multiple linear regression equation. The results show that vertical sidetracking gravity fire flooding can improve the recovery of thick heavy oil reservoir by 42%; the better recovery effect can be obtained when the sidetracking length is about 1/2 of the well spacing; the coincidence degree between the established recovery evaluation model and the results of numerical simulation is more than 85%. The research results of this paper can help the mine fire flooding development to change the mining mode and provide some guidance for the medium- and long-term planning.

The stability of combustion in the process of fire flooding requires not only a reasonable gas injection rate but also a matching exhaust rate. A reasonable injection-production balance system is very important. Based on the material balance of injection-production, the expression of injection-production ratio suitable for normal fire flooding production is established. The air injection rate of fire flooding combustion and oxygen consumption of formation pressurization is analyzed by this formula to calculate the gas production and liquid production in combustion. The reasonable injection and production parameters for the oilfield are calculated by using the oilfield parameters. It can be seen that the calculated value of injection-production ratio is consistent with the actual value, which shows that the injection-production ratio is reasonable and can guide the adjustment of production parameters in the oilfield.

The complex fault block reservoir has the characteristics of small area and many layers in vertical. Due to the influence of formation heterogeneity and well pattern, the situation that “water fingering is serious with water injection, on the contrary, driving energy is low” frequently occurs in water flooding, which makes it difficult to enhance oil recovery. Asynchronous injection-production (AIP) process divides the conventional continuous injection-production process into two independent processes: injection stage and production stage. In order to study oil recovery in the fault block reservoir by AIP technology, a triangle closed block reservoir is divided into 7 subareas. The result of numerical simulation indicates that all subareas have the characteristic of fluid diverting and remaining oil in the central area is also affected by injected water at injection stage of AIP technology. Remaining oil in the central area is driven to the included angle and border area by injected water and then produced at the production stage. Finally, the oil recovery in the central area rises by 5.2% and in the noncentral area is also increased in different levels. The AIP process can realize the alternative change of reservoir pressure, change the distribution of flow field, and enlarge the swept area by injected water. To sum it up, the AIP process is an effective method to improve the oil recovery in complex fault-block reservoir by water flooding.