| In-situ combustion is one of the most important techniques for enhanced oil recovery.During in-situ combustion process for heavy oil reservoirs,electrical ignition is a technique that heat energy is converted from electricity and carried into the oil reservoir by air,which has the advantage of high safety,high ignition success rate and temperature can be controlled.But the electrical ignition technique used in China has disadvantages such as low heat utilization rate and large size of electrical ignition installation,which lead to difficulty as the electrical ignition installation is enter and out of the oil wells,causing great economic losses.In order to solve the dilemma,the theory of oil ignition by electrical ignition installation was studied,a new type of electrical ignition installation was designed,performance test and oil ignition test of electrical ignition installation were carried out and safety of oil ignition process was analyzed.The main research contents and results were listed as follows.1)An electrical ignition model was established by analyzing the process of oil ignition with electrical ignition installation and applying the theory of thermal ignition.The model can effectively describe the ignition process of the oil layer,determine the ignition characteristic parameters and the temperature distribution in the reservoir,provide theoretical guidance for the design of the electrical ignition installation.2)In this paper,a new type of electrical ignition installation for in-situ combustion of heavy oil reservoir was developed.Thermal insulation layer was firstly used in this new type of electrical ignition installation.Heating performance test of electrical ignition installation with and without insulation material under different gas injection rate was carried out.The results showed that the average time it needs to heat air to 350 ℃with thermal insulation material in electrical ignition installation is less 40 minutes than without thermal insulation material.It also showed that temperature difference inside and outside the electrical ignition installation of the former is more than the latter.The insulating layer structure has good thermal insulation performance,can effectively reduce the heat exchange between the electrical ignition installation and the outside,and improve the heat utilization rate of the electrical ignition installation.3)In this paper,the simulated oil layer ignition experiment of electrical ignition installation with and without insulation material under different gas injection rate was carried out.The results showed that the ignition time of the electrical ignition installation with thermal insulation material is shorter than that of the non-thermal insulation material,and the ignition efficiency is increased by about 28%.Thus,the electrical ignition installation can be shortened,which is a breakthrough in the research of electrical ignition installation.4)In this paper,the safety in the in-situ combustion process ignited by electrical ignition installation was analyzed.It can be seen that the thermal insulation layer used in the new electrical ignition installation can reduce size of the electrical ignition installation.Thereby,the difficulty of entering the electrical ignition installation into oil well is reduced,and the safety during the electrical ignition process is improved.In addition,it is very important to determine the applicability of oil flooding in oil field and suitable gas injection rate before fire flooding. |
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