High-energy Substances for Petroleum Wells Stimulation
Method of Raising Productivity of Petroleum and Gas-Condensate Wells with the Help of a Two-Stage Thermal and Gas Treatment of a Productive Layer Accompanied by Thermochemical Destruction of Hydrocarbons
Tech Area / Field
- CHE-IND/Industrial Chemistry and Chemical Process Engineering/Chemistry
8 Project completed
Senior Project Manager
Evstyukhin K N
Institute of Biochemical Physics, Russia, Moscow
- TsNIIKhM (Chemistry and Mechanics), Russia, Moscow
- Caveny Production Company, USA, MD, Washington\nAdvanced Power Technologies, Inc., USA, DC, Washington
Project summaryThe goal of the project is to enhance the productivity of oil wells at the viscous and, probably, bituminized oil fields by using the high-energy reactive compositions developed earlier.
Wells are commonly stimulated by hot or cold methods, i.e., with or without energy release and temperature rise in the productive-layer region, respectively.
The hydraulic fracturing (hydrofrac) method, typically used for cold stimulation, consists of two stages: at the first stage, liquid injection into the well results in pressure rise and fracturing in the productive layer; at the second stage, a liquid carrying solid particles is injected, starting with the pressure drop that corresponds to the formation of cracks. The new cracks filled (wedged out) with the solid particles are called the trunk cracks.
Typical of hot stimulation is the single-stage combustion of fuel-oxidizer mixtures in a well (the SSC method). This single-stage method is not accompanied by the wedging of cracks, and the additional amount of the product (gas or oil) obtained under hot stimulation is smaller as compared to that obtained through cold stimulation of the well. Nevertheless, the hot method is competitive because the corresponding treatment cost is lower by a factor of 5 - 10 as compared to the hydrofrac method.
The method of thermal productive-layer stimulation proposed in the present project is based on the two-stage combustion of fuel-oxidizer mixtures in the well (the TSC method). In addition to ordinary fracturing, it ensures the wedging of the cracks at a cost 2 - 5 times lower as compared to that of hydrofrac treatment. The combustion of substances introduced into the well proceeds in two stages. The first stage of combustion, which involves temperature and pressure rise, results in the formation of a gaseous fuel. The gas penetrates deep into the pores and cracks, thus widening them and forming the new cracks. At the second stage, a gaseous oxidizer is released, which also penetrates into the pores and cracks to form an explosive mixture. The secondary (local) explosions that occur in cracks create the zones of shattered rock, distort the complementary pattern of crack edges and thus promote the wedging of the cracks and their gradual transformation into trunk cracks. Thus, as in the hydrofrac method, the cracks created at the first stage are wedged out at the second stage of productive-layer stimulation. However, in contrast to the hydrofrac method, in which the wedging material is introduced externally, the wedging material is produced in situ as the second stage of combustion results in the explosions that shatter the rock constituting the crack walls. It should be noted that the energy released in pores and cracks provides the greater part of the total energy released.
The high-energy compositions applied in the proposed method react by a chain mechanism, and the reaction centers are carried by hot gas, thus promoting thermal and chain destruction of hydrocarbons in pores and cracks.
The use of high-energy compounds can vastly extend the potential utility of thermal bed stimulation.
The project will be accomplished in several steps:
- study of the properties of the productive-layer reservoirs of various fields;
- selection and testing of high-energy compounds to be used at particular oil fields and wells;
- full-scale tests of the method.
The simplest variant of the method proposed has been tested on gas-condensate wells in the middle of 1996. The four wells subjected to the treatment had been abandoned since 1986. The average post-treatment daily output of three of the four wells amounted to 70,000 m3. Currently, these wells remain in operation, and the relative decrease in their productivity over the past year has not exceeded 15 %. In the three successful cases, the expenses associated with the experimental treatment were returned in 4 - 5 months. However, the experimental treatment of the fourth well resulted in a failure. Therefore, further optimization of the compositions of fuel-oxidizer mixtures to be utilized in the TSC method is required, and a preliminary investigation of the efficiency of treatment of rock samples taken from various gas and oil fields should be conducted.
The applications of high-energy compounds can be extended beyond the scope of the project. In particular, these compositions can be used in chemical purification of hydrocarbons, in diagnostics of underground gas storages, etc. We believe that the results to be obtained under the project will lead to the significant progress in the technology of well productivity enhancement.
This document may be considered as an invitation addressed to qualified organizations in the USA, EU, Japan, and Norway to evaluate the proposed project and projected results and become partners in the prospective activities concerning the commercialization of the results.
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