Research of the Influence of the Grid Density of Injection Wells on the Gas Extraction Coefficient When Injecting Carbon Dioxide into Reservoir

Abstract

The object of research is gas and gas condensate reservoirs developed under the conditions of the manifestation of the water pressure mode of development and the negative effect of formation water on the process of natural gas production. In order to improve the existing technologies for the development of natural gas fields in the conditions of the manifestation of a water-driven mode of development of productive reservoirs, a study was carried out using the main tools of hydrodynamic modeling Eclipse and Petrel from Schlumberger (USA). On the basis of a three-dimensional digital model of gas condensate, the influence of the density of injection wells on the coefficient of natural gas extraction during the injection of carbon dioxide into productive reservoirs on the verge of a gas-water contact was investigated. The study was carried out for a different number of injection wells (4, 6, 8, 12, 16 wells), which are evenly spaced along the perimeter of the initial gas-water contact. According to the results of the calculations, it was found that the production of formation water decreases with an increase in the density of the well grid. In the case of using 4 wells to inject carbon dioxide into a productive reservoir, the accumulated production of formation water at the end of development amounted to 169.71 thousand m3. With an increase in the number of injection wells to 16 units, the accumulated production of produced water decreased to 0.066 m3. This result is achieved due to a more complete coverage of the perimeter of gas content with carbon dioxide and the creation of an artificial barrier between water and natural gas, which leads to a more effective blocking of the movement of produced water into productive reservoirs. According to the results of statistical processing of the calculated data, the optimal value of the number of injection wells was determined when injecting carbon dioxide into the reservoir. The optimal value of the number of injection wells at the time of the breakthrough of carbon dioxide into the first production well is 7.86 (8) wells. The maximum value of the number of injection wells according to the results of statistical processing is 6.8 (7) wells. The final gas recovery ratio for the given optimal injection value is 61.88 %. On the basis of the calculations, the technological efficiency of using as an agent for injecting carbon dioxide at the boundary of the gas-water contact was established in order to prevent selective watering of productive reservoirs and production wells.