Field test and initial response characteristics of fire flooding in Menggulin conglomerate reservoir

The Menggulin conglomerate reservoir is an ordinary heavy oil reservoir undergoing water flooding development. Various stimulation measures have been implemented in this reservoir, and it has now entered a high-water-cut period, showing limited potential in further increasing the recovery rate through water flooding. In order to improve the development efficiency, a field test of fire flooding was conducted. In comparison with other successful fire flooding projects in China, this block is relatively low in crude oil viscosity, porosity, and permeability, while thick in oil layer, which poses high challenges on technological processes. Therefore, based on the characteristics of an ordinary heavy oil reservoir, the fire flooding gas injection and ignition process were optimized. The commonly used four-stage gas injection process was replaced by a three-stage gas injection process, and the four-stage gradual heating ignition was simplified to one-stage heating ignition. As a result, the gas injection duration of the tubing was shortened from 3 d to 1–2 h, and the igniter temperature rose to 400 ℃ after 19 hours of ignition. This reduced the gas injection duration of the tubing and increased the temperature rise rate during ignition, achieving safe ignition. Within three months after ignition, the oil well showed initial positive results. As of May 2023, the daily oil production had increased by 230.5%, and it is still steadily increasing, accompanied by a 16.5% decrease in overall water cut. In comparison with other fire flooding blocks, this one exhibited early and rapid response. Additionally, during the initial production stage, N₂ was the main component of the produced gas, while O₂ and CO₂ were relatively low. The produced crude oil also showed significant improvement, with increased saturation hydrocarbon content and decreased heavy components. These findings provide valuable insights for implementing fire flooding in similar reservoirs.