Field testing of the formation heat treatment process

A novel matrix stimulation concept, formation heat treatment (FHT), which involves the application of intense heat for the treatment of water-blockage and clay-related formation damage in water-sensitive formations was developed and tested in the laboratory. Initial bench-scale heating tests on water-sensitive sandstone cores showed that heat treatment at 600 °C can improve air permeability of a damaged core by 50% above the initial permeability. Dramatic permeability increases of 750% and 1,000% above the initial reservoir permeability occurred at 800 °C for the cores taken from the gas- and oil-bearing formations, respectively. To prove the FHT technology in the field, an electrical down-hole heater was designed and constructed. After testing the heater on surface, the heater was lowered into the target reservoir, 1.5 km downhole, heated up and retrieved from the well-bore. Results of the field test showed that there was a significant increase in the post heat-treatment gas injectivity. To quantify the heating effect, pressure transient analyses on pressure falloff data were carried out and the post heat-treatment permeability was found to increase by several fold. The field logistics and the field test results are presented in this paper.