Field testing of the formation heat treatment process

A novel matrix stimulation concept, formation heat treatment (FHT), which i nvolves the application of intense heat for the treatment of water-blockage and clay-related formation damage in water-sensitive formations was develo ped and tested in the;laboratory. Initial bench-scale heating tests on wate r-sensitive sandstone cores showed that heat treatment at 600 degrees C can improve air permeability of a damaged core by 50% above the initial permea bility. Dramatic permeability increases of 750% and 1,000% above the initia l reservoir permeability occurred at 800 degrees C for the cores taken from the gas- and oil-bearing formations, respectively. To prove the FHT technology in the field, an electrical downhole 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 retri eved from the well-bore. Results of the field test showed that there was a significant increase in the post heat-treatment gas injectivity. To quantif y the heating effect, pressure transient analyses on pressure falloff data were carried out and the post heat-treatment permeability was found to incr ease by several fold. The field logistics and the field test results are pr esented in this paper.