关键词: 超临界二氧化碳, 钻井流体, 携岩, 模拟装置, 最低返速

Abstract:

The supercritical CO₂ drilling fluid has been successfully applied to lateral drilling in the secondary development of oilfields. The minimum up-hole velocity of carrying cuttings for the supercritical CO₂ drilling fluid under various conditions was calculated with the Angel model, and a correlation curve of the minimum up-hole velocity and pressure required by carrying cuttings of the supercritical CO₂ drilling fluid at different temperatures was drawn. On the basis of the similarity principle, an experimental device for circulating simulation of the supercritical CO₂ drilling fluid was designed and developed. Experiments revealed a variation trend of the carrying cuttings capability with the change of the deviation angle, i.e. the deviation section with the angle between 0°~36° was the easiest for carrying cuttings, the one between 36°～54° became somewhat difficult, the one between 54°~72° was the most difficult, and the one between 72°～90° became relatively easy again. The minimum up-hole velocity required by carrying cuttings under the conditions of 40°C and 8.5 MPa ranged between 0.637~1.019 m/s. Moreover, the minimum up-hole velocity required by carrying cuttings decreased with the increase of borehole pressure, namely the carrying cuttings capability was gradually increasing. On the contrary, the minimum up-hole velocity required by carrying cuttings increased gradually with the increase of borehole temperature, namely the carrying cuttings capability was gradually decreasing. These experimental results were basically consistent with the calculated outcome by the Angel theoretical model.

Key words: supercritical carbon dioxide, drilling fluid, carrying cuttings, simulating experiment equipment, minimum up-hole velocity