Description:
This paper presents an analysis of the well productivity enhancement possible by drilling multi-legged (or “forked” or “multilateral”) wells in geothermal fields at temperatures in the 100 to 250°C range. A parameter, Productivity Enhancement Factor (“PEF”), is introduced to quantify productivity enhancement; it is defined as the ratio of the downhole productivity index of the multi-legged well to that of the original hole before the forked leg was added. Assuming the original hole to be vertical, it is shown that PEF rises sharply with deviation angle of the forked leg upto about 5 degrees; beyond this, PEF continues to increase with deviation angle albeit at a slower rate.