Productivity Improvement of Gas-Condensate Wells by Fracturing

The objective of this thesis was to study the effect of vertical fractures in improving the productivity of gas-condensate wells by conducting numerical simulations. A single-well fracture-model, that includes a hydraulic fracture, was simulated using UTCOMP compositional simulator. The results show that a vertical fracture can significantly help in recovering the loss of productivity that occurs because of the condensate dropout near the wellbore. Effect of various factors such as fracture length, fracture conductivity, formation permeability, gas relative permeability, production mode, gas composition, and permeability heterogeneity was studied. It is demonstrated that the gas-condensate well productivity can be theoretically improved by a factor of eight by creating idealized (long and highly conductive) vertical fractures. The effect of formation permeability is also analyzed. It is demonstrated that high-: permeability reservoirs encounter lower amount of condensate accumulation near the wellbore, and thus, lower extent of productivity decline, compared to low-permeability reservoirs. The effect of production mode - i.e., constant-rate versus constant-bottomhole-pressure production has been analyzed. Also, the effect of gas-relative-permeability endpoint was studied. A simulation study of the effect of gas composition on well productivity was performed. Two gases of very different compositions, one - a case of highly rich gas, and the other, a case of highly lean gas were studied. It is demonstrated that the productivity decline in these two cases is not significantly different, although the calculated liquid-dropouts being significantly different. It is to be noted that the above conclusions are based on the results of a set of simulations performed for a short period of time and with limited rate of production. A simulation study of permeability heterogeneity was performed. This preliminary study demonstrated that the effect of permeability heterogeneity on the gas-condensate well productivity is very significant. It also clearly shows that this is a complex problem and needs a thorough analysis of all the parameters involved.Petroleum and Geosystems Engineerin