| Description |
The growth of production from liquid shale plays has been phenomenal. However, the recoveries are low of the order of 10% and more efficient methods of producing liquids are necessary. This research is aimed at understanding production performances involving complex interaction between phase behavior and flow in unconventional reservoirs like shales. A new rapid semianalytical forecast tool for transient state linear flow in ultralow permeability (100 nD to 5000 nD) fractured reservoir was developed. The tool is useful for well inflow performance, condensate drop out and material balance calculations of condensate production in unconventional reservoirs. Effects of individual parameters such as reservoir properties (matrix permeability, heterogeneity, rock compressibility and reservoir pressure) on production oil were studied using reservoir simulations with an appropriate number of grid blocks. The matrix permeability, initial reservoir pressure, fracture spacing were the most influencing factors in recoveries from gas-condensate as well as from oil reservoirs. Operating the well at higher flowing bottom hole pressure (FBHP) is preferable for low permeability (100 nD) reservoir and low FBHP for higher permeability (1000 nD) reservoir to recover more liquid. Production data, including Gas Oil Ratios (GOR) are valuable in assessing reservoir performance. A single characteristic factor affecting the produced gas oil ratio was found to be (1- Rsw/Rsb) (1-Pwf/Pb) /(1-Pwf/Pi) that predicts deviation of gas oil ratio from its initial value. Effect of the interaction of parameters on recovery was examined using experimental design and response surface methodology. This study resulted in surrogate reservoir models for a quick assessment of production performance from ultralow permeability black oil and condensate reservoirs. Risks of production performance and investment were quantified by preparing the probability density functions (PDF) of production outcomes and the hierarchy of the most significant input factors using the surrogate reservoir models for given input distributions. Average condensate recoveries from gas condensate reservoirs and oil recoveries from oil reservoirs were 16% and 13%, respectively, after 10 years of production. Abandonment time for well with 18 fractures in ultralow permeability oil reservoir was approximately 7 years. |
