Optimization Of Hydraulic Fracturing Process Parameters In Condensate Gas Reservoirs

Due to the low permeability and condensate blockage around the near-wellbore area, single well production of a low-permeable gas condensate reservoir is low without human-interference. Most of the time, wells are hydraulic fracture stimulated. Common analytical methods or maps used to optimize hydraulic fracture parameters are usually too simplified to effectively handle the complex phase state behavior and flow behavior caused by capillary number effect. Thus, it is necessary to develop a new suitable methodology of optimizing hydraulic fracturing parameters, which considers the special behaviors of gas condensate reservoirs, so as to instruct fracturing design and improve post-fracture production.Based on a sufficient survey of domestic and international studies of gas condensate relative permeability model and hydraulic fracturing optimization methods, a system research about reservoir simulation, hydraulic fracturing optimization and post-fracture production prediction is conducted for two different lean and rich gas condensate reservoirs, with numerical simulation method and disciplines of multiple subjects including gas engineering and formation stimulation etc. Specific contents are as follows:(1) The unique capillary number effect on gas-condensate relative permeability is studied, and the relative permeability model which includes the effects of saturation and velocity is built. Measurement data includes two-phase flash experiment, viscosity measurement, constant composition expansion experiment and constant volume depletion experiment is analyzed and matched. Together with other basic parameters like porosity and permeability, two verified single well numerical models are built.(2) In the light of the ideas of Unified Fracture Design optimization method, optimal parameters for a given amount of proppant are calculated using numerical models in order to make up for the original shorts of proppant index optimization method. Some practical limits like net pressure, proppant concentration in the fracture, and the fact of uneven proppant distribution in the height direction are considered. The influences of fluid type, permeability and thickness on the optimal results are also studied.(3) Stimulation target is determined separately. The final pump schedules are given and the fracture profiles are simulated. A post-fracture production forecast model which integrates the length of fracture propagation model and gas reservoir numerical model is built, factors like the non-uniform fracture conductivity and fluid leak-off results etc. are embedded into the reservoir model. Two pump designs are evaluated by comparing predicted results with the target production. The influence of possible filter-cake and damage caused by water sensitivity is also analyzed.The conclusions of this paper have a certain reference value for the onsite gas condensate reservoir stimulation design and analysis of production history and fracture parameters of hydraulic fractured wells. The research methods and ideas can also be used in numerical simulation and stimulation studies of other similar formations.