Abstract
Fractured horizontal well is the most important method for the exploitation in tight gas reservoirs or unconventional gas reservoir. And liquid loading may become a serious problem in fractured horizontal wells when gas product capacities are reducing.
This paper will propose a transient model for liquid loading process of fractured horizontal wells over time.it is obvious that these wells have a large stable rate and all fluids produced from reservoir could be carried to the surface when the gas rate is larger than critical rate; then, the effect of liquid-loading makes the gas rate smaller to be a metastable rate as soon as the gas rate is below critical rate.
A model is introduced for understanding liquid-loading process better in fractured horizontal wells. It is assumed that gas and water coproduction and water reinjection both exist in hydraulic fracture. And part of water produced from reservoir is carried to the surface and the rest water will first accumulate at the bottom of the hydraulic fracture with the help of gravity when liquid loading starts and part of water in fracture may reinject into reservoir later. Then, the water column will reach the horizontal section or even get up to the inclined section and the vertical section. Finally, a metastable rate could be observed when water produced from reservoir is equal to the sum of water carried to the surface and water reinjection.
Then, the sensitivity analysis of several parameters such as the fracture parameters (the length, the width, the height, and number of fractures) and water gas ratio of the surface have been taken to influence the metastable rate and the time reached to the metastable rate.
With this model, liquid-loading process in fractured horizontal wells can be understood better and predicted. And it is very important for the optimization of fracture parameters and well production parameters to prevent and control the liquid-loading process.
