Abstract:

The complex fracture networks are often formed after large-scale hydraulic fracturing in shale gas reservoirs, and the shale gas production rates decrease quickly due to the stress sensitivity. Therefore, it is necessary to study the influence of the stress sensitivity and production schedule under the controlled pressure for shale gas wells to determine the reasonable pressure drop and optimize the production schedule. Firstly, the natural and hydraulic fractures in shale gas reservoir are accurately characterized based on the embedded discrete fracture model（EDFM）, and the numerical simulation models of the shale gas wells based on the complex fracture networks are established. Then, the gas production performance of shale gas wells under different stress sensitivity conditions of fractures and matrix are analyzed. Finally, the numerical simulation on the production schedule optimization under the controlled pressure is performed. Forty groups of different production pressure schemes are designed to clarify the relationship between production pressure and performance of shale gas wells. The relationship curves of the accumulative gas and production pressure are established for Block A of W shale gas reservoir, and the optimal production pressure drop under controlled pressure is determined to be 14 MPa. The results show that the production under the controlled pressure is important for enhancing the production of shale gas wells and can reduce the influence of stress sensitivity on gas production. The optimization method and results of the production schedule under the controlled pressure can provide guidance for the production optimization of the shale gas wells.

Key words: shale gas, embedded discrete fracture, stress sensitivity, production schedule optimization, numerical simulation