doi:10.16186/j.cnki.1673-9787.2019080026

Received:2019/08/07

Revised:2020/03/20

Published:2021/05/15

Discrete fracture network model and numerical simulation of bedrock gas reservoirsconsidering stress sensitivity

LIU Yong1, FU Ying1, FENG Xinyuan1, REN Guangcong2, CHEN Ming2, ZHANG Chengjuan1

1.Drilling and Production Technology Research Institute， PetroChina Qinghai OH Field， Dunhuang  736200 ， Gansu， China;2.College Petroleum Engineering， China University of Petroleum （ Beijing ） ， Beijing  102249 ， China

Abstract:In order to accurately simulate gas well productivity in fractured bedrock gas reservoirs， taking Dongping block in the Qaidam basin as an example and regarding the fractured bedrock gas reservoir in the study area as the dual medium of discrete fracture medium and matrix rock mass， the production model of fractured bedrock gas reservoir based on discrete fracture model was established. The stress sensitivity of hydraulic fractures ，the nonlinearity of gas flow viscosity， density with pressure， and the random distribution of natural fractures in the formation were considered in the model. The discretized equation was obtained by Galerkin weighted residual method and the nonlinear equations were solved iteratively by the Newton-Raphson method. Furtherly， The effect of fractures， including natural fractures and hydraulic fractures ， on the productivity simulation results of horizontal well after segmented fracturing in the study block was analyzed. The results showed that the production prediction was overestimated without considering stress sensitivity， while the results could be more accurate by considering stress sensitivity. The seepage pressure field of bedrock gas reservoir was mainly controlled by the hydraulic fracture conductivity， and the influence of the discrete distribution of natural fracture permeability on the pressure field was weak ； The effect of discrete distribution of natural fractures on productivity was not obvious， hydraulic fracturing should mainly improve the conductivity of hydraulic fractures or connect more natural fractures by hydraulic fractures. For the bedrock gas reservoirs in Dongping block， the optimal conductivity and fracture half-length for the case study were 15 D ， cm and 200  m， respectively.

Key words:Dongping block;bedrock gas reservoir;discrete fracture network;stress sensitivity;seepage characteristic;numerical simulation

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