库车山前超深裂缝性致密砂岩边水气藏试井特征分析OA

The gas fields in the Kuqa piedmont of the Tarim Basin consist of a series ultra-deep fractured tight sandstone edge-water gas reservoirs,featuring multi-scale discrete fractures including matrix-fracture-fault systems,which pose great challenges to well test interpretation.Based on actual test data and the basic principles of well test interpretation,this paper systematically analyzes the characteristics of well test type curves for fractured water-bearing gas reservoirs in the Kuqa piedmont.Results show that:(i)for edge gas wells,the late-stage upward warping of the pressure derivative may be a false boundary formed by the viscosity difference between gas and water,and the pressure derivative curve generally shrinks to the upper left in the log-log plot with the gradual advancement of water;(ii)the late-stage pressure derivative presents a straight line with a slope between 0.5 and 1 for gas wells at high structural positions.The slope value reflects the development degree of fracture networks.The more complex the fracture network,the larger the slope.The slope of the pressure derivative curve changes before and after water breakthrough in the wells at high structural positions,and resumes to the original state after complete water flooding;(iii)comparison of well test pressure derivative curves normalized using production data of a single well at different stages indicates no significant change in formation coefficient without edge water influence;(iv)there exists gas supply from matrix to fracture system.To sum up,for the fractured gas reservoirs with tight matrix in the field group in the Kuqa piedmont,their key parameters such as permeability and storativity ratio cannot be interpreted using analytical well test methods when the total system radial flow does not appear on the derivative curve.The late-stage upward warping of the pressure derivative curves for gas wells at edge is not necessarily a boundary characteristic,and this phenomenon should be analyzed combining dynamic and static data.During the development process,the reservoir permeability does not show obvious stress sensitivity characteristics.