柴达木盆地涩北气田储层表征与稳产调控新技术:大型九分量纵横波地震技术OA

The Sebei Gas Field of the Qaidam Basin has entered the mid-to-late development stage,when the stable gas production faces great challenges.Due to high gas saturation and varying formation velocity,conventional compressional(P)-wave seismic survey yields unclear structural imaging and low-accuracy reservoir identification in gas cloud areas,seriously restricting the recovery of remaining gas reserves.Under this background,the world's first nine-component(9C)P-and shear(S)-wave 3D seismic survey was deployed and implemented.Based on the 9C P-and S-wave 3D seismic data,the structure and reservoir within the gas cloud area were precisely characterized,and the intrinsic relationships between different reservoir types and gas-water distribution patterns in the edge-water gas reservoir were revealed.Accordingly,targeted strategies for stable production control were proposed,and have demonstrated a significantly enhanced recovery of remaining reserves.The following results are obtained.First,the 9C P-and S-wave 3D seismic survey provides high-quality S-wave data in the gas cloud area,which offer technical advantages including true structural imaging,high vertical resolution,and accurate reservoir identification,thereby enabling fine characterization of interwell micro-structures and thin reservoirs.Second,the depositional model was reconstructed using the S-wave data,facilitating the innovative insight that shallow-water deltaic system develops in the study area,beyond the traditional understanding that shore-shallow lacustrine deposits exist across the area.Third,it is systematically revealed that in high-permeability zones,underwater distributary channels dominate water invasion pathways.Consequently,a development adjustment strategy was proposed as:targeting channels in water-uninvaded high structural areas,while tapping the potential in low-permeability zones and draining high-permeability zones in water-invaded middle–low structural areas.Application of this strategy to over 50 well has shown an increase of the estimated ultimate recovery(EUR)per well by 0.12×108 m3.It is concluded that the 9C P-and S-wave 3D seismic survey provides a critical technical support for maintaining the stable annual production of the Sebei Gas Field over 50×108 m3.This technique is highly promising for engineering application and offers significant guidance for the development adjustment of similar gas reservoirs.