A gas discovery in the Shengping area of the Daqing Oilfield in China was made recently in a large-scale volcanic depositional environment. Because gas in the heterogeneities of formations broken by tectonic activity and localized volcanic eruptions is not common, researchers sought a more detailed reservoir characterization before developing the field. Crosswell seismic data were used to augment existing 3D surface seismic, log, and core data. This provided data at five times the resolution of the surface seismic data to bridge the gap in resolution between surface seismic and well data. Crosswell seismic data were acquired in two wells, apart, and processed to provide images of reflectivity, velocity, and formation properties from sections produced by amplitude-versus-angle (AVA) inversion. The state of the art in crosswell seismic is summarized briefly, reviewing progress in data acquisition and data processing over several decades of crosswell technology development. A detailed description of the data acquisition and data processing applied to the data from the Shengping area is also given. An integrated interpretation of the crosswell images with the surface seismic and log data was used to produce a more detailed geologic model. The enhanced geologic model is being used to plan strategic development of the reservoir and to evaluate possible infill well locations.