The complex fault block oilfields in the craton basin contain vast reserves of oil and gas resources. During the development of an oilfield, the flow of oil, gas, and water, is controlled by faults and configuration boundaries. The distribution of remaining oil and gas depends on the interpretation of the reservoir’s architecture. However, recognizing the faults and the architecture boundary remains a challenge, hindering the efficient development of these resources. This study proposes a new idea for interpreting the configuration of thick sand bodies. This study was conducted in order to interpret the fine architecture of thick sand bodies in the Sangtamu area, using core samples, well logging, and production data, guided by sedimentation patterns from ancient to modern times. Results indicate that the Sangtamu area is a braided river delta front sedimentary system, dominated by the backbone underwater distributary channel and branch-type underwater distributary channels. The backbone channel is larger in scale, with a relatively large rock grain size and a box-shaped logging curve, whereas the smaller-scale branch channels have a bell-shaped logging curve resulting from the gradual weakening of water energy. Sandstone bodies from different types of underwater distributary channels are spatially overlapped, forming thick plate-like sandstones. The architecture interface between channels can be used as the fluid seepage boundary and can help prevent bottom water intrusion to a certain extent. The remaining oil is primarily concentrated in the architecture boundary area, which presents the next potential tapping area.

The sandstone reservoir of the Pinghu Formation in the Xihu Depression, East China Sea is characterized by great depth, small thickness, radical facies change and a widespread coal bed. It is difficult to describe the reservoir accurately using conventional reservoir prediction methods. In order to analyze the influence of coal-bearing strata on the prediction of the mid-low thickness sandstone reservoir, the seismic response of different sandstone–coal stratigraphic assemblages was simulated by seismic forward modeling. The modeling result indicates that the post-stack seismic response is dominated by coal bed, whereas the response of sandstone can hardly be recognized. In contrast, the difference between the pre-stack AVO (amplitude versus offset) response characteristics of coal seams and gas-bearing sandstones has been clarified based on the statistics pertaining to AVO characteristics of drilled wells. Therefore, we propose a method to reduce the interference of coal beds in sandstone reservoir prediction using far-gather seismic information. This method has significantly improved the accuracy of reservoir prediction and sand description in sand–coal coupled environments and has been applied successfully in the exploration of coal-rich strata in the Pingbei slope belt, Xihu Depression.

The sand architecture interpretation and modeling of the different orders sedimentary bodies are of great significance to the efficient development of the unconventional reservoir. However, sand architecture interpretation and modeling using a small amount of observation information are extraordinarily difficult. The X36 gas field in Xihu Sag was taken as an example to study the distribution and superimposition characteristics of sandbodies under the influence of tides. A set of architecture characterization and modeling methods suitable for the condition of few wells was proposed. Firstly, a variety of seismic attributes from the original seismic data were extracted. And the correlations between seismic attributes and sandstone thickness interpreted by logging were fitted. Then, the seismic attributes with high correlation were classified and integrated to calculate the fusion seismic attributes. The fusion seismic attribute has a higher correlation with sandstone thickness. The boundary of the sandstone in the fusion seismic attribute is clearer than a single attribute. The sand body distribution model of the study area was established with the constraints of fusion seismic attribute and the distance attribute volume. The results showed that the sand body distribution in the model was more consistent with the sand body development model under the influence of the tide. The results can guide architecture characterization and remaining oil potential tapping of the oil and gas fields offshore.